Czech J. Food Sci. Vol. 23, No. 6: 217–223 Phthalates: Toxicology and Food Safety – a Review PŘEMYSL MIKULA1, ZDEŇKA SVOBODOVÁ1 and MIRIAM SMUTNÁ2 1Department of Veterinary Public Health and Toxicology and 2Department of Biochemistry and Biophysics, Faculty of Veterinary Hygiene and Ecology, University of Veterinary and Pharmaceutical Sciences, Brno, Czech Republic Abstract MIKULA P., SVOBODOVÁ Z., SMUTNÁ M. (2005): Phthalates: toxicology and food safety – a review. Czech J. Food Sci., 23: 217–223. Phthalates are organic substances used mainly as plasticisers in the manufacture of plastics. They are ubiquitous in the environment. Although tests in rodents have demonstrated numerous negative effects of phthalates, it is still unclear whether the exposure to phthalates may also damage human health. This paper describes phthalate toxicity and toxicokinetics, explains the mechanisms of phthalate action, and outlines the issues relating to the presence of phthalates in foods. Keywords: di(2-ethylhexyl)phthalate; dibutyl phthalate; peroxisome proliferators; reproductive toxicity Phthalic acid esters, often also called phtha- air, soil, food, etc.). People as well as animals lates, are organic substances frequently used can be exposed to these compounds through in many industries. They are usually colourless ingestion, inhalation or dermal exposure, and or slightly yellowish oily and odourless liquids iatrogenic exposure to phthalates from blood only very slightly soluble in water. Phthalates are bags, injection syringes, intravenous canyllas much more readily soluble in organic solvents, and catheters, and from plastic parts of dialysers and the longer their side chain, the higher their is also a possibility (VELÍŠEK 1999; ČERNÁ 2000; liposolubility and the boiling point. Phthalates LOVEKAMP-SWAN & DAVIS 2003). HAUSER et al. have a broad variety of uses. They are used as the (2004) described abnormally high concentrations so-called plasticisers, i.e. substances that improve of monobutyl phthalate (MBP) in urine of a pa- mechanical properties of plastic materials, mainly tient treated for ulcerative colitis. As part of his PVC. They are also used in the manufacture of therapy, the patient received Asacol tablets for floorings, children’s toys, and are added to printing three months. The tablets with controlled release inks and to perfumes and nail varnishes. Such a were coated with a polymethacrylate film, which broad range of applications in the industry brings was the probable source of phthalates. about the problem of an extensive phthalates – caused contamination of the environment where Toxicity they are nowadays ubiquitous. This is because phthalates are not chemically bound in plastics Acute toxicity of phthalates is very low. Low in any way, and they are relatively easily released molecular phthalates, e.g. diethyl phthalate (DEP), from them to the external environment (water, may cause irritation of the skin, conjunctiva, and Supported by the Ministry of Education, Youth and Sports of the Czech Republic, Project MSM 6215712402. 217 Vol. 23, No. 6: 217–223 Czech J. Food Sci. the mucous membrane of the oral and nasal cavities yet. The authors reported hepatocyte proliferation, in animals. However, similar reactions are not as increased liver weight, and subsequent appear- a rule encountered in humans (API 2001; GÓMEZ- ance of liver tumours in both sexes of rats and HENS & AGUILAR-CABALLOS 2003). mice exposed to high doses of DEHP in food, i.e. Much more important are subchronic and chronic at least 2500 mg/kg of food. toxic effects of phthalates. Most important, numer- ous experiments in rodents have shown adverse Toxicokinetics effects of phthalates on the reproductive system and on the intrauterine development of foetuses. In the case of human exposure to phthalates, EMA et al. (1995, 1996) monitored the effects of phthalate diesters are relatively rapidly hydrolysed monobenzyl phthalate (MBzP) and monobutyl to their respective monoesters in the intestine by phthalate (MBP) administered to female rats dur- pancreatic or liver hydrolases (the first stage of ing pregnancy. It follows from their studies that the phthalate biotransformation). The monoesters exposure to phthalates at doses of about 500 mg/kg thus produced are bioactive molecules responsible during pregnancy may cause in female rats an for the adverse effects of phthalates. Monoesters increase in the number of foetus resorptions and are absorbed in the blood stream and then me- dead foetuses, lower weights of the offspring at tabolised in liver. They are subject in a varying birth and, last but not least, foetus malforma- degree to hydroxylation and oxidation reactions tions, e.g. cleft palate, atresia ani, and skeletal that enhance water solubility of the products. deformations. Phthalate monoesters with a short side chain are Female rats exposed to di(2-ethylhexyl) phtha- oxidised to a lesser extent. The second stage of late (DEHP) at a dose of 2000 mg/kg also dem- phthalate biotransformation is conjugation with onstrated a prolongation in their estrous cycles glucuronic acid mediated by the enzyme UDP-glu- and anovulation as a result of a decrease in serum curonyl transferase. The conjugation affects mainly estradiol levels. The anovulation was related to the monoesters and their oxidised metabolites with a absence of the corpus luteum in the ovary and the long side chain because the conjugation facilitates occurrence of follicular cysts (LOVEKAMP-SWAN the excretion of relatively lipophilic metabolites. & DAVIS 2003). Both the conjugated and the free (non-conjugated) Testicular lesions, hypospadia, cryptorchidism phthalate metabolites are excreted in urine and and other disorders in sexual organs of male rats partly also faeces (SILVA et al. 2003; KATO et al. were also found, which testify to antiandrogenic 2004). effects of some phthalates, particularly of dibutyl Diethyl phthalate (DEP) deviates in some respects phthalate (DBP) and di(2-ethylhexyl) phthalate from the above pattern. On the basis of their meas- (DEHP) (MOORE et al. 2001). Although there are urements, SILVA et al. (2003) assumed that DEP no doubts about adverse effects of phthalates on was absorbed unchanged from the intestine and the reproduction and development in rodents, the was hydrolysed to monoethyl phthalate (MEP) in effects of phthalates on humans have not been kidneys. Because MEP is relatively readily soluble satisfactorily clarified to date. The main reason is in water, it need not be transported to liver for that only very few studies of the effects of phtha- conjugation and is excreted in urine mainly in the lates on humans are available. COLÓN et al. (2000) non-conjugate form. monitored levels of certain phthalates in the blood A mechanism similar to that described in the serum of young Puerto Rican girls aged 6 months human takes place during phthalate metabolism to 8 years with a premature breast development in rodents. A relatively large number of metabo- (thelarche). The authors demonstrated significantly lite types have been reported in urine of rats ex- higher phthalate levels in 68% of patients, which posed to butyl benzyl phthalate (BBP), including suggests possible negative effects of phthalates on phthalic acid, hippuric acid, and trace amounts the human reproduction and development. of benzoic acid. Hippuric acid is a conjugate of Other negative effects of the exposure to phtha- toxic benzoic acid and glycine (NATIVELLE et al. lates may have in rodents are hepatotoxicity and 1999). The conjugation of phthalate metabolites carcinogenicity (DAVID et al. 1999; ELCOMBE et with glucuronic acid takes place in mice only, it al. 2002). These effects have not, however, been practically does not occur at all in rats (ALBRO described in other animal species or the human 1986; NATIVELLE et al. 1999). 218 Czech J. Food Sci. Vol. 23, No. 6: 217–223 Mode of action an increased activity of enzymes participating in the breakdown of estradiol in the liver of fe- Some phthalic acid esters are well-known peroxi- males exposed to DEHP and DBP was confirmed some proliferators (PPs). A very potent peroxisome (LOVEKAMP-SWAN & DAVIS 2003). LOVEKAMP- proliferator is di(2-ethylhexyl) phthalate (DEHP), SWAN and DAVIS (2003) also assumed that the while dibutyl phthalate, butyl benzyl phthalate, female reproductive system may be damaged as and diisononyl phthalate (DBP, BBP, DINP) are a result of processes related to the peroxisome somewhat less effective (VALLES et al. 2003; SEO proliferation mediated not only through PPARα et al. 2004). It should be stressed that adverse ef- but also through PPARγ. fects of diester phthalates are attributable to their The mode of action of the toxic effects of phtha- monoesters produced when diesters are hydrolysed lates to the male reproductive system has not yet in the gastrointestinal tract (HURST & WAXMAN been satisfactorily explained. An impairment of 2003; SILVA et al. 2003). Peroxisome proliferators testosterone metabolism in testes of adolescent are bound by PPARα - PPARδ, i.e. peroxisome pro- male rats has been observed, which is probably due liferator-activated receptors, which they activate to a number of factors. KIM et al. (2004) reported (MELNICK 2001). that testicular impairment and tubular atrophy A role in the process of hepatotoxicity and car- were especially aggravated by hormone regulation cinogenesis is played by subtype PPARα. The ac- disturbances that cause a decrease in the produc- tivated PPARα and the retinoid X receptor (RXR) tion