Abstract

Air pollution is a risk factor for cancer. Outdoor air pollution is a complex mixture of gases (e.g. NO2, SO2 and O3) and particles (e.g. PM2.5) that arise from a diverse range of sources, including motor vehicles and industrial facilities. An increased risk of lung cancer is consistently seen in epidemiological studies and in animal toxicology and the risk is most clearly associated with exposure to particulate matter. Epidemiological studies have mostly been carried out in Europe and North America where PM2.5 concentrations are typically between around 10 and 30 micro-g/m3; much higher concentrations are seen in emerging economies in Southeast Asia and elsewhere. There is limited evidence that bladder cancer risks are associated with outdoor pollution.  In Europe and North America air pollution levels are steadily decreasing over time as a result of technological developments reducing emissions, but in other parts of the world levels are increasing. There are limited possibilities for reduction in exposure from behavioral interventions. There is uncertainty about the magnitude of the risk and the shape of the exposure-response curve, but a 10 micro-g/m3 in outdoor PM2.5 could result in a reduction in the lung cancer population attributable fraction of between around 3% and 30%