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

Biologically relevant reductions in fetal testosterone and Insl3 induced by in utero exposure to high levels of di-isononyl phthalate (DINP) in male rats

Some phthalate esters alter male rat reproductive development during sexual differentiation by interfering with fetal testis maturation resulting in reduced Leydig Cell synthesis of testosterone and insulin-like 3 (Insl3) hormones. Gene transcripts associated with steroid hormone and cholesterol transport, and cholesterol synthesis and lipid metabolism also are reduced. These alterations cause permanent malformations of hormone-dependent tissues, sperm production and fertility in male offspring; effects known as the "Phthalate Syndrome." We have shown that administration of a high dose of 750 mg diisononyl phthalate (750 mg/kg/d DINP) during sex differentiation reduced fetal testis testosterone production (T Prod), testis gene expression and induced a low incidence of reproductive malformations in male rat offspring. In the current study we administered DINP at even higher dose levels (1.0 and 1.5 g/kg/d) from gestational day (GD) 14 to postnatal (PND) 3 to determine if these effects were dose related and if the magnitude of the effects could be predicted from a statistical model of fetal testosterone production (T Prod) and Insl3 mRNA levels. These models were previously developed using dipentyl phthalate (DPeP) data from fetal T Prod and postnatal studies. We found that the severity of the demasculinizing effects on the androgen-dependent organs and gubernaculum by DINP were accurately predicted from the statistical models of fetal T prod and Insl3 mRNA, respectively. Taken together, our results indicate that reductions fetal T prod and Insl3 predict the severity of demasculinizing effects in utero exposure to the phthalates DINP and DPeP regardless of potency.

Phthalates and Alternative Plasticizers Differentially affect Phenotypic Parameters in Gonadal Somatic and Germ Cell Lines

The developmental and reproductive toxicity associated with exposure to phthalates has motivated a search for alternatives. However, there is limited knowledge regarding the adverse effects of some of these chemicals. We used high-content imaging to compare the effects of mono (2-ethylhexyl) phthalate (MEHP) with six alternative plasticizers: di-2-ethylhexyl terephthalate (DEHTP); diisononyl-phthalate (DINP); di-isononylcyclohexane-1,2-dicarboxylate (DINCH); 2-ethylhexyl adipate (DEHA); 2,2,4-trimethyl 1,3-pentanediol diisobutyrate (TXIB) and di-iso-decyl-adipate (DIDA). A male germ spermatogonial cell line (C18-4), a Sertoli cell line (TM4) and two steroidogenic cell lines (MA-10 Leydig and KGN granulosa) were exposed for 48h to each chemical (0.001-100 μM). Cell images were analyzed to assess cytotoxicity and effects on phenotypic endpoints. Only MEHP (100 μM) was cytotoxic and only in C18-4 cells. However, several plasticizers had distinct phenotypic effects in all four cell lines. DINP increased Calcein intensity in C18-4 cells, whereas DIDA induced oxidative stress. In TM4 cells, MEHP, and DINCH affected lipid droplet numbers, while DEHTP and DINCH increased oxidative stress. In MA-10 cells, MEHP increased lipid droplet areas and oxidative stress; DINP decreased the number of lysosomes, while DINP, DEHA and DIDA altered mitochondrial activity. In KGN cells, MEHP, DINP and DINCH increased the number of lipid droplets, whereas DINP decreased the number of lysosomes, increased oxidative stress and affected mitochondria. The Toxicological Priority Index (ToxPi) provided a visual illustration of the cell line specificity of the effects on phenotypic parameters. The lowest administered equivalent doses were observed for MEHP. We propose that this approach may assist in screening alternative plasticizers.

The Impact of Di-Isononyl Phthalate Exposure on Specialized Epithelial Cells in the Colon

Di-isononyl phthalate (DiNP) is a high-molecular-weight phthalate commonly used as a plasticizer for polyvinyl chloride and other end products, such as medical devices and construction materials. Most of our initial exposure to DiNP occurs by ingestion of DiNP-contaminated foods. However, little is known about the effects of DiNP on the colon. Therefore, the goal of this study was to test the hypothesis that DiNP exposure alters immune responses and impacts specialized epithelial cells in the colon. To test this hypothesis, adult female mice were orally dosed with corn-oil vehicle control or doses of DiNP ranging from 20 µg/kg/d to 200 mg/kg/d for 10-14 days. After the dosing period, mice were euthanized in diestrus, and colon tissues and sera were collected for histological, genomic, and proteomic analysis of various immune factors and specialized epithelial cells. Subacute exposure to DiNP significantly increased protein levels of Ki67 and MUC2, expression of a Paneth cell marker (Lyz1), and estradiol levels in sera compared with control. Gene expression of mucins (Muc1, Muc2, Muc3a, and Muc4), Toll-like receptors (Tlr4 and Tlr5), and specialized epithelial cells (ChgA, Lgr5, Cd24a, and Vil1) were not significantly different between treatment groups and control. Cytokine levels of IL-1RA and CXCL12 were also not significantly different between DiNP treatment groups and control. These data reveal that DiNP exposure increases circulating estradiol levels and gene expression in specialized epithelial cells with immune response capabilities (eg, goblet and Paneth cells) in the mouse colon, which may initiate immune responses to prevent further damage in the colon.

Subacute exposure to di-isononyl phthalate alters the morphology, endocrine function, and immune system in the colon of adult female mice

Di-isononyl phthalate (DiNP), a common plasticizer used in polyvinyl chloride products, exhibits endocrine-disrupting capabilities. It is also toxic to the brain, reproductive system, liver, and kidney. However, little is known about how DiNP impacts the gastrointestinal tract (GIT). It is crucial to understand how DiNP exposure affects the GIT because humans are primarily exposed to DiNP through the GIT. Thus, this study tested the hypothesis that subacute exposure to DiNP dysregulates cellular, endocrine, and immunological aspects in the colon of adult female mice. To test this hypothesis, adult female mice were dosed with vehicle control or DiNP doses ranging from 0.02 to 200 mg/kg for 10–14 days. After the treatment period, mice were euthanized during diestrus, and colon tissue samples were subjected to morphological, biochemical, and hormone assays. DiNP exposure significantly increased histological damage in the colon compared to control. Exposure to DiNP also significantly decreased sICAM-1 levels, increased Tnf expression, decreased a cell cycle regulator (Ccnb1), and increased apoptotic factors (Aifm1 and Bcl2l10) in the colon compared to control. Colon-extracted lipids revealed that DiNP exposure significantly decreased estradiol levels compared to control. Collectively, these data indicate that subacute exposure to DiNP alters colon morphology and physiology in adult female mice.

The effects of the phthalate DiNP on reproduction†

Di-isononyl phthalate (DiNP) is a high molecular weight, general purpose, plasticizer used primarily in the manufacture of polymers and consumer products. It can be metabolized rapidly and does not bioaccumulate. The primary metabolite of DiNP is monoisononyl-phthalate (MiNP) and the secondary metabolites include three oxidative derivatives of DiNP, which have been identified mainly in urine: mono-oxoisononyl phthalate (MOINP or oxo-MiNP), mono-carboxyisooctyl phthalate (MCIOP, MCOP or cx-MiNP), and mono-hydroxyisononyl phthalate (MHINP or OH-MiNP). The secondary metabolites are very sensitive biomarkers of DiNP exposure while primary metabolites are not. As the usage of DiNP worldwide increases, studies evaluating its potential reproductive toxicity are becoming more prevalent in the literature. In studies on female animals, the researchers found that the exposure to DiNP appears to induce negative effects on ovarian function and fertility in animal models. Whether or not DiNP has direct effects on the uterus is still controversial, and the effects on human reproduction require much more research. Studies on males indicate that DiNP exposure has disruptive effects on male reproduction and fertility. Occupational studies also indicate that the exposure to DiNP might induce negative effects on male reproduction, but larger cohort studies are needed to confirm this. This review presents an overview of the literature regarding the reproductive effects of exposure to DiNP.

Grouping of phthalates for risk characterization of human exposures

The European Food Safety Authority (EFSA) has developed a group tolerable daily intake (TDI) for low molecular weight phthalates (LWP) including diisononyl phthalate (DINP). The LWP covered by the group TDI induce clear adverse effects on rat testicular development and pronounced reductions in fetal testicular testosterone. In contrast, DINP has a very low potency regarding changes in testicular testosterone in fetal rodents and does not induce adverse effects on reproductive endpoints. The most sensitive toxicity endpoint for DINP is liver toxicity. Due to the much lower potency of DINP for effects on testosterone, absence of reproductive toxicity, and its noted liver toxicity as compared to the LWP in the group, DINP should not be included in the group TDI.

Subchronic Exposure to Di(2-ethylhexyl) Phthalate and Diisononyl Phthalate During Adulthood Has Immediate and Long-Term Reproductive Consequences in Female Mice

Di(2-ethylhexyl) phthalate (DEHP) is a plasticizer used in a variety of consumer products. This is concerning because DEHP is an endocrine disruptor and ovarian toxicant. Diisononyl phthalate (DiNP) is a DEHP replacement that is a rising human toxicant due to its increased use as a DEHP substitute. However, little is known about the effects of DEHP or DiNP exposure during adulthood on female reproduction. Thus, this study tested the hypothesis that DEHP or DiNP exposure during adulthood has long-term consequences for female reproduction in mice. Adult female CD-1 mice (39-40 days) were orally dosed with vehicle control (corn oil), DEHP (20 µg/kg/day-200 mg/kg/day), or DiNP (20 µg/kg/day-200 mg/kg/day) for 10 days. Females were paired with untreated male mice for breeding trials immediately post-dosing and again at 3 and 9 months post-dosing. Immediately post-dosing, DEHP and DiNP did not affect fertility. At 3 months post-dosing, DiNP (20 and 100 µg/kg/day and 200 mg/kg/day) significantly disrupted estrous cyclicity, and DiNP and DEHP (20 µg/kg/day) significantly reduced the ability of females to get pregnant. At 9 months post-dosing, DiNP significantly disrupted estrous cyclicity (100 µg/kg/day), reduced time to mating (100 µg/kg/day-200 mg/kg/day), and borderline reduced percent of females who produced offspring (20 mg/kg/day). At 9 months post-dosing, DEHP (200 µg/kg/day and 200 mg/kg/day) and DiNP (100 µg/kg/day and 20 and 200 mg/kg/day) increased numbers of male-biased litters. These data show that DEHP and DiNP exposure has long-term consequences for female reproduction, even long after cessation of exposure.

Update of the risk assessment of di-butylphthalate (DBP), butyl-benzyl-phthalate (BBP), bis(2-ethylhexyl)phthalate (DEHP), di-isononylphthalate (DINP) and di-isodecylphthalate (DIDP) for use in food contact materials

The EFSA Panel on Food Contact Materials, Enzymes and Processing Aids (CEP Panel) was asked by the European Commission to update its 2005 risk assessments of di‐butylphthalate (DBP), butyl‐benzyl‐phthalate (BBP), bis(2‐ethylhexyl)phthalate (DEHP), di‐isononylphthalate (DINP) and di‐isodecylphthalate (DIDP), which are authorised for use in plastic food contact material (FCM). Dietary exposure estimates (mean and high (P95)) were obtained by combining literature occurrence data with consumption data from the EFSA Comprehensive Database. The highest exposure was found for DINP, ranging from 0.2 to 4.3 and from 0.4 to 7.0 μg/kg body weight (bw) per day for mean and high consumers, respectively. There was not enough information to draw conclusions on how much migration from plastic FCM contributes to dietary exposure to phthalates. The review of the toxicological data focused mainly on reproductive effects. The CEP Panel derived the same critical effects and individual tolerable daily intakes (TDIs) (mg/kg bw per day) as in 2005 for all the phthalates, i.e. reproductive effects for DBP (0.01), BBP (0.5), DEHP (0.05), and liver effects for DINP and DIDP (0.15 each). Based on a plausible common mechanism (i.e. reduction in fetal testosterone) underlying the reproductive effects of DEHP, DBP and BBP, the Panel considered it appropriate to establish a group‐TDI for these phthalates, taking DEHP as index compound as a basis for introducing relative potency factors. The Panel noted that DINP also affected fetal testosterone levels at doses around threefold higher than liver effects and therefore considered it conservative to include it within the group‐TDI which was established to be 50 μg/kg bw per day, expressed as DEHP equivalents. The aggregated dietary exposure for DBP, BBP, DEHP and DINP was estimated to be 0.9–7.2 and 1.6–11.7 μg/kg bw per day for mean and high consumers, respectively, thus contributing up to 23% of the group‐TDI in the worst‐case scenario. For DIDP, not included in the group‐TDI, dietary exposure was estimated to be always below 0.1 μg/kg bw per day and therefore far below the TDI of 150 μg/kg bw per day. This assessment covers European consumers of any age, including the most sensitive groups. Based on the limited scope of the mandate and the uncertainties identified, the Panel considered that the current assessment of the five phthalates, individually and collectively, should be on a temporary basis.

This publication is linked to the following EFSA Supporting Publications article: http://onlinelibrary.wiley.com/doi/10.2903/sp.efsa.2019.EN-1747/full

Perinatal exposures to phthalates and phthalate mixtures result in sex-specific effects on body weight, organ weights and intracisternal A-particle (IAP) DNA methylation in weanling mice

Developmental exposure to phthalates has been implicated as a risk for obesity; however, epidemiological studies have yielded conflicting results and mechanisms are poorly understood. An additional layer of complexity in epidemiological studies is that humans are exposed to mixtures of many different phthalates. Here, we utilize an established mouse model of perinatal exposure to investigate the effects of three phthalates, diethylhexyl phthalate (DEHP), diisononyl phthalate (DINP) and dibutyl phthalate (DBP), on body weight and organ weights in weanling mice. In addition to individual phthalate exposures, we employed two mixture exposures: DEHP+DINP and DEHP+DINP+DBP. Phthalates were administered through phytoestrogen-free chow at the following exposure levels: 25 mg DEHP/kg chow, 25 mg DBP/kg chow and 75 mg DINP/kg chow. The viable yellow agouti (A vy ) mouse strain, along with measurement of tail DNA methylation, was used as a biosensor to examine effects of phthalates and phthalate mixtures on the DNA methylome. We found that female and male mice perinatally exposed to DINP alone had increased body weights at postnatal day 21 (PND21), and that exposure to mixtures did not exaggerate these effects. Females exposed to DINP and DEHP+DINP had increased relative liver weights at PND21, and females exposed to a mixture of DEHP+DINP+DBP had increased relative gonadal fat weight. Phthalate-exposed A vy /a offspring exhibited altered coat color distributions and altered DNA methylation at intracisternal A-particles (IAPs), repetitive elements in the mouse genome. These findings provide evidence that developmental exposures to phthalates influence body weight and organ weight changes in early life, and are associated with altered DNA methylation at IAPs.

Low-Level Prenatal Toxin Exposures and Breastfeeding Duration: A Prospective Cohort Study

Introduction Maternal exposure to tobacco smoke is associated with shortened breastfeeding duration, but few studies have examined the effects on breastfeeding outcomes of low level exposures to other toxic chemicals. Moreover, it is unclear if passive smoking is associated with duration of breastfeeding. Our objective was therefore to examine the effect of low-level prenatal exposures to common environmental toxins (tobacco smoke, lead, and phthalates) on breastfeeding exclusivity and duration. Methods We conducted an analysis of data from the Health Outcomes and Measures of the Environment (HOME) Study. Serum and urine samples were collected at approximately 16 and 26 weeks gestation and at delivery from 373 women; 302 breastfed their infants. Maternal infant feeding interviews were conducted a maximum of eight times through 30 months postpartum. The main predictor variables for this study were gestational exposures to tobacco smoke (measured by serum cotinine), lead, and phthalates. Passive smoke exposure was defined as cotinine levels of 0.015-3.0 μg/mL. Primary outcomes were duration of any and exclusive breastfeeding. Results Serum cotinine concentrations were negatively associated with the duration of any breastfeeding (29.9 weeks unexposed vs. 24.9 weeks with passive exposure, p = 0.04; and 22.4 weeks with active exposure, p = 0.12; p = 0.03 for linear trend), but not duration of exclusive breastfeeding. Prenatal levels of blood lead and urinary phthalate metabolites were not significantly associated with duration of any or exclusive breastfeeding. Conclusions Passive exposure to tobacco smoke during pregnancy was associated with shortened duration of any breastfeeding.

The effects of phthalates in the cardiovascular and reproductive systems: A review

Every year millions of tons of plastic are produced around the world and humans are increasingly exposed to them. This constant exposure to plastics has raised some concerns against human health, particularly when it comes to phthalates. These compounds have endocrine-disrupting properties, as they have the ability to bind molecular targets in the body and interfere with hormonal function and quantity. The main use of phthalates is to give flexibility to polyvinyl chloride (PVC) polymers. Phthalates are found in a variety of industrial and consumer products, and as they are not covalently bound to the plastic, phthalates contaminate the environment from which human exposure occurs. Studies in human and animal populations suggest a correlation between phthalate exposure and adverse health outcomes, particularly at the reproductive and cardiovascular systems, however there is much less information about the phthalate toxicity of the later. Thus, the main purpose of this review is to present the studies relating the effects already stated of phthalates on the cardiovascular and reproductive systems, and also present the link between these two systems.

Comparison of the short term toxicity of phthalate diesters and monoesters in sprague-dawley male rats

This study was carried out to investigate the short term toxicity of nine phthalate diesters including di-2 (ethylhexyl) phthalate (DEHP) , di (n-butyl) phthalate (DBP) , di-n-octyl phthalate (DnOP) , diethyl phthalate (DEP) , butylbenzyl phthalate (BBP) , dimethyl phthalate (DMP) , di-isodecyl phthalate (DIDP) , diundecyl phthalate (DUP) , and di-isononyl phthalate (DINP) and five phthalate monoesters including mono- (2-ethylhexyl) phthalate (MEHP) , monobutyl phthalate (MBuP) , monobenzyl phthalate (MBeP) , monoethyl phthalate (MEP) , monomethyl phthalate (MMP) and phthalic acid (PA) in Sprague-Dawley male rats. Animals were administered 250 mg/kg/day (monoesters and PA) or 500 mg/kg/day (diesters) of phthalate for two weeks. All animals were examined for body and organ weights, blood hematology, serum biochemistry, and urine analysis. The body weight gain was significantly lower in rats treated with BBP, DBP, DINP, MEHP, MBuP, and PA than that of control. Liver weights were significantly increased in the DEHP,DBP, DnOP, DIDP, and MEHP groups as compared to the control group. Testes weights were significantly decreased only in the DEHP-, DnOP-, and DIDP-treated groups as compared to the control. Significant differences in hematological changes were not observed in any treatment groups. Significant increases in blood glucose levels were observed in the DEHP, MEHP, and MBeP groups. Aspartate aminotransferase (AST) levels were significantly increased in the DBP, DUP, DINP, MBuP, and MBeP groups, whereas alanine aminotransferase (ALT) levels were significantly increased only in the DEHP and MEHP groups. Serum ALP levels were significantly higher in phthalate diester (500 mg/kg/day) -treated rats as compared to control. However, the total cholesterol level was significantly reduced in the DEHP- and DIDP-treated groups, whereas serum triglyceride (TG) levels were higher in the DINP-, MEHP-, and MBuP-treated groups. These results suggest that short term toxicity of phthalate monoesters produces adverse effects as similar to phthalate diesters in Sprague-Dawley rats.

Reproductive and developmental effects of phthalate diesters in females

Phthalate diesters, widely used in flexible plastics and consumer products, have become prevalent contaminants in the environment. Human exposure is ubiquitous and higher phthalate metabolite concentrations documented in patients using medications with phthalate-containing slow release capsules raises concerns for potential health effects. Furthermore, animal studies suggest that phthalate exposure can modulate circulating hormone concentrations and thus may be able to adversely affect reproductive physiology and the development of estrogen sensitive target tissues. Therefore, we conducted a systematic review of the epidemiological and experimental animal literature examining the relationship between phthalate exposure and adverse female reproductive health outcomes. The epidemiological literature is sparse for most outcomes studied and plagued by small sample size, methodological weaknesses, and thus fails to support a conclusion of an adverse effect of phthalate exposure. Despite a paucity of experimental animal studies for several phthalates, we conclude that there is sufficient evidence to suggest that phthalates are reproductive toxicants. However, we note that the concentrations needed to induce adverse health effects are high compared to the concentrations measured in contemporary human biomonitoring studies. We propose that the current patchwork of studies, potential for additive effects and evidence of adverse effects of phthalate exposure in subsequent generations and at lower concentrations than in the parental generation support the need for further study.

Occupational exposure to diisononyl phthalate (DiNP) in polyvinyl chloride processing operations

PURPOSE

Diisononyl phthalate (DiNP) is primarily used as a plasticizer in polyvinyl chloride (PVC) materials. While information is available on general population exposure to DiNP, occupational exposure data are lacking. We present DiNP metabolite urinary concentrations in PVC processing workers, estimate DiNP daily intake for these workers, and compare worker estimates to other populations.

METHODS

We assessed DiNP exposure in participants from two companies that manufactured PVC materials, a PVC film manufacturer (n = 25) and a PVC custom compounder (n = 12). A mid-shift and end-shift urine sample was collected from each participant and analyzed for the DiNP metabolite mono(carboxy-isooctyl) phthalate (MCiOP). Mixed models were used to assess the effect on MCiOP concentrations of a worker being assigned to (1) a task using DiNP and (2) a shift where DiNP was used. A simple pharmacokinetic model was used to estimate DiNP daily intake from the MCiOP concentrations.

RESULTS

Creatinine-adjusted MCiOP urinary concentrations ranged from 0.42-80 μg/g in PVC film and from 1.11-13.4 μg/g in PVC compounding. PVC film participants who worked on a task using DiNP (n = 7) had the highest MCiOP geometric mean (GM) end-shift concentration (25.2 μg/g), followed by participants who worked on a shift where DiNP was used (n = 11) (17.7 μg/g) as compared to participants with no task (2.92 μg/g) or shift (2.08 μg/g) exposure to DiNP. The GM end-shift MCiOP concentration in PVC compounding participants (4.80 μg/g) was comparable to PVC film participants with no task or shift exposure to DiNP. Because no PVC compounding participants were assigned to tasks using DINP on the day sampled, DiNP exposure in this company may be underestimated. The highest DiNP intake estimate was 26 μg/kg/day.

CONCLUSION

Occupational exposure to DiNP associated with PVC film manufacturing tasks were substantially higher (sixfold to tenfold) than adult general population exposures; however, all daily intake estimates were less than 25% of current United States or European acceptable or tolerable daily intake estimates. Further characterization of DiNP occupational exposures in other industries is recommended.

Selecting adequate exposure biomarkers of diisononyl and diisodecyl phthalates: data from the 2005-2006 National Health and Nutrition Examination Survey

BACKGROUND

High-molecular-weight phthalates, such as diisononyl phthalate (DINP) and diisodecyl phthalate (DIDP), are used primarily as polyvinyl chloride plasticizers.

OBJECTIVES

We assessed exposure to DINP and DIDP in a representative sample of persons ≥ 6 years of age in the U.S. general population from the 2005-2006 National Health and Nutrition Examination Survey (NHANES).

METHODS

We analyzed 2,548 urine samples by using online solid-phase extraction coupled to isotope dilution high-performance liquid chromatography-tandem mass spectrometry.

RESULTS

We detected monocarboxyisooctyl phthalate (MCOP), a metabolite of DINP, and monocarboxyisononyl phthalate (MCNP), a metabolite of DIDP, in 95.2% and 89.9% of the samples, respectively. We detected monoisononyl phthalate (MNP), a minor metabolite of DINP, much less frequently (12.9%) and at concentration ranges (> 0.8 µg/L-148.1 µg/L) much lower than MCOP (> 0.7 µg/L- 4,961 µg/L). Adjusted geometric mean concentrations of MCOP and MCNP were significantly higher (p < 0.01) among children than among adolescents and adults.

CONCLUSIONS

The general U.S. population, including children, was exposed to DINP and DIDP. In previous NHANES cycles, the occurrence of human exposure to DINP by using MNP as the sole urinary biomarker has been underestimated, thus illustrating the importance of selecting the most adequate biomarkers for exposure assessment.

Reproductive and behavioral effects of diisononyl phthalate (DINP) in perinatally exposed rats

Diisononyl phthalate (DINP) is a plasticizer abundantly used in consumer products as a substitute for other plasticizers prohibited in certain products due to reproductive toxicity. As anti-androgenic effects of DINP are suspected, DINP effects on reproduction and sexually dimorphic behavior were studied. Pregnant Wistar rats were gavaged from gestation day 7 to postnatal day (PND) 17 with vehicle, 300, 600, 750 or 900 mg DINP/kg bw/day. In fetal testes histopathological effects typical of phthalates were observed. In male offspring, DINP caused increased nipple retention, reduced anogenital distance, reduced sperm motility and increased sperm count. DINP affected spatial learning as female offspring performed better than controls and similarly to control males in the Morris Water Maze, indicating masculinization of behavior in DINP exposed females. These results show that DINP causes anti-androgenic effects on reproductive development, though less potent than DEHP, DBP and BBP, and further safety evaluation of DINP appears warranted.

Comparative toxicological evaluation of phthalate diesters and metabolites in Sprague-Dawley male rats for risk assessment

In order to comparatively assess the systemic toxicity and sperm parameters, nine phthalate diesters, including di(2-ethylhexyl) phthalate (DEHP), di(n-butyl) phthalate (DBP), di-n-octyl phthalate (DnOP), diethyl phthalate (DEP), butylbenzyl phthalate (BBP), dimethyl phthalate (DMP), di-isodecyl phthalate (DIDP), diundecyl phthalate (DUP), and di-isononyl phthalate (DINP), and five phthalate monoesters, including mono(2-ethylhexyl) phthalate (MEHP), monobutyl phthalate (MBuP), monobenzyl phthalate (MBeP), monoethyl phthalate (MEP), monomethyl phthalate (MMP), and phthalic acid (PA) were administered orally to Sprague-Dawley male rats at 250 (phthalate monoesters and PA) or 500 mg/kg body weight (bw)/d (phthalate diesters) for 4 wk. Liver weights were significantly increased in g roups treated with DEHP, DBP, BBP, DIDP, DINP, MEHP, and MBuP compared to the control. Testes weights were significantly reduced only in DEHP, DBP, and MEHP-treated groups compared to the control. Significant decreases in red blood cell (RBC) and hematocrit (Ht) levels were observed in DEHP-treated rats, whereas significant increases in mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), and platelet (PLT) levels were found in the DEHP-treated group. Hemoglobin (Hb) level was reduced only in the DMP group. Similar to effects on testis and epididymal weights, DEHP and MEHP significantly reduced sperm numbers and motility. In particular, DnOP, DBP, BBP, MEP, MBuP, DUP, DINP, and MBeP significantly lowered the sperm counts and sperm motility of epididymal sperm, detected by a change in the sperm motion parameters. The strongest to the weakest adverse effects for sperm motility were as follows: DEHP > DBP > DnOP > DUP > DIDP > BBP among diesters and MBuP > MEP > MEHP among monoesters, respectively. These results suggest that the adverse effects of phthalate esters (PEs) on sperm parameters in male rats are greater with phthalate diesters than monoesters, which may be useful for the risk assessment of phthalates.

Fifteen years after "Wingspread"--environmental endocrine disrupters and human and wildlife health: where we are today and where we need to go

In 1991, a group of expert scientists at a Wingspread work session on endocrine-disrupting chemicals (EDCs) concluded that "Many compounds introduced into the environment by human activity are capable of disrupting the endocrine system of animals, including fish, wildlife, and humans. Endocrine disruption can be profound because of the crucial role hormones play in controlling development." Since that time, there have been numerous documented examples of adverse effects of EDCs in invertebrates, fish, wildlife, domestic animals, and humans. Hormonal systems can be disrupted by numerous different anthropogenic chemicals including antiandrogens, androgens, estrogens, AhR agonists, inhibitors of steroid hormone synthesis, antithyroid substances, and retinoid agonists. In addition, pathways and targets for endocrine disruption extend beyond the traditional estrogen/androgen/thyroid receptor-mediated reproductive and developmental systems. For example, scientists have expressed concern about the potential role of EDCs in increasing trends in early puberty in girls, obesity and type II diabetes in the United States and other populations. New concerns include complex endocrine alterations induced by mixtures of chemicals, an issue broadened due to the growing awareness that EDCs present in the environment include a variety of potent human and veterinary pharmaceutical products, personal care products, nutraceuticals and phytosterols. In this review we (1) address what have we learned about the effects of EDCs on fish, wildlife, and human health, (2) discuss representative animal studies on (anti)androgens, estrogens and 2,3,7,8-tetrachlorodibenzo-p-dioxin-like chemicals, and (3) evaluate regulatory proposals being considered for screening and testing these chemicals.

Occurrence and daily variation of phthalate metabolites in the urine of an adult population

Phthalates like di-(2-ethylhexyl) phthalate (DEHP) are commonly used as plasticizers and their metabolites are suspect of especially reproductive toxicity. The aim of our study was to assess phthalate exposure in adults by measuring urinary phthalate metabolite levels and to explore individual temporal variability. Urine samples were collected by 27 women and 23 men aged 14-60 years during 8 consecutive days. We quantified four monoesters, four oxidative DEHP metabolites, and two secondary metabolites of di-isononyl phthalate (DiNP) by a LC/LC-MS/MS method. If we analyzed all 399 available samples independent of classification, the highest median values of primary metabolites in this study were found for mono-n-butyl phthalate (MnBP: 49.6 microg/l), followed by mono-isobutyl phthalate (MiBP: 44.9 microg/l), mono-benzyl phthalate (MBzP: 7.2 microg/l), and mono-2-ethylhexyl phthalate (MEHP: 4.9 microg/l). The median concentrations of the oxidized metabolites of DEHP were 8.3 microg/l for mono-(2-carboxymethylhexyl) phthalate (2cx-MMHP), 19.2 microg/l for mono-(2-ethyl-5-hydroxyhexyl) phthalate (5OH-MEHP), 14.7 microg/l for mono-(2-ethyl-5-oxohexyl) phthalate (5oxo-MEHP), and 26.2 microg/l for mono-(2-ethyl-5-carboxypentyl) phthalate (5cx-MEPP). The concentrations of the two DiNP secondary metabolites mono (oxoisononyl) phthalate (oxo-MiNP) and mono(hydroxyisononyl) phthalate (OH-MiNP) ranged from <LOD to 304 microg/l (median: 3.0 microg/l, 2.9 microg/g creatinine) and <LOD to 698 microg/l (median: 5.5 microg/l, 5.2 microg/g creatinine), respectively. Phthalate metabolite levels did not consistently differ by sex or age. There was substantial day-to-day variation of urinary levels with considerable within-subject variability. Intraclass correlation coefficients adjusted for sex and age ranged between 0.21 and 0.48 for unadjusted metabolite levels and between 0.20 and 0.57 for creatinine-adjusted levels. The secondary metabolites of DiNP were detectable in nearly all samples and were therefore sensitive biomarkers of DiNP exposure. Our results of within-subject variability suggest that exposure assessment should not be based on a single urine measurement.

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.

NTP center for the evaluation of risks to human reproduction reports on phthalates: addressing the data gaps

Between 1998 and 2000 an Expert Panel convened by the National Toxicology Program's Center for the Evaluation of Risks to Human Reproduction (NTP-CERHR) reviewed information related to the developmental and reproductive toxicity of seven phthalate esters; DBP, BBP, DnHP, DEHP, DnOP, DINP, and DIDP. Information on exposures was also considered. The objectives were to determine whether any of these phthalates posed potential human reproductive risks, and if so, to define the circumstances. The Expert Panel also identified some areas of uncertainty. These assessments, ultimately published in 2002, concluded that reproductive risks were minimal to negligible in most cases although some specific uses were considered potentially more problematic. Since the evaluations were completed, numerous studies dealing with both hazard characterization and underlying mechanism have been carried out. Additionally, exposures of the general population have been much better characterized through the use of urinary measurements developed by the Centers for Disease Control (CDC). This additional information makes several important points. First, calculations based on the urinary metabolite measurements indicate that exposures within the general population are at levels similar to or lower than the estimates used by the NTP-CERHR. The demonstration that exposures were not underestimated by the CERHR has removed a substantial portion of the uncertainty. Second, new hazard characterization studies on several phthalates have established NOAELs similar to or higher than those used by the Expert Panel. Thus, these data demonstrate that, to the extent that the rodent data are useful for human health risk assessment, the no effect levels and dose-response relationships are now more precisely defined. In some cases, the no effect levels may be substantially higher than those estimated by the Expert Panel. Third, studies of underlying mechanism and/or hazard characterization studies in other species suggest that primates may be less sensitive than rodents to the reproductive effects of certain phthalates. Finally, the two specific situations that the CERHR identified as potentially problematic, the exposure of young children to DINP through the use of toys or to DEHP from medical devices, have been assessed by the responsible regulatory authorities. The Consumer Product Safety Commission concluded that exposure to DINP from toys was well below effect levels in animals, and, therefore, there was no risk. The Food and Drug Administration estimates of exposures from medical devices indicated that for some limited, intensive medical procedures, DEHP exposures could be similar to or greater than the NOAELs selected by the NTP-CERHR. However, the FDA also acknowledged that more recent information indicates that the NOAELs identified in rodent studies may be substantially higher than values previously proposed by the NTP-CERHR. In summary, much of the uncertainty identified by the CERHR has now been addressed, and the overall conclusions that levels of concern are minimal to negligible in most situations are much better established. The overall objective of this report is to summarize this new research and comment on its relevance to the NTP-CERHR assessments.

Steroidogenesis in fetal male rats is reduced by DEHP and DINP, but endocrine effects of DEHP are not modulated by DEHA in fetal, prepubertal and adult male rats

The plasticizer di(2-ethylhexyl)phthalate (DEHP) exhibits antiandrogenic effects in perinatally exposed male rats. Di(2-ethylhexyl) adipate (DEHA) and diisononyl phthalate (DINP) are currently being evaluated as potential substitutes for DEHP, but similarities in structure and metabolism of DEHP with DEHA and DINP have led to the hypothesis that similarities in action may also exist. Pregnant Wistar rats were gavaged during gestation and lactation with vehicle, DEHP (300 or 750 mg/kg bodyweight per day), DINP (750 mg/kg bodyweight per day), DEHP (750 mg/kg bodyweight per day) in combination with DEHA (400 mg/kg bodyweight per day), or DEHP (300 mg/kg bodyweight per day) in combination with DINP (750 mg/kg bodyweight per day). DINP and DEHP were both shown to reduce testicular testosterone production ex vivo and testosterone levels in testes and plasma of male fetuses at gestation day 21, indicating a similar mechanism of action for DINP and DEHP. Additionally, plasma LH levels in male fetuses were elevated. Neonatal anogenital distance was reduced and the number of nipples at postnatal day 13 increased in DEHP-exposed male offspring. Serum inhibin B levels were significantly reduced in DEHP-exposed prepubertal male offspring, and in a few adult males. No modulating effects of DEHA on the endocrine effects of DEHP were detected, but a tendency towards an accumulating effect of DEHP and DINP in combination on suppression of testosterone synthesis was seen.

[Estimation of daily oral exposure to phthalates derived from soft polyvinyl chloride baby toys]

Daily oral exposure of babies to phthalate was estimated on the basis of the mouthing time of infants and the oral concentration of diisononyl phthalate (DINP) released from polyvinyl chloride (PVC) toy specimens. Total mouthing time, including the use of pacifiers, ranged widely from 11.4 min to 351.8 min with the mean of 105.3 +/- 72.1 min. The mean of the total mouthing time without pacifiers was 73.9 +/- 32.9 min. The average amount of DINP in saliva was 92.4 +/- 56.8 micrograms/10 cm2/hr, ranging from 13.2 micrograms/10 cm2/hr to 240.4 micrograms/10 cm2/hr. The exposure of phthalate in two different trials was estimated by the method of Monte Carlo simulation, one with the total mouthing time with pacifiers and the other with the total mouthing time without pacifiers. The average exposure in the former trial was 21.4 micrograms/kg/day and the 95th percentile was 65.8 micrograms/kg/day, while in the latter it was 14.8 micrograms/kg/day and the 95th percentile was 35.7 micrograms/kg/day.

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.

Endocrine active agents: implications of adverse and non-adverse changes

The US Environmental Protection Agency (EPA) is currently in the process of developing screening and testing methodologies for the assessment of agents that may possess endocrine-like activity--the so-called endocrine disruptors. Moreover, the EPA has signaled its intention of placing information arising from such studies on the worldwide web. This has created significant interest in how such information may be used in risk assessment and by policymakers and the public in the potential regulation or deselection of specific chemical agents. The construction of lists of endocrine disruptors, although fulfilling the requirements of some parties, is really of little use when the nature of the response, the dose level employed, and the lifestage of the test species used are not given. Thus, we have already seen positive in vitro information available on the interaction with a receptor being used as a key indicator when the results of large, high quality in vivo studies showing no adverse changes have been ignored. Clearly a number of in vitro systems are available to ascertain chemical interaction with specific (mainly steroid) hormone receptors including a number of reporter gene assays. These assays only provide indicators of potential problems and should not be, in isolation, indicators of toxicity. Likewise, short-term in vivo screens such as the uterotrophic and Hershberger studies are frequently conducted in castrated animals and thus indicate the potential for a pharmacological response in vivo rather than an adverse effect. A number of new end points have been added to standard rodent testing protocols in the belief of providing more sensitivity to detect endocrine related changes. These include the measurement of anogenital distance (AGD), developmental landmarks [vaginal opening (VO), preputial separation (PPS)], and in some studies the counting of nipples and areolae on males. AGD, VO, and PPS are all affected by the size of the pup in which they are measured and should always be compared using bodyweight as a covariate. The historical control database for such changes is gradually growing, albeit that if pups are not individually identified it becomes problematic to associate any change with a specific malformation or to assess whether a delay or advance in, for example, developmental landmarks is biologically significant. Agents that significantly reduce AGD in males (it is an androgen-dependent variable) frequently have other more adverse changes associated with this end point (eg, reproductive tract malformations), but a 2 to 3% change in AGD although measurable is unlikely to be biologically of importance and in isolation would not necessarily be considered adverse. Retention of thoracic nipples in male rat pups is also an indicator of impaired androgen status. Recent studies have also shown that this retention for some endocrine active chemicals is permanent. Thus, the presence of a permanent structural change that is rarely found in adult control animals could be considered a malformation and therefore a developmental adverse effect on which risk assessment decisions could be made. The advent of multigeneration reproduction studies as the definitive studies for the assessment of the dose-response relationships and risk assessment for endocrine disruptors has shown that current testing protocols may be inadequate to reliably detect the adverse effects of concern as only 1 adult/sex/litter is examined. A number of the effects on reproductive development although, due to an in utero exposure, will not be manifest until after puberty or at adulthood. The use of only a limited number of animals to examine such changes, particularly for weaker acting materials indicates that some agents may have been examined in well-conducted, modern protocols but have insufficient power to detect low incidence phenomena (eg, a 5% incidence of malformations).

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.