Particulate Air Pollution Contributes to Lung Cancer Risk in Huge European Study

A study including 17 cohorts with a total of more than 300,000 individuals found that ambient air pollution of various types contributes to lung cancer incidence across nine European countries.

“Ambient air pollution, specifically particulate matter with absorbed polycyclic aromatic hydrocarbons and other genotoxic chemicals, is suspected to increase the risk for lung cancer,” wrote researchers led by Ole Raaschou-Nielsen, PhD, of the Danish Cancer Society Research Center in Copenhagen, online in the Lancet. The new study, known as ESCAPE, analyzed data from a number of cohorts across Europe featuring patients with a wide range of exposure levels to pollution.

Among a total of 312,944 participants and 4,013,131 person-years at risk, there were 2,095 lung cancer cases over an average follow-up period of 12.8 years. The analysis showed a significant association between the risk of lung cancer and concentrations of particulate matter (PM) with a diameter of less than 10 µm (PM10) near where participants live; the hazard ratio (HR) was 1.22 (95% CI, 1.03–1.45) per 10 µg/m³. For smaller particles known as PM2.5, the HR was not significant, at 1.18 (95% CI, 0.96–1.46) per 5 µg/m³.

PM10 was associated with an HR for adenocarcinoma specifically of 1.51 (95% CI, 1.10–2.08), while PM2.5 yielded an HR of 1.55 (95% CI, 1.05–2.29). Furthermore, though it did not reach significance, the amount of road traffic near a residence appears to play a role in lung cancer risk: an increase of 4,000 vehicle-kilometers per day within 100 meters of the residence gave an HR for lung cancer of 1.09 (95% CI, 0.99–1.21). There was no association between cancer and nitrogen oxide concentration or traffic intensity on the nearest street.

The authors concluded that the associations seen in this study add “substantially to the weight of the epidemiological evidence.” The study does have limitations, including the combination across cohorts and the fact that “the effects of single air pollutants are difficult to disentangle in an epidemiological study because pollutants are part of complex mixtures.” Previous research, though, does suggest that particulate matter is the most important component of those mixtures to lung cancer risk.

Notably, there did not appear to be a point below which the risk associated with particulate matter pollution disappears. According to a press release, the authors said that the association persisted even at concentrations below the European Union air quality limit values. “We found no threshold below which there was no risk; the results showed a picture that ‘the more the worse, the less the better.’ ”

In an accompanying editorial in the Lancet, Takashi Yorifuji, MD, PhD, of Okayama University Graduate School of Environmental and Life Science in Japan, said that “we might have to add air pollution, even at current concentrations, to the list of causes of lung cancer and recognize that air pollution has large effects on public health, although fortunately, like tobacco smoking, it is a controllable factor.”