Ambient PM2.5 exposure and pancreatic cancer risk in a Northern Ireland population-based case-control study

Abstract Fine particulate matter (PM 2.5 ) has been associated with several cancers, but evidence for pancreatic cancer remains limited. We examined whether long-term residential exposure to PM 2.5 is associated with pancreatic cancer risk in Northern Ireland. We conducted a population-based case–control study of 475 incident pancreatic cancer cases diagnosed in 2019–2020 and 8,316 cancer-free controls from the Northern Ireland Cohort for the Longitudinal Study of Ageing (NICOLA), all aged ≥ 50 years. Annual PM 2.5 concentrations at 1 km 2 spatial resolution were obtained from modelled surfaces. Seven-year mean exposure was assigned to residential postcodes and categorised into tertiles (< 7.46, 7.46–9.66 and > 9.66 µg/m 3 ). Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for PM 2.5 tertiles and per-µg/m 3 increases. Models were adjusted for age (5-year bands), sex, smoking status and area-level deprivation. Stratified analyses were conducted by sex, age group (< 74/≥74 years), smoking status, urban–rural classification and histologically confirmed adenocarcinoma. Compared with the lowest PM 2.5 tertile, the fully adjusted OR for pancreatic cancer was 0.90 (95% CI 0.69, 1.16) for medium exposure and 1.02 (95% CI 0.79, 1.31) for high exposure. When modelled continuously, each 1 µg/m 3 increase in PM 2.5 was associated with an OR of 1.02 (95% CI 0.97, 1.06). Stratified analyses showed no clear differences in associations across subgroups. In this population-based study in Northern Ireland, long-term exposure to ambient PM 2.5 was not associated with pancreatic cancer risk. These findings provide an important contribution to current limited evidence regarding air pollution and pancreatic cancer in regions with relatively low ambient PM 2.5 concentrations.