Long-term exposure to air pollution and risk of non-Hodgkin lymphoma in Denmark: A population-based case–control study

There is limited evidence regarding a possible association between exposure to ambient air pollutants and the risk of non-Hodgkin lymphoma (NHL). Previous epidemiological studies have relied on crude estimations for air pollution exposure and/or small numbers of NHL cases. The objective of our study was to analyze this association based on air pollution modeled at the address level and NHL cases identified from the nationwide Danish Cancer Registry. We identified 20,874 incident NHL cases diagnosed between 1989 and 2014 and randomly selected 41,749 controls matched on age and gender among the entire Danish population. We used conditional logistic regression to estimate odds ratios (ORs) and adjusted for individual and neighborhood level sociodemographic variables. There was no association between exposure to PM_2.5, BC, O₃, SO₂ or NO₂ and overall risk of NHL but several air pollutants were associated with higher risk of follicular lymphoma, but statistically insignificant, for example, PM_2.5 (OR = 1.15 per 5 μg/m³; 95% CI: 0.98–1.34) and lower risk for diffuse large B-cell lymphoma (OR = 0.92 per 5 μg/m³; 95% CI: 0.82–1.03). In this population-based study, we did not observe any convincing evidence of a higher overall risk for NHL with higher exposure to ambient air pollutants.