In summary, based on evidence from PBPK and neurotoxicity studies supporting the plausibility of additive joint action at the shared target of toxicity at relatively low levels of exposure, the hazard index approach is recommended for assessing possible neurotoxic health hazards from environmental exposures to BTEX. This is a conservative approach for assessing BTEX due to the protective nature of the MRLs and guidance values on which it is based, the