The link between lung cancer and indoor air pollution

Abstract

www.thelancet.com/oncology Vol 13 October 2012 e415 A retrospective cohort study of more than 37 000 residents of Xuanwei County in China’s Yunnan Province has concluded that the domestic use of smoky (bituminous) coal substantially increases the risk of lung cancer. The study—led by scientists at the National Cancer Institute (NCI), Bethesda, MD, USA—found that male users of smoky coal had an 18% absolute risk of dying from lung cancer before they reached the age of 70 years. Female users, nearly all of whom were non-smokers, had a 20% risk. Male and female users of smokeless coal (anthracite), by contrast, had a lung cancer risk of less than 0·5%. “Lung cancer alone accounted for about 40% of all deaths before age 60 among individuals using smoky coal”, wrote the authors. About half the world’s population relies on solid fuels or coal for cooking and heating. The International Agency for Research on Cancer (IARC; Lyon, France) classifi es indoor emissions from the combustion of coal as a group 1 carcinogen. 2 years ago the UN Foundation launched the Global Alliance for Clean Cook Stoves, aiming to ensure universal access to such devices. In China, where most people live in rural areas, the use of coal is especially prevalent. Moreover, households in Xuanwei, which has some of the highest lung cancer rates in the world, are poorly ventilated, so the internal concentration of coal smoke is particularly intense. “There are several factors that come together in Xuanwei, but the risk for lung cancer in using smoky coal, compared with smokeless coal, is much higher”, co-author Qing Lan (NCI) told The Lancet Oncology. The study period (1976–96) saw a total of 8976 deaths, 2377 of which were due to lung cancer. Co-author Nathaniel Rothman (NCI) described the fi ndings as a “striking example of an environmental contribution to cancer”. Lan added that “the use of less carcinogenic types of coal or other fuels would likely translate to a substantial reduction in lung cancer risk in Xuanwei”. However, this strategy might not always be feasible: good quality coal might not be locally available. Fortunately, other interventions can be highly eff ective. “Construct a chimney and ensure that people’s exposure to coal smoke is reduced”, urges IARC’s Robert Baan. Indeed, an earlier study co-authored by Lan showed that simply installing a household stove with a chimney can halve the risk of lung cancer.