Air pollution raises lung cancer risk for women

Recent air pollution exposure in the form of particles smaller than 2.5 micrometers (PM_2.5) exposure may significantly impact lung cancer in women who have never smoked, with notable differences in stage IV diagnoses among EGFR+ patients, according to research presented today at the International Association for the Study of Lung Cancer (IASLC) 2024 World Conference on Lung Cancer.

The International Agency for Research on Cancer (IARC) categorized outdoor air pollution and its key component, particulate matter PM_2.5, as Group 1 carcinogens in 2013, indicating that they cause lung cancer. Associations between tobacco use and lung cancer account for a majority of lung cancers. Still, researchers and public health experts have not been able to identify an association that explains why individuals who do not smoke or have never smoked are diagnosed with lung cancer.

The timing and duration of PM_2.5 exposure that are most relevant for the development of lung cancer and lung cancer risk have not been well characterized. The purpose of our study is to compare the associations between recent versus long-term cumulative PM_2.5 exposure in men and women who had never smoked and lung cancer EGFR mutation status."

Dr. Yixian Chen, Researcher, British Columbia Cancer Research Institute

The research team collected data from newly diagnosed lung cancer patients who never smoked that included information on their residential history from birth to the date of diagnosis.

Dr. Chen and the team then geocoded each residential address and analyzed high-resolution concentration estimates of PM_2.5 exposure from satellite data, chemical transport models, and ground measurements within roughly 10 x 10 kilometer areas corresponding to the time the individual lived at each address. The team obtained annual exposure data going back to 1996 when accurate air pollution information became available globally.

A total of 255 patients with known EGFR mutation status were included in the analysis. Significant associations were observed between EGFR mutation and cancer stage among women (p=0.197 in men, p<0.001 in women). Patients diagnosed with stage IV lung cancer displayed higher proportions of EGFR mutations compared to those without. Notable differences were also identified in the cumulative 3-year PM_2.5 exposure before diagnosis in women who never smoked with EGFR mutations compared to those without (e.g., 19.0 vs 17.3 μg/m³, p=0.031).

This trend persisted when examining cumulative 5-year exposure (33.7 vs 29.5 μg/m³, p=0.024) before diagnosis, with higher exposure observed in the EGFR-mutation positive group (EGFR+). Surprisingly, these associations were not evident in men who never smoked. Moreover, long-term exposure, such as 10-, 15-, and 20-year cumulative exposure to PM_2.5, was not associated with EGFR mutation status in either men or women.

"These findings suggest a potential impact of recent exposure to PM_2.5 on lung cancer in people who never smoked, particularly among women, with significant differences in stage IV diagnoses among EGFR+ patients," said Dr. Chen. "Further studies are needed to confirm if PM_2.5 measurement over 3 to 5 years is adequate for lung cancer risk assessment."