Aspects of biological monitoring of exposure to glycol ethers

Glycol ethers are frequently used as solvents, detergents, and emulsifiers alone or as components in industrial and consumer products. The monomethyl and monoethyl ethers of ethylene glycol, and their acetate esters, are teratogenic and embryotoxic and cause testicular damage in laboratory animals, while the monobutyl ether causes hemolysis of the red blood cells. The adverse effects are attributed to the acid metabolites methoxy-, ethoxy- and butoxyacetic acid, respectively. The glycol ethers may readily enter the body by inhalation as well as dermal uptake. Biological monitoring of exposure to glycol ethers has therefore been suggested. This paper reviews physical properties, occurrence, analysis, toxicity, and toxicokinetics of the most common glycol ethers and then discusses toxicokinetic aspects of biological monitoring. The effect of physical exercise and the relative importance of respiratory and percutaneous absorption on the internal exposure to glycol ethers are illustrated. Monitoring the acid metabolite in urine is suggested as the best index of exposure. Intra- and inter-individual variability, dose-dependent toxicokinetics, and metabolic induction and inhibition are examples of possible sources of error in the estimation of internal exposure from the urinary excretion of acid metabolite.