Urinary polycyclic aromatic hydrocarbon metabolites, plasma p-tau231 and mild cognitive impairment in coke oven workers

As a group of environmental pollutants, polycyclic aromatic hydrocarbons (PAHs) may be neurotoxic，especially in high-exposure occupational populations. However, the effect of PAHs on mild cognitive impairment (MCI) is still unclear. We aimed to investigate the relationship between PAH metabolites and MCI and to explore whether plasma p-tau231 can be used as a potential biomarker to reflect MCI in coke oven workers. A total of 330 workers were recruited from a coke oven plant as the exposure group, and 234 workers were recruited from a water treatment plant as the control group. The concentrations of eleven PAH metabolites and plasma p-tau231 were determined by high-performance liquid chromatography–mass spectrometry (HPLC–MS/MS) and ELISA. Cognitive function was measured by the Montreal Cognitive Assessment (MoCA) questionnaire. A multivariate logistic regression model and multiple linear regression model were used to analyze the associations of urinary PAH metabolites with the detection rate of MCI, MoCA scores and plasma p-tau231. The dose–response relationships were evaluated using restricted cubic spline models. We found 146 MCI-positive workers in coke oven plant (44.24%), and 69 MCI-positive workers in water treatment plant (29.49%). In addition, the urinary sum of PAH metabolites (Ʃ-OH PAHs) was significantly associated with MCI (OR, 1.371; 95% CI:1.102–1.705). Each one-unit increase in ln-transformed Ʃ-OH PAHs was associated with a 0.429 decrease in the sum of MoCA, a 0.281 reduction in the visuospatial/executive function and a 9.416 increase in the level of plasma P-Tau231. We found a negative association between plasma P-Tau231 and visuospatial/executive function (β = −0.007, 95% CI: −0.011, −0.003). Our data indicated that urinary Ʃ-OH PAHs levels of workers were positively associated with MCI and the level of plasma P-Tau231.