PM2.5, O3 and survival gains from China's clean air actions among patients with lung cancer: a 20-year registry-based cohort study in Beijing.

BACKGROUND

In recent years, China has experienced declining fine particulate matter (PM2.5) levels but rising ozone (O3) levels. We aimed to examine the independent and joint associations of long-term exposure to PM2.5 and O3 with all-cause mortality among patients with lung cancer and to estimate potential survival gains.

METHODS

We included 172 845 lung cancer patients diagnosed in 2003-2022 from the Beijing Cancer Registry. Three-year average pre-diagnosis PM2.5 and O3 were assigned using the ChinaHighAirPollutants dataset. Cox proportional hazards models were used to estimate associations of PM2.5 and O3 with mortality. Joint exposure-response patterns were examined using a two-dimensional tensor-product spline and quantified by the multiplicative interaction index. Model-estimated avoided deaths and extended expected lifespan (EEL) were calculated using counterfactual simulations based on 2013 exposure levels.

RESULTS

Both PM2.5 and O3 were associated with increased mortality among patients with lung cancer, with HRs of 1.111 for PM2.5 (95% CI 1.083 to 1.140) and 1.117 for O3 (95% CI 1.070 to 1.166) per 10 μg/m3 increase. A significant multiplicative interaction was observed between PM2.5 and O3, with statistically significant positive interactions mainly occurring at higher O3 concentrations (>105 µg/m3). During 2016-2022, reductions in pre-diagnosis PM2.5 exposure were associated with 13 229 model-estimated avoided deaths and a 7.8-month increase in 5-year EEL. However, O3 and the PM2.5-O3 interaction offset approximately 40% of these benefits.

DISCUSSION: PM2.5 reduction was associated with substantial survival gains among lung cancer patients, but rising O3 and pollutant interactions partly offset these benefits, supporting coordinated multipollutant control.