Biological monitoring of occupational exposure to methyl ethyl ketone in Japanese workers

Biomonitoring of Exposures to Solvents and Metals in Electronics Manufacturing Facilities in Batam, Indonesia

Concerns about chemical exposure in the electronics manufacturing industry have long been recognized, but data are lacking in Southeast Asia. We conducted a study in Batam, Indonesia, to evaluate chemical exposures in electronics facilities, using participatory research and biological monitoring approaches. A convenience sample of 36 workers (28 exposed, 8 controls) was recruited, and urine samples were collected before and after shifts. Five solvents (acetone, methyl ethyl ketone, toluene, benzene, and xylenes) were found in 46%-97% of samples, and seven metals (arsenic, cadmium, cobalt, tin, antimony, lead, and vanadium) were detected in 60%-100% of samples. Biological monitoring and participatory research appeared to be useful in assessing workers' exposure when workplace air monitoring is not feasible due to a lack of cooperation from the employer. Several logistical challenges need to be addressed in future biomonitoring studies of electronics workers in Asia in factories where employers are reluctant to track workers' exposure and health.

Gases and organic solvents in urine as biomarkers of occupational exposure: a review

A brief review of urine analysis in studies of occupational exposure to volatile organic compounds and gases is provided. Analysis of exhaled breath for volatile compounds does not have a long history in occupational medicine. A number of studies has been undertaken since the 1980s, and the methods are well enough accepted to be put forward as biological equivalents of threshold limit values (TLVs) for some volatile organic compounds (VOCs) such as acetone; methanol; methyl ethyl ketone (MEK); methyl isobutyl ketone (MIBK); tetrahydrofurane; dichloromethane. In the last 20 years many scientific articles have shown that the urinary concentrations of unchanged solvents are correlated with environmental exposure and could be used for biological monitoring. The use of urine analysis of unchanged solvents in occupational applications is not yet widespread. Nonetheless, in the short time since its application, a number of important discoveries has been made, and the future appears bright for this branch of analysis. In this paper, the basic concepts and methodology of urine analysis are briefly presented with a critical revision of the literature on this matter. The excretion mechanisms of organic solvents in urine are discussed, with regard to biological variability, and the future directions of research are described.

Development of a physiologically based pharmacokinetic model for methyl ethyl ketone in F344 rats

A physiologically based pharmacokinetic (PBPK) model to describe the absorption, distribution, metabolism, and elimination of methyl ethyl ketone (MEK) in rats was developed. Partition coefficients were experimentally determined in rat tissues and blood samples using an in vitro vial equilibration technique. These solubility ratios were in agreement with previous human-based estimates that MEK is uniformly soluble within all tissues. The in vivo metabolism of MEK was evaluated using groups of three F344 male rats exposed to 100-2000 ppm MEK in a closed, recirculating gas uptake system. An optimal fit of a family of uptake curves was obtained by adjusting Michaelis-Menten metabolic constants, Km (affinity), and Vmax (capacity) using the PBPK model. At the highest chamber concentration, the uptake curve could not be modeled without the addition of a first-order (Kfo) metabolic pathway. Pretreatment with pyrazole, an inhibitor of oxidative microsomal metabolism, decreased the slope of the gas uptake curve but did not abolish metabolism. Optimal model fit to the gas uptake curve from pyrazole-pretreated animals required the apparent Km to be increased roughly 50 times the value determined in naive rats. The completed PBPK model was evaluated against real-time exhaled breath data collected from rats receiving an intravenous (iv) injection of MEK via a jugular vein cannula. Model simulation of the iv-treated animals required alveolar ventilation to be reduced 30% in order to match the data. Exhaled breath profiles from animals treated with MEK by oral gavage or intraperitoneal (ip) injection were evaluated and absorption rates was determined. Development of a comprehensive PBPK model for MEK in rats is the first step toward future extrapolations to apply to humans.