EPA says it lacks adequate data to assess the carcinogenicity of the three isomers of trimethylbenzene (TMB), a chemical mixture found in petroleum products and engine exhaust and also used in some hydraulic fracturing fluids, for which the agency has set toxicity values for preventing adverse neurological effects. The agency June 26 posted the assessment for the isomers 1,2,3-TMB, 1,2,4-TMB and 1,3,5-TMB, chemicals that EPA says are "produced during petroleum refining and production of aromatic hydrocarbons with nine carbons (i.e.,...