Background
Long-term exposure to fine particulate matter (PM2.5) is an established carcinogen; however, evidence on whether short-term PM2.5 exposure acts as an acute trigger of mortality among individuals with cancer remains limited.
Objective
We examined the association between short-term PM2.5 exposure and daily cancer mortality in Japan, overall and by cancer site.
Methods
We compiled daily counts of cancer mortality and air pollution data from all 47 prefectures in Japan for the period 2013–2022. A two-stage analytical approach was applied. In the first stage, prefecture-specific quasi-Poisson regression models were fitted to estimate associations between PM2.5 exposure (lag 0–2 days) and daily cancer mortality, adjusting for temperature, relative humidity, long-term and seasonal trends, and day of the week. In the second stage, prefecture-level estimates were pooled using random-effects meta-analysis. Stratified analyses were conducted by sex, age group, and cancer site (lung, stomach, colorectal, liver, pancreas, and breast). Sensitivity analyses further adjusted for co-pollutants, including NO? and SO?.
Results
A total of 171,550 cancer deaths were included in the analysis. A 10-µg/m³ increase in PM2.5 (lag 0–2) was associated with a significant increase in total cancer mortality (relative risk [RR] = 1.09; 95% CI: 1.04–1.15). Associations were observed across age groups and were slightly stronger in males (RR = 1.10) than females (RR = 1.07). In site-specific analyses, significant associations were identified for lung cancer (RR = 1.07; 95% CI: 1.02–1.12), with elevated risks also observed for colorectal cancer (RR = 1.11) and breast cancer (RR = 1.20; 95% CI: 1.07–1.36). Estimates were robust to alternative model specifications but were attenuated after adjustment for NO? (RR = 1.05) and SO? (RR = 1.03).
Conclusions/Implications for practice or policy
Short-term increases in PM2.5 exposure are associated with higher daily mortality among cancer patients in Japan. These findings suggest that air pollution may act as an acute stressor that accelerates death in vulnerable populations, with potential effects extending beyond respiratory cancers to systemic malignancies. The results highlight the relevance of short-term air quality management for protecting individuals living with cancer.
 

Figure 1: Prefecture-level estimates and random-effects meta-analysis of PM2.5 effects on all-cancer mortality