Significance. While there is general consensus that chemical interactions pose significant human health risks, identification of such risk remains a largely intractable problem. Detailed metabolic analyses combined with bioinformatic methods provides a potentially powerful approach to identify such risk in terms of perturbed metabolic profile. However, the large variety of foods and drugs consumed by different individuals complicates the already difficult task to distinguish between signal and noise and validate stability and recovery for hundreds of metabolites. The significance of the current proposal is that we will use repetitive measures within individuals under highly controlled environmental and dietary conditions to determine whether exposure to a chemical under non-toxic conditions results in a sufficient perturbation of metabolism to be detected by this promising analytical approach. The results will show whether 1H-NMR has the sensitivity to detect metabolic effects due to variations of chemical exposure and dietary intake that are common among humans. If so, the results will establish that 1H-NMR analysis can be used not only to study consequences of chemical toxicity but also to study risk of toxicity due to chemical interactions that occur under usual occupational and therapeutic conditions.