Correlation of xylene exposure and methyl hippuric acid excretion in urine among paint industry workers

Examination of xylene exposure in the U.S. Population through biomonitoring: NHANES 2005-2006, 2011-2016

Aim: Xylenes are aromatic hydrocarbons used for industrial applications such as the production of petrochemicals and plastics. Acute xylene exposures can negatively impact health through neurotoxicity and irritation of respiratory and dermal tissues. We quantified urinary biomarkers of xylene exposure [2-methylhippuric acid (2MHA) and a mixture of 3- and 4-methylhippuric acids (34MH)] in a representative sample of the U.S. population. Methods: Spot urine obtained during the National Health and Nutrition Examination Survey 2005-2006 and 2011-2016 was analysed using ultra-high-performance liquid chromatography/tandem mass spectrometry. Exclusive smokers were distinguished from non-users using a combination of self-report and serum cotinine data. Results: The median 2MHA and 34MH levels were higher for exclusive smokers (100 µg/g and 748 µg/g creatinine, respectively) than for non-users (27.4 µg/g and 168 µg/g creatinine, respectively). Participants who smoked cigarettes had significantly higher 2MHA and 34MH levels (p < 0.0001) than unexposed participants. Smoking 1-10, 11-20, and >20 cigarettes per day (CPD) was significantly associated with 181%, 339% and 393% higher 2MHA levels, respectively. For 34MH, smoking 1-10, 11-20, and >20 CPD was significantly associated with 201%, 398%, and 471% higher 34MH levels, respectively. Conclusion: We confirm that tobacco smoke is a significant source of xylene exposure as measured by urinary 2MHA and 34MH levels.

Evaluation of dermal absorption and protective effectiveness of respirators for xylene in spray painters

OBJECTIVES

To determine the contribution of dermal absorption on the total exposure dose and the performance of respirators in the field for xylene in spray painters.

METHODS

Eighteen male spray painters worked at shipyard were recruited for this study. The subjects were monitored during a 3-day-work period using a repeated-measures study design. Personal exposure to xylene outside and inside mask were collected using two 3 M model 3500 organic vapor monitors, respectively. Urine was collected before and after the work shift and urinary methyl hippuric acid (MHA) was determined. Total 98 of air and urine samples were obtained, respectively.

RESULTS

Air sampling results showed that workers were primarily exposed to xylene and ethyl benzene. Xylene and ethyl benzene concentrations outside the mask were 52.6+/-63.7 (mean+/-SD) and 33.2+/-32.4 ppm, and concentrations inside the mask were 2.09+/-2.74 and 1.79+/-2.16 ppm, respectively. The median workplace protection factors of respirators for xylene and ethyl benzene were 25.0 and 17.4, respectively. On average, workers could reduce xylene inhalation by 96% and ethyl benzene inhalation by 94% for wearing respirators. A significant correlation (R(2)=0.935; P<0.001) was found between the WPFs for xylene and ethyl benzene. Total urinary MHA concentration was 240.2+/-42.3 (mean+/-SE) mg/g creatinine, whereas urinary MHA via skin absorption was estimated to be 202.1+/-40.1 mg/g creatinine. The contribution of dermal absorption to the total exposure dose of xylene was 64+/-4.3%.

CONCLUSION

The present study showed that inhalation of solvent vapors in workers decreased as a result of wearing respirators and dermal exposure became the main contributor to the total body burden of solvents. Because workers had different attitude and behavior to wear respirators, the measured workplace protection factors varied. It is therefore equally important to prevent from being exposed to solvents through skin for shipyard spray painters.

ATSDR evaluation of health effects of chemicals. V. Xylenes: health effects, toxicokinetics, human exposure, and environmental fate

Xylenes, or dimethylbenzenes, are among the highest-volume chemicals in production. Common uses are for gasoline blending, as a solvent or component in a wide variety of products from paints to printing ink, and in the production of phthalates and polyester. They are often encountered as a mixture of the three dimethyl isomers, together with ethylbenzene. As part of its mandate, the Agency for Toxic Substances and Disease Registry (ATSDR) prepares toxicological profiles on hazardous chemicals found at Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) National Priorities List (NPL) sites that are of greatest concern for public health purposes. These profiles comprehensively summarize toxicological and environmental information. This article constitutes the release of the bulk of this profile (ATSDR, 1995) into the mainstream scientific literature. An extensive listing of known human and animal health effects, organized by route, duration, and end point, is presented. Toxicological information on toxicokinetics, biomarkers, interactions, sensitive subpopulations, reducing toxicity after exposure, and relevance to public health is also included. Environmental information encompasses physical properties, production and use, environmental fate, levels seen in the environment, analytical methods, and a listing of regulations. ATSDR, as mandated by CERCLA (or Superfund), prepares these profiles to inform and assist the public.

Skin contamination, airborne concentrations, and urinary metabolite excretion of propoxur during harvesting of flowers in greenhouses

In eight greenhouses used for carnation culture, workers engaged in harvesting (n = 16), were monitored for dermal and respiratory exposure and urinary excretion of propoxur. Dermal exposure of hands and forearms was estimated from dislodgable foliar residue, using a transfer factor (a measure of transfer of pesticides from leaves to the skin) and the total number of working hours. Total estimated dermal and respiratory exposure during harvesting ranged from 0.2 to 46 mg and from 3 to 278 micrograms, respectively. To study the relationship between external and internal exposure to propoxur, respiratory and dermal exposure levels were compared with the total amount of 2-isopropoxyphenol (IPP), the major metabolite of propoxur, excreted in urine in 24 hr. The Pearson correlation coefficient between dermal exposure and the total amount of excreted IPP was 0.95. A correlation coefficient of 0.84 was found between respiratory exposure and the amount of IPP excreted. The latter association was probably caused by the covariation of respiratory and dermal exposure levels (r = 0.85). Assuming negligible oral absorption, calculations indicated that dermal exposure could account for > 80% of the amount of excreted IPP. On the basis of the amount of IPP excreted, there was no reason to suspect increased health risks for workers from exposure to propoxur during harvesting.

A new derivatization procedure for the analysis of hippuric acid and m-methyl-hippuric acid by gas chromatography

The industrial solvents, toluene and xylene, have physicochemical properties that can be hazardous to the workers exposed. Since hippuric acid and m-methyl-hippuric acid represent the products of toluene and xylene biotransformation in urine, they are used as biological markers in studies on occupational exposure to these solvents. Several methods have been used to determine hippuric acid and m-methyl-hippuric acid--either based on gas chromatography or on high-performance liquid chromatography. In this study we propose the derivatization of hippuric acid and methyl-hippuric acid using methanol in acid medium (HCl), a low-cost reagent with a low level of toxicity. The method has been routinely used in our laboratory for 1 year and has proven to be a reliable procedure for the biological control of occupational exposure to toluene and/or xylene.