Long-term Exposure to Low Concentrations of Polycyclic Aromatic Hydrocarbons and Alterations in Platelet Indices: A Longitudinal Study in China

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Background High concentrations of polycyclic aromatic hydrocarbons (PAHs) can induce inflammatory and immune responses by affecting platelet indices. However, studies into low-concentration, non-occupational exposures are inconclusive in cross-sectional cohorts. We investigated low-concentration exposure to PAHs and alterations in platelet indices using a longitudinal dataset. Methods We recruited 418 participants from Northern China between 2014 and 2017 and followed each subject for three consecutive years; 222 were included in the analysis. Demographic information was collected by questionnaire and blood and urine were sampled annually. We measured the levels of eight urinary PAH metabolites representative of exposure to PAHs. Generalised mixed models and general linear mixed models were used to estimate correlations between PAH exposure, platelet indices, and covariates. Results We found dose–response correlations between urinary 1-hydroxynaphthalene, 2-hydroxyphenanthrene, 1-hydroxyphenanthrene, and 1-hydroxypyrene and platelet counts, as well as correlations between urinary 9-hydroxyfluorene levels and platelet distribution width, mean platelet volume, and platelet-large cell ratio. In subgroup analysis, 9-hydroxyfluorene levels were associated with mean platelet volume in participants exposed to second-hand smoke (odds ratio: 0.983; 95% confidence interval: 0.971–0.994) and with platelet distribution width in participants who were not exposed to second-hand smoke (odds ratio: 0.955; 95% confidence interval: 0.913–0.999). Conclusions Long-term exposure to low concentrations of PAHs affects platelet count, platelet distribution width, mean platelet volume, and platelet-large cell ratio, and the effects may be modified by exposure to second-hand smoke.