Results of the L5178Y mouse lymphoma assay and the Balb/3t3 cell in vitro transformation assay for eight phthalate esters

Risk assessment of phthalates in pharmaceuticals

Phthalates are used for industrial plasticizers to impart flexibility and durability to polyvinyl chloride. Despite widespread use of phthalates, reported endocrine-disrupting properties raise safety concerns for consumers. Since phthalates are permitted as excipients in controlled-release capsules and enteric coatings, patients taking drugs containing these chemicals may potentially be at some health risk. In this study, 102 distinct pharmaceutical products were analyzed by gas chromatography/mass spectrometry to determine phthalate content and maximal phthalate exposure rate was calculated. In 102 drug samples, di(2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP), and diethyl phthalate (DEP) were detected in 9.8, 27.45, and 5.88% of cases, respectively. The highest level of DEP was found in extended-release (ER) capsules with concentrations ranging from 935.5 to 1535.37 ppb. The highest levels of DBP (1.32-7.07 ppb) were detected in tablets, whereas highest level (7.07 ppb) of DEHP was found in suspension preparations. The phthalate hazard index (HI) (human exposure tolerable daily intake) was calculated for each sample, but no sample exhibited an HI value exceeding 1; the minimum value taken to indicate a serious health risk. Thus, no apparent serious health risk from phthalate exposure arises from taking these medications. The low HI values suggest that phthalate contamination in pharmaceuticals may not pose an apparent significant risk to humans. However, the sources of phthalate present in pharmaceutical products still needs to be investigated and verified through on-site inspections in manufacturing processes in order to minimize human exposure. It is recommended that measures be taken to prevent phthalate contamination in pharmaceuticals.

Identification of potential biomarkers of exposure to diundecyl phthalate

Diundecyl phthalate (DUP) is a high production volume chemical used as a plasticizer in polyvinyl chloride and other plastics. Specific biomarkers of DUP would be useful for human exposure assessment. To identify such biomarkers, we investigated the in vitro metabolism of DUP with human liver microsomes using online solid phase extraction coupled to HPLC-mass spectrometry. Using high resolution mass spectrometry, we conclusively confirmed the structures of four DUP specific metabolites: monoundecyl phthalate (MUP), mono-hydroxyundecyl phthalate (MHUP), mono-oxoundecyl phthalate (MOUP), and mono-carboxydecyl phthalate (MCDP). We also used high resolution mass spectrometry to isolate MCDP and MHUP from co-eluting isobaric metabolites of diisononyl phthalate (i.e., monocarboxyisononyl phthalate) and diisododecyl phthalate (i.e., monohydroxyisododecyl phthalate), respectively, that could not be separated with low resolution tandem mass spectrometry. To evaluate the potential usefulness of the newly identified DUP metabolites as exposure biomarkers, we analyzed 36 human urine samples by high resolution mass spectrometry. We detected MHUP and MCDP in >83% of the samples; median concentrations were 0.21ng/mL and 0.36ng/mL, respectively. MOUP was detected only in 14% of the samples analyzed, and MUP was not detected. All three metabolites eluted as peak clusters likely because of the presence of multiple oxidation sites and multiple isomers in DUP technical mixtures. Taken together, these findings suggest that with the appropriate mass spectrometry quantification techniques, MHUP and MCDP may serve as suitable biomarkers for assessing background exposure to DUP.

In utero exposure to dicyclohexyl and di-n-hexyl phthalate possess genotoxic effects on testicular cells of male rats after birth in the comet and TUNEL assays

Phthalates are diester derivatives of phthalic acid widely used in many commercial applications. The aim of this study is therefore to evaluate possible genotoxicity of di- n-hexyl phthalate (DHP) and dicyclohexyl phthalate (DCHP) at different concentrations using single-cell gel electrophoresis (comet) and terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end-labeling (TUNEL) assays in testes samples of male rat pups. DCHP and DHP in corn oil were administered to the pregnant rats by gavage at the doses of 0 (vehicle), 20, 100, and 500 mg kg−1 day−1 from gestational day 6 (GD6) to GD19. After delivery, male rats were allowed to grow until prepubertal, pubertal, and adulthood. At necropsy, the blood samples were collected from heart and were excised immediately. The apoptotic cells of prepubertal, pubertal, and adult testis were detected using TUNEL assay. The comet assay was performed on blood lymphocytes and testes samples of adult male rats. The comet assay results showed that tail length, tail intensity, olive tail moment (OTM), and percentage of DNA present in tail were higher when DHP content was increased. Judging from the values of OTM and percentage of DNA, DHP could significantly induce DNA breakage at doses of 100 and 500 mg kg−1 day−1 compared with the control group. An increase in TUNEL-positive cells of prepubertal, pubertal, and adult testicular cells was observed in the treated groups. In conclusion, prenatal exposure to DHP and DCHP may possess genotoxic risk to testicular cells of rats at all stages of development, even at adulthood.

Integrating biomonitoring exposure data into the risk assessment process: phthalates [diethyl phthalate and di(2-ethylhexyl) phthalate] as a case study

The probability of nonoccupational exposure to phthalates is high given their use in a vast range of consumables, including personal care products (e.g., perfumes, lotions, cosmetics), paints, industrial plastics, and certain medical devices and pharmaceuticals. Phthalates are of high interest because of their potential for human exposure and because animal toxicity studies suggest that some phthalates affect male reproductive development apparently via inhibition of androgen biosynthesis. In humans, phthalates are rapidly metabolized to their monoesters, which can be further transformed to oxidative products, conjugated, and eliminated. Phthalate metabolites have been used as biomarkers of exposure. Using urinary phthalate metabolite concentrations allows accurate assessments of human exposure because these concentrations represent an integrative measure of exposure to phthalates from multiple sources and routes. However, the health significance of this exposure is unknown. To link biomarker measurements to exposure, internal dose, or health outcome, additional information (e.g., toxicokinetics, inter- and intraindividual differences) is needed. We present a case study using diethyl phthalate and di(2-ethylhexyl) phthalate as examples to illustrate scientific approaches and their limitations, identify data gaps, and outline research needs for using biomonitoring data in the context of human health risk assessment, with an emphasis on exposure and dose. Although the vast and growing literature on phthalates research could not be covered comprehensively in this article, we made every attempt to include the most relevant publications as of the end of 2005.

Risk assessment of oral exposure to diisononyl phthalate from children's products

Dialkyl phthalates are plasticizers used in household products made from polyvinyl chloride (PVC). Diisononyl phthalate (DINP) is the principal phthalate in soft plastic toys. Because DINP is not tightly bound to PVC, it may be released when children mouth PVC products. The potential chronic health risks of phthalate exposure to infants have been under scrutiny by regulatory agencies in Europe, Canada, Japan, and the U.S. This report describes a risk assessment of DINP exposure from children's products, by the U.S. Consumer Product Safety Commission (CPSC) staff. This report includes the findings of a CPSC Chronic Hazard Advisory Panel (CHAP) which: (1) concluded that DINP is unlikely to present a human cancer hazard and (2) recommended an acceptable daily intake (ADI) level of 120 microg/kg-d, based on spongiosis hepatis in rats. The risk assessment incorporates new measurements of DINP migration rates from 24 toys and a new observational study of children's mouthing activities, with a detailed characterization of the objects mouthed. Probabilistic methods were used to estimate exposure. Mouthing behavior and, thus, exposure depend on the child's age. Approximately 42% of tested soft plastic toys contained DINP. Estimated DINP exposures for soft plastic toys were greatest among children 12-23 months old. The mean exposure for this age group was 0.08 (95% confidence interval 0.04-0.14) microg/kg-d, with a 99th percentile of 2.4 (1.3-3.2) microg/kg-d. The authors conclude that oral exposure to DINP from mouthing soft plastic toys is not likely to present a health hazard to children. The opinions expressed by the authors have not been reviewed or approved by, and do not necessarily reflect the views of, the U.S. Consumer Product Safety Commission. Because this material was prepared by the authors in their official capacity, it is in the public domain and may be freely copied or reprinted.

Tumor induction in mouse liver: di-isononyl phthalate acts via peroxisome proliferation

Recently several chronic toxicity/carcinogenicity studies of di-isononyl phthalate (DINP) have been reported. These studies defined effect levels for liver tumors in male and female F344 rats at dietary levels exceeding 700 mg/kg/day; the no effect levels were 359 mg/kg/day in males and 442 mg/kg/day in females. Similar results were found in male B6C3F1 mice, but in female mice a significant increase in liver tumors was found at 336 mg/kg/day, making 112 mg/kg/day the NOAEL for liver tumors in that sex and species. DINP induces peroxisomal proliferation, and that, along with evidence that DINP is not mutagenic, is presumptive evidence for peroxisomal proliferation as the underlying mode of action for liver tumor development. To further explore the relationship between peroxisome proliferation and tumor induction in male and female mice, indicators of peroxisomal proliferation including liver weight, peroxisomal volume density, induction of peroxisomal enzyme activity, enhanced replicative DNA synthesis, and rates of apoptosis were measured at all of the dietary levels used in the chronic study in mice (500, 1500, 4000, and 8000 ppm, or approximately 100, 300, 800, and 1600 mg/kg/day). Liver weights, peroxisomal volume, and peroxisomal enzyme activity were significantly elevated in both male and female mice at the tumorigenic levels. Cell proliferation was also elevated in male and female mice, although the increases at levels below 4000 ppm in female mice were not significantly different from control values. Apoptosis was elevated at the 4000 and 8000 ppm levels, paralleling the increases in liver weight. These data along with previous results satisfy the criteria of the International Agency for Research on Cancer (IARC) and demonstrate that peroxisomal proliferation was indeed the mode of action for DINP-induced liver tumor induction in mice.

Absorption, disposition and metabolism of di-isononyl phthalate (DINP) in F-344 rats

Di-isononyl phthalate (DINP; CAS no. 68515-48-0) is a general-purpose plasticizer for polyvinyl chloride. It produced liver and kidney effects when given to rodents at high oral doses, but there were no target organ effects in primates treated under similar conditions. To assist in understanding the basis for these species differences, the pharmacokinetic properties of DINP were evaluated in rodents following both oral and dermal administration. These studies demonstrated that the pharmacokinetic properties of DINP are similar to those of other high-molecular-weight phthalates. When orally administered to rodents, DINP is rapidly metabolized in the gastrointestinal tract to the corresponding monoester, absorbed and excreted, primarily in the urine. Shortly after administration, DINP is found primarily in liver and kidneys, but it does not persist or accumulate in any organ or tissue. It is very poorly absorbed from the skin, but once absorbed it behaves in the same way as the orally administered material. The results of these rodent studies contrast with data from studies involving humans or other primates, which indicate low absorption at low oral doses and much more limited total absorption at high doses. It appears that many, if not all, of the effects of DINP in rodent studies are associated with internal doses that would be difficult, if not impossible, to achieve in humans under any circumstances. Thus, the results of rodent studies may not be very useful in assessing the potential risks to humans from high-molecular-weight phthalates.

Comparative effects of phthalate monoesters on gap junctional intercellular communication and peroxisome proliferation in rodent and primate hepatocytes

Several phthalate esters, compounds used as plasticizers in a variety of commercial products, have been shown to induce hepatic tumors in rodents. In this study, the comparative effects of phthalate monoesters on inhibition of gap junctional intercellular communication and induction of peroxisomal beta-oxidation were assessed in primary cultured hepatocytes from rats, mice, hamsters, cynomolgus monkeys, and humans. A human liver cell line was also utilized. Eight monoesters examined included mono-2-ethylhexyl phthalate (MEHP), mono-n-octyl phthalate (MNOP), mono-isononyl phthalate (MINP, 3 types, -1, -2, and -3), mono-isoheptyl phthalate (MIHP), mono-isodecyl phthalate (MIDP), and mono-(heptyl, nonyl, undecyl) phthalate (M711P). Gap junctional intercellular communication was measured 4 and 24 h after treatment by lucifer yellow dye coupling. Gap junctional intercellular communication was inhibited in rat and mouse hepatocytes by all eight monoesters in a concentration-dependent manner. In most cases, gap junctional intercellular communication was significantly reduced at the lowest concentrations tested (50 pM). Inhibition of gap junctional intercellular communication in rodent cells was substantially reversed within 24 h of monoester removal. In contrast, cell-to-cell communication was not inhibited in hamster, cynomolgus, or human hepatocytes or in a human liver cell line at any concentration examined. In rat hepatocytes, peroxisomal beta-oxidation was elevated after treatment with MEHP, MINP, MIHP, and MIDP but not MNOP or M711P, and with all but MIHP in mouse hepatocytes. The eight phthalates produced no marked change on peroxisomal beta-oxidation in hepatocytes from other species. These data provide additional evidence that the toxicological effects of phthalate esters are species specific.

Two-generation reproduction studies in Rats fed di-isodecyl phthalate

Di-isodecyl phthalate (DIDP) is a commercial plasticizer with low toxicity in many animal studies. The effects of dietary DIDP administration on fertility and developmental parameters were assessed in Sprague-Dawley rats utilizing two generation reproductive toxicity studies generally consistent with current regulatory guidelines. Dietary levels ranged from 0.02 to 0.8% (or approximately 15 to 600 mg/kg/day). In the reproductive studies, there were no effects on fertility, but there were decreases in adult body weight along with corresponding increases in liver and kidney weights and histopathologic changes indicative of peroxisomal proliferation. There were no effects on live birth index, but reduced offspring survival was observed at postnatal days 1 to 4. This reduced survival was more pronounced in the F2 generation in which statistical significance was achieved at levels of 0.2% DIDP and greater. There were also transient decreases in offspring body weights prior to weaning, corresponding to rapid offspring growth, and high levels of food consumption. There were no notable alterations in developmental landmarks. Overall, these studies provided experimentally defined No-Observed-Adverse-Effect Levels (NOAELs) of 0.06% (approximately 50 mg/kg/day) for F2 offspring survival and 0.8% (approximately 600 mg/kg/day) for fertility, other measures of reproductive function, and developmental landmarks. Statistical evaluation of the data from both studies identified 108 mg/kg/day with a 95% lower bound value of 86 mg/kg/day as a theoretical NOAEL for reduced F2 offspring survival.

Di(isononyl) phthalate (DINP) and di(isodecyl) phthalate (DIDP) are not mutagenic

Recently there have been reports of liver and kidney tumors in rodents following long-term exposure to di(isononyl) phthalate (DINP). Mechanistic studies suggested that the liver tumors were a consequence of peroxisomal proliferation, whereas the kidney tumors (found only in male rats) were associated with induction of alpha(2u)-globulin. Because both peroxisomal proliferation and alpha(2u)-globulin are considered to be non-genotoxic carcinogenic processes, it seemed appropriate to investigate the genotoxic potential of DINP. Additional studies were also conducted on di(isodecyl) phthalate (DIDP), a structurally related substance that also induces peroxisomal proliferation, although it has not been tested in a carcinogenicity bioassay. The DINP was tested in Salmonella, in vitro cytogenetics and mouse micronucleus assays, whereas DIDP was evaluated in a mouse micronucleus test. All of these tests produced negative results, i.e. neither phthalate was mutagenic in any of the test systems. These data are consistent with results of other published and unpublished genotoxicity tests and provide support for the hypothesis that the liver and kidney tumors induced by DINP were the result of non-genotoxic processes.

The role of inhibition of gap junctional intercellular communication in rodent liver tumor induction by phthalates: review of data on selected phthalates and the potential relevance to man

Inhibition of gap junctional intercellular communication (GJIC) has been postulated as a nongenotoxic carcinogenic mechanism, probably related to tumor promotion. Recent studies assessed the role of GJIC in the induction of rodent liver tumors by high levels of phthalate esters. Studies with di(2-ethylhexyl) (DEHP) and diisononyl (DINP) phthalates demonstrated that inhibition of GJIC in rats and mice was well correlated with induction of both liver tumors and markers for peroxisomal proliferation. However, GJIC was unaffected in hamsters and primates, species in which phthalate treatment does not induce peroxisomal proliferation. In vitro studies which extended the database to include human liver cells mirrored the in vivo situation; GJIC was inhibited in rat and mouse cells but not in cells from unresponsive species including humans. Peroxisomal proliferation has been characterized as a species-specific process essential for phthalate-induced rodent liver tumor induction. That GJIC was not inhibited in primate liver or human liver cells provides evidence for a second species-specific carcinogenic process. Thus the GJIC data along with those from studies of peroxisomal proliferation support the view that the carcinogenic effects of DEHP and DINP in rodents are not relevant to humans.

Two-generation reproduction study in rats given di-isononyl phthalate in the diet

The potential reproductive toxicity of di-isononyl phthalate (DINP: CAS RN 68515-48-0) was assessed in one- and two-generation reproductive toxicity studies. Groups of 30 male and female CRL : CD(SD)BR rats were given DINP via dietary administration at levels of either 0.0, 0.5, 1, or 1.5% (one-generation study) or 0.0, 0.2, 0. 4, or 0.8% (two-generation study). There were no changes in any of the classic reproductive parameters, i.e. mating, male or female fertility, fecundity, gestational index, or length of gestation in either study. The overall NOAELs for these effects were the highest Dietary Level (%)s tested, approximately 500 mg/kg/day in the two-generation study and 1000 mg/kg/day in the one-generation study. There were no testicular effects in parental animals exposed as juveniles and young adults at 960 mg/kg/day in the one-generation study. In the two-generation study, there were no testicular effects in either the P(1) males, exposed as juveniles and young adults or the P(2) (F(1)) offspring exposed in utero, through lactation, and continuously to terminal sacrifice. The NOAEL was 470 mg/kg/day. Offspring survival was reduced at the 1.5% level ( approximately 1100 mg/kg/day) but unaffected at the 1% level ( approximately 760 mg/kg/day). There were decreased offspring body weights both at postnatal day (PND) 0 and during lactation; however, the PND 0 effects were only clearly related to treatment at the 1.5% level. Weights of offspring during lactation were significantly reduced but within the historical control range at Dietary Level (%)s below 1%. As there was rapid recovery at the lower levels, even though treatment continued, the toxicologic significance is unclear. Adult survival was unaffected at any level in either study, but weight gain was significantly reduced at the 1% level ( approximately 600 mg/kg/day). Liver and kidney weights were elevated at Dietary Level (%)s above approximately 110 mg/kg/day, consistent with evidence from other studies of peroxisomal proliferation at these levels. This study showed that DINP treatment does not affect fertility or male reproductive development at doses of up to approximately 1000 mg/kg/day.