CAS No. 120-83-2
Metabolite of 2,4-Dichlorophenoxyacetic acid and other chlorophenols
The chemical 2,4-dichlorophenol has been used in the synthesis of phenoxy acid herbicides, including 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid. It can also be formed as a byproduct during the manufacturing of various chlorinated chemicals, the chlorination processes involving water treatment and wood pulp bleaching, and from the incineration or combustion of municipal solid waste, coal, and wood (HSDB, 2009; IARC, 1999). The major source of 2,4-dichlorophenol in the environment is degradation of 2,4-D in contaminated soil and water (HSDB, 2009). 2,4-Dichlorophenol has been detected in soils and waste streams near industrial sites, and it may volatilize into air. In humans and animals, 2,4-dichlorophenol is a minor metabolite of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D), and it can also result from the metabolism of several other environmental chemicals.
General population exposure to 2,4-dichlorophenol can occur by inhaling contaminated air, ingesting contaminated water, or from dermal contact with this lipid soluble chemical. In addition, 2,4-D and other chlorophenols that are absorbed into the body can be metabolized to 2,4-dichlorophenol. In humans, 2,4-dichlorophenol is rapidly absorbed from the skin, intestine, or lungs, and then rapidly metabolized and eliminated in urine, largely as glucuronide conjugates.
Chronic high dose administration to pregnant and to young laboratory animals resulted in reduced litter size and reduced body weight, respectively, but there was no increase in tumor incidence compared to unexposed animals (NTP, 1989). It is unclear whether 2,4-dichlorophenol has androgenic effects (Kim et al., 2002 and 2005). 2,4-Dichlorophenol was not mutagenic in bacterial assays, and it was not teratogenic in rats (HSDB, 2009; Rodwell et al., 1989).
IARC considers that there is evidence suggesting a lack of carcinogenicity for 2,4-dichlorphenol in experimental animals, but further, considers that combined exposures to polychlorophenols or to their sodium salts are possibly carcinogenic to humans (IARC, 1999). More information about external exposure (i.e., environmental levels) and health effects is available from the ATSDR's toxicological profiles at: http://www.atsdr.cdc.gov/ToxProfiles/tp.asp?id=941&tid=195.
Urinary 2,4-dichlorophenol levels reflect recent exposure. CDC (2012) reported median levels of urinary 2,4-dichlorophenol during four NHANES survey periods (2003-2010) that ranged from 0.68 to 0.88 µg/g creatinine in adults, or slightly lower than the median of 1.8 µg/g creatinine in a subsample of NHANES III (1988-1994) adult participants (Hill et al., 1995). Becker et al. (2003) reported urinary 2,4-dichlorophenol levels in German adults that were more than four times lower than those reported in NHANES III. In a study of Arkansas children, 27% of urine samples had detectable levels of 2,4-dichlorophenol (>1 µg/L) (Hill et al., 1989). Pregnant women living in a largely agricultural region of California had urinary 2,4-dichlorophenol levels that were approximately the same in second and third trimester specimens, with a median of 1.8 and 1.1 μg/L, respectively (Castorina et al., 2010). Two studies of workers with potential for excessive chlorophenol exposure found urinary 2,4-dichlorophenol levels that were not elevated above those measured in non-exposed workers or in the general population (Mari et al., 2009; Radon et al., 2004).
Finding a measurable amount of 2,4-dichlorophenol in urine does not imply that the level of the 2,4-dichlorophenol will result in an adverse health effect. Biomonitoring studies of 2,4-dichlorophenol will provide physicians and public health officials with reference values so that they can determine whether other people have been exposed to higher levels of 2,4-dichlorophenol than levels found in the general population. Biomonitoring data can also help scientists plan and conduct research on exposure and health effects.
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