Water Pollution: Causes, Sources, Effects & Prevention/Solutions

Water Pollution: Causes, Sources, Effects & Prevention/Solutions

Water pollution is one of the leading environmental issues in the world.

Pollution includes both fresh water pollution (lakes, rivers and groundwater), and ocean/marine water pollution.

In this guide, we’ve outlined what water pollution is, as well the types, causes, sources, examples, effects & prevention/solutions of water pollution.


Summary – What To Know About Water Pollution

  • Water pollution can involve pollution of ground water (freshwater), surface water (freshwater), or the ocean (saltwater)
  • Water can become polluted from a number of sources and in a number of ways
  • Agricultural run off (fertilizers, pesticides, agricultural chemicals, and animal waste) is the main cause of freshwater pollution
  • Sewage and wastewater are the main causes of ocean water pollution (More than 80 percent of the world’s wastewater flows back into the environment without being treated or reused)
  • These causes differ between developed and developing countries – in developing countries, lack of sewage waste treatment and lack of sanitation can lead to water pollution
  • Water pollution impacts humans who can experience a lack of drinking water or freshwater to use. It impacts animals who live in and drink the water. And there are environmental effects.
  • Water pollution is tied to other environmental issues like  eutrophication (oxygen dead spots in water where aquatic life can’t live), ocean acidification (carbon uptake by the ocean of the atmosphere’s carbon in the air), acid rain (rains down on water sources) and other environmental issues
  • Potential solutions on the social level might be aimed at addressing agricultural pollution, and wastewater and sewage pollution 


What Is Water Pollution?

  • Water pollution occurs when harmful substances—often chemicals or microorganisms—contaminate a stream, river, lake, ocean, aquifer, or other body of water, degrading water quality and rendering it toxic to humans or the environment.

– NRDC.org


Types Of Water Pollution

Three types:

  • Surface water pollution (includes freshwater sources like rivers and lakes)
  • Ground water pollution (underground freshwater sources. Over time, water from rain and rivers seeps into the ground and accumulates within cracks or pores in the rocks (aquifers), forming groundwater under the earth’s surface.)
  • Salt water/ocean water (self explanatory)


Surface Water Pollution

  • Surface water from freshwater sources accounts for more than 60 percent of the water delivered to American homes. 

– NRDC.org/pubs.USGS.gov


  • According to the most recent surveys on national water quality from the U.S. Environmental Protection Agency, nearly half of the rivers and streams, and more than one-third of the lakes are polluted and unfit for swimming, fishing, and drinking.

– NRDC.org/EPA.gov


  • In specific numbers, a 2000 survey published in EPA’s National Water Quality Inventory found almost 40 percent of U.S. rivers and 45 percent of lakes are polluted
  • A major cause of this pollution in surface freshwater sources is fertilizer, pesticides and animal waste from agriculture. A lot of this pollution simply runs off the land and is nonpoint (coming from not one point, but many points) source pollution

– PollutionIssues.com


You can read more about surface water pollution and contamination here – http://www.pollutionissues.com/Ve-Z/Water-Pollution-Freshwater.html 


Groundwater Pollution

  • Nearly 40 percent of Americans rely on groundwater, pumped to the earth’s surface, for drinking water. For some people in rural areas, it’s their only freshwater source.

– NRDC.org/NGWA.org.


  • Some figures say groundwater use for drinking use in the USA is as high as 50%

– Groundwater.org


  • Groundwater gets polluted when contaminants—from pesticides and fertilizers to waste leached from landfills and septic systems—make their way into an aquifer, rendering it unsafe for human use.
  • Ridding groundwater of contaminants can be both difficult and costly.
  • Once polluted, an aquifer/groundwater source may be unusable for decades, or even thousands of years.
  • Groundwater can also spread contamination far from the original polluting source as it seeps into streams, lakes, and oceans.

– NRDC.org


You can read more about groundwater contamination and pollution here – http://www.groundwater.org/get-informed/groundwater/contamination.html 


Marine/Ocean Water Pollution

  • Eighty percent of ocean pollution originates on land—whether along the coast or far inland.

– OceanService.NOAA.org/NRDC.org


  • Contaminants such as chemicals, nutrients, and heavy metals are carried from farms, factories, and cities by streams and rivers into bays and estuaries; from there they travel out to sea. 
  • Meanwhile, marine debris—particularly plastic and other waste—is blown in by the wind or washed in via storm drains and sewers.
  • Seas also suffer oil pollution (spills, and general oil pollution from cars and household) and are consistently soaking up carbon pollution from the air. The ocean absorbs as much as a quarter of man-made carbon emissions.

– NRDC.org


You can read more about ocean/marine water pollution facts here – https://www.nrdc.org/stories/ocean-pollution-dirty-facts 


The Point At Which Water Is Polluted

Water isn’t always polluted at one single source or point. The points at which water is polluted are:

  • Point Source (pollution from a single point/source)
  • Non Point Source (pollution from multiple points/sources)
  • Transboundary (pollution from over the border/another country)


Point Source Water Pollution

  • Examples include wastewater (also called effluent) discharged legally or illegally by a manufacturer, oil refinery, or wastewater treatment facility, as well as contamination from leaking septic systems, chemical and oil spills, and illegal dumping.

– NRDC.org/OceanService.noaa.gov


Nonpoint Source Water Pollution

  • Nonpoint source pollution is contamination derived from diffuse (spread out or scattered) sources. These may include agricultural or stormwater runoff or debris blown into waterways from land.

– NRDC.org


  • Nonpoint source pollution is the leading cause of water pollution in U.S. waters, but it’s difficult to regulate, since there’s no single, identifiable culprit.

– EPA.gov/NRDC.org 


Transboundary Water Pollution

  • Transboundary pollution is the result of contaminated water from one country spilling into the waters of another.
  • Contamination can result from a disaster—like an oil spill—or the slow, downriver creep of industrial, agricultural, or municipal discharge.

– NRDC.org


  • Another way to say it is, sometimes pollution that enters the environment in one place has an effect hundreds or even thousands of miles away.
  • One example is the way radioactive waste travels through the oceans from nuclear reprocessing plants in England and France to nearby countries such as Ireland and Norway.

– ExplainThatStuff.com 


Causes & Sources Of Water Pollution (Human, & Natural)

Causes of water pollution can be natural, or anthropogenic (caused by humans).

Read more about the causes of water pollution and contamination in this guide.


  • Natural causes include things like naturally decaying plant matter, naturally occurring water bacteria and organisms, animal waste (from wild animals), and natural events like volcano eruptions, earthquakes, flooding and tsunamis that contaminate water sources.
  • However, by far and away … human based sources … are the main contributors to water pollution.

– NRDC.org


Some of the most common and major causes and sources of human based water pollution are:

  • Agricultural pollution (a major cause of pollution in freshwater lakes, rivers etc.)
  • Sewage and wastewater pollution (a major cause of pollution in oceans)
  • Oil pollution
  • Radioactive pollution
  • Chemical waste
  • Plastic Waste
  • Alien species pollution
  • Heat/Thermal pollution
  • Sediment pollution
  • Air pollution
  • + more

You can read more about each of these in the FAO, NRDC, EPA, UNESCO,


Agricultural Pollution

  • Around the world, agriculture is the leading cause of water degradation. 

– FAO/NRDC.org


  • In the United States, agricultural pollution is the top source of contamination in rivers and streams, the second-biggest source in wetlands, and the third main source in lakes. It’s also a major contributor of contamination to estuaries and groundwater. 

– Ofmpub.EPA.gov.au/NRDC.org


  • Every time it rains, fertilizers, pesticides, and animal waste from farms and livestock operations wash nutrients and pathogens—such bacteria and viruses—into our waterways.
  • They often seep from the soil they absorb into, into these water sources.
  • Nutrient pollution, caused by excess nitrogen (nitrates) and phosphorus (phosphates) in water or air, is the number-one threat to water quality worldwide and can cause algal blooms, a toxic soup of blue-green algae that can be harmful to people and wildlife.

– EPA.gov/NRDC.org


  • Nutrient pollution is the leading type of contamination for freshwater sources (rivers, lakes, streams etc.) in particular. While plants and animals need these nutrients to grow, they have become a major pollutant due to farm waste and fertilizer runoff. 

– NRDC.org/EPA.gov


Together, fertilizers AND sewage can cause a massive increase in the growth of algae or plankton that overwhelms huge areas of oceans, lakes, or rivers.

Eutrophication is when a body of water becomes overly enriched with minerals and nutrients that induce excessive growth of plants and algae. Eutrophication is almost always induced by the discharge of nitrate or phosphate – containing detergents, fertilizers, or sewage into an aquatic system.


Sewage and Wastewater Pollution

  • Used water is wastewater. It comes from sinks, showers, and toilets (think sewage) and from commercial, industrial (factories), and agricultural activities (think metals, solvents, and toxic sludge).
  • The term also includes stormwater runoff, which occurs when rainfall carries road salts, oil, grease, chemicals, and debris from impermeable surfaces into our waterways.

– NRDC.org


  • More than 80 percent of the world’s wastewater flows back into the environment without being treated or reused, according to the United Nations; in some least-developed countries, the figure tops 95 percent.

– UNESCO.org/NRDC.org


  • Sewage contains all kinds of other chemicals, from the pharmaceutical drugs people take to the paper, plastic, and other wastes they flush down their toilets.
  • When people are sick with viruses, the sewage they produce carries those viruses into the environment. It is possible to catch illnesses such as hepatitis, typhoid, and cholera from river and sea water.

– Explainthatstuff.com


  • In the United States, wastewater treatment facilities process about 34 billion gallons of wastewater per day. These facilities reduce the amount of pollutants such as pathogens, phosphorus, and nitrogen in sewage, as well as heavy metals and toxic chemicals in industrial waste, before discharging the treated waters back into waterways. 
  • That’s when all goes well. But according to EPA estimates, the USA’s aging and easily overwhelmed sewage treatment systems also release more than 850 billion gallons of untreated wastewater each year.

– EPA.gov/NRDC.org


  • Another way to say the above is – around half of all ocean pollution is caused by sewage and waste water. 
  • Each year, the world generates perhaps 5–10 billion tons of industrial waste, much of which is pumped untreated into rivers, oceans, and other waterways. In the United States alone, around 400,000 factories take clean water from rivers, and many pump polluted waters back in their place. 
  • However, there have been major improvements in waste water treatment recently. Since 1970, in the United States, the Environmental Protection Agency (EPA) has invested about $70 billion in improving water treatment plants that, as of 2015, serve around 88 percent of the US population (compared to just 69 percent in 1972). 
  • However, another $271 billion is still needed to update and upgrade the system. 
  • Factories are point sources of water pollution, but quite a lot of water is polluted by ordinary people from nonpoint sources; this is how ordinary water becomes waste water in the first place. 

– ExplainThatStuff.com 


Oil Pollution 

  • Consumers account for the vast majority of oil pollution in our seas, including oil and gasoline that drips from millions of cars and trucks every day.

– NRDC.org


  • Nearly half of the estimated 1 million tons of oil that makes its way into marine environments each year comes not from tanker spills but from land-based sources such as factories, farms, and cities.

– WorldOceanReview.com/NRDC.org


  • At sea, tanker spills account for about 10 percent of the oil in waters around the world, while regular operations of the shipping industry—through both legal and illegal discharges—contribute about one-third.

– IMO.org/Justice.gov/NRDC.org


  • Oil is also naturally released from under the ocean floor through fractures known as seeps.

– Response.Restoration.NOAA.gov/NRDC.org 


Radioactive Substance Pollution (Nuclear Pollution)

  • Radioactive waste is any pollution that emits radiation beyond what is naturally released by the environment. 
  • It’s generated by uranium mining, nuclear power plants, and the production and testing of military weapons, as well as by universities and hospitals that use radioactive materials for research and medicine. 
  • Radioactive waste can persist in the environment for thousands of years, making disposal a major challenge.

– NRDC.org


  • The decommissioned Hanford nuclear weapons production site in Washington cleanup of 56 million gallons of radioactive waste is expected to cost more than $100 billion and last through 2060.

– TheBulletin.org/NRDC.org


  • Accidentally released or improperly disposed of contaminants threaten groundwater, surface water, and marine resources.

– STLToday.com/NRDC.org


  • At high enough concentrations it can kill; in lower concentrations it can cause cancers and other illnesses.
  • The biggest sources of radioactive pollution in Europe are two factories that reprocess waste fuel from nuclear power plants: Sellafield on the north-west coast of Britain and Cap La Hague on the north coast of France.
  • Both discharge radioactive waste water into the sea, which ocean currents then carry around the world. Countries such as Norway, which lie downstream from Britain, receive significant doses of radioactive pollution from Sellafield. 
  • The Norwegian government has repeatedly complained that Sellafield has increased radiation levels along its coast by 6–10 times. Both the Irish and Norwegian governments continue to press for the plant’s closure. 

– ExplainThatStuff.com


Other Water Pollution Causes & Sources…

Some of these sources are related to the above sources, whilst some are their alone separate sources:

Chemical Waste Pollution

According to ExplainThatStuff.com:

  • Chemical waste can come in varying forms and extremities.
  • They can come from households – like detergents and cleaning products.
  • But, they can come from commercial and industrial sources like factories, plants, and mines. We are talking about asbestos, lead, mercury, petrochemicals etc.
  • Detergents are relatively mild substances, while at the opposite end of the spectrum are highly toxic chemicals such as polychlorinated biphenyls (PCBs).( They were once widely used to manufacture electronic circuit boards)
  • Another kind of toxic pollution comes from heavy metals, such as lead, cadmium, and mercury. Lead was once commonly used in gasoline (petrol), though its use is now restricted in some countries.
  • Mercury and cadmium are still used in batteries (though some brands now use other metals instead). Until recently, a highly toxic chemical called tributyltin (TBT) was used in paints to protect boats from the ravaging effects of the oceans.
  • Ironically, however, TBT was gradually recognized as a pollutant: boats painted with it were doing as much damage to the oceans as the oceans were doing to the boats.

– ExplainThatStuff.com


  • Virtually everyone pours chemicals of one sort or another down their drains or toilets. Even detergents used in washing machines and dishwashers eventually end up in rivers and oceans. So do the pesticides people use on their gardens. 
  • A lot of toxic and chemical pollution also enters waste water from highway runoff. Highways are typically covered with toxic chemicals—everything from spilled fuel and brake fluids to bits of worn tires (themselves made from chemical additives) and exhaust emissions. 
  • When it rains, these chemicals wash into drains and rivers. It is not unusual for heavy summer rainstorms to wash toxic chemicals into rivers in such concentrations that they kill large numbers of fish overnight. 
  • It has been estimated that, in one year, the highway runoff from a single large city leaks as much oil into our water environment as a typical tanker spill. Some highway runoff runs away into drains; others can pollute groundwater or accumulate in the land next to a road, making it increasingly toxic as the years go by. 

– ExplainThatStuff.com 


Plastic & Waste Pollution

Plastic is one of the most common things that washes up on a beach.

There are three reasons for this:

  • plastic is one of the most common materials, used for making virtually every kind of manufactured object from clothing to automobile parts;
  • plastic is light and floats easily so it can travel enormous distances across the oceans;
  • most plastics are not biodegradable (they do not break down naturally in the environment), which means that things like plastic bottle tops can survive in the marine environment for a long time. (A plastic bottle can survive an estimated 450 years in the ocean and plastic fishing line can last up to 600 years.).

While plastics are not toxic in quite the same way as poisonous chemicals, they nevertheless present a major hazard to seabirds, fish, and other marine creatures.

– ExplainThatStuff.com


When we look at waste in general, littering, improper waste disposal and dumping in landfills can cause waste to spill over into water sources.

In addition to plastic, glass, aluminum, styrofoam, cigarette butts and more can be found in water sources. 


Alien Species Pollution (Biological Pollution)

  • Most people’s idea of water pollution involves things like sewage, toxic metals, or oil slicks, but pollution can be biological as well as chemical.
  • In some parts of the world, alien species are a major problem. Alien species (sometimes known as invasive species) are animals or plants from one region that have been introduced into a different ecosystem where they do not belong.
  • Outside their normal environment, they have no natural predators, so they rapidly run wild, crowding out the usual animals or plants that thrive there. Examples are Zebra Mussels, algae, jellyfish, clams etc.  In 1999, Cornell University’s David Pimentel estimated that alien invaders like this cost the US economy $123 billion a year.

– Cornell.edu/ExplainThatStuff.com


Heat Or Thermal Pollution

  • Heat or thermal pollution from factories and power plants also causes problems in rivers.
  • By raising the temperature, it reduces the amount of oxygen dissolved in the water, thus also reducing the level of aquatic life that the river can support.

– ExplainThatStuff.com 


Sediment Pollution

  • Another type of pollution involves the disruption of sediments (fine-grained powders) that flow from rivers into the sea.
  • Dams built for hydroelectric power or water reservoirs can reduce the sediment flow. This reduces the formation of beaches, increases coastal erosion (the natural destruction of cliffs by the sea), and reduces the flow of nutrients from rivers into seas (potentially reducing coastal fish stocks).
  • Increased sediments can also present a problem. During construction work, soil, rock, and other fine powders sometimes enters nearby rivers in large quantities, causing it to become turbid (muddy or silted).
  • The extra sediment can block the gills of fish, effectively suffocating them. Construction firms often now take precautions to prevent this kind of pollution from happening.

– ExplainThatStuff.com 


Air Pollution 

Air pollution can cause water pollution in some of the following ways:

  • Ocean Acidification –  is the ongoing decrease in the pH of the Earth’s oceans, caused by the uptake of carbon dioxide (CO2) from the atmosphere. – Wikipedia – https://en.wikipedia.org/wiki/Ocean_acidification
  • Acid rain – SO2 and NOX  emitted into the air from fossil fuel burning, vehicles and manufacturing react with water, oxygen and other chemicals to form sulfuric and nitric acids.  These then mix with water and other materials before falling to the ground. It can get into water sources via the soil it has polluted and fallen onto – https://www.epa.gov/acidrain/what-acid-rain
  • Global Warming –  a result of greenhouse gases like carbon dioxide contributing to climate change and causing an increase in water temperature 


Other Pollutants

  • Underground storage leakages
  • Damming of rivers – WaterWise.co.za
  • Deforestation


Summary Of Pollutants 

  • Microorganisms, toxins, pathogens – from waste water, sewage, animal waste (agriculture)
  • Chemicals & Nutrients – fertilizer, pesticides/herbicides, detergents, cleaning products, oils (oil spills, household oils, and car oil), PTBs, phosphates, nitrates
  • Heavy Metals – lead, mercury, cadmium etc,
  • Hard Waste – plastic, aluminium, cigarette butts, glass etc.
  • Air Pollution – carbon, other air pollutants that mix together
  • Soil Pollution – seep and runoff from soil
  • Natural Pollution – plant decay, natural waste and bacteria, natural events

This is not an extensive list – just some of the main contaminants.


Ocean/Marine Water Pollution

  • As a summary to the above for saltwater – around half of all ocean pollution is caused by sewage and waste water

– Explainthatstuff.com


Freshwater Pollution

  • As a summary to the above for freshwater – agricultural pollution (fertilisers, pesticides/herbicides and animal waste) is the top source of contamination in rivers and streams, the second-biggest source in wetlands, and the third main source in lakes. It’s also a major contributor of contamination to estuaries and groundwater.

– Ofmpub.EPA.gov.au/NRDC.org 


Effects Of Water Pollution

Some water pollution is inevitable as a result of human and economic activity – it can’t completely be eliminated.

However, water pollution also has human, environmental and economic costs – so it’s in everyone’s best interests to minimise it or find a way to address it.


Some of the effects are as follows:

Human Health Effects

  • Water pollution can cause death. It caused 1.8 million deaths in 2015, according to a study published in The Lancet.

– TheLancet.com/NRDC.org


  • Contaminated water can also make you ill. Every year, unsafe water sickens about 1 billion people. And low-income communities are disproportionately at risk because their homes are often closest to the most polluting industries.

– NRDC.org


Pathogens are found in polluted/contaminated water and diseases spread in the water include cholera, giardia, and typhoid.


  • Thousands of people across the United States are sickened every year by Legionnaires’ disease (a severe form of pneumonia contracted from water sources like cooling towers and piped water), with cases cropping up from California’s Disneyland to Manhattan’s Upper East Side.

– EPA.gov/LATimes.com/NYTimes.com/NRDC.org


  • Flint, Michigan was the result of cost-cutting measures and aging water infrastructure creating a lead contamination crisis

– NRDC.org


  • The problem goes far beyond Flint and involves much more than lead, as a wide range of chemical pollutants—from heavy metals such as arsenic and mercury to pesticides and nitrate fertilizers—are getting into water supplies. Once they’re ingested, these toxins can cause a host of health issues, from cancer to hormone disruption to altered brain function. Children and pregnant women are particularly at risk.

– NRDC.org


  • Even swimming can pose a risk. Every year, 3.5 million Americans contract health issues such as skin rashes, pinkeye, respiratory infections, and hepatitis from sewage-laden coastal waters, according to EPA estimates.

– EPA.gov/NRDC.org 


Environmental Effects

  • Interruption with how animals, plants, bacteria, and fungi in an ecosystem interact with each other
  • [algal blooms from excess nutrients like fertilizers can cause oxygen depleted dead spots in water – which aquatic animals can’t live in]
  • Chemicals and heavy metals from industrial and municipal wastewater contaminate waterways as well. These contaminants are toxic to aquatic life [and can find their way up the food chain when big animals eat smaller ones]

– NRDC.org


  • Marine ecosystems are also threatened by marine debris, which can strangle, suffocate, and starve animals. [plastic and fishing gear are two big examples of this]

– OceanService.NOAA.gov/Coast.NOAA.gov/NRDC.org


  • Meanwhile, ocean acidification is making it tougher for shellfish and coral to survive. Though they absorb about a quarter of the carbon pollution created each year by burning fossil fuels, oceans are becoming more acidic. 

– NRDC.org 


Economic Effects

On top of the human health and environmental effects of water pollution, there are also economic effects such as:

  • Cleaning up oil spills
  • Killing fish which harms the fishing industry
  • Treating humans who get sick from water pollution
  • Costs to lost tourism
  • Costs of lower supplies of freshwater – restriction or increased prices can restrict business growth and employment

Plus much more. 


How To Measure Water Quality

It should be noted that water quality depends on the purpose for the water, or what you want to use it for.

For example, water that could be unfit for human consumption could be still usable in industrial or agriculture applications like irrigation.


Once you know the purpose of the water, there are two main ways of measuring the quality of water:

Chemical Indicators

  • One is to take samples of the water and measure the concentrations of different chemicals that it contains.


Biological Indicators

  • Another way to measure water quality involves examining the fish, insects, and other invertebrates that the water will support.
  • If many different types of creatures can live in a river, the quality is likely to be very good; if the river supports no fish life at all, the quality is obviously much poorer.


Water Pollution & Quality – Developing vs Developed Countries

Access to, and availability of safe drinking and usable water (and also sanitation) is certainly an issue in developing countries.

A lack of income certainly plays a role in this – not being able to purchase and set up drinkable and useable water infrastructure, and having the same financial restrictions with sanitation and waste water/sewage treatment facilities and infrastructure.

However, water pollution is more of a country by country issue which depends on a lot of factors.

Water quality in developing countries is often hampered by lack of or limited enforcement of:

  • emission standards
  • water quality standards
  • chemical controls
  • non-point source controls (e.g. agricultural runoff)
  • market based incentives for pollution control/water treatment
  • follow-up and legal enforcement
  • integration with other related concerns (solid waste management)
  • trans-boundary regulation on shared water bodies
  • environmental agency capacity (due to resources or lack of political will)
  • understanding/awareness of issues and laws

– Wikipedia


Having said this, developed countries also face significant issues of their own with an excess of resources at the consumer and household level producing contaminants and waste, and the various business, industries and agriculture sectors doing the same.


Countries That Pollute Water The Most

According to All-About-Water-Filters.com, the 7 biggest water polluting countries are:

  1. China
  2. United States
  3. India
  4. Japan
  5. Germany
  6. Indonesia
  7. Brazil


  • As an example in China, 54% of the Hai River basin surface water is so polluted that it is considered un-usable

– Wikipedia.com


  • Another example is India, where 80% of the health issues come from waterborne diseases. Part of this challenge includes addressing the pollution of the Ganges (Ganga) river, which is home to about 400 million people.
  • The river receives about over 1.3 billion litres of domestic waste, along with 260 million litres of industrial waste, run off from 6 million tons of fertilizers and 9,000 tons of pesticides used in agriculture, thousands of animal carcasses and several hundred human corpses released into the river every day for spiritual rebirth.
  • Two-thirds of this waste is released into the river untreated.

– GlobalWaterForum/Treehugger/Wikipedia


Countries With Some Of The Worst Water Quality

According to IBTimes.co.uk, the 10 countries with the poorest water quality in 2017 are:

  1. India
  2. Nigeria
  3. Democratic Republic Of The Congo
  4. Papua New Guinea
  5. China
  6. Haiti
  7. Russia
  8. Ethiopia
  9. Indonesia
  10. Afghanistan


Potential Water Pollution Solutions, & How To Prevent It

You can read more about potential solutions to water pollution in this guide.


On an individual level – we can use environmentally friendly detergents and household products, not pour oil and harmful chemicals down drains, maintain our cars and make sure they don’t leak, reduce pesticides and fertilisers in our gardens, recycle as opposed to use plastic, and so on.

We can take community action too, by helping out on beach cleans. We can also take action as countries to support and pass laws and regulations (like the the Clean Water Rule, which clarifies the Clean Water Act’s scope and protects the drinking water of one in three Americans) that will make pollution harder and the world less polluted.

– ExplainThatStuff.com



1. https://www.nrdc.org/stories/water-pollution-everything-you-need-know

2. https://www.explainthatstuff.com/waterpollution.html

3. https://www.water-pollution.org.uk/the-causes-of-water-pollution/

4. http://www.waterwise.co.za/site/water/environment/causes-of-water-pollution.html

5. http://www.groundwater.org/get-informed/groundwater/contamination.html

6. http://www.pollutionissues.com/Ve-Z/Water-Pollution-Freshwater.html

7. https://www.nrdc.org/stories/ocean-pollution-dirty-facts

8. http://all-about-water-filters.com/producers-water-pollution-around-the-world/

9. https://www.ibtimes.co.uk/world-water-day-2017-countries-poorest-water-quality-earth-1612684

10. https://en.wikipedia.org/wiki/Water_issues_in_developing_countries#Water_quality

Outdoor Air Pollution: Causes, Sources, Effects & Prevention/Solutions

Outdoor Air Pollution: Causes, Sources, Effects & Prevention/Solutions

When it comes to air pollution, there are two main types – indoor air pollution, and outdoor air pollution.

This guide focuses on ambient outdoor air pollution, and we look at causes, sources, examples, effects and potential ways to prevent or solve it.


(*It should be noted that general ambient outdoor air pollution is a lower atmosphere issue which has a separate set of sub issues to deal with than upper atmosphere Greenhouse Gases, Carbon emissions and Climate Change/Global Warming (all of which also affects the outside air environment).

This is a guide specifically about lower atmosphere (non Greenhouse gas) ambient outdoor air pollution.)


Summary – What To Know About Outdoor Air Pollution

First off, outdoor air pollution should be distinguished from greenhouse gas emissions (an upper atmosphere air issue) and global warming – these are separate issues.

Outdoor air pollution is mainly the release of air contaminants into the air that not only lower air quality and contribute to a range of human illnesses (and related deaths), but also contribute to other environmental issues like acid rain for example.

Combustion of fossil fuels in the generation of electricity, industrial activities, and the operation of vehicles/cars are huge emitters of air pollutants. In cities and densely populated areas – vehicles and road transport is the main source.

Air pollution is particularly heavy around cities and heavily populated areas, as it’s mainly an issue caused by humans.

We can measure the levels of outdoor air pollution with outdoor air quality indexes, amongst other measures.

Side effects can be lowering in air quality for humans, which can have health effects, but also environmental side effects like acid rain for example.

The World Health Organisation (WHO) highlights air pollution as the greatest environmental risk to human health – but a changing climate may be the biggest risk in the future.

Cleaner electricity sources like wind and solar, and cleaner vehicle technology (developing electric battery, hybrid, hydrogen and other vehicle types) could go a long way to helping us decrease outdoor air pollution.

You can read about examples of cities that have done something about their air pollution in this guide.


What Is Outdoor (Ambient) Air Pollution?

  • Air pollution in general can be defined as the ’emission of harmful substances to the atmosphere [i.e. the outside environment]’

– OurWorldInData


[Outdoor air pollution] usually has a harmful effect on the living and non-living things that breathe in, absorb or come into contact with that air – such as humans, animals and even the ocean.


Air Pollution Contaminants

When we talk about outdoor air pollution, we are usually talking about the following pollutants:

  • particulate matter (PM10, & PM2.5) (small suspended particles of varying sizes)
  • sulphur dioxide (SO2)
  • nitrogen oxides (NOx)
  • ozone (O3)
  • carbon monoxide (CO)
  • and volatile organic compounds (VOCs)


  • Some of these pollutants are emitted singularly, but some form when two or more pollutants mix together.
  • For example, SO2 and NOx can react in the Earth’s atmosphere to form particulate matter (PM) compounds

– OurWorldInData


  • Note that carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), ozone (O3), and synthetic gases, such as chlorofluorocarbons (CFCs) and hydrofluorocarbons (HFCs) are more likely to be treated as upper atmosphere/ozone greenhouse gases

– ClimateChangeAustralia.gov.au


Causes, Sources & Examples Of Outdoor Air Pollution

  • The sources and causes of the pollutants listed above can vary
  • They can come from both non-natural, and natural sources.
  • However, most are generally linked to human sources like fuel combustion and industrial (factories, business etc.) activities; pollutants are released as by-products of these processes

– OurWorldInData


  • Examples [of sources might] include petrol and diesel vehicles, burning fuel in houses for cooking and heating (Cookers, heaters, stoves and open fires), emissions from power generation, factories and business, and agriculture.

– British Lung Foundation


Specific examples of air contaminants include:

  • sulphur dioxide (SO2) – About 99% of the sulfur dioxide in air comes from human sources. The main source of sulfur dioxide in the air is industrial activity that processes materials that contain sulfur, eg the generation of electricity from coal, oil or gas that contains sulfur. [and, industrial activities and motor vehicles] – Environment.gov.au.
  • Sulphur dioxide can also be produced by volcanoes – Wikipedia


  • nitrogen oxides (NOx) – comes from the burning of fossil fuels like coal, oil and gas. Most of the nitrogen dioxide in cities comes from motor vehicle exhaust (about 80%) – Environment.gov.au. Can also come from electrical storms via electrical discharge, and plants, soil and water – although only a very small amount comes from these natural sources. Other sources of nitrogen dioxide are petrol and metal refining, electricity generation from coal-fired power stations, other manufacturing industries and food processing. Unflued gas heaters and cookers are the major sources of nitrogen dioxide in Australian homes – Environment.gov.au


  • ozone (O3) – Tropospheric, or ground level ozone, is not emitted directly into the air, but is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC). It is formed when pollutants emitted by cars, power plants, industrial boilers, refineries, chemical plants, and other sources chemically react in the presence of sunlight – Epa.gov


  • particulate matter (PM10, & PM2.5) (small suspended particles of varying sizes) – Particulate matter, also known as particle pollution or PM, is a term that describes extremely small solid particles and liquid droplets suspended in air. Particulate matter can be made up of a variety of components including nitrates, sulphates, organic chemicals, metals, soil or dust particles, and allergens (such as fragments of pollen or mould spores). Particle pollution mainly comes from motor vehicles, wood burning heaters and industry – Health.NSW.Gov.Au. 
  • Most particles form in the atmosphere as a result of complex reactions of chemicals such as sulfur dioxide and nitrogen oxides, which are pollutants emitted from power plants, industries and automobiles. Some are emitted directly from a source, such as construction sites, unpaved roads, fields, smokestacks or fires. – EPA.gov
  • The friction of brakes and tyres on the road also creates particulate matter. – British Lung Foundation


  • carbon monoxide (CO) – It is a product of combustion of fuel such as natural gas, coal or wood. Vehicular exhaust contributes to the majority of carbon monoxide let into our atmosphere. In 2013, more than half of the carbon monoxide emitted into our atmosphere was from vehicle traffic and burning one gallon of gas will often emit over 20 pounds of carbon monoxide into the air. – Wikipedia/Union Of Concerned Scientists, is produced in the incomplete combustion of carbon-containing fuels, such as gasoline, natural gas, oil, coal, and wood. The largest anthropogenic source of CO in the United States is vehicle emissions. – NAP.edu


  • volatile organic compounds (VOCs) – VOCs comprise volatile hydrocarbons and other organic molecules released into the atmosphere. They may have biogenic or anthropogenic sources. In the UK it is estimated that less than 5% of the VOCs (2.3 million tonnes per year, expressed in terms of carbon) emitted into the atmosphere are emitted from vegetation. The rest comes from transport, including distribution and extraction losses (50%), solvent use (30%) and other industrial processes (15%). Road transport alone accounts for 30% of VOC emissions. – APIS.ac.uk.
  • Common VOCs include acetone, benzene, ethylene glycol, formaldehyde, methylene chloride, perchloroethylene, toluene and xylene. – SOE.environment.gov.au


  • Overall, in towns and cities, the main source of air pollution is road transport

– British Lung Foundation


  • Other more minor sources may include smoke from bushfires, windblown dust, and biogenic emissions from vegetation (pollen and mould spores)

– NSW Government


How Much Outdoor Air Pollution Is Released Each Year, & What Are The Trends (Increasing or Decreasing)?

Obviously different cities and countries release different amounts of outdoor air pollution and have different policies and measures in place to control outdoor air pollution.

But, here are some amounts and trends from different countries:

  • sulphur dioxide (SO2) – In the US, sulfur dioxide emissions have been decreasing, and are down to 2709 thousand tons in 2016 – Statista.com.
  • Air quality regarding sulfur dioxide in improving in the US – EPA.gov.
  • In Australia, the amount of sulfur dioxide in air is at acceptable low levels in most Australian towns and cities. – Environment.gov.au. In Australia, the highest concentrations of sulfur dioxide in the air are found around petrol refineries, chemical manufacturing industries, mineral ore processing plants and power stations. – Environment.gov.au


  • nitrogen oxides (NOx) – There’s been a 60% decrease in the US national average of nitrogen dioxide from 1980 to 2017 – EPA.gov.
  • In the US, there was 12,412 thousand tons of nitrogen oxide emissions in 2014 – Statista.com.
  • In Australia, since the early 1990s, even the highest levels of nitrogen dioxide reached in most Australian towns and cities are thought to be acceptable for humans. – Environment.gov.au


  • ozone (O3) – there’s been a 32% decrease in ground level ozone national average in the US from 1980 to 2017 – EPA.gov


  • particulate matter (PM10, & PM2.5) (small suspended particles of varying sizes) – there’s been a 41% decrease in the particulate matter 2.5 national average in the US from 1980 to 2017. There’s also been a 34% decrease in the particulate matter 10 national average in the US from 1980 to 2017  – EPA.gov. 
  • Particle pollution is a major air quality issue in Australia. – Environment.gov.au


  • carbon monoxide (CO) – there’s been a 84% decrease in the carbon monoxide national average in the US from 1980 to 2017 – EPA.gov. 
  • In most Australian towns and cities, the levels of carbon monoxide in air are below levels that are hazardous for human health. Only larger cities, like some capital cities, have the potential to have harmful levels of carbon monoxide. – Environment.gov.au


  • and volatile organic compounds (VOCs) – there are different VOC’s such as Butadiene, Dichlorobenzene,  Benzene, Chloroform, Methylene Chloride, m,p-Xylene, o-Xylene, and Toluene.
  • DEC.ny.gov has done some studies on the levels of these VOCs across the NY state. VOCs particularly affect indoor air quality—concentrations of many VOCs are consistently higher indoors (up to 10 times higher) than outdoors. – SOE.environment.gov.au


OurWorldInData also shows levels of the different levels of different air pollutants over the years. You can see that there was a huge increase up until 1970/1980 for most regions, followed by a steady decline – https://ourworldindata.org/air-pollution

Although some pollutants have decreased since 1980, there has been small increases or flatlines in progress in the years before 2017. Particulate matter 10 levels are one example of this – with minimal progress being made since 2004.


Effects Of Outdoor Air Pollution

  • Outdoor air pollution can have an impact on human health, damage to ecosystems, food crops and the built environment 
  • The World Health Organisation (WHO) highlights air pollution as the greatest environmental risk to human health (note that this is based on current risk, and that longer-term environmental threats such as climate change may exceed this in the future). 
  • The World Health Organization estimates that 3 million people die from ambient outdoor pollution every year

– OurWorldInData/WHO


  • Although that number can vary by up to a million depending on the source and year you read it from.
  • It is important to emphasize the difficulties in directly attributing deaths to air pollution. A ‘death’ from air pollution is defined as someone who dies prematurely (could be in the range of months or years) than would be expected in the absence of air pollution.
  • In many cases, air pollution exacerbates pre-existing cardiorespiratory illnesses—individuals suffering from asthma, for example, are particularly vulnerable.

– OurWorldInData/StateOfGlobalAir.org


The three key sources of air pollution deaths are from the indoor burning of solid fuels (indoor air/household pollution), exposure to ambient outdoor ozone (O3), and ambient outdoor particulate matter (PM) pollution.

In 2015, deaths from these 3 pollutants were as follows (as total %’s):

  • Ozone – 3.45%
  • Particulate Matter – 57.54%
  • Indoor Air Pollution/Solid Fuels – 38.72%

– OurWorldInData


Aside from death, ambient outdoor air pollution can cause other health related problems such as:

  • sulphur dioxide (SO2) – affects people when it is breathed in. People most at risk are those with asthma or breathing conditions. It irritates the nose, throat, and airways to cause coughing, wheezing, shortness of breath, or a tight feeling around the chest. – Environment.gov.au


  • nitrogen oxides (NOx) – causes increased likelihood of respiratory problems. Nitrogen dioxide inflames the lining of the lungs, and it can reduce immunity to lung infections. This can cause problems such as wheezing, coughing, colds, flu and bronchitis. People with asthma, and in particular children and older people are most at risk. – Environment.gov.au


  • ozone (O3) – ground level ozone can cause the muscles in the airways to constrict, trapping air in the alveoli. This leads to wheezing and shortness of breath. People with asthma and children, older adults, and people who are active outdoors, especially outdoor workers are most at risk. There are other health issues ground ozone can cause as well – EPA.gov


  • particulate matter (PM10, & PM2.5) (small suspended particles of varying sizes) – Studies have linked exposure to particle pollution to a number of health problems including respiratory illnesses (such as asthma and bronchitis) and cardiovascular disease. In addition, the chemical components of some particles, particularly combustion products, have been shown to cause cancer. These effects are often more pronounced for vulnerable groups, such as the very young and the elderly. Particle pollution is the major cause of reduced visibility. – Environment.gov.au


  • carbon monoxide (CO) – Increased levels of carbon monoxide reduce the amount of oxygen carried by haemoglobin around the body in red blood cells. The result is that vital organs, such as the brain, nervous tissues and the heart, do not receive enough oxygen to work properly. For healthy people, the most likely impact of a small increase in the level of carbon monoxide is that they will have trouble concentrating. Some people might become a bit clumsy as their coordination is affected, and they could get tired more easily. People with heart problems are likely to suffer from more frequent and longer angina attacks, and they would be at greater risk of heart attack. Children and unborn babies are particularly at risk because they are smaller and their bodies are still growing and developing. – Environment.gov.au


  • volatile organic compounds (VOCs) – Different VOCs have different health effects, and range from those that are highly toxic to those with no known health effect. Breathing low levels of VOCs for long periods of time may increase some people’s risk of health problems. Several studies suggest that exposure to VOCs may make symptoms worse in people who have asthma or are particularly sensitive to chemicals. – SOE.environment.gov.au


Countries Where Outdoor Air Pollution Can Be An Issue

Some interesting trends in air pollution related deaths according to OurWorldInData are:

  • Death rates from air pollution—across countries of all income levels—have shown a general decline over the last few decades. [usually] by more than 50 percent.
  • Globally, it’s estimated that outdoor air pollution resulted in 4.2 million deaths in 2016; this represents an increase from 3.4 million in 1990. Overall, we see that the majority of pollution-related deaths are in Asia – South, Southeast and East Asia alone accounted for nearly 3 million in 2016.

You can read more about air pollution related deaths by type, country and more here – https://ourworldindata.org/air-pollution 


We’ve also put together a guide that details the countries where outdoor and indoor air pollution might be the worst.


Measuring Outdoor Air Pollution – Air Quality Index

  • One way to measure and keep track of outdoor air pollution in a particular area or city is with an Air Quality Index.
  • An Air Quality Index can give you a range of information, but should usually tell you the main pollutants in an area and give you a general health rating for the air in that area.
  • There are large online sites that keep track of the Air Quality Index (such as WAQI, Airnow and AQICN), and individual governments also have their own tracking programs.
  • The NSW Government in Australia for example has their own air monitoring networks where they measure particles (PM10, PM2.5), sulfur dioxide (SO2), carbon monoxide (CO), ozone (O3), nitrogen dioxide (NO2) and visibility. Wind speed and direction, air temperature and humidity are also recorded


  • In metropolitan areas (greater Sydney, Newcastle, and Wollongong regions), the main air pollutants of concern are ozone (O3) and particles (particulate matter or PM). For regional areas in NSW, particle pollution is the main concern.

– NSW Government


Countries & Cities With The Most & Least Polluted Outdoor Air In The World

Obviously pollution can vary from city to city within a country, and even from year to year.


  • For example, the most polluted city in a 2016 report, Zabol in Iran, has had its pollution level cut fourfold in the latest version of the database, and now appears to be cleaner than Australia’s capital Canberra
  • Based on the amount of particulate matter under 2.5 micrograms found in every cubic metre of air, Indian regions and cities are the most polluted in the world in 2018, followed by China. Some places in Saudi Arabia are also highly polluted

– WeForum.org


  • Egypt, Mauritania, Libya, Niger, Cameroon and Pakistan also show high mean annual averages of migrograms per cubic meter of PM 2.5 air pollution in 2015 
  • Some of the least polluted countries in the world in terms of mean annual averages of migrograms per cubic meter of PM 2.5 air pollution in 2015 are Kirbati, Samoa, Brunei, Solomon Islands, Sweden, Finland, Australia, Canada, United States, New Zealand, Norway, Spain, and Iceland. 
  • It’s important to note that there is an additional key factor at play, which has some impact on pollution concentrations over time and space: the weather. Local weather conditions, and seasonal and weather patterns have an important influence on the year-round fluctuations in exposure levels reported in each place

– OurWorldInData


Potential Solutions To, & Prevention Of Outdoor Air Pollution

Solutions to, and prevention of outdoor air pollution involves a wide ranging approach.

It’s definitely not a simple issue with one simple solution, and no solution is perfect.

It really does centre around reducing, or finding alternatives to fuel combustion and other human related air pollution producing activities, and becoming more environmentally friendly with the way we run our households and businesses/industries.


Some things that might be done to reduce the level of outdoor air pollution and lower pollutant emissions are:

  • Switching to electric vehicles
  • Reducing reliance on vehicles in heavily populated cities, and favoring public transport and walking/bikes
  • Switching to cleaner renewable energy over fossil fuels for households and business/industry, and agriculture
  • Switch to diets and agriculture that produces less air contaminants, or becoming more environmentally friendly with production

People can also check air quality websites to see how polluted the air is in the city or area they are living. Moving to places with less air pollution can be an option for better short term and long term health.



1. Hannah Ritchie and Max Roser (2018) – “Air Pollution”. Published online at OurWorldInData.org. Retrieved from: ‘https://ourworldindata.org/air-pollution’ [Online Resource]

2. http://www.health.nsw.gov.au/environment/air/Pages/outdoor-air-pollution.aspx

3. https://www.blf.org.uk/support-for-you/air-pollution/where-does-it-come-from

4. https://www.environment.nsw.gov.au/topics/air/monitoring-air-quality

5. http://www.environment.gov.au/protection/publications/factsheet-sulfur-dioxide-so2

6. http://www.environment.gov.au/protection/publications/factsheet-nitrogen-dioxide-no2

7. https://en.wikipedia.org/wiki/Air_pollution

8. https://archive.epa.gov/ozonedesignations/web/html/faq.html#whatisozone

9. https://www.climatechangeinaustralia.gov.au/en/climate-campus/climate-system/greenhouse-gases/

10. http://www.health.nsw.gov.au/environment/air/Pages/particulate-matter.aspx

11. https://www.epa.gov/pm-pollution/particulate-matter-pm-basics#PM

12. https://www.nap.edu/read/10378/chapter/3

13. http://www.apis.ac.uk/overview/pollutants/overview_VOCs.htm

14. https://www.statista.com/statistics/501303/volume-of-sulfur-dioxide-emissions-us/

15. https://www.epa.gov/air-trends/sulfur-dioxide-trends

16. https://www.epa.gov/air-trends/nitrogen-dioxide-trends

17. https://www.statista.com/statistics/501284/volume-of-nitrogen-oxides-emissions-us/

18. https://www.epa.gov/air-trends/ozone-trends

19. https://www.epa.gov/air-trends/carbon-monoxide-trends

20. https://www.epa.gov/air-trends/particulate-matter-pm25-trends

21. https://www.epa.gov/air-trends/particulate-matter-pm10-trends

22. https://www.dec.ny.gov/chemical/66472.html

23. https://www.epa.gov/ozone-pollution/health-effects-ozone-pollution

24. http://www.environment.gov.au/protection/publications/factsheet-carbon-monoxide-co

25. https://soe.environment.gov.au/theme/ambient-air-quality/topic/2016/volatile-organic-compounds

26. https://www.weforum.org/agenda/2018/05/these-are-the-worlds-most-polluted-cities

Indoor Air Pollution: Causes, Sources, Effects & Prevention/Solutions

Indoor Air Pollution: Causes, Sources, Effects & Prevention/Solutions

When it comes to air pollution, there are two main types – indoor, and outdoor air pollution.

This guide focuses on indoor air pollution, and specifically in parts of the world where it causes the most harm – which is mostly the poorer/lower income countries and regions.

We look at causes, sources, examples, effects and potential ways to prevent or solve it.


Summary – What To Know About Indoor Air Pollution

It’s goes without saying that indoor air pollution happens inside dwellings and buildings, and not out in the atmosphere.

Much of the most harmful indoor air pollution happens in developing countries where people don’t have access to safe electricity and energy production (natural gas or renewable energy, for example).

People use solid fuels (like wood and organic matter) for cooking, cleaning, heating etc.

A range of health related diseases and illnesses can occur as a result of particulates and other air contaminants that enter the air.

Providing cleaner, safer energy to people to use within dwellings and their houses could go a long way towards helping with the issue of indoor air pollution.


What Is Indoor Air Pollution?

Indoor air pollution is a change in the Indoor Air Quality, usually by the introduction of an air contaminant, that has a harmful effect on any living thing that consumes that air


  • Indoor Air Quality ‘refers to the air quality within and around buildings and structures, especially as it relates to the health and comfort of building occupants’



There’s really two distinct types of indoor air pollution – indoor air pollution in developed countries, and indoor air pollution in poorer parts of the world.


Causes, Sources & Examples Of Indoor Air Pollution

  • Indoor air pollution in poorer parts of the world is far more severe, and is usually caused by the inefficient use of solid fuels for cooking and cleaning [and heating]
  • There is smoke and other contaminants released from burning non modern energy sources inside the house like wood, crop residues, dung, charcoal, coal and kerosene.

– OurWorldInData. 


  • In 2018, around 3 billion people still cook using polluting open fires or simple stoves fuelled by these types of fuels
  • Small particulate matter in smoke is one of the main indoor air pollutants [Small particles of less than 10 microns in diameter (PM10), are among the most dangerous]

– WHO.int


  • Indoor air pollution in developed countries is less severe (but can still causes short and long term health problems) and is caused by things like mold, household sprays (aerosols for example), cleaning chemicals, garden sprays (insecticides for example) and so on.
  • Particulate matter, carbon monoxide and VOC’s also come from things like second hand tobacco smoke, the use of space heaters and paints/coatings.

– Wikipedia


Effects Of Indoor Air Pollution

Indoor air pollution can lead:

  • … acute lower respiratory disease, chronic obstructive pulmonary disease, cancers, and other illnesses.

– WHO.int


  • In total, 2.6 million people died prematurely in 2016 from illness attributable to household air pollution

– OurWorldInData/Institute for Health Metrics and Evaluation (IHME)


The World Health Organisation says ‘close to 4 million people die prematurely from illness attributable to household air pollution from inefficient cooking practices using polluting stoves paired with solid fuels and kerosene. Household air pollution causes noncommunicable diseases including stroke, ischaemic heart disease, chronic obstructive pulmonary disease (COPD) and lung cancer’

Deaths are attributable to the following diseases in the following %’s:

  • 27% are due to pneumonia
  • 18% from stroke
  • 27% from ischaemic heart disease
  • 20% from chronic obstructive pulmonary disease (COPD)
  • 8% from lung cancer.

– World Health Organization (WHO)


  • Close to half of deaths due to pneumonia among children under 5 years of age are caused by particulate matter (soot) inhaled from household air pollution

– WHO.int


The trends with indoor air pollution is:

  • Overall, ‘we see a decline in the number of pollution-related deaths since 1990, falling from 3.7 million to 2.6 million in 2016.’
  • It is predominantly women and young children who are killed by indoor air pollution

– OurWorldInData


Countries Where Indoor Air Pollution Can Be An Issue

  • Deaths from air pollution are ‘largely concentrated in Asia and Africa. Approximately three-quarters of all deaths in 2016 were in Asia, with 22-23 percent in Africa & the Middle East, and only a couple of percent across the Americas and Europe (with most of these originating in Latin America & the Caribbean)’. 
  • At the country level – ‘India followed by China had the highest mortality figures in 2016 with 783,000 and 605,000 respectively. These numbers have, however, shown a significant decline in recent years. In the last decade alone the number of deaths from household air pollution in China has approximately halved.’ 
  • This decline is ‘also true for countries in Sub-Saharan Africa (SSA) with high mortality figures. Ethiopia and Nigeria – who have the two highest death tolls in SSA – have both seen a inverse-U trend of increase-peak-decline since 1990. This is however not true everywhere: the Democratic Republic of Congo appears to still be on the upward slope of this pattern.’

– OurWorldInData

You can read more about indoor air pollution related death rates, overall trends, and how different countries are affected here – https://ourworldindata.org/indoor-air-pollution, and here 


Indoor Air Pollution In Developed Countries

Indoor air pollution in developed countries tends not to be anywhere near as severe:

  • … it might only usually result in short term side effects such as irritation of the eyes, nose, and throat, headaches, dizziness, and fatigue. But, some more severe cases can also cause long term health side effects.
  • People most at risk might be people who may be exposed to indoor air pollutants for the longest periods of time such as the young, the elderly and the chronically ill, especially those suffering from respiratory or cardiovascular disease. People with breathing conditions like asthma also
  • In developed countries, ‘while pollutant levels from individual sources may not pose a significant health risk by themselves, most homes have more than one source that contributes to indoor air pollution. There can be a serious risk from the cumulative effects of these sources.’



Potential Solutions For Indoor Air Pollution/How To Prevent It

  • In developing countries and poorer countries, the best way to prevent indoor air pollution and it’s harmful effects it is to switch to modern energy sources which don’t release smoke and other harmful indoor air contaminants.
  • This involves switching to non solid fuels for heating and cooking such as natural gas, ethanol or electric technologies.

– OurWorldInData


An example of where and how this might be occurring is with the AKON Lighting Africa Project, which is replacing solid fuels with clean and affordable electricity in the form of solar panels/solar energy.

Specifically, the following demographics may need more help with indoor air pollution prevention:

  • Low income countries and areas (that don’t have access to, or can’t afford cleaner energy)
  • Women and children
  • People in more isolated rural areas (vs more highly populated urban areas for example)

Improved design of stoves and ventilation systems can also reduce indoor air pollution in many poor communities, as well as raising more awareness about the issue to those most at risk

– WHO.int


In developed countries, limiting the number of contaminants in or around your house, having proper ventilation, and keeping at risk people (those who spend a lot of time inside) in a part of the house with high air quality can help minimise the effects of indoor air pollution.



1. https://www.epa.gov/indoor-air-quality-iaq/introduction-indoor-air-quality

2. Max Roser and Hannah Ritchie (2018) – “Indoor Air Pollution”. Published online at OurWorldInData.org. Retrieved from: ‘https://ourworldindata.org/indoor-air-pollution’ [Online Resource]

3. https://www.epa.gov/indoor-air-quality-iaq/inside-story-guide-indoor-air-quality

4. http://akonlightingafrica.com/our-activities/overview/

5. http://www.who.int/news-room/fact-sheets/detail/household-air-pollution-and-health

6. https://en.wikipedia.org/wiki/Indoor_air_quality

7. http://www.who.int/heli/risks/indoorair/indoorair/en/

A List Of Different Global Water Issues Words/Phrases, & What They Might Mean

The Different Phrases/Words Used To Describe Global Water Issues, & What They Mean

When we talk about global water issues, there are more than a few different phrases and words used to describe them.

The problem you may encounter, especially if you’re learning about these water issues for the first time, is that different sources use the same phrases to describe different issues to each other.

Because the phrases are used in different contexts in different industries, and by different organisations or individuals – there is no consensus definition/meaning for some or even most of them.

What we’ve tried to do in this guide is gather a general meaning on each phrase so you at least have a starting idea of what they might mean in relation to one another.

We hope this enables you to understand each water issue better and more clearly.

*We should differentiate between ocean (saltwater) and freshwater (drinkable/potable water) issues – this guide is mainly about freshwater and drinkable water issues

*Also note that we treat sanitation as separate (but equally important) to most water issues, because, although sanitation involves water, it also usually involves other factors like human waste, plumbing and pipe infrastructure for example


Water Availability

  • Water Availability is having fresh water sources (which may or may not be accessible) physically present within an area (like a city)
  • Very hot/dry or very cold/snowy regions for example may have lesser water availability


Water Access

  • Water Access is being able to physically and economically access the available fresh water in an area
  • There’s two types of water access – physical water access, and economic water access
  • Physical Water Access is being able to physically get to and use the available fresh water in an area
  • Fresh water is usually physically accessible as surface water (such as lakes, rivers, reservoirs) and less commonly in groundwater (found underground in rock or soil layers, and accessed through wells or natural springs), but not in snow, ice and glaciers
  • Fresh water might also be too far away, too deep in the ground, or you may not be able to create infrastructure or devices suitable enough to physically use/consume the water
  • Economic Water Access is whether a group of people have enough money to access the available fresh water around them, or build infrastructure to access the available water. This usually affects low income regions, and/or places with political instability


Water Quality

  • Water Quality essentially refers to whether the fresh water is safe to use or consume – either directly or after fresh water treatment
  • Fresh water sources can be contaminated for example with certain pollutants like chemicals and bacteria


Water Pollution

  • Water Pollution is any chemical, physical or biological change in the quality of water that has a harmful effect on any living thing that drinks, uses or lives (in) it – Lentech
  • Water pollution can be natural or caused by human activity


Water Resource Improvement, & Water Quality Improvement

  • Water Resource Improvement is improving water accessibility usually by improving water infrastructure or innovating (with water packs, water wells etc.)
  • Water Quality Improvement is improving water quality by cleaning up pollution and contaminants in a fresh water source, managing the source of the pollution to reduce or eliminate it, or creating polluted water treatment devices or systems (such as water purifiers)


Water Scarcity (A Lack Of Water Supply To Meet Demand)

  • You can read more in depth about water scarcity in this guide
  • Water Scarcity is more extreme than water stress, and occurs when water demand exceeds internal water resources


  • If the amount of renewable water in a country is below 1,700 m3 per person per year, that country is said to be experiencing water stress; below 1,000 m3 it is said to be experiencing water scarcity; and below 500 m3, absolute water scarcity.
  • An area could conceivably be highly water stressed, but not water scarce, if, for example, it had significant water pollution, but plentiful supplies of contaminated water

– Pacinst


Water Stress (Water Demand/Use Vs Supply Ratio)


  • Water stress is the ratio of total withdrawals to total renewable supply in a given area. A higher percentage means more water users are competing for limited water supplies, and therefore that area/country is more stressed 

– wri.org


  • Compared to Water Scarcity, Water Stress is a more inclusive and broader concept. It considers several physical aspects related to water resources, including water scarcity, but also water quality, environmental flows, and the accessibility of water

– Pacinst


  • Countries scarce on fresh water supply, or dry countries, are usually most likely to be water stressed because they have a smaller quantity of fresh water available, and therefore a smaller quantity of fresh water to use and consume. The more water they use and consume, the more water stressed they become
  • Water Stress is also a term used to describe countries that are using more fresh water than is being renewed annually – they can be stressing their water supply with high water use
  • If a country is using/withdrawing 80% or more of their total water supply, they might be classified as ‘highly water stressed’. You can read more about country water stress levels at http://www.wri.org/blog/2013/12/world%E2%80%99s-36-most-water-stressed-countries
  • Some of the world’s projected most water stressed countries by 2040 are Bahrain, Kuwait, Qatar, San Marino, Singapore, United Arab Emirates and Israel – World Resources Institute. Read more about them at http://www.wri.org/blog/2015/08/ranking-world%E2%80%99s-most-water-stressed-countries-2040


The World Resources Institute (WRI) define baseline water stress based on the ratio of annual water withdrawals to renewable resources.

It defines water stress categories based on this percentage (% of withdrawals to renewable resources) as follows:

  • <10% = low stress
  • 10-20% = low-to-medium stress
  • 20-40% = medium-to-high stress
  • 40-80% = high stress
  • >80% = extremely high stress

– OurWorldInData/WRI


Water Shortage

  • A Water Shortage is when an area’s total quantity of clean fresh water is getting close to zero
  • Water Shortages can be created by many factors such as water use, water scarcity, water pollution, water stress, and more

You can read a case study of the Cape Town water shortage in this guide.


Water Security

  • Water Security is ‘the capacity of a population to safeguard sustainable access to adequate quantities of acceptable quality water for sustaining livelihoods, human well-being, and socio-economic development, for ensuring protection against water-borne pollution and water-related disasters, and for preserving ecosystems in a climate of peace and political stability’

– UN-Water


  • Water Security can be made up of water access (especially economic access), water scarcity, water pollution, water quality and other factors
  • You might say a country has good Water Security if they have high amounts of fresh water sources, good access to that water, and low usage/withdrawal rates (lower than annual average renewable supply levels)
  • High Water Stress countries tend to have poorer water security


Water Risk

  • Water Risk refers to the possibility [or probability] of an entity experiencing a water-related challenge (e.g. water scarcity, water stress, flooding, infrastructure decay, drought) 


  • The extent of risk is a function of the likelihood of a specific challenge occurring and the severity of the challenge’s impact 
  • The severity of impact itself depends on the intensity of the challenge, as well as the vulnerability of the actor [the area or country in question]

– CEOWaterMandate


  • Companies and organizations and governments cannot gain robust insight into water risk unless they have a firm understanding of the various components of water stress (i.e., water scarcity, accessibility, environmental flows, and water quality), as well as additional factors, such as water governance
  • Many water-related conditions, such as water scarcity, pollution, poor governance, inadequate infrastructure, climate change, and others, create water risk for many different sectors and organizations simultaneously

– Pacinst


The Water Crisis

  • A Water Crisis (or The Water Crisis) is a term generally used to describe a situation where people lack access to safe water, or access to a toilet 
  • In 2018, 1 in 9 people lack access to safe water, and 1 in 3 people lack access to a toilet 
  • There can be serious consequences to places experiencing a water crisis such as serious short term and long term health implications, and/or death
  • Areas in Africa, Asia & Latin America are where significant work is being done to improve the Water Crisis situation

– Water.org



1. https://pacinst.org/water-definitions/

2. Hannah Ritchie and Max Roser (2018) – “Water Access, Resources & Sanitation”. Published online at OurWorldInData.org. Retrieved from: ‘https://ourworldindata.org/water-access-resources-sanitation’ [Online Resource]

3. https://en.wikipedia.org/wiki/Water_issues_in_developing_countries#Challenges_to_Water_Quality

4. https://www.lenntech.com/water-pollution-faq.htm

5. http://www.unwater.org/publications/water-security-infographic/

6. http://www.wri.org/blog/2015/08/ranking-world%E2%80%99s-most-water-stressed-countries-2040

7. http://www.wri.org/blog/2013/12/world%E2%80%99s-36-most-water-stressed-countries

8. https://ceowatermandate.org/posts/water-scarcity-water-stress-water-risk-actually-mean/

9. https://water.org/our-impact/water-crisis/

10. https://water.org/our-impact/

How Much Land Is There On Earth, & What Is It Used For?

How Much Land Is There On Earth? - Total, Inhabitable, Arable, Agricultural & Cultivated

This is a guide about how much land there is on earth.

Below we’ve outlined some of the more important land quantity and usage stats such as total land, habitable land, agricultural land and arable land.

We’ve also noted what arable land is used for, and countries that have the most cultivated land in total.

Note that these numbers are estimates, and are to be used as a general guide only.


Summary – How Much Land Is There On Earth?

  • About 29% of the total surface of the earth is land (the rest is water)
  • Of that, there is habitable land (that we can live on) and non habitable land, and agricultural (including land that livestock can be produced on) and arable land (more fertile land with topsoil for growing crops)


How Much Land Is There On Earth/In The World In Total?

  • Of the land’s total surface, about 29% of that surface is land, and 71% is ocean

The quantities that make up those %’s are:

  • Land – 149 million km², or 92.5 million mi.²
  • Ocean – 361 million km², or 224.3 million mi.²

– OurWorldInData/FAO


You can read more about the how much water there is on earth in this guide.


How Much Habitable Land Is There On Earth?

About 71% of the total land surface on earth is habitable, with the rest being glaciers (10%) and barren land (19%).

The quantities that make up those %’s are:

  • Habitable Land – 104 million km², or 64.6 million mi.²
  • Glaciers – 15 million km², or 9.32 million mi.²
  • Barren Land – 28 million km², 17.3 million mi.²

– OurWorldInData/FAO


How Much Agricultural/Farmable Land Is There On Earth?

Agricultural land includes arable land for crops, but also land that can be used for rearing livestock.


  • According to World Bank data, in 2015, approximately 37% of the world’s land surface was agricultural land.

– data.worldbank.org


  • Roughly between 32 and 36 million square kilometers (12 and 14 million square miles) of land is used to raise livestock

– Sciencing/University of Wisconsin-Madison


How Much Arable Land Is There On Earth?

Arable land just includes land that can be used for growing crops, and not livestock rearing land.


  • According to World Bank data, in 2015, approximately almost 11% of the world’s land surface was arable land.

– data.worldbank.org


  • Approximately 17.6 million square kilometers (6.8 million square miles) of land is used to grow crops

– Sciencing/University of Wisconsin-Madison


What Is The World’s Habitable Land Used For?

  • About 50% of the world’s habitable land is used for agriculture, 37% for forests, 11% for shrubland, 1% for urban development, and 1% is freshwater

– OurWorldInData/FAO


The quantities that make up those %’s are:

  • Agriculture – 51 million km², or 31.6 million mi.²
  • Forests – 39 million km², or 24.2 million mi.²
  • Shrubs – 12 million km², or 7.4 million mi.²
  • Urban – 1.5 million km², or 0.93 million mi.²
  • Freshwater – 1.5 million km², or 0.93 million mi.²


What Is The World’s Agricultural Land Used For?

  • Of the world’s land that is used for agriculture, about 77% is used for livestock rearing/meat and dairy production, and 23% is used for growing crops.

– OurWorldInData/FAO


The quantities that make up those %’s are:

  • Livestock – 40 million km², or 24.8 million mi.²
  • Crops – 11 million km², or 6.83 million mi.²

Even with the above numbers, it’s interesting to note that 83% of the world’s caloric consumption supply comes from plant based food, whilst only 17% comes from meat and dairy production. 

Likewise, about 67% of the world’s protein consumption supply comes from plant based food, whilst only 33% comes from meat and dairy. 

– OurWorldInData/FAO


  • Current estimates (as of 2017) put the remaining amount of farmable land at about 27 million square kilometers (10.5 million square miles), most of which is concentrated in Africa and Central and South America. 

– Sciencing


Of course, population growth significantly affects how much land we can or are using for agriculture at any one time.


What Is The World’s Arable Land Used For?

You can view a list of the world’s most valuable crops, and crop production by metric tonnes here – https://en.wikipedia.org/wiki/List_of_most_valuable_crops_and_livestock_products


In order, some of the top value producing crops are (not including meat and dairy):

  1. Rice, paddy
  2. Wheat
  3. Soybean
  4. Tomatoes
  5. Sugarcane
  6. Maize (corn)
  7. Potatoes
  8. Vegetables (not listed elsewhere)
  9. Grapes
  10. Cotton
  11. Apples
  12. Bananas
  13. Cassava (yuca)
  14. Mangos, Mangosteens, Guava
  15. Coffee
  16. Palm Oil
  17. Onion, dry
  18. Beans, dry and green
  19. Peanuts
  20. Olives

– Wikipedia/FAO


What Do Different Countries Use Their Cultivated Land For?

You can view a list of land use statistics by country here – https://en.wikipedia.org/wiki/Land_use_statistics_by_country 


In order, the countries with the most total cultivated land area are:

  1. India
  2. United States
  3. China
  4. Russia
  5. Brazil
  6. Canada
  7. Australia
  8. Indonesia
  9. Nigeria
  10. Argentina
  11. Ukraine
  12. Sudan
  13. Mexico
  14. Kazakhstan
  15. Turkey
  16. Pakistan
  17. France
  18. Thailand
  19. Iran
  20. Ethiopia

– Wikipedia/CIA World Factbook


Will We Have Enough Agricultural Land To Grow Food In The Future?

Read more in this guide about the future availability and capacity of agricultural land to grow/produce food into the future.



1. https://ourworldindata.org/agricultural-land-by-global-diets ( by Hannah Ritchie)

2. https://data.worldbank.org/

3. https://sciencing.com/much-earths-land-farmable-16685.html

4. https://en.wikipedia.org/wiki/List_of_most_valuable_crops_and_livestock_products

5. https://en.wikipedia.org/wiki/Land_use_statistics_by_country

6. https://data.worldbank.org/indicator/AG.LND.AGRI.ZS

7. https://data.worldbank.org/indicator/AG.LND.ARBL.ZS?view=chart 

8. https://www.bettermeetsreality.com/how-much-land-in-the-world-is-used-for-agriculture-do-we-have-enough-arable-agricultural-land-left-for-food-other-resources-in-the-future/

How Much Water Is There On Earth? – Ocean, Fresh Water & Drinkable Water

How Much Water Is There On Earth? - Ocean, Fresh Water & Drinkable Water

This is a guide about how much water there is on earth.

Below we’ve outlined some of the more important water quantity stats such as total water, fresh water and drinkable water numbers.

Note that these numbers are estimates, and are to be used as a general guide only.


Summary – How Much Water Is There On Earth?

The water on earth can be divided into:

  • Saltwater from the ocean – most of the world’s water is ocean salt water > around 97%
  • Freshwater – composed of under ground water (ground water), and above ground water (lakes, rivers, etc). There’s also the water locked up in ice and snow
  • Drinking water – water that is accessible and safe to drink, or able to be drunk once treated. Less than 1 percent of the world’s total freshwater supply is readily accessible from the various freshwater sources


How Much Total Water Is There In The World/On Earth?

  • About 71% of the world’s surface is covered by water



If water quantities were to be described in spheres, the water distributions are as follows:

  • All water on earth (in the oceans, ice caps, lakes, rivers, groundwater, atmospheric water, and even the water in you, animals, and plants) – sphere volume of about 332,500,000 cubic miles (mi3) (1,386,000,000 cubic kilometers (km3)), and diameter is about 860 miles
  • All the world’s liquid fresh water (groundwater, lakes, swamp water, and rivers and DOES NOT include glaciers, snow and ice) – sphere volume comes to about 2,551,100 mi3 (10,633,450 km3), and diameter is about 169.5 miles (272.8 kilometers)
  • All of the world’s immediately accessible fresh water (in lakes and rivers) – sphere volume of 22,339 mi3 (93,113 km3), and diameter of 34.9 miles (56.2 kilometers).



How Much Water Is In The Ocean?

  • Of the world’s surface water, about 96.5% is the ocean



  • The average depth of the ocean is several thousand feet (about 1000 metres)

– HowStuffWorks


This gives us a rough idea of the volume of saltwater on earth.


How Much Fresh Water Is There On Earth?

  • About 2-3% percent of the planet’s water is fresh, but 1.6 percent (around 70%) of the planet’s fresh water is locked up in the polar ice caps, snowfields and glaciers
  • 0.36 percent of freshwater is found underground in aquifers and wells (also called groundwater)
  • Only about 0.036 percent of the planet’s total water supply is found in lakes and rivers 

– HowStuffWorks


The rest of the water on the planet is either floating in the air as clouds and water vapor, or is locked up in plants and animals and living things like humans

There’s also billions of gallons of drinkable water in bottles of water in shops on shelves around the world at any one time.

It’s important to note water is constantly moving on the Earth between the atmosphere, ocean, rivers and streams, snowpacks and ice sheets, and underground.


How Much Drinkable Water Is On Earth?

  • Less than 1 percent of the world’s total freshwater supply is readily accessible from the various freshwater sources

– Livescience


  • That’s still thousands of trillions of gallons, but it’s a very small amount compared to all the water available
  • As a % of the total amount of water available on earth that is ready and available to drink and use, that % number works out to be about 0.007 percent

– National Geographic


In other words, when you subtract all the salt water, water trapped in ice/snow and water not physically accessible, you have about 0.007% left to drink, and use for business and the community.

Much of that water we get from rivers and lakes.

Some of it is not going to be drinking quality – because of water pollution or contaminants for example.

There are no clear numbers at the moment of how much of the available/accessible freshwater is contaminated because that varies depending on where the water source is found, but it’s reasonable to say most of it is not contaminated.

The fresh water that isn’t contaminated can be run through water treatment plants and consumed as drinking water.

Some developing countries drink the water directly without water treatment.


Summary Of The World’s Water Sources (Salt, Fresh & Drinkable)

  • Of the world’s total water supply of about 332.5 million miof water, over 96 percent is saline. Of total freshwater, over 68 percent is locked up in ice and glaciers. Another 30 percent of freshwater is in the ground. Rivers are the source of most of the fresh surface water people use, but they only constitute about 300 mi3 (1,250 km3), about 1/10,000th of one percent of total water.



You can look at a detailed table showing the estimate of global water distribution here at https://water.usgs.gov/edu/earthhowmuch.html , or at  https://water.usgs.gov/edu/gallery/global-water-volume.html 


Countries With The Most Freshwater

  • 6 countries (Brazil, Russia, Canada, Indonesia, China and Colombia) have 50 percent of the world’s freshwater reserves
  • One-third of the world’s population lives in “water-stressed” countries, defined as a country’s ratio of water consumption to water availability. Countries labeled as moderate to high stress consume 20 percent more water than their available supply.

– LiveScience


  • Due to geography, climate, engineering, regulation, and competition for resources, some regions seem relatively flush with freshwater, while others face drought and debilitating pollution.
  • In much of the developing world, clean water is either hard to come by or a commodity that requires laborious work or significant currency to obtain

– National Geographic


Will We Have Enough Water In The Future For Human Use?

Read this guide about the availability of freshwater for humans in the future.



1. https://water.usgs.gov/edu/earthhowmuch.html

2. https://science.howstuffworks.com/environmental/earth/geophysics/question157.htm

3. https://www.livescience.com/29673-how-much-water-on-earth.html

4. https://www.nationalgeographic.com/environment/freshwater/freshwater-crisis/

5. https://water.usgs.gov/edu/gallery/global-water-volume.html