Albumin Adducts of Naphthalene Metabolites as Biomarkers of Exposure to Polycyclic Aromatic Hydrocarbons

Abstract

We investigated the utility of adducts formed by the reaction of the naphthalene metabolites naphthalene-1,2-oxide, 1,2-naphthoquinone (1,2-NPQ), and 1,4-naphthoquinone (1,4-NPQ) with serum albumin (AIb) as biomarkers of exposure to polycyclic aromatic hydrocarbons. Cysteinyl serum AIb adducts of 1,2- and 1,4-NPQ (1,2-NPQ-AIb and 1,4-NPQ-AIb, respectively) but not of naphthalene-1,2-oxide were detected in 28 coke oven workers and 22 controls from the steel industry of northern China. The median level of 1,2-NPQ-AIb in coke oven workers (76.6 pmol/g) was significantly higher than that observed in controls (44.9 pmol/g; P = 0.0027). However, the median level of 1,4-NPQ-AIb in exposed subjects was not significantly different from that of controls (48.6 versus 44.2 pmol/g; P = 0.296). Levels of 1,2-NPQ-AIb were significantly correlated with exposure category (controls, side and bottom workers, and top-of-oven workers) as well as with previously measured levels of urinary naphthalene, 1- and 2-naphthol, and 1-pyrenol in these subjects. Multiple linear regression analysis revealed that 35% of the variation in 1,2-NPQ-AIb could be explained by the work category and age. A negative relationship between 1,2-NPQ-AIb and age was observed, suggesting that cytochrome P450 c metabolism diminished with age at ∼3%/year of life.