Abstract
The International Agency for Research on Cancer (IARC) has classified outdoor air pollution and the particulate matter (PM) in outdoor air pollution as carcinogenic to humans, as based on sufficient evidence of carcinogenicity in humans and experimental animals and strong support by mechanistic studies. The data with important contributions to the evaluation are reviewed, highlighting the data with particular relevance to China, and implications of the evaluation with respect to China are discussed. The air pollution levels in Chinese cities are among the highest observed in the world today and frequently exceed health-based national and international guidelines. Data from high-quality epidemiologic studies in Asia, Europe, and North America consistently show positive associations between lung cancer and PM exposure and other indicators of air pollution, which persist after adjustment for important lung cancer risk factors, such as tobacco smoking. Epidemiologic data from China are limited but nevertheless indicate an increased risk of lung cancer associated with several air pollutants. Excess cancer risk is also observed in experimental animals exposed to polluted outdoor air or extracted PM. The exposure of several species to outdoor air pollution is associated with markers of genetic damage that have been linked to increased cancer risk in humans. Numerous studies from China, especially genetic biomarker studies in exposed populations, support that the polluted air in China is genotoxic and carcinogenic to humans. The evaluation by IARC indicates both the need for further research into the cancer risks associated with exposure to air pollution in China and the urgent need to act to reduce exposure to the population.
Highlights
The International Agency for Research on Cancer (IARC) has classified outdoor air pollution and the particulate matter (PM) in outdoor air pollution as carcinogenic to humans, as based on sufficient evidence of carcinogenicity in humans and experimental animals and strong support by mechanistic studies
Cui et al.[28] studied the chromosomal aberrations (CAs) frequencies in the chorionic villi of 2,698 women having abortions in 3 cities with different levels of air pollution, and the results indicated that the incidences of polyploidy, trisomy, and chromosome structural abnormalities in heavily polluted Shenyang and moderated polluted Zhengzhou were significantly higher than those in Dalian, which was the least polluted
It has been estimated that approximately 223,000 deaths from lung cancer—nearly 15% of all lung cancer deaths—worldwide are attributable to particulate air pollution in 2010, with 139,000 of those deaths (9% of all lung cancer deaths) occurring in China alone[45]
Summary
The International Agency for Research on Cancer (IARC) has classified outdoor air pollution and the particulate matter (PM) in outdoor air pollution as carcinogenic to humans, as based on sufficient evidence of carcinogenicity in humans and experimental animals and strong support by mechanistic studies. The association between an increased risk of lung cancer and exposure to polluted air measured by several indicators, including the concentrations of PM and NO2 and measures of potential exposure to traffic emissions, was consistently observed in both cohort and case-control studies after adjustment for important potential confounders, including tobacco smoking. Increased risk of lung cancer with exposure to outdoor air pollution was observed in analyses restricted to non-smokers[16], and the magnitude of association was not appreciably affected by adjustment for indicators of socioeconomic status[15].
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