The association between ambient air pollutants and pancreatic cancer in the Multiethnic Cohort Study

Background: Prior studies examining the association between ambient air pollutants and pancreatic cancer have been conducted in racially/ethnically homogeneous samples and have produced mixed results, with some studies supporting evidence of an association with fine particulate matter.

Methods: To further investigate these findings, we estimated exposure levels of particulate matter (PM_2.5, PM₁₀) and oxides of nitrogen (NO_X, and NO₂) using kriging interpolation for 100,527 men and women from the Multiethnic Cohort Study, residing largely in Los Angeles County from 1993 through 2013. We measured the association between these air pollutants and incident pancreatic cancer using Cox proportional hazards models with time-varying pollutant measures, with adjustment for confounding factors.

Results: A total of 821 incident pancreatic cancer and 1,660,488 person-years accumulated over the study period, with an average follow-up time of over 16 years. PM_2.5 (per 10 μg/m³) was associated with incident pancreatic cancer (hazard ratio [HR] = 1.61; 95% CI, 1.09, 2.37). This PM_2.5 -association was strongest among Latinos (HR = 3.59; 95% CI, 1.60, 8.06) and ever smokers (HR = 1.76; 95% CI, 1.05, 2.94). There was no association for PM₁₀ (HR = 1.12; 95% CI, 0.94, 1.32, per 10 μg/m³), NO_x (HR = 1.14; 95% CI, 0.88, 1.48, per 50 ppb), or NO₂ (HR = 1.14; 95% CI, 0.85, 1.54, per 20 ppb).

Conclusions: Our findings support prior research identifying an association between fine particulate matter, PM_2.5, and pancreatic cancer. Although not statistically heterogeneous, this association was most notable among Latinos and smokers. Future studies are needed to replicate these results in an urban setting and in a racially/ethnically diverse population.