Phthalates are industrial chemicals that are added to plastics to impart flexibility and resilience and are often referred to as plasticizers. Phthalates also are used as solubilizing or stabilizing agents in other applications. There are numerous products that may contain phthalates: adhesives; automotive plastics; detergents; lubricating oils; some medical devices and pharmaceuticals; plastic raincoats; solvents; vinyl tiles and flooring; and personal-care products, such as soap, shampoo, deodorants, lotions, fragrances, hair spray, and nail polish. Phthalates are often used in polyvinyl chloride type plastics, such as plastic packaging film and sheet, garden hoses, inflatable recreational toys, blood product storage bags, intravenous medical tubing, and toys (ATSDR, 2001, 2002). Because they are not chemically bound to the plastics to which they are added, phthalates can be released into the environment during use or disposal of the product. Various phthalate esters have been measured in specific foods, indoor and ambient air, indoor dust, water sources, and sediments (Clark et al., 2003).
People are exposed through ingestion, inhalation, and, to a lesser extent, dermal contact with products that contain phthalates. For the general population, dietary sources have been considered as the major exposure route, followed by inhaling indoor air. Infants may have relatively greater exposures from ingesting indoor dust containing some phthalates (Clark et al., 2003). Human milk can be a source of phthalate exposure for nursing infants (Calafat et al., 2004; Mortensen et al., 2005). The intravenous or parenteral exposure route can be important in patients undergoing medical procedures involving devices or materials containing phthalates. In settings where workers may be exposed to higher air phthalate concentrations than the general population, urinary metabolite and air phthalate concentrations are roughly correlated (Liss et al., 1985; Nielsen et al., 1985; Pan et al., 2006).
Phthalates are metabolized and excreted quickly and do not accumulate in the body (Anderson et al., 2001). Ingested phthalate diesters are initially hydrolyzed in the intestine to the corresponding monoesters, which are then absorbed (Albro et al., 1982; Albro and Lavenhar, 1989). Absorbed monoester metabolites are usually oxidized in the body and, in humans, excreted in urine largely as glucuronide conjugates (Albro et al., 1982; Dirven et al,. 1993). The table shows the phthalate diesters, corresponding monoester metabolites, and other oxidized metabolites included in the National Report on Human Exposure to Environmental Chemicals (CDC, 2013).
Human health effects from phthalates at low environmental doses or at biomonitored levels from low environmental exposures are unknown. Phthalates have low acute animal toxicity. In chronic rodent studies, several of the phthalates produced testicular injury, liver injury, liver cancer, and teratogenicity, but these effects either have not been demonstrated when tested in non-human primates or are yet to be studied. In vitro studies showed that certain phthalates can bind to estrogen receptors and may have weak estrogenic or anti-estrogenic activity (Coldham et al., 1997; Harris et al., 1997; Jobling et al., 1995), but in vivo studies did not support phthalates having estrogenic effects (Milligan et al., 1998; Okubo et al., 2003; Parks et al., 2000; Zacharewski et al., 1998); however, not all phthalates and metabolites have been tested. In animals, phthalates produced anti-androgenic effects by reducing testosterone production and, at very high levels, reducing estrogen production, effects that may be mediated by inhibiting testicular and ovarian steroidogenesis. High doses of di-2-ethylhexyl phthalate (DEHP), dibutyl phthalate (DBP), and benzylbutyl phthalate (BzBP) during the fetal period produced lowered testosterone levels, testicular atrophy, and Sertoli cell abnormalities in the male animals and, at higher doses, ovarian abnormalities in the female animals (Jarfelt et al., 2005; Lovekamp-Swan and Davis, 2003; McKee et al., 2004; NTP-CERHR, 2003a, 2003b, 2006). Phthalate urinary metabolite levels in men evaluated at an infertility clinic were associated with several measures of sperm function and morphology (Duty et al., 2004; Hauser et al., 2007), but similar findings were not present in young Swedish men with comparable or higher median levels of urinary metabolites (Jonsson et al., 2005).
The monoester metabolites are thought to mediate toxic effects for some of the phthalates, but there are known species-related differences in the hydrolysis of diester phthalates, efficiency of intestinal absorption, and extent of metabolite conjugation to glucuronide (Albro et al., 1982; Kessler et al., 2004; Rhodes et al., 1986). These differences may contribute to species-specific differences in toxicity (ATSDR, 2001, 2002). Also, phthalates have been shown to induce peroxisomal proliferation in rodents, which may be a pathway to the development of liver toxicity and cancers in these animals. However, peroxisomal proliferation may not be a relevant pathway in humans (Rusyn et al., 2006).
The National Toxicology Program's Office of Health Assessment and Translation, formerly Center for the Evaluation of Risks to Human Reproduction (NTP-CERHR) has reviewed the developmental and reproductive effects of specific phthalates (https://www.niehs.nih.gov/research/atniehs/dntp/ohat/index.cfmexternal icon). Information about external exposure (i.e., environmental levels) and health effects is also available for some phthalates from ATSDR at https://www.atsdr.cdc.gov/toxprofiles/index.asp.
Phthalates and Urinary Metabolites Measured in the National Biomonitoring Program
|Phthalate name (CAS number)||Abbreviation||Urinary metabolite (CAS number)||Abbreviation|
|Benzylbutyl phthalate (85-68-7)||BzBP||Mono-benzyl phthalate (2528-16-7)
(some mono-n-butyl phthalate)
|Dibutyl phthalates (84-74-2)||DBP||Mono-n-butyl phthalate (131-70-4)
|Dicyclohexyl phthalate (84-61-7)||DCHP||Mono-cyclohexyl phthalate (7517-36-4)||MCHP|
|Diethyl phthalate (84-66-2)||DEP||Mono-ethyl phthalate (2306-33-4)||MEP|
|Di-2-ethylhexyl phthalate (117-81-7)||DEHP||Mono-2-ethylhexyl phthalate (4376-20-9)
Mono-(2-ethyl-5-carboxypentyl) phthalate (40809-41-4)
|Di-isononyl phthalate (28553-12-0)||DiNP||Mono-isononyl phthalate||MiNP|
|Di-isodecyl phthalate||DiDP||Mono-(carboxynonyl) phthalate||MCNP|
|Dimethyl phthalate (131-11-3)||DMP||Mono-methyl phthalate (4376-18-5)||MMP|
|Di-n-octyl phthalate (117-84-0)||DOP||Mono-(3-carboxypropyl) phthalate
Mono-n-octyl phthalate (5393-19-1)
Urinary levels of phthalate metabolites reflect recent exposure to the parent phthalate diester. The proportions of each metabolite for a given phthalate may vary by differing routes of exposure (Liss et al., 1985; Peck and Albro, 1982). Variation occurs from person to person in the proportions or amounts of a metabolite excreted after similar doses (Anderson et al., 2001); variation also occurs in the same person during repetitive monitoring (Fromme et al., 2007; Hauser et al., 2004; Hoppin et al., 2002). Population estimates of concentrations of specific phthalate metabolites may differ by age, gender, and race/ethnicity (Silva et al., 2004).
Finding a measurable amount of one or more phthalate metabolites in urine does not imply that the levels of the metabolites or the parent phthalate cause an adverse health effect. Biomonitoring studies on levels of phthalate metabolites provide physicians and public health officials with reference values so that they can determine whether people have been exposed to higher levels of phthalates than are found in the general population. Biomonitoring data can also help scientists plan and conduct research on exposure and health effects.
CAS No. 84-61-7
Dicyclohexyl phthalate (DCHP) is used to stabilize some rubbers, resins, and polymers, including nitrocellulose, polyvinyl acetate, and polyvinyl chloride. People exposed to DCHP will excrete mono-cyclohexyl phthalate (MCHP) in their urine. Neither IARC nor NTP has evaluated DCHP with respect to human carcinogenicity.
Urinary levels of MCHP are infrequently measured and the limited population-based surveys available to date have reported most levels below the limit of detection. In the National Report on Human Exposure to Environmental Chemicals, only levels at or above the 90th percentile could be characterized (CDC, 2013).
Finding a measurable amount of MCHP in urine does not imply that the levels of MCHP or the parent compound cause an adverse health effect. Biomonitoring studies on levels of urinary MCHP provide physicians and public health officials with reference values so that they can determine whether people have been exposed to higher levels of DHCP than are found in the general population. Biomonitoring data can also help scientists plan and conduct research on exposure and health effects.
Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological profile for di-n-butyl phthalate update [online]. September 2001. Available at URL: https://www.atsdr.cdc.gov/toxprofiles/tp.asp?id=859&tid=167. 6/21/13
Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological profile for di(2-ethylhexyl)phthalate update [online]. September 2002. Available at URL: https://www.atsdr.cdc.gov/toxprofiles/tp.asp?id=684&tid=65. 6/21/13
Albro PW, Corbett JT, Schroeder JL, Jordan S, Matthews HB. Pharmacokinetics, interactions with macromolecules and species differences in metabolism of DEHP. Environ Health Perspect 1982;45:19-25.
Albro PW and Lavenhar SR. Metabolism of di(2-ethylhexyl) phthalate. Drug Metab Rev 1989;21:13-34.
Anderson WA, Castle L, Scotter MJ, Massey RC, Springall C. A biomarker approach to measuring human dietary exposure to certain phthalate diesters. Food Addit Contam 2001;18(12):1068-1074.
Calafat AM, Slakman AR, Silva MJ, Herbert AR, Needham LL. Automated solid phase extraction and quantitative analysis of human milk for 13 phthalate metabolites. J Chromatogr B 2004;805:49-56.
Centers for Disease Control and Prevention (CDC). Fourth National Report on Human Exposure to Environmental Chemicals. Updated Tables, 2013. [online] Available at URL: https://www.cdc.gov/exposurereport/. 6/21/13
Clark K, Cousins IT, Mackay D. Assessment of critical exposure pathways. In Staples CA (ed), The Handbook of Environmental Chemistry, Vol, 3, Part Q: Phthalate Esters. 2003;New York, Springer, pp. 227-262.
Coldham NG, Dave M, Silvapathasundaram S, McDonnell DP, Connor C, Sauer MJ. Evaluation of a recombinant yeast cell estrogen screening assay. Environ Health Perspect 1997; 105:734-742.
Dirven HA, van der Broek PH, Jongeneelen FJ. Determination of four metabolites of the plasticizer di (2-ethylhexyl) phthalate in human urine samples. Int Arch Occup Environ Health 1993;64(8):555-560.
Duty SM, Calafat AM, Silva MJ, Brock JW, Ryan L, Chen Z, et al. The relationship between environmental exposure to phthalates and computer-aided sperm analysis motion parameters. J Androl 2004;25(2):293-302.
Fromme H, Bolte G, Koch HM, Angerer J, Boehmer S, Drexler H, et al. Occurrence and daily variation of phthalate metabolites in the urine of an adult population. Int J Hyg Environ Health 2007;210:21-33.
Harris CA, Henttu P, Park MG, Sumpter JP. The estrogenic activity of phthalate esters in vitro. Environ Health Perspect 1997;105:802-811.
Hauser R, Meeker JD, Park S, Silva MJ, Calafat AM. Temporal variability of urinary phthalate metabolite levels in men of reproductive age [published erratum appears in Environ Health Perspect 2004;112(17):1740]. Environ Health Perspect 2004;112(17):1734-1740.
Hauser R, Meeker JD, Singh NP, Silva MJ, Ryan L, Duty S, et al. DNA damage in human sperm is related to urinary levels of phthalate monoester and oxidative metabolites. Hum Reprod 2007;22(3):688-695.
Hoppin JA, Brock JW, Davis BJ, Baird DD. Reproducibility of urinary phthalate metabolites in first morning urine samples. Environ Health Perspect 2002;110(5):515-518.
Jarfelt K, Dalgaard M, Hass U, Borch J, Jacobsen H, Ladefoged O. Antiandrogenic effects in male rats perinatally exposed to a mixture of di(2-ethylhexyl) phthalate and di(2-ethylhexyl) adipate. Reprod Toxicol 2005;19(4):505-515.
Jobling S, Reynolds T, White R, Parker MG, Sumpter JP. A variety of environmentally persistent chemicals including some phthalate plasticizers are weakly estrogenic. Environ Health Perspect 1995;103:582-587.
Jonsson BAG, Richthoff J, Rylander L, Giwercman A, Hagmar L. Urinary phthalate metabolites and biomarkers of reproductive function in young men. Epidemiol 2005;16(4):487-493.
Kessler W, Numtip W, Grote K, Csanády G, Chahoud I, Filser J. Blood burden of di(2-ethylhexylphthalate (DEHP) and its primary metabolite mono(2-ethylhexyl) phthalate (MEHP) in pregnant and non-pregnant rats and marmosets. Toxicol Appl Pharmacol 2004;195:142-153.
Liss GM, Albro PW, Hartle RW, Stringer WT. Urine phthalate determinations as an index of occupational exposure to phthalic anhydride and di (2-ethylhexyl) phthalate. Scand J Work Environ Health 1985;11(5):381-387.
Lovekamp-Swan T, Davis BJ. Mechanisms of phthalate ester toxicity in the female reproductive system. Environ Health Perspect 2003;111(2):139-145.
McKee RH, Butala JH, David RM, Gans G. NTP center for the evaluation of risks to human reproduction reports on phthalates: addressing the data gaps [review]. Reprod Toxicol 2004;18(1):1-22.
Milligan SR, Balasubramanian AV, Kalita JC. Relative potency of xenobiotic estrogens in an acute in vivo mammalian assay. Environ Health Perspect 1998;106(1):23-26.
Mortensen GK, Main KM, Andersson A-M, Leffers H, Skakkebaek NE. Determination of phthalate monoesters in human milk, consumer milk, and infant formula by tandem mass spectrometry (LC-MS-MS). Anal Bioanal Chem 2005;382:1084-1092.
Nielsen J, Akesson B, Skerfving S. Phthalate ester exposure—air levels and health of workers processing polyvinylchloride. Am Ind Hyg Assoc J 1985;46(11):643-647.
NTP-CERHR. National Toxicology Program-Health Assessment and Translation (formerly CERHR). Monograph on the Potential Human Reproductive and Developmental Effects of Butyl Benzyl Phthalate (BBP). Research Triangle Park (NC). 2003a [online]. Available at URL: https://ntp.niehs.nih.gov/ntp/ohat/phthalates/bb-phthalate/BBP_Monograph_Final.pdfpdf iconexternal icon. 6/21/13
NTP-CERHR. National Toxicology Program-Health Assessment and Translation (formerly CERHR). Monograph on the Potential Human Reproductive and Developmental Effects of Di-n-Butyl Phthalate (DBP). Research Triangle Park (NC). 2003b [online]. Available at URL: https://ntp.niehs.nih.gov/ntp/ohat/phthalates/dbp/DBP_Monograph_Final.pdfpdf iconexternal icon.6/21/13
NTP-CERHR. National Toxicology Program-Health Assessment and Translation (formerly CERHR). Monograph on the Potential Human Reproductive and Developmental Effects of Di(2-ethylhexyl) Phthalate (DEHP). Research Triangle Park (NC). 2006 [online]. Available at URL: https://ntp.niehs.nih.gov/ntp/ohat/phthalates/dehp/DEHP-Monograph.pdfpdf iconexternal icon. 6/21/13
Okubo T, Suzuki T, Yokoyama Y, Kano K, Kano I. Estimation of estrogenic and anti-estrogenic activities of some phthalate diesters and monoesters by MCF-7 cell proliferation assay in vitro. Biol Pharm Bull 2003;26(8):1219-24.
Pan G, Hanaoka T, Yoshimura M, Zhang S, Wang P, Tsukino H, et al. Decreased serum free testosterone in workers exposed to high levels of di-n-butyl phthalate (DBP) and di-2-ethylhexyl phthalate (DEHP): a cross-sectional study in China. Environ Health Perspect 2006;114(11):1643-1648.
Parks LG, Ostby JS, Lambright CR, Abbott BD, Klinefelter GR, Barlow NJ, et al. The plasticizer diethylhexyl phthalate induces malformations by decreasing fetal testosterone synthesis during sexual differentiation in the male rat. Toxicol Sci 2000;58:339-349.
Peck CC, Albro PW. Toxic potential of the plasticizer di (2-ethylhexyl) phthalate in the context of its disposition and metabolism in primates and man. Environ Health Perspect 1982;45:11-17.
Rhodes C, Orton TC, Pratt IA, Batten PL, Bratt H, Jackson SJ, et al. Comparative pharmacokinetics and subacute toxicity of di(2-ethylhexyl)phthalate (DEHP) in rats and marmosets: Extrapolation of effects in rodents to man. Environ Health Perspect 1986;65:299-308.
Rusyn I, Peters JM, Cunningham ML. Modes of action and species-specific effects of di-(2-ethylhexyl) phthalate in the liver. Crit Rev Toxicol 2006;36:459-479.
Silva MJ, Barr DB, Reidy JA, Malek NA, Hodge CC, Caudill SP, et al. Urinary levels of seven phthalate metabolites in the U.S. population from the National Health and Nutrition Examination Survey (NHANES) 1999-2000 [published erratum appears in Environ Health Perspect 2004; 112(5):A270]. Environ Health Perspect 2004;112(3):331-338.
Zacharewski TR, Meek MD, Clemons JH, Wu ZF, Fielden MR, Matthews JB. Examination of the in vitro and in vivo estrogenic activities of eight commercial phthalate esters. Toxicol Sci 1998;46:282-293.