Burden of cancer attributable to air pollution in Japan in 2015

PM_2.5 is a major environmental health problem and a risk factor for lung cancer. Exposure to PM_2.5 has attracted growing public concern nationwide. Here, we aimed to estimate the cancer in 2015 attributable to PM_2.5 in Japan. Ambient air pollution level due to excess concentration of PM_2.5 was estimated using geophysically based satellite-derived PM_2.5 concentrations in 2005, with a spatial resolution of 0.5° × 0.5° longitude-latitude, and population data presented in a 1 km by 1 km grid. We used the WHO guideline value for PM_2.5 exposure (≤ 10 μg/m³) as the optimal level of PM_2.5 exposure. By using relative risk from a large-scale cohort study in Japan, we estimated the population attributable fraction (PAF) for lung cancer, which is positively associated with PM_2.5, and aggregated the results to obtain the PAF among total cancer incidence and mortality. Population-weighted mean PM_2.5 level in 2005 was 14.9 μg/m³. Approximately 95.7% of the population was exposed to levels above the WHO guideline value. Lung cancer attributable to PM_2.5 exposure corresponded to 11,922 cases and 7,264 deaths, which accounted for 9.7% and 9.8% of total lung cancer incidence and mortality, respectively, and 1.2% and 2.0% of total cancer incidence and mortality, respectively. Substantial geographic variation in PM_2.5-attributable incidence and mortality fractions was found, with cities in western Japan and metropolitan areas having a higher PAF than other municipalities. This study provides useful information to aid policy-makers and public health agencies in the efficient establishment of environmental cancer prevention policies.