Respiratory and Dermal Exposure to Creosote

The aims of the study were to investigate occupational exposure and the exposure routes of coal tar creosote, and to evaluate the suitability of methods for monitoring occupational exposure to the PAHs in creosote. The composition of four creosotes used in Finland was studied by gas chromatography/mass spectrometry. Creosotes contain polycyclic aromatic hydrocarbons (over 60%), phenols, and heterocyclic sulphur and nitrogen compounds. The mutagenicity of four creosotes and their chemical fractions was studied with the Ames Salmonella tests. All creosotes were mutagenic with Salmonella typhimurium TA98 in the presence of metabolic activation. The potency of the mutagenicity correlated with the content of benzo(a)pyrene in the creosotes. The mutagenicity of the creosotes was nevertheless higher than that of the distillated fractions containing more BaP than the creosotes. The kinetics of naphthalene was investigated in two volunteers after intake by oral, dermal and respiratory routes. The kinetic pilot study confirmed that naphthalene is absorbed into the body by all routes in humans, and that the metabolism is route-specific. Airborne concentrations of vapours and particulate PAHs were measured in two impregnation plants and at five work sites where impregnated wood was handled. The workers were exposed via the lungs to the airborne impurities consisting mainly (over 95%) of vaporous compounds. The main compounds were naphthalene, its alkyl homologues, indene, phenol, benzothiophene and diphenyl. The total TWA concentration of the vapours ranged from 0.5-9.1 mg/m in the impregnation plants, and from 0.111 mg/m in the handling of treated wood. The TWA airborne concentration of particulate BaP was low (0.01 μg/m and 0.02 μg/m), except when the creosote or treated wood was heated. Concurrently with the monitoring of the air impurities, the urinary 1-OHN and 1-OHP concentration of six wood preservers and three assemblers handling treated wood was monitored during one work week. The arithmetic mean concentration of urinary 1-OHN in the impregnation plant workers was as high as in the assemblers (1330-1350 μmol/mol creatinine). The urinary 1-OHP concentration was 10 times higher in the impregnation plant workers (64 μmol/mol creatinine) than in the assemblers. The significance of the skin as a route of exposure was estimated from the daily output of the urinary 1OHN and 1-OHP and the daily inhaled uptake of naphthalene and pyrene. The results suggest that 5060% of the naphthalene uptake, and over 99% of the pyrene were absorbed percutaneously. Urinary 1-OHN and 1-OHP are better indicators of total exposure to creosote than the measurement of airborne impurities, because they reflect also dermal exposure. The suitability of urinary 1-OHN and 1OHP as biomarkers of PAH exposure depends on how well they predict the uptake of other PAHs. More knowledge is needed to estimate whether urinary 1-OHP is a reliable indicator of dermal absorption for other PAHs, e.g. BaP. For occupational exposure and risk management purposes, one can assume that the relative dermal bioavailability of other PAHs is not higher than that of naphthalene and pyrene. National Library of Medicine Classification: WA 465, QV 627 Medical Subject Headings: occupational exposure; creosote; coal tar; inhalation exposure; skin absorption; creosote/analysis; polycyclic hydrocarbons, aromatic; mutagens; mutagenicity tests; naphthalenes; air pollutants; occupational; aerosols; biological markers