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The World Health Organization has classified air pollution as a human carcinogen (like tobacco smoke, asbestos and arsenic) and is calling it a leading cause of cancer deaths globally.[1]

For years, air pollution has been linked to a variety of ailments. Some compounds, such as diesel exhaust, have already been labeled as carcinogens.[2] But this is the first time that air pollution, in its entirety, has been classified as a carcinogen.

Air pollution is a broad term used to refer to a complex mix of particulates in the air. Air pollution can be caused by transportation, power generation, industrial or agricultural emissions and residential heating and cooking. The composition and levels of air pollution vary over space and time—but the International Agency for Research on Cancer (IARC), a scientific working group of the WHO, was tasked with evaluating the air that everyone breathes, rather than focusing on specific pollutants. As such, they concluded that air pollution poses a risk to anyone exposed to it.

The IARC reviewed thousands of studies on air pollution and found that exposure to air pollution increased the risk of lung cancer and bladder cancer. Depending on the level of exposure, the risk may be equivalent to breathing secondhand tobacco smoke. The group concluded that air pollution is a leading environmental cause of cancer deaths.

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Research has indicated that exposure to air pollution has risen dramatically in some parts of the world, including Asia, South Asia, North Africa, Mexico, Central America, and eastern North America.

The agency concluded that air pollution is carcinogenic to humans, which is the highest of the agency’s four-level classification system. They note that both air pollution and particulate matter (a component of air pollution) will now be classified among its Group 1 human carcinogens.


[1] Straif K, Cohen A, Samet J, et al. IARC Scientific Publication No. 161
Air Pollution and Cancer. Available here

[2] International Agency for Research on Cancer: Diesel engine exhaust carcinogenic. [World Health Organization Press Release]. Available here