title: The effects of simultaneous exposure to methyl ethyl ketone and toluene on urinary biomarkers of occupational N,N-dimethylformamide exposure.
abstract: General regulations and risk assessment regarding toxicants are single-compound oriented even though humans are exposed to multi-chemicals in the general environment. This study investigated the effects of different levels of N,N-dimethylformamide (DMF) and co-exposure levels of methyl ethyl ketone (MEK) and toluene (TOL) on two biomarkers of DMF exposure: non-metabolized urinary (U-)DMF and the DMF metabolite urinary N-methylformamide (NMF). Thirty-five workers were selected from a two-stage field investigation strategy and were classified into four groups based on DMF exposure and co-exposure levels. Breathing-zone air concentrations of DMF, MEK, and TOL as well as dermal DMF exposure were determined. Post-shift U-DMF and U-NMF levels were determined for each individual. U-DMF concentrations were significantly higher in high-DMF groups than in low-DMF groups, but U-NMF concentrations were significantly (P<0.05) lower in the high-DMF-high-co-exposure group than in the high-DMF-low-co-exposure group; there were no significant differences between two low-DMF groups. The ratio of U-NMF to U-DMF showed the biotransformation from DMF to NMF was significantly suppressed at high co-exposure (P<0.001) for high-DMF exposure groups, possibly because of competitive inhibition of CYP2E1, the responsible enzyme involved. Due to the ubiquity of MEK/TOL in DMF-exposed occupational settings, the biological exposure index for occupational DMF exposure should be re-evaluated at high co-exposure levels.
authors.affiliation: Department of Environmental and Occupational Health, Medical College, National Cheng Kung University, 138 Sheng-Li Road, Tainan 70428, Taiwan. h7154@mail.ncku.edu.tw
authors.forename: Ho-Yuan
authors.initials: HY
authors.lastname: Chang
authors.forename: Yuan-Der
authors.initials: YD
authors.lastname: Yun
authors.forename: Yi-Chun
authors.initials: YC
authors.lastname: Yu
authors.forename: Tung-Sheng
authors.initials: TS
authors.lastname: Shih
authors.forename: Ming-Song
authors.initials: MS
authors.lastname: Lin
authors.forename: Hsien-Wen
authors.initials: HW
authors.lastname: Kuo
authors.forename: Kuo-Ming
authors.initials: KM
authors.lastname: Chen
mesh_terms: D000328:Adult; D000395:Air Pollutants, Occupational / Q000032:analysis* / Q000652:urine; D015415:Biomarkers / Q000652:urine; D002074:Butanones / Q000032:analysis* / Q000494:pharmacology; D004126:Dimethylformamide / Q000032:analysis* / Q000493:pharmacokinetics / Q000592:standards; D004784:Environmental Monitoring / Q000592:standards; D005559:Formamides / Q000032:analysis*; D006801:Humans; D008658:Inactivation, Metabolic; D008297:Male; D016273:Occupational Exposure / Q000032:analysis* / Q000592:standards; D013624:Taiwan; D013784:Textiles; D014050:Toluene / Q000032:analysis* / Q000494:pharmacology
chemical_list: D000395:Air Pollutants, Occupational; D015415:Biomarkers; D002074:Butanones; D005559:Formamides; D014050:Toluene; C005222:methylethyl ketone; D004126:Dimethylformamide; C002950:methylformamide