m-Xylene (1,3-Dimethylbenzene)

m-Xylene is the most abundant xylene isomer in mixed xylenes from petroleum, typically comprising 40-70% of commercial mixed xylenes [1]. It is produced during catalytic reforming of naphtha in petroleum refining and is also found in coal tar [2]. m-Xylene is used primarily in isophthalic acid production (a phthalate resin precursor for PET bottles and coatings), as a solvent in paints and coatings, and as a component of aviation fuel [1]. It is a major component of the BTEX mixture that leaches from gasoline into groundwater at underground storage tank spill sites — one of the most ubiquitous groundwater contamination problems in the United States [2].

Gasoline exposure (refueling, underground storage tank leaks) is a major source for the general population [1]. Occupational exposure in petroleum refining, solvent manufacturing, and coating/paint applications [2]. Contaminated groundwater from UST spill sites [1].

m-Xylene is metabolized to 3-methylhippuric acid by oxidation to m-methylbenzoic acid and conjugation with glycine [1]. At occupational concentrations, it causes CNS effects (dizziness, headache, impaired coordination) and potentially vestibular toxicity [2]. EPA classifies xylenes as Group D (not classifiable as carcinogenic) — CNS and liver toxicity rather than cancer are the primary health concerns [1].

Petroleum and chemical workers, painters, and people in BTEX-contaminated water communities [1].

1. Water-based coatings instead of solvent-based products [1]. 2. Test wells near gas stations and underground storage tanks [2]. 3. Ventilate painting and coating operations [1].