Summary of the Public Health Goal for Xylene
A Public Health Goal (PHG) of 1.8 ppm is developed for xylene(s) in drinking water. The State of California’s Maximum Contaminant Level (MCL) for xylene in drinking water is 1.75 ppm based on minimal effects in a chronic rat study. The U.S. Environmental Protection Agency’s (U.S. EPA’s) MCL is 10 ppm based on the same chronic rat study. Xylene does not appear to be carcinogenic in animals or humans. The calculated PHG considers noncarcinogenic effects in both animals and humans and is based on subjective reports of neurotoxic effects in chronic exposures to xylene in humans. The lowest-observed-adverse-effect level (LOAEL) from this study was divided by a factor of 30 [three for extrapolation from a LOAEL to a no-observed-adverse-effect level (NOAEL) and 10 for potential variations in sensitivity among humans] to calculate a public health-protective level. This value was further divided by two to account for extra exposure by the inhalation route to xylene in the household water supply, and corrected for an assumed relative source contribution from drinking water of 40%. Based on these considerations and assumptions, OEHHA calculates a PHG of 1.8 mg/L (1.8 ppm) for individual xylene isomers or the sum of xylene isomers in drinking water.
- Xylenes (technical mixture of m, o, p-isomers)