Exposure to PM constituents and risk of adult leukemia in Denmark: A population-based case-control study.

BACKGROUND

Leukemia is one of the most common forms of hematologic malignancy, which can affect people of all ages. We previously showed an association between exposure to ambient particulate matter 2.5 μg (PM) and risk for leukemia in adults. The aim of this study was to investigate which PM constituents were responsible for our previous observation.

METHODS

This is a nationwide register-based case-control study. We identified 14,983 persons diagnosed with leukemia at age 20 or above, 1989-2014, in the Danish Cancer Registry. We selected up to four sex and age-matched controls per case at random from the entire Danish population (n = 51,613). We modelled concentrations of ambient PM and its constituents at the addresses of cases and controls for the 10-year period before index date with a state-of-the-art multiscale air pollution modeling system. We used conditional logistic regression to estimate odds ratios (ORs) adjusted for individual and neighborhood level socio-demographic variables.

RESULT

The results showed higher risk for overall leukemia in association with interquartile range exposure to PM (OR = 1.09; 95% CI: 1.02, 1.17), black carbon (BC) (OR = 1.02; 95% CI: 1.00, 1.03), secondary inorganic aerosols (SIA) (OR = 1.15; 95% CI: 1.03, 1.29) and its components ammonium (NH) (OR = 1.08; 95% CI: 1.00, 1.17) and nitrate (NO) (OR = 1.08; 95% CI: 1.02, 1.14). In leukemia subtype analysis, statistically significant associations were found for AML with PM (OR = 1.14; 95% CI: 1.00, 1.29), BC (OR = 1.03; 95% CI: 1.00, 1.07), SIA (OR = 1.23; 95% CI: 1.01, 1.51), NH (OR = 1.16; 95% CI: 1.01, 1.34) and NO (OR = 1.12; 95% CI: 1.01, 1.24). The association between PM and leukemia persisted in two pollutants models including sum of primary emitted black and organic carbon (BC + OC), secondary organic aerosols (SOA), or sea-salt. The association between black carbon (BC) and leukemia persisted in two pollutants models including organic carbon (OC). The three pollutant model with sulfate (SO), NH and NO showed an association with NO but not with SO or NH.

CONCLUSION

Ambient concentrations of the PM components BC, NH and NO at the residence showed associations with risk of incident leukemia in adults.