tokens: 2 . Our study involved a group of 60 male and female subjects who were exposed to MTBE and benzene -contaminated water concentrations up to 76 PPB for MTBE and 14 PPB for benzene , for a period of 5 to 8 years .
folded_tokens: 2 . our study involved a group of 60 male and female subjects who were exposed to mtbe and benzene -contaminated water concentrations up to 76 ppb for mtbe and 14 ppb for benzene , for a period of 5 to 8 years .
labels: O O O O O O O O O O O O O O O O O B-other_organic_compound O B-other_organic_compound O O O O O O O O B-other_organic_compound O O O O B-other_organic_compound O O O O O O O O O O