90% of people breathe polluted air; New Delhi is world's most polluted big city

Doyle Rice | USA TODAY

Show Caption Hide Caption Breathing the air in Delhi, India, like smoking 44 cigarettes a day The air quality in India is so bad, its the equivalent of smoking 44 cigarettes a day. Veuer's Nick Cardona (@nickcardona93) has that story.

Nine out of 10 people around the world breathe polluted air, according to a report released Wednesday by the World Health Organization (WHO).

An "alarming" 7 million people die each year from air pollution, the report said, as air pollution levels remain dangerously high in many parts of the world.

More than 90% of pollution-related deaths occur in low- and middle-income countries, mainly in Asia and Africa.

“Air pollution threatens us all, but the poorest and most marginalized people bear the brunt of the burden,” said Tedros Adhanom Ghebreyesus, director-general of the WHO. Breathing polluted air can lead to heart disease, a stroke and lung cancer, the WHO said.

This report is the largest air pollution survey undertaken of world cities.

The WHO survey also named New Delhi as the world's most polluted big city. Other polluted megacities, with populations over 14 million, include Cairo; Dhaka, Bangladesh; Mumbai, India; and Beijing.

“Many of the world’s megacities exceed WHO’s guideline levels for air quality by more than five times, representing a major risk to people’s health,” said Maria Neira, the WHO director for environment and public health.

Air pollution is measured by how many grains of "particulate matter" (PM) are in a cubic meter. PM is broken down into two groups: PM10 and PM2.5, which are measurements of the particle in micrometers.

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For human health, the toxic PM2.5 particles of black carbon and sulfate "pose the greatest problems, because they can get deep into your lungs, and some may even get into your bloodstream," the Environmental Protection Agency said.

For perspective, the width of a human hair is 30 times larger than a single PM2.5 particle.

India has 14 of the 15 top polluted cities in the world, in terms of the dangerous PM2.5 particles, the report said. .

Indian environment officials told Reuters that the WHO findings were embarrassing but not surprising.

The report also shows some countries are trying to reduce air pollution. China, for example, is taking serious strides to clean up its air, and the WHO said India should follow China's example.

This is the WHO's fourth report on air quality. compiling air pollution levels from more than 4,300 cities and towns in 108 countries.