Articles on pollution and pollutants. Health effects of airborne pollution like black carbon aerosols, particulate matter and photochemical smog; toxic waste from fossil fuels and nuclear plants; microplastics in the ocean.

Smog over city of Krakow, Poland

Smog: Urban Air Pollution

Smog is a toxic haze which forms in and around cities from a mixture of gases and particles emitted from motor vehicles, coal-fired power plants, factories, and other sources, which can react with heat and sunlight in the atmosphere. It is a particular problem in many Asian cities, where air quality can be further reduced by the burning of crop stubble. We explain the main types of smog pollution and the pollutants involved. We also look at their impact on health and their links with climate change.

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Open fire cooking pots, Africa

Particulate Matter (PM2.5 particles)

Particulate matter (also called particulates or atmospheric aerosol particles) are microscopic airborne particles emitted during the burning of fossil fuels or other industrial processes. Some are so small that they can pass into the bloodstream and enter the major organs, including the brain. We explain the causes, types, prevalence and health effects of these pollutants, which are a major constituent of indoor and outdoor air pollution.

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Heavy air pollution in China

Health Effects of Air Pollution

We examine the respiratory and other health impacts of indoor and outdoor air pollution. We explain the health problems associated with particulate matter, aerosols, black carbon, nitrogen dioxide, ground-level ozone and sulfur dioxide. We ask: which are the most dangerous pollutants? Whose health is most at risk from air pollution? How many Americans die from ambient air pollution each year? And we explain why World Health Organization estimates of deaths from pollution could be way too low.

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Forest fire with plumes of smoke, Canada

Black Carbon: A Deadly Air Pollutant

We explain the formation, composition and health effects of black carbon (BC) particles typically emitted during the incomplete combustion of fossil fuels, wood and other forms of biomass. We also look at the effects of these soot-like particulates on clouds as well as glacier melt and ice/snow albedo in the Arctic. BC is a significant component of emissions from ships and of the huge Asian brown cloud that appears over parts of China and the Indian subcontinent.

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Smog in New Delhi

Asian Brown Cloud: Toxic Haze

We explain the extraordinary regional-size layer of toxic air pollution, known as the ‘Asian Brown Cloud’, that appears for several months every winter over India and China. A form of smog, caused by a combination of emissions from coal-fired power plants, motor vehicles and burning crop stubble, it causes widespread respiratory heath problems across the region.

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Woman cooking indoors, air pollution

Indoor Air Pollution: The Facts

We look at the causes, types and health effects of household air pollution from the burning of wood and solid fossil fuels like coal. The main pollutants include particulate matter, black carbon and toxic gases including carbon monoxide. Driven by poverty, indoor air pollution is mostly confined to the poorest sections of developing countries in Africa and Asia. We explain all you need to know.

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Air Pollution: Types, Causes & Effects

We explain the most common types of natural and man-made air pollution, as well as the main outdoor and indoor air pollutants. We highlight the close connections between air quality and fossil fuel burning, and look at the most important sources of naturally occurring airborne pollution, including wildfires and volcanic eruptions. We also explain the effects of air pollution on human health and the environment.

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Plastic bag in ocean

Microplastics: A Pollution Disaster

Each year, at least 100,000 animals in the sea choke or starve to death because they ingest small pieces of plastic. To explain this issue, we ask: What are microplastics? How do they end up in the ocean? Why are they so dangerous to marine animals? What are the main sources of plastic pollution? Are microplastics harmful to ingest? How much of them are we swallowing?

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Ground Level Ozone from car fumes

Ground Level Ozone: The Facts

Ground-level ozone is a major constituent of photochemical smog, a toxic haze which forms mostly in summer in warm urban areas across the globe. Smog is particularly severe in India, Pakistan and China, many of whose cities are notorious for their unhealthy air quality. Ground level ozone is a secondary pollutant, meaning it is not emitted, but instead forms in the air when certain airborne gases react together. Motor vehicles are a major source of these gases, which is why the introduction of electric vehicles (EVs) may significantly reduce this type of air pollution.

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Crop burning creates aerosols

How Do Aerosols Affect Global Warming?

What are aerosols? Are they pollutants? What effect do they have on albedo, cloud formation and climate change? Do they reflect sunlight? On balance do aerosols have a warming or cooling effect? Will their numbers increase or decrease in the future? What effects does aerosol air pollution have on human health? We answer these questions and more.

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Information & Facts about Pollution

• The WHO calculates that air pollution kills 8 million people annually, but this is almost certainly a serious underestimate.  

• The primary cause of air pollution is the burning of fossil fuels.  

• China and Indonesia between them account for one-third of all plastic pollution in the ocean. Overall, 80 percent of plastic pollution comes from 20 countries.

• The American Lung Association estimates that around 40 percent of the U.S. population (134 million people) are at risk of disease and premature death due to the unhealthy state of air quality. 

• If you are living in Los Angeles or San Francisco, 1 in 3 breaths of air you take can be traced directly back to Asia. This air contains 75 percent of the black carbon pollution that reaches the West Coast.

• Every year, Americans generate 220 million tires, 1.8 billion disposable diapers and 30 billion foam cups.

• Most global deaths from household pollution occur in poorer countries and are caused by wood burning on open fires for cooking.  

• In 2005, the WHO laid down global guidelines for particulate pollution along with interim targets to enable countries to gauge their progress. As of Sept 2020, the air breathed by 81 percent of China’s population still fails to meet the first interim target.

• 21 of the top 30 most polluted cities in the world are located in India and 5 are in Pakistan.