Relationship between particulate matter exposure and female breast cancer incidence and mortality: a systematic review and meta-analysis

The associations of PM with the risk and prognosis of breast cancer have not been determined. This systematic review aimed to provide an updated understanding of the relationship between PM exposure level and breast cancer incidence and mortality. Articles from Web of Science and PubMed databases were methodically inspected until March 8, 2020. In final, 15 studies were kept for analysis, which provided necessary information to estimate the impact of PM on breast cancer risk and prognosis. These studies were combined for quantitative analyses to evaluate the effect of per 10 μg /m3 increment exposure of PM2.5 (< 2.5 μm in aerodynamic diameter) and PM10 (< 10 μm in aerodynamic diameter) using random-effects model. PM2.5 exposure was associated with increased breast cancer mortality (relative risk [RR] = 1.09; 95% confidence interval [CI]: 1.02, 1.16; PQ-test = 0.158). No association of PM2.5 (1.02; 0.97, 1.18; 0.308) and PM10 (1.03; 0.98, 1.09; 0.009) with the increase incidence of breast cancer was observed. Stratified analysis suggested that PM2.5 was associated with the increase mortality of breast cancer (1.10; 1.03, 1.17; 0.529) in subgroup of developed country. PM10 was associated with breast cancer incidence based on studies published after 2017 (1.08; 1.00, 1.15; 0.157) and European studies (1.15; 1.06, 1.25; 0.502). Our study indicated that PM2.5 exposure was related to breast cancer mortality. Further researches in this field are needed to validate the conclusion.