Last Thursday the World Health Organization’s International Agency for Research on Cancer (IARC) formally classified outdoor air pollution as carcinogenic (PDF). “The air we breathe has become polluted with a mixture of cancer-causing substances,” the IARC’s Kurt Straif told the South China Morning Post. “We consider this to be the most important environmental carcinogen, more so than passive smoking.” According to data from the WHO’s Global Burden of Disease project, air pollution was responsible for 3.2 million deaths worldwide in 2010, and 223,000 specifically from lung cancer.
The WHO’s grim pronouncement came two days after an Oct. 15 study published in the Lancet linked ambient air pollution to low birth weights. Researchers from several European universities and hospitals examined records for 74,178 full-term births from 1994 to 2011. Records of the mothers’ street addresses helped researchers estimate their likely exposure to a variety of pollutants, including those associated with traffic emissions. Both exposure to ambient air pollution and maternal smoking increased the likelihood of babies born with low birth weights and reduced head circumferences. (Premature babies were not included in the study.) Women exposed to levels of PM2.5—fine air particles less than 2.5 micrometers in diameter—below 10 μg/m³ during pregnancy were 22 percent less likely to give birth to premature babies than those exposed to higher levels of the pollutant. Maternal smoking was linked to 14 percent of premature births.
The steady drumbeat of evidence about the harmful long-term health impacts of air pollution comes as no surprise to residents of China’s smoggy capital, where cooler seasonal temperatures bring more coal burning on Beijing’s outskirts—and so more soot blown into the city. In late September, the Beijing government announced a 1 trillion yuan ($164 billion) plan to rein in air pollution by limiting traffic and increasing fines for environmental violations. On Thursday the municipal government announced additional measures to limit the number of cars on the road, a chief contributor to PM2.5, on days deemed “red alert” for air pollution.