Albumin and hemoglobin adducts as biomarkers of exposure to styrene in fiberglass-reinforced-plastics workers

Abstract

Objective: The purpose of this work was to compare levels of styrene-7,8-oxide (SO) adducts of albumin (Alb) and hemoglobin (Hb) with those of two urinary metabolites of styrene, mandelic acid (MA) and phenylglyoxylic acid (PGA), among workers exposed to styrene in the reinforced-plastics industry and in unexposed subjects. We also wished to determine whether cigarette smoking influenced adduct levels among these subjects.

Methods: A group of 22 male workers was selected on basis of an expectedly high level of exposure to styrene, and a group of 15 controls was selected from hospital blood donors and hospital staff. In the exposed group, MA and PGA were quantified by high-performance liquid chromatography (HPLC) analysis of urine samples collected prior to the work shift. The SO adducts were cleaved from cysteine residues by reaction with Raney nickel to give 1-phenylethanol (1-PE) and 2-phenylethanol (2-PE), which, after derivatization, were measured using gas chromatography-mass spectrometry (GC-MS) in the negative-chemical-ionization (NCI) mode.

Results: The estimated mean levels of MA and MA+PGA were 74 and 159 mg/g creatinine, respectively. Using the levels of urinary metabolites, an average styrene concentration of about 100 mg/m³ in the workplace air was estimated. The mean levels of 2-PE and 1-PE adducts in exposed workers were 2.84 and 0.60 nmol/g Alb and 5.44 and 0.43 nmol/g Hb, respectively. When subjects were stratified by level of urinary metabolites [zero (controls), low-level exposure (MA+PGA ≤159 mg/g creatinine), and high-level exposure (MA+PGA> 159 mg/g creatinine)] and smoking status (smokers versus nonsmokers), a difference in Alb adduct levels was found among the groups (2-PE P=0.002, 1-PE P=0.052). The difference in 2-PE-Alb levels was related to exposure category, to smoking status, and to their interaction. Correlations at or near a 0.05 level of significance were observed among the workers (n=22) between individual levels of SO-protein adducts and MA+PGA (2-PE Alb, r=0.54, 2-PE Hb, r=0.40).

Conclusion: Our data suggest that only exposure to relatively high levels of styrene allows a clear relationship to be detected between styrene exposure and SO adducts, due in part to the effects of cigarette consumption and to the high background levels of these adducts observed in unexposed subjects.