Chlorobenzene

Chlorobenzene was one of the first large-scale organic chemical products of the German chemical industry, produced by the Baeyer and Kekule laboratories in the 1860s-70s [1]. Its largest historical use was as a chemical intermediate in DDT synthesis (chlorobenzene + chloral → DDT) and in phenol production by the Raschig process. It was also used as an industrial solvent for paints and rubber, and as a heat transfer fluid [2]. The massive DDT production era (1945-1972) left significant chlorobenzene contamination at former DDT manufacturing sites, and its use as a phenol production intermediate created Superfund-scale contamination at numerous chlorobenzene production facilities [1]. Today, it remains in use as a solvent and chemical intermediate but at reduced volumes [2].

Groundwater contamination at former DDT manufacturing sites and chlorobenzene production facilities represents the primary community exposure pathway [1]. Drinking water from contaminated wells above the EPA MCL (0.1 mg/L) is a concern for private well users near these sites [2]. Occupational inhalation and dermal exposure occurs in chemical synthesis and solvent applications [1].

Chlorobenzene is metabolized by CYP450 enzymes to chlorophenol metabolites and benzene oxide (epoxide) intermediates that cause liver and kidney toxicity [1]. At high concentrations it causes CNS depression (headache, dizziness, narcosis). EPA classifies it as a Group D (not classifiable as to carcinogenicity) based on current evidence, though liver effects are well established [2]. It is primarily a CNS and liver toxicant at occupational levels rather than a confirmed carcinogen [1].

Private well users near former DDT manufacturing and chlorobenzene production sites [1]. Chemical synthesis workers using chlorobenzene as a solvent [2].

1. Test your well if near former chemical or pesticide manufacturing sites [1]. 2. Activated carbon filtration for contaminated water [2]. 3. Occupational: local exhaust ventilation and organic vapor respirators [1].