Chloroacetic acid

Chloroacetic acid (monochloroacetic acid, MCA) is produced by chlorinating acetic acid and is used as an intermediate in the production of herbicides (2,4-D, MCPA, dalapon), pharmaceuticals (ibuprofen, carboxymethylcellulose), and various other specialty chemicals [1]. Global production exceeds 600,000 tonnes annually [2]. As a drinking water contaminant, it is one of five haloacetic acids (HAA5: mono-, di-, and trichloroacetic acid; and mono- and dibromoacetic acid) regulated by the EPA Total Disinfection Byproducts Rule at a combined maximum contaminant level of 60 µg/L [1]. Chloroacetic acid forms in chlorinated water when hypochlorous acid reacts with acetaldehyde or other organic precursors from natural organic matter [2].

The primary pathway for most people is drinking chlorinated tap water containing trace HAA5 [1]. Showering and bathing in chlorinated water provides some additional inhalation exposure, though less than for THMs [2]. Occupational exposure to industrial MCA occurs in herbicide synthesis, pharmaceutical manufacturing, and chemical plant workers through skin contact and inhalation [1]. MCA's extreme corrosiveness to skin means industrial accidents cause deep chemical burns with systemic absorption [2].

Chloroacetic acid reacts with glutathione by S-alkylation, depleting cellular antioxidant capacity and generating reactive oxygen species [1]. It forms DNA adducts with guanine and induces chromosomal aberrations. Epidemiological studies of chlorinated drinking water suggest modest associations between HAA5 exposure and bladder and colon cancer risk [2]. Acute high-level industrial exposure to MCA causes chemical burns, CNS toxicity, and cardiac arrhythmias through membrane-active ion transport disruption [1].

Everyone drinking chlorinated tap water has low-level chloroacetic acid exposure [1]. Workers in herbicide and pharmaceutical synthesis face occupational exposure [2]. Industrial accident victims with high-dose skin contact face severe systemic toxicity [1].

1. Activated carbon filtration removes HAAs from drinking water [1]. 2. Let water stand in an open container for 30-60 minutes — HAAs do not volatilize readily (unlike THMs) but some will degrade [2]. 3. Use point-of-use reverse osmosis or activated carbon block filters for drinking water [1]. 4. Industrial MCA handlers require impermeable gloves, face shields, and chemical-resistant clothing [2].