Air pollution world’s worst environmental health risk

Every day you inhale extremely small toxic particles that can cause asthma, lung cancer, and heart problems. Some of them are so small they can move into the bloodstream. People living in cities are typically more exposed. The UN calls Air pollution the world’s worst environmental health risk.

A problem of a global scale

93 percent of the world’s children breathe toxic air every single day. That’s over 1.8 billion children worldwide. The WHO estimates that 600,000 children die annually from respiratory infections caused by air pollution.

Types of air pollution

Air pollution is the emission of harmful substances into the atmosphere, including:

• Sulphur dioxide (SO2): associated with damage to respiratory symptoms and premature death
• Nitrogen oxides (NOx): associated with airway inflammation and increased respiratory symptoms in people with asthma.
• Ozone (O3): affects the respiratory, cardiovascular, central nervous system and reproductive systems.
• Chlorofluorocarbons (CFCs) – harmful to the ozone layer.
• Carbon monoxide (CO): highly toxic and the most common type of fatal air poisoning in many countries.
• Volatile organic compounds (VOCs): long-term negative health effects on the respiratory system and the immune system.
• Particulate matter (small particles of different sizes): Very harmful. See below for more info.

The emission of carbon dioxide (CO2) and other greenhouse gases are not typically considered air pollution (see our section on Energy & Climate for more on greenhouse gas emissions).

Sources of air pollution

Major sources of outdoor pollution include vehicles, power generation, heating for housing, burning of waste, and industry.

Particulate matter air pollution

Particulate matter is an air pollutant in the form of extremely small toxic particles. The smallest particles called nanoparticles are less than 100 nanometers (or 0.0001 millimeters). Recently, there has been increasing interest in these ultra fine particles because they can move through cell membranes into the bloodstream and further into our organs including the brain.

The effects of inhaling ultra fine particulate matter include asthma, cardiovascular issues, and premature death. But we don’t know enough about them.

We do know though that modern diesel engines emit these nanoparticles that by the way also carry known carcinogens such as benzopyrenes.

Air pollution is worst in cities

Car exhaust is a major source of particulate matter and the problem is therefore worse in cities. 

97% of cities with more than 100,000 inhabitants in low- and middle-income countries do not meet WHO air quality guidelines. The mortality in cities with high levels of air pollution is 15-20 percent higher than in cleaner cities.

Staggering levels of air pollution in cities across the world

The WHO guidelines on air pollution (annual average in micrograms per m3) from particulate matter (PM) of 10 and 2.5 micrometers are: 

• PM 2.5: 10 µg/m3
• PM 10: 20 µg/m3

The WHO has listed 500 cities across the word where these limits are exceeded by a factor of more than two and a half for BOTH PM 2.5 and PM 10 meaning a PM 2.5 over 25 µg/m3 and a PM 10 of over 50 µg/m3.

Some cities exceed the limits by a factor of more than 15!

The majority of the most polluted cities are found in China, India, Iran, Poland, Chile. China alone has over 250 of the top 500 cities and India has 9 of the top 10 most polluted cities, the “winner” being Kanpur with a population of almost 3 million people.

Air pollution and climate change linked 

The main driver of air pollution as well as climate change (CO2-emissions) is the burning of fossil fuels, meaning the two are closely linked. Action to cut fossil fuel combustion is therefore a win-win strategy for both climate and human health.

Solutions to air pollution

Electric cars or cars with very effective filters can help reduce the problem of air pollution in cities but fundamental changes to reduce air pollution from all sourcers is needed - including air pollution from power generation, industry etc. 

But projections not particularly good 

The OECD predicts that between 2000 and 2050, SO2 emissions will increase by 90 percent and NOx emissions by 50 percent.