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Biomonitoring Summary

2,4-Dichlorophenol

CAS No. 120-83-2
Metabolite of 2,4-Dichlorophenoxyacetic acid and other chlorophenols

General Information

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.

Biomonitoring Information

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.

References

Becker K, Schulz C, Kaus S, Seiwert M, Seifert B. German environmental survey 1998 (GerES III): environmental pollutants in the urine of the German population. Int J Hyg Environ Health 2003;206:15-24.

Castorina R, Bradman A, Fenster L, Barr DB, Bravo R, Vedar MG, et al. Comparison of current-use pesticide and other toxicant urinary metabolite levels among pregnant women in the CHAMACOS cohort and NHANES. Environ Health Perspect 2010;118(6):856-63.

Centers for Disease Control and Prevention (CDC). Fourth National Report on Human Exposure to Environmental Chemicals. Updated Tables, 2012. [online] Available at URL: http://www.cdc.gov/exposurereport/. 10/15/12

Hazardous Substances Data Bank (HSDB). 2,4-dichlorophenol. National Library of Medicine, Bethesda, MD: National Institutes of Health; Updated 11/16/2009

Available at URL: http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?HSDB. 12/28/12

Hill RH Jr, Head SL, Baker S, Gregg M, Shealy DB, Bailey SL, et al. Pesticide residues in urine of adults living in the United States: reference range concentrations. Environ Res 1995;71:99-108.

Hill RH Jr, To T, Holler JS, Fast DM, Smith J, Needham LL, et al. Residues of chlorinated phenols and phenoxy acid herbicides in the urine of Arkansas children. Arch Environ Contam Toxicol 1989;18:469-74.

International Agency for Research on Cancer (IARC). IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. Vol. 71, 1999. Re-evaluation of some organic chemicals, hydrazine and hydrogen peroxide (part one, part two, part three. Available at URL: http://monographs.iarc.fr/ENG/Monographs/vol71/mono71-34.pdf. 10/15/12

Kim HJ, Kim WD, Kwon TH, Kim DH, Park YI, Dong MS. Mechanism of phenoxy compounds as an endocrine disruptor. J Toxicol Pub Health 2002;18:331-9.

Kim HJ, Park YI, Dong MS. Effects of 2,4-D and DCP on the DHT-induced androgenic action in human prostate cancer cells. Toxicol Sci 2005;88(1):52-9.

Mari M, Schuhmacher M, Domingo JL. Levels of metals and organic substances in workers at a hazardous waste incinerator: a follow-up study. Int Arch Occup Environ Health 2009;82:519-28.

National Toxicology Program (NTP). Toxicology and carcinogenesis studies of 2,4-dichlrophenol (CAS no. 120-83-2) in F334/N rats and B6C3F1 mice (feed studies). NTP TR 353. NIH Publication no. 89-2808. June 1989. Available at URL: http://ntp.niehs.nih.gov/ntp/htdocs/LT_rpts/tr353.pdf. 10/15/12

Radon K, Wegner R, Heinrich-Ramm R, Baur X, Poschadel B, Szadkowski D. Chlorophenol exposure in harbor workers exposed to river silt aerosols. Am J Ind Med 2004;45:440-5.

Rodwell DE, Wilson RD, Nemec MD, Mercieca MD. Teratogenic assessment of 2,4-dichlorophenol in Fischer 344 rats. Fundam Appl Toxicol 1989;13(4):635-40.


 
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