Metabolites of the plasticizer di(2-ethylhexyl)phthalate in urine samples of workers in polyvinylchloride processing industries

Assessment of the plasticizer exposure of hospital workers regularly handling medical devices: A pilot study

Plastic medical devices, e.g. infusion sets, blood bags or tubing material, that are used manifold in the medical treatment of hospital patients, usually contain considerable amounts of plasticizers. Whereas several studies showed highly elevated inner plasticizer levels of patients treated with plasticized medical devices, little is known about the exposure situation of hospital staff. The present pilot study aimed to evaluate the urinary plasticizer metabolite levels of selected hospital workers of the blood bank (medical technical assistants, MTA) and of perfusionists that are regularly handling plasticized medical devices in order to estimate the work-related amount of the inner individual plasticizer exposure. The study subjects were asked to collect pre- and post-shift spot urine samples over the course of a working week, that were subsequently analyzed for selected urinary metabolites of the plasticizers DEHP, DINCH, DEHTP and TEHTM. Although the observed differences were rather low, a differentiated approach revealed a perceptible impact of the respective workplace environment on the individual urinary plasticizer metabolite levels. Thus, the group of blood bank MTA showed significantly elevated increment levels of urinary DEHP and DINCH metabolites, while the group of perfusionists, showed a considerable higher detection frequency of the main urinary TEHTM metabolite. All in all, however, it can be cautiously concluded by the results of the presented pilot study that a regular handling of plasticized medical devices by hospital employees (via inhalation or dermal contact) contributes demonstrably but yet only marginally to the individual internal plasticizer exposure.

Simultaneous and sensitive determination of the main metabolites of the plasticizer DEHP and its substitutes DEHTP, DINCH and TEHTM in human urine by coupling of on-line SPE, UHPLC and tandem mass spectrometry

With the prominent but toxicologically critical plasticizer di-(2-ethylhexyl) phthalate (DEHP) declining, alternative plasticizers are increasingly used leading to a continuously more diverse exposure situation of humans with multiple plasticizers. Therefore, an on-line SPE-LC-MS/MS method for the simultaneous determination of the most relevant urinary biomarkers of exposure to DEHP and the alternative plasticizers 1,2-cyclohexane dicarboxylic acid diisononyl ester (DINCH), di-(2-ethylhexyl) terephthalate (DEHTP) and tri-(2-ethylhexyl) trimellitate (TEHTM) was developed. The method is characterized by a high sensitivity with limits of detection ranging from 0.006 to 0.047 μg L^-1 combined with an easy and straightforward sample preparation procedure. The wide linear working range of the method enables a reliable determination of analyte background levels in the general population as well as its potential use for monitoring studies investigating elevated plasticizer exposure settings. The method was successfully applied to urine samples from ten volunteers without occupational exposure to plasticizers revealing ubiquitous background exposure levels of the common plasticizers DEHP, DEHTP and DINCH.

Toxicology and carcinogenesis studies of di(2-ethylhexyl) phthalate administered in feed to Sprague Dawley (Hsd:Sprague Dawley SD) rats

Di(2-ethylhexyl) phthalate (DEHP) is a member of the phthalate ester chemical class that occurs commonly in the environment and to which humans are widely exposed. Lifetime exposure to DEHP is likely to occur, including during the in utero and early postnatal windows of development. To date, no carcinogenicity assessments of DEHP have used a lifetime exposure paradigm that includes the perinatal period (gestation and lactation). The National Toxicology Program (NTP) tested the hypothesis that exposure during the perinatal period would alter the DEHP carcinogenic response quantitatively (more neoplasms) or qualitatively (different neoplasm types). Two chronic carcinogenicity assessments of DEHP were conducted in which Sprague Dawley (Hsd:Sprague Dawley SD) rats were exposed to dosed feed containing 0, 300, 1,000, 3,000, or 10,000 ppm DEHP for 2 years using different exposure paradigms. In Study 1, groups of 45 F0 time-mated females were provided dosed feed beginning on gestation day (GD) 6 through lactation. On postnatal day (PND) 21, groups of 50 F1 rats per sex continued on the study and were provided dosed feed containing the same DEHP concentration as their respective dam for 2 years. In Study 2, groups of 50 rats per sex, aged 6 to 7 weeks at study start, were provided dosed feed containing DEHP for 2 years. (Abstract Abridged).

Protective effect of vitamin E on sperm quality and in vitro fertilizing potential and testosterone concentration in polyvinyl chloride treated male rats

Polyvinyl chloride (PVC) has toxic effects through the induction of oxidative stress in the body and testicles. Vitamin E (Vit E) is a dietary compound that functions as an antioxidant scavenging toxic free radicals. The present study aimed to probe the protective effect of Vit E against PVC-induced reprotoxicity in male rats. In this experimental study, 24 male rats were randomly divided into four groups (n=6) including control, Vit E (150 mg kg^-1 per day; orally), PVC (1000 mg kg^-1 per day; orally) and PVC + Vit E. After 40 days, rats were euthanized and epididymal sperms characteristics, embryo development and malondialdehyde (MDA) and testosterone levels were examined. The PVC decreased sperm count, motility and viability as well as testosterone level and increased sperms with damaged chromatin in comparison with controls. Also, the percentages of fertilization, two-cell embryos and blastocysts as well as MDA levels were decreased in PVC-treated rats. However, Vit E improved PVC-induced alterations in aforesaid parameters. The results indicated that PVC can reduce fertility potential in male rats probably through androgen and sperm quality and quantity reductions, while Vit E can exert protective effects in PVC-related reproductive toxicities.

Characterization of phthalates exposure and risk for cosmetics and perfume sales clerks

High levels of phthalates in name-brand cosmetics products have raised concerns about phthalate exposure and the associated risk for cosmetics sales clerks. We assessed the exposure and risk of phthalates in 23 cosmetics, 4 perfume, and 9 clothing department store sales clerks. We collected 108 urine samples pre- and post-shift and analyzed for phthalate monoesters through liquid chromatography-electrospray ionization-tandem mass spectrometry. Phthalates in 32 air samples were collected and analyzed through gas chromatography-mass spectrometry. Demographic characteristics and information on the exposure scenarios were obtained through questionnaires. Principal component analysis, cluster and risk analysis were applied to identify the exposure profile and risk of phthalate. Median post-shift levels of urinary mono-2-ethylhexyl phthalate (MEHP) and monomethyl phthalate (MMP) were significantly higher than the corresponding pre-shift levels in cosmetics group (53.3 vs. 30.9 μg/g-c for MEHP; 34.4 vs. 22.5 μg/g-c for MMP; both P < 0.05) and the post-shift levels of urinary MMP was significantly higher than the corresponding pre-shift levels in perfume group (26.6 vs. 14.9 μg/g-c, P < 0.05). Median levels of air diethyl phthalate (DEP) in cosmetics (1.77 μg/m³) and perfume (1.75 μg/m³) groups and di-(2-ethylhexyl) phthalate (DEHP) in perfume group (6.98 μg/m³) were higher than those in clothing group (DEP: 0.89; DEHP: 2.16 μg/m³). Over half of cosmetic (70%) and perfume sale clerks had exceeded cumulative risk of phthalate exposure for anti-androgenic effect. We concluded that cosmetic and perfume workers had increased risks of reproductive or hepatic effects for DBP and DEHP exposure. We suggest that not only inhalation but dermal exposure is important route of phthalate exposure for cosmetics and perfume workers.

Associations between paternal urinary phthalate metabolite concentrations and reproductive outcomes among couples seeking fertility treatment

INTRODUCTION

Limited evidence suggests that male exposure to ubiquitous environmental phthalates may result in poor reproductive outcomes among female partners.

METHODS

This analysis included male-female couples undergoing in vitro fertilization (IVF) and/or intrauterine insemination (IUI). We evaluated associations between the geometric mean of paternal specific gravity-adjusted urinary phthalate concentrations prior to the female partners' cycle and fertilization, embryo quality, implantation, and live birth using generalized linear mixed models.

RESULTS

Two-hundred eighteen couples underwent 211 IVF and 195 IUI cycles. Trends were observed between paternal urinary mono-3-carboxypropyl phthalate (MCPP; P=0.01) and mono(carboxyoctyl) phthalate (MCOP; P=0.01) and decreased odds of implantation. MCPP and MCOP were also associated with decreased odds of live birth following IVF (P=0.01 and P=0.04, respectively), and monobutyl phthalate above the first quartile was significantly associated with decreased odds of live birth following IUI (P=0.04). However, most urinary phthalate metabolites were not associated with these reproductive outcomes.

CONCLUSION

Selected phthalates were associated with decreased odds of implantation and live birth.

Characterization of Urinary Phthalate Metabolites Among Custodians

Phthalates, a ubiquitous class of chemicals found in consumer, personal care, and cleaning products, have been linked to adverse health effects. Our goal was to characterize urinary phthalate metabolite concentrations and to identify work and nonwork sources among custodians using traditional cleaning chemicals and 'green' or environmentally preferable products (EPP). Sixty-eight custodians provided four urine samples on a workday (first void, before shift, end of shift, and before bedtime) and trained observers recorded cleaning tasks and types of products used (traditional, EPP, or disinfectant) hourly over the work shifts. Questionnaires were used to assess personal care product use. Four different phthalate metabolites [monoethyl phthalate (MEP), monomethyl phthalate (MMP), mono (2-ethylhexyl) phthalate (MEHP), and monobenzyl phthalate (MBzP)] were quantified using liquid chromatography mass spectrometry. Geometric means (GM) and 95% confidence intervals (95% CI) were calculated for creatinine-adjusted urinary phthalate concentrations. Mixed effects univariate and multivariate modeling, using a random intercept for each individual, was performed to identify predictors of phthalate metabolites including demographics, workplace factors, and personal care product use. Creatinine-adjusted urinary concentrations [GM (95% CI)] of MEP, MMP, MEHP, and MBzP were 107 (91.0-126), 2.69 (2.18-3.30), 6.93 (6.00-7.99), 8.79 (7.84-9.86) µg g(-1), respectively. An increasing trend in phthalate concentrations from before to after shift was not observed. Creatinine-adjusted urinary MEP was significantly associated with frequency of traditional cleaning chemical intensity in the multivariate model after adjusting for potential confounding by demographics, workplace factors, and personal care product use. While numerous demographics, workplace factors, and personal care products were statistically significant univariate predictors of MMP, MEHP, and MBzP, few associations persisted in multivariate models. In summary, among this population of custodians, we identified both occupational and nonoccupational predictors of phthalate exposures. Identification of phthalates as ingredients in cleaning chemicals and consumer products would allow workers and consumers to avoid phthalate exposure.

Human urinary phthalate metabolites level and main semen parameters, sperm chromatin structure, sperm aneuploidy and reproductive hormones

The aim of the study was to assess the association of phthalate metabolites levels in urine with semen parameters (sperm concentration, motility, morphology, CASA parameters), sperm chromatin structure, sperm aneuploidy and reproductive hormones. The study population consisted of 269 men who were attending an infertility clinic and had normal semen concentration (20-300mln/ml) or slight oligozoospermia (15-20mln/ml). Participants were interviewed and provided a semen sample. The phthalate metabolites were analysed in the urine using a procedure based on the LC-MS/MS method. Urinary phthalate metabolites levels were significantly associated with a decrease in sperm motility (5OH MEHP, MEHP, MINP), CASA parameters (MBP), testosterone level (MEHP) and an increase sperm DNA damage (MBP) and sperm aneuploidy (MBzP, MBP, MEHP, MEP). In view of the importance of human reproductive health and the widespread usage of phthalates, it is important to further investigate these correlations.

Exposure to widespread environmental toxicants and children's cognitive development and behavioral problems

Nowadays a special attention is focused on prenatal and childhood exposures to a variety of contaminants in the environment, especially toxicants widely present in the environment and their impact on children's health and neurodevelopment. This article aims at evaluating the impact of exposure to several widespread toxicants including: polycyclic aromatic hydrocarbons (PAHs), phthalates, bisphenol A, brominated flame retardants and gas cooking on children's cognitive development and behavioral problems by reviewing most recent published literature. Epidemiological studies focusing on exposure to widespread toxicants and children's development for the last eleven years were identified by a search of the PubMed, Medline, Ebsco and Toxnet literature bases. The combination of following key words was used: 1) referring to the exposure: pregnancy, prenatal exposure, postnatal exposure, gas cooking, exposure to phthalates, bisphenol A, brominated flame retardants, PAHs and 2) referring to outcome: neurodevelopment, neurobehavior, psychomotor development, behavioral problems, cognitive development, mental health, school achievements, learning abilities. The results from the presented studies suggest that there are strong and rather consistent indications that the developing nervous system is particularly vulnerable to insult from low levels of exposure to widespread environmental contaminants such as: phthalates, bisphenol A, brominated flame retardants, polycyclic aromatic hydrocarbons, gas cooking. Considering the suggested health effects, more epidemiologic data is urgently needed and, in the meantime, precautionary policies must be implemented.

Accuracy investigation of phthalate metabolite standards

Phthalates are ubiquitous compounds whose metabolites are usually determined in urine for biomonitoring studies. Following suspect and unexplained results from our laboratory in an external quality-assessment scheme, we investigated the accuracy of all phthalate metabolite standards in our possession by comparing them with those of several suppliers. Our findings suggest that commercial phthalate metabolite certified solutions are not always accurate and that lot-to-lot discrepancies significantly affect the accuracy of the results obtained with several of these standards. These observations indicate that the reliability of the results obtained from different lots of standards is not equal, which reduces the possibility of intra-laboratory and inter-laboratory comparisons of results. However, agreements of accuracy have been observed for a majority of neat standards obtained from different suppliers, which indicates that a solution to this issue is available. Data accuracy of phthalate metabolites should be of concern for laboratories performing phthalate metabolite analysis because of the standards used. The results of our investigation are presented from the perspective that laboratories performing phthalate metabolite analysis can obtain accurate and comparable results in the future. Our findings will contribute to improving the quality of future phthalate metabolite analyses and will affect the interpretation of past results.

The association between semen quality in workers and the concentration of di(2-ethylhexyl) phthalate in polyvinyl chloride pellet plant air

OBJECTIVE

To investigate potential associations between semen quality in workers and the concentrations of di(2-ethylhexyl) phthalate (DEHP) in personal air collected from polyvinyl chloride (PVC) plants.

DESIGN

Cross-sectional study.

SETTING

PVC plants in Taiwan.

PATIENT(S)

Forty-five male workers employed in two PVC pellet plants.

INTERVENTION(S)

None.

MAIN OUTCOME MEASUREMENT(S)

Sperm concentration, motility, morphology, and chromatin DNA integrity were accessed.

RESULT(S)

The workers were divided into low- and high-DEHP-exposed groups in accordance with the median levels of DEHP (23.7 μg/m(3)) in personal air. In the high-DEHP-exposed group, significant increases were found in the tendency for sperm DNA denaturation (αT) induction, the DNA fragmentation index (DFI), and propensity for coffee drinking. After adjusting for coffee drinking, cigarette smoking, and age, personal air concentrations of DEHP showed positive associations with αT (β = 0.038) and DFI (β = 0.140) and negative associations with sperm motility (β = -0.227).

CONCLUSION(S)

This is the first study to demonstrate a link between DEHP concentration in ambient air and the adverse effects in sperm motility and chromatin DNA integrity. Given the current wide use of these PVC products, the implications for phthalates toxicity and occupational health could be considerable.

Exposure to phthalates: reproductive outcome and children health. A review of epidemiological studies

Phthalates are a family of industrial chemicals that have been used for a variety of purposes. As the potential consequences of human exposure to phthalates have raised concerns in the general population, they have been studied in susceptible subjects such as pregnant women, infants and children. This article aims at evaluating the impact of exposure to phthalates on reproductive outcomes and children health by reviewing most recent published literature. Epidemiological studies focusing on exposure to phthalates and pregnancy outcome, genital development, semen quality, precocious puberty, thyroid function, respiratory symptoms and neurodevelopment in children for the last ten years were identified by a search of the PubMed, Medline, Ebsco, Agricola and Toxnet literature bases. The results from the presented studies suggest that there are strong and rather consistent indications that phthalates increase the risk of allergy and asthma and have an adverse impact on children's neurodevelopment reflected by quality of alertness among girls, decreased (less masculine) composite score in boys and attention deficit hyperactivity disorder. Results of few studies demonstrate negative associations between phthalate levels commonly experienced by the public and impaired sperm quality (concentration, morphology, motility). Phthalates negatively impact also on gestational age and head circumference; however, the results of the studies were not consistent. In all the reviewed studies, exposure to phthalates adversely affected the level of reproductive hormones (luteinizing hormone, free testosterone, sex hormone-binding globulin), anogenital distance and thyroid function. The urinary levels of phthalates were significantly higher in the pubertal gynecomastia group, in serum in girls with premature thelarche and in girls with precocious puberty. Epidemiological studies, in spite of their limitations, suggest that phthalates may affect reproductive outcome and children health. Considering the suggested health effects, more epidemiologic data is urgently needed and, in the meantime, precautionary policies must be implemented.

Determination of Phthalate Metabolites in Human Serum and Urine as Biomarkers for Phthalate Exposure Using Column-Switching LC-MS/MS

Objectives

Although phthalates like dibutyl phthalate (DBP) and di-2-ethylhexyl phthalate (DEHP) are commonly used as plasticizers and their metabolites are especially suspected of reproductive toxicity, little is known about occupational exposure to those phthalates. The aim of this study was to assess the utility of measuring the metabolite concentrations of DBP and DEHP in serum and urine samples as an indicator of occupational exposure to those phthalates.

Methods

Phthalate metabolites were analyzed by using column-switching high-performance liquid chromatography tandem mass spectrometry (LC-MS/MS).

Results

We detected phthalate metabolites in serum and urine matrices at approximately 10-fold lower than the limit of detection of those metabolites in the same matrix by LC-MS/MS without column switching, which was sufficient to evaluate concentrations of phthalate metabolites for industrial workers and the general population.

Conclusion

The accuracy and precision of the analytical method indicate that urinary metabolite determination can be a more acceptable biomarker for studying phthalate exposure and adverse health outcomes.

Estimated daily intake of phthalates in occupationally exposed groups

Improved analytical methods for measuring urinary phthalate metabolites have resulted in biomarker-based estimates of phthalate daily intake for the general population, but not for occupationally exposed groups. In 2003-2005, we recruited 156 workers from eight industries where materials containing diethyl phthalate (DEP), dibutyl phthalate (DBP), and/or di(2-ethylhexyl) phthalate (DEHP) were used as part of the worker's regular job duties. Phthalate metabolite concentrations measured in the workers' end-shift urine samples were used in a simple pharmacokinetic model to estimate phthalate daily intake. DEHP intake estimates based on three DEHP metabolites combined were 0.6-850 μg/kg/day, with the two highest geometric mean (GM) intakes in polyvinyl chloride (PVC) film manufacturing (17 μg/kg/day) and PVC compounding (12 μg/kg/day). All industries, except phthalate manufacturing, had some workers whose DEHP exposure exceeded the U.S. reference dose (RfD) of 20 μg/kg/day. A few workers also exceeded the DEHP European tolerable daily intake (TDI) of 50 μg/kg/day. DEP intake estimates were 0.5-170 μg/kg/day, with the highest GM in phthalate manufacturing (27 μg/kg/day). DBP intake estimates were 0.1-76 μg/kg/day, with the highest GMs in rubber gasket and in phthalate manufacturing (17 μg/kg/day, each). No DEP or DBP intake estimates exceeded their respective RfDs. The DBP TDI (10 μg/kg/day) was exceeded in three rubber industries and in phthalate manufacturing. These intake estimates are subject to several uncertainties; however, an occupational contribution to phthalate daily intake is clearly indicated in some industries.

Human body burdens of chemicals used in plastic manufacture

In the last decades, the availability of sophisticated analytical chemistry techniques has facilitated measuring trace levels of multiple environmental chemicals in human biological matrices (i.e. biomonitoring) with a high degree of accuracy and precision. As biomonitoring data have become readily available, interest in their interpretation has increased. We present an overview on the use of biomonitoring in exposure and risk assessment using phthalates and bisphenol A as examples of chemicals used in the manufacture of plastic goods. We present and review the most relevant research on biomarkers of exposure for phthalates and bisphenol A, including novel and most comprehensive biomonitoring data from Germany and the United States. We discuss several factors relevant for interpreting and understanding biomonitoring data, including selection of both biomarkers of exposure and human matrices, and toxicokinetic information.

Pre-pubertal Di(2-ethylhexyl) Phthalate (DEHP) Exposure of Young Boars Did Not Affect SpermIn vitroPenetration Capacity of Homologous Oocytes Post-puberty

Di(2-ethylhexyl) phthalate (DEHP), a plastic softener used in polyvinylchloride (PVC) products (e.g., plastic bags and medical equipment), has been reported to have toxic effects on animal reproduction and is considered an environmental hazard based, mostly, on rodent studies. However, the doses used in these studies are often considerably higher than that presumed in human exposure. In the present study we used young boars as model animals to assess the effects of pre-pubertal DEHP exposure on the ability of spermatozoa to penetrate homologous oocytes in vitro. Eight pairs of cross-bred male boar siblings were used. One brother in each pair became, at random, the test animal exposed to DEHP per os, three times a week, from 3 to 7 weeks of age while the other acted as the control, i.e., placebo-exposed. Semen was collected and frozen between 8 and 9 months of age and stored until spermatozoa were evaluated for their ability to in vitro penetrate in vitro-matured homologous oocytes post-thaw. Both the penetration rate and the number of spermatozoa per oocyte were considered within expected ranges for frozen boar semen of good quality. Penetration rate did not significantly differ (p > 0.05) between the groups with DEHP-exposed: 50%; control: 59%, which could be owing to a large variation between boars, and between replicates. The number of spermatozoa in the ooplasm was low and similar (p > 0.05) between the groups with DEHP-exposed: 1.5 and the control: 1.7. Under the conditions of the present experiment, pre-pubertal exposure to DEHP does not seem to cause a deleterious effect on the in vitro fertilizing ability of frozen spermatozoa post-puberty.

Urinary phthalate metabolite concentrations among workers in selected industries: a pilot biomonitoring study

Phthalates are used as plasticizers and solvents in industrial, medical and consumer products; however, occupational exposure information is limited. We sought to obtain preliminary information on occupational exposures to diethyl phthalate (DEP), di-n-butyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) by analyzing for their metabolites in urine samples collected from workers in a cross-section of industries. We also obtained data on metabolites of dimethyl phthalate (DMP), benzylbutyl phthalate (BzBP), di-isobutyl phthalate and di-isononyl phthalate. We recruited 156 workers in 2003-2005 from eight industry sectors. We assessed occupational contribution by comparing end-shift metabolite concentrations to the US general population. Evidence of occupational exposure to DEHP was strongest in polyvinyl chloride (PVC) film manufacturing, PVC compounding and rubber boot manufacturing where geometric mean (GM) end-shift concentrations of DEHP metabolites exceeded general population levels by 8-, 6- and 3-fold, respectively. Occupational exposure to DBP was most evident in rubber gasket, phthalate (raw material) and rubber hose manufacturing, with DBP metabolite concentrations exceeding general population levels by 26-, 25- and 10-fold, respectively, whereas DBP exposure in nail-only salons (manicurists) was only 2-fold higher than in the general population. Concentrations of DEP and DMP metabolites in phthalate manufacturing exceeded general population levels by 4- and >1000-fold, respectively. We also found instances where GM end-shift concentrations of some metabolites exceeded general population concentrations even when no workplace use was reported, e.g. BzBP in rubber hose and rubber boot manufacturing. In summary, using urinary metabolites, we successfully identified workplaces with likely occupational phthalate exposure. Additional work is needed to distinguish occupational from non-occupational sources in low-exposure workplaces.

Cross validation and ruggedness testing of analytical methods used for the quantification of urinary phthalate metabolites

Since the publication of our first analytical method in 2000 to detect and quantify phthalate metabolites in human urine, we have modified the method several times to improve performance, reduce the volume of matrix and solvents used, and to increase the number of analytes in one analytical run. We performed cross method validation and ruggedness testing after each modification to ensure that the analytical method adopted is robust and produces accurate and reproducible data when compared to the previously used method. Here, we present the results from the evaluation of the ruggedness of our analytical approach under variable experimental conditions, using the current analytical method. Minor deviations of the standard experimental conditions, i.e., pH, incubation time, amount of deconjugation enzyme, and incubation temperature, had no effect on final analyte concentrations. Furthermore, we validated the method to ensure accuracy at concentrations beyond the highest calibration standard. The concentrations obtained by using a lower volume of urine agreed well with original levels, suggesting broad linear calibration range as well as complete hydrolysis of the glucuronide conjugates with the standard amount of beta-glucuronidase used for deglucuronidation; also, the time of incubation (90 min) was adequate regardless of the amount of glucuronide present. We also summarize the precision of concentration data acquired by the five different analytical approaches we have used since 2000. The correlation plots of concentration data for each analyte obtained from split sample analysis, using three of these approaches, produced linear curves (R(2)>0.98) with slopes and intercepts that were not statistically different (p>0.05) from 1 and 0, respectively. These results suggest that the data are reproducible and accurate, regardless of the analytical method used. Furthermore, analysis of quality control urine samples made over the years confirmed the stability of the phthalate metabolites in urine at -70 degrees C for several years and the consistency of the analytical measurements obtained by using various methodological approaches over time.

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.

Modes of action and species-specific effects of di-(2-ethylhexyl)phthalate in the liver

The industrial plasticizer di-(2-ethylhexyl)phthalate (DEHP) is used in manufacturing of a wide variety of polyvinyl chloride (PVC)-containing medical and consumer products. DEHP belongs to a class of chemicals known as peroxisome proliferators (PPs). PPs are a structurally diverse group of compounds that share many (but perhaps not all) biological effects and are characterized as non-genotoxic rodent carcinogens. This review focuses on the effect of DEHP in liver, a primary target organ for the pleiotropic effects of DEHP and other PPs. Specifically, liver parenchymal cells, identified herein as hepatocytes, are a major cell type that are responsive to exposure to PPs, including DEHP; however, other cell types in the liver may also play a role. The PP-induced increase in the number and size of peroxisomes in hepatocytes, so called 'peroxisome proliferation' that results in elevation of fatty acid metabolism, is a hallmark response to these compounds in the liver. A link between peroxisome proliferation and tumor formation has been a predominant, albeit questioned, theory to explain the cause of a hepatocarcinogenic effect of PPs. Other molecular events, such as induction of cell proliferation, decreased apoptosis, oxidative DNA damage, and selective clonal expansion of the initiated cells have been also been proposed to be critically involved in PP-induced carcinogenesis in liver. Considerable differences in the metabolism and molecular changes induced by DEHP in the liver, most predominantly the activation of the nuclear receptor peroxisome proliferator-activated receptor (PPAR)alpha, have been identified between species. Both sexes of rats and mice develop adenomas and carcinomas after prolonged feeding with DEHP; however, limited DEHP-specific human data are available, even though exposure to DEHP and other phthalates is common in the general population. This likely constitutes the largest gap in our knowledge on the potential for DEHP to cause liver cancer in humans. Overall, it is believed that the sequence of key events that are relevant to DEHP-induced liver carcinogenesis in rodents involves the following events whereby the combination of the molecular signals and multiple pathways, rather than a single hallmark event (such as induction of PPARalpha and peroxisomal genes, or cell proliferation) contribute to the formation of tumors: (i) rapid metabolism of the parental compound to primary and secondary bioactive metabolites that are readily absorbed and distributed throughout the body; (ii) receptor-independent activation of hepatic macrophages and production of oxidants; (iii) activation of PPARalpha in hepatocytes and sustained increase in expression of peroxisomal and non-peroxisomal metabolism-related genes; (iv) enlargement of many hepatocellular organelles (peroxisomes, mitochondria, etc.); (v) rapid but transient increase in cell proliferation, and a decrease in apoptosis; (vi) sustained hepatomegaly; (vii) chronic low-level oxidative stress and accumulation of DNA damage; (viii) selective clonal expansion of the initiated cells; (ix) appearance of the pre-neoplastic nodules; (x) development of adenomas and carcinomas.

The Effects of Subacute Inhalation of Di (2‐ethylhexyl) Phthalate (DEHP) on the Testes of Prepubertal Wistar Rats

In animal studies using oral dosing for short periods, di (2-ethylhexyl) phthalate (DEHP) is well known for its reproductive toxicity, especially for its testicular toxicity. However, extending the period of DEHP exposure in prepubertal rats resulted in significant increases in testosterone. This suggests that the reproductive effect of DEHP might be associated with the timing and the term of exposure. Moreover, the route of exposure may induce differences in its effect because tissue levels of metabolites of DEHP after inhalation are thought to be different from those after oral administration. We researched the effects of inhalation of DEHP on testes of prepubertal rats. Our results showed that inhalation of DEHP by 4-wk-old male Wistar rats at doses of 5 or 25 mg/m(3), 6 h per day, for 4 and 8 wk significantly increased the concentration of plasma testosterone and weight of seminal vesicles. However, the concentration of luteinizing hormone (LH), follicular stimulating hormone (FSH) and the expression of mRNAs of androgen biosynthesis enzyme, cytochrome P450 cholesterol side-chain-cleavage enzyme (P450scc), 3beta-hydroxysteroid dehydrogenase (3beta-HSD), cytochrome P450 17alpha-hydroxylase/17, 20 lyase (CYP17) and aromatase (CYP19) did not change. Rats with precocious testes did not increase in any of the DEHP groups. We also found that the estimated effective dose in this study was less than those reported in previous studies which used oral dosing. Our study showed that inhaled DEHP increased plasma testosterone concentrations in prepubertal rats and suggested that their effects were more sensitive to inhalation of DEHP than oral dosing.

On the use of different measures of exposure-experiences from a case-control study on testicular cancer and PVC exposure

Associations between exposure to PVC plastics and testicular cancer have been reported. To improve the exposure-response analysis in a matched case-control study on testicular cancer and occupational exposures, a self-administered exposure questionnaire and expert assessment was applied and different exposure measures were developed. The questionnaires regarding work histories and employment in PVC production, manufacturing, and handling of PVC products were completed by 1582 subjects (90%). By expert assessment, 360 subjects were considered exposed, and the exposure intensity to PVC plastics for different working periods was determined. Different exposure measures to PVC plastics were then developed, such as ever/never exposed, duration, maximum intensity, median intensity, and cumulative median intensity. The correlation between the different measures of exposure was high for exposure duration and the cumulative median exposure intensity (Spearman rank coefficient r(s) = 0.94), as was the correlation between the maximum intensity and the median intensity (r(s) = 0.94). The agreement between the answers in the questionnaire and the expert assessments was moderate, Kappa value 0.56. The odds ratio for "ever" exposed based on the exposure as reported in the questionnaire was 1.1 (95%, CI 0.82-1.56), and as determined by expert assessment 1.3 (CI 1.05-1.69). The odds ratios for all four different categories of exposure measures varied between 0.86 and 2.6 but decreased by increasing exposure. An overall excess of testicular cancer for the PVC exposed vs. the unexposed was not supported by the pattern seen in a standard exposure-response analysis based on several exposure measures. The findings stress the importance of using several exposure measures as dose surrogates when the underlying toxic mechanisms are unknown and when there are indications of an overall effect.

Role of PPARα in mediating the effects of phthalates and metabolites in the liver

Phthalate esters belong to a large class of compounds known as peroxisome proliferators (PP). PP include chemicals that activate different subtypes of the peroxisome proliferator-activated receptor (PPAR) family. The ability of phthalate esters and their metabolites to activate responses through different PPAR subtypes is not fully characterized. We investigated the ability of two phthalate esters di-(2-ethylhexyl) phthalate (DEHP) and di-n-butyl phthalate (DBP) and selected metabolites to activate PPAR (alpha, beta/delta, gamma) using a transient transfection assay. The monoester of DEHP, mono-(2-ethylhexyl) phthalate (MEHP) activated all three subtypes of PPAR, but preferentially activated PPARalpha. A second metabolite of DEHP, 2-ethylhexanoic acid (2-EHXA) was a weaker activator of all three subtypes. DBP, but not the primary metabolite mono-n-butyl phthalate weakly activated all three PPAR subtypes. MEHP and DBP but not DEHP and MBP interacted directly with human PPARalpha and PPARgamma as determined by scintillation proximity assays. Both DEHP and DBP activated expression of PP-inducible gene products in wild-type but not PPARalpha-null mice suggesting that both of these phthalates exert their effects by activation of PPARalpha in vivo. The preferential activation of PPARalpha by phthalate ester metabolites suggests that these phthalates mediate their toxic effects in rodent liver in a manner indistinguishable from other PP.

The use of mini-organ cultures of human upper aerodigestive tract epithelia in ecogenotoxicology

The carcinogenic potential of xenobiotics and possible confounders are often difficult to differentiate in in vivo studies. In contrast, in vitro studies allow investigation of the impact of carcinogens on human target cells under standardized conditions. The aim of the present study is to demonstrate whether three-dimensional mini organ-cultures (MOCs) of human inferior nasal turbinate epithelia may represent a useful model to study genotoxic effects of xenobiotics in vitro. Culture of mini organs was performed by cutting 1mm3 pieces from fresh specimens of inferior nasal turbinates. After a period of 5-6 days the specimens were fully covered with epithelium. On days 7, 9, and 11 of culture, intact MOCs from 25 tissue donors were incubated with dimethyl sulfoxide (DMSO) as a negative control, or with mono(2-ethylhexyl) phthalate (MEHP), benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE), or N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). On days 7 and 11, MOCs were analyzed by the alkaline Comet assay to detect DNA-single-strand breaks, alkali-labile sites and incomplete excision-repair sites. DNA migration after single exposure of non-cultivated fresh specimens was also analyzed. In order to detect regimen-specific effects, DNA fragmentation after single exposure of intact MOCs was compared with that of cells after separation of MOCs on day 7 of culture and consecutive exposure of individual cells. Significant DNA migration as a measure of DNA single-strand breaks, alkali-labile sites and incomplete excision repair sites, was found after electrophoresis due to single and triple exposure of MOCs to MEHP, BPDE and MNNG. Triple exposure of MOCs compared to single exposure revealed no difference after exposure to DMSO or MEHP, and an increased migration after exposure to BPDE and MNNG. When single exposure of isolated cells from fresh specimens was compared with that of intact MOCs, DMSO and MNNG had no significantly different effect, whereas exposure to MEHP or BPDE caused a reduced migration in cells from MOCs. When exposure of isolated cells harvested from MOCs was compared with exposure of intact MOCs, MEHP and BPDE caused a significantly lower DNA migration in intact MOCs. MOCs provide an in vitro model suitable for the assessment of genotoxic effects of environmental pollutants both after single or repetitive exposure. Due to the intact structure of the exposed mucosa this model may be a helpful tool in mimicking the in vivo situation in ecogenotoxicology studies.

High-throughput analysis of phthalate esters in human serum by direct immersion SPME followed by isotope dilution?fast GC/MS

Solid-phase microextraction (SPME) coupled to gas chromatography/mass spectrometry (GC/MS) was applied to the determination of phthalate esters in human serum. The present method decreased the sample preparation time by a factor of 50 by using direct immersion SPME with an 85-microm polyacrylate fiber to extract phthalate esters from the matrix. The use of fast GC/MS further improves total analysis time when compared to other techniques. Isotope dilution was successfully applied to improve the precision, reproducibility, and repeatability of the SPME method. The linear dynamic range spans several orders of magnitude from low ppb to ppm levels, and the LOD for the method is 15 pg microL(-1) on average with RSDs less than 4% for the six phthalate esters included in this study.

Mono(2-ethylhexyl)phthalate exhibits genotoxic effects in human lymphocytes and mucosal cells of the upper aerodigestive tract in the comet assay

Phthalic acid esters such as di(2-ethylhexyl)phthalate (DEHP) are widely used as plasticizers in PVC products manufactured for commercial, medical, and consumer purposes. Humans are exposed to phthalates originating, e.g., from blood storage bags, tubing materials, and from food-wrapping. While xenoestrogenic and chronic toxic effects of phthalates have been extensively discussed, there is little data on genotoxic effects in human cells. The alkaline comet assay was used to detect single-strand breaks and alkali labile sites of DNA after incubation of human nasal mucosal cells (n = 11) and peripheral lymphocytes (n = 11) with mono(2-ethylhexyl)phthalate (MEHP), the principal hydrolysis product of DEHP. MEHP showed a dose-dependent enhancement of DNA migration both in human mucosal cells and in lymphocytes. This effect indicates a genotoxic potential of MEHP in human mucosal cells. It confirms previous data obtained on the effect of MEHP on lymphocytes.

Testicular cancer and occupational exposure to polyvinyl chloride plastics: a case-control study

Exposure to polyvinyl chloride (PVC) plastics as a risk factor for testicular cancer was investigated. In total, 981 cases who were 20-75 years old and had reported to the Swedish Cancer Registry during 1993-1997 were included. One matched control from the population registry was used. Exposure was assessed by a questionnaire that was supplemented over the phone. Furthermore, an occupational hygienist qualified all exposures. In all, 791 matched pairs completed the questionnaire. Overall exposure to PVC plastics gave the odds ratio (OR)=1.35, 95% confidence interval (CI)=1.06-1.71, increasing with >10 year latency period to OR=1.45, 95% CI=1.06-1.98. No dose-response relationships were found but rather an inverse relationship with the highest odds ratios in the lowest exposure category. In conclusion, no clear association with testicular cancer and exposure to PVC could be found in our study in contrast to a previous observation.

A biomarker approach to measuring human dietary exposure to certain phthalate diesters

Three groups of eight volunteers were administered stable isotope-labelled phthalate diesters in a single dose and the amount of the corresponding phthalate monoesters excreted in the urine was measured. Amongst the phthalates administered were the symmetrical dibutyl-, di-2-ethyl- and diisooctyl- phthalates along with the unsymmetrical benzylbutylphthalate. The control group received no dose, the low dose group received 168-255 microg of each phthalate and the high dose group received 336 to 510 microg of each phthalate. The excreted phthalate monoesters were measured by LC-MS following hydrolysis of conjugates. The bulk of phthalate monoester was excreted in the first 24 hour period following the dose. For dibutylphthalate, 64% and 73% on a mole basis of the low, and high dose respectively was excreted as monobutylphthalate. For dioctylphthalate (sum of the 2-ethylhexyl and the isooctyl species) the yield was 14 and 12% of the low and high dose excreted as monooctylphthalate. For benzylbutylphthalate, 67% and 78% was eliminated as monobenzylphthalate and only 6% (measured for the high dose only) was eliminated as monobutylphthalate. These conversion factors can be used in future studies to assess exposure to phthalate esters via measuring urinary levels of the monoester metabolites.

Genotoxicity of di-butyl-phthalate and di-iso-butyl-phthalate in human lymphocytes and mucosal cells

The genotoxicity of phthalates, widely used plasticizers, has been shown previously for di-butyl-phthalate (DBP) and di-iso-butyl-phthalate (DBP) in human mucosal cells of the upper aerodigestive tract in a previous study using the Comet assay. Furthermore, higher genotoxic sensitivities of patients with squamous cell carcinomas of either the larynx or the oropharynx compared to non-tumor patients were described. Other authors have demonstrated DNA damage by a different phthalate in human lymphocytes. It was the aim of the present study to determine whether there is a correlation between the genotoxic sensitivities to DBP and its isomer DiBP in either mucosal cells or lymphocytes. The single-cell microgel electrophoresis assay (Comet assay) was applied to detect DNA strand breaks in human epithelial cells of the upper aerodigestive tract (n=132 specimens). Human mucosa was harvested from the oropharynx in non-tumor patients and patients with squamous cell carcinomas of the oropharynx. Laryngeal mucosa of patients with laryngeal squamous cell carcinomas was harvested as well. Peripheral lymphocytes (n=49 specimens) were separated from peripheral blood. Xenobiotics investigated were DBP, DiBP, and N'methyl-N'-nitro-N-nitrosoguanidine (MNNG) as positive control, respectively. For statistical analysis, the SPSS correlation analysis according to Pearson and the Wilcoxon test were performed. Genotoxicity was found for DBP and DiBP in epithelial cells and lymphocytes (P<0.001). MNNG caused severe DNA damage. In analyzing DBP and DiBP results, genotoxic impacts in mucosal cells showed an intermediate correlation (r=0.570). Correlation in lymphocytes was the same (r=0.570). Phthalates have been investigated as a potential health hazard for a variety of reasons, including possible xenoestrogenic impact, peroxisome proliferation, and membrane destabilization. The present investigation suggests a correlated DNA-damaging impact of DBP and DiBP in human mucosal cells and in lymphocytes, respectively.

Health risks posed by use of Di-2-ethylhexyl phthalate (DEHP) in PVC medical devices: a critical review

BACKGROUND

Polyvinyl chloride plastics (PVC), made flexible through the addition of di-2-ethylhexyl phthalate (DEHP), are used in the production of a wide array of medical devices. From the late 1960s, leaching of DEHP from PVC medical devices and ultimate tissue deposition have been documented.

METHODS

A critical review of DEHP exposure, metabolism, and toxicity data from human and animals studies was undertaken. A brief analysis of alternatives to DEHP-plasticized PVC for use in medical device manufacture was completed.

RESULTS

DEHP leaches in varying concentrations into solutions stored in PVC medical devices. Certain populations, including dialysis patients and hemophiliacs may have long-term exposures to clinically important doses of DEHP, while others, such as neonates and the developing fetus, may have exposures at critical points in development. In vivo and in vitro research links DEHP or its metabolites to a range of adverse effects in the liver, reproductive tract, kidneys, lungs, and heart. Developing animals are particularly susceptible to effects on the reproductive system. Some adverse effects in animal studies occur at levels of exposure experienced by patients in certain clinical settings. DEHP appears to pose a relatively low risk of hepatic cancer in humans. However, given lingering uncertainties about the relevance of the mechanism of action of carcinogenic effects in rodents for humans and interindividual variability, the possibility of DEHP-related carcinogenic responses in humans cannot be ruled out.

CONCLUSIONS

The observed toxicity of DEHP and availability of alternatives to many DEHP-containing PVC medical devices presents a compelling argument for moving assertively, but carefully, to the substitution of other materials for PVC in medical devices. The substitution of other materials for PVC would have an added worker and community health benefit of reducing population exposures to DEHP, reducing the creation of dioxin from PVC production and disposal, and reducing risks from vinyl chloride monomer exposure.

Concentrations of phthalate esters and identification of other additives in PVC children's toys

This study was intended to provide data on the composition of soft PVC toys, addressing the widest practicable range of chemical additives and including non-phthalate additives. The study also included toys from as many countries as possible, since for many, no data were available. A total of 72 toys were purchased in 17 countries. The majority (64) were PVC or had PVC sections. In almost all the soft PVC toys analysed, phthalates comprised a sizeable proportion (most frequently 10-40%) of the total weight of the toy. The predominant phthalates detected were diisononyl phthalate (DINP) and di(2-ethylhexyl) phthalate (DEHP). Other phthalates identified in high concentrations in some toys include isomeric mixes of diisooctyl phthalate (DIOP) and diisodecyl phthalate (DIDP). The estrogenic chemical nonylphenol was isolated from 13 toys, while 2 toys were found to contain the fungicide Fungitrol 11 (Folpet). 78% of PVC toys contained one or more extractable organic compounds in addition to those reported above.

Phthalates demonstrate genotoxicity on human mucosa of the upper aerodigestive tract

Various phthalate compounds are used as softeners and plasticizers in a wide range of plastic materials. There has been a growing concern regarding a possible health hazard to humans. The mucosa of the upper aerodigestive tract is the organ of first contact for the majority of xenobiotics, such as phthalates, entering the body. Still, there is a lack of information concerning possible carcinogenicity of phthalates in the upper aerodigestive tract. This motivated us to investigate their genotoxic effects on human epithelia: human mucosal cells derived from biopsies harvested during surgery of the oropharynx and the inferior nasal turbinate, respectively. The alkaline version of the microgel electrophoresis assay was used to detect single-strand breaks in the DNA following incubation with dibutylphthalate (DBP) and diisobutylphthalate (DiBP). DNA damage was induced by both DBP and DiBP in oropharyngeal and nasal mucosa, though the effect of DiBP was more pronounced than that of DBP. Nasal mucosa proved to be more sensitive than oropharyngeal epithelia. The results demonstrate genotoxic effects of phthalates on human mucosal cells of the upper aerodigestive tract, in contrast to earlier findings in animal models.

Exposure of hemodialysis patients to di-2-ethylhexyl phthalate

The migration of di-2-ethylhexyl phthalate (DEHP) from dialyzers was studied in 21 patients with chronic renal failure undergoing maintenance hemodialysis. The circulating concentrations of DEHP were measured by high performance liquid chromatography in blood of patients obtained from the inlet and the outlet of the dialyzer during a 4-h dialysis session. During treatment of renal failure using plasticized tubing, the plasma level of DEHP increased. On average, an estimated 75.2 mg of DEHP was extracted from the dialyzer during a single dialysis session, with a range of 44.3-197. 1 mg. On the other hand, the total amount of DEHP retained by the patient during the dialysis session was evaluated by the difference between the AUCout and the AUCin and ranged from 3.6 to 59.6 mg. The rate of extraction of DEHP from the dialyzer was correlated (r=0.705, P<0.05) with serum lipid content (cholesterol and triglyceride).So, we confirmed that patients on hemodialysis are always regularly exposed to considerable amounts of DEHP. However, several metabolic effects have been reported in various animal species following treatment with DEHP, such as changes in lipid metabolism and in hepatic microsomal drug-metabolizing enzyme activities. DEHP is now a well-known hepatic peroxisomal proliferator in rodents and an inducer of many peroxisomal and non-peroxisomal enzymes. So, lipid metabolism modifications and hepatic changes observed in hemodialysis patients could be explained from chronic exposition to DEHP. In the coming years, it seems necessary to reconsider the use of DEHP as a plasticizer in medical devices. Highly unacceptable amounts of DEHP leached during the dialysis session could be easily avoided by careful selection of hemodialysis tubing.

Hepatocarcinogenic potential of di(2-ethylhexyl)phthalate in rodents and its implications on human risk

The plasticizer di(2-ethylhexyl) phthalate (DEHP), to which humans are extensively exposed, was found to be hepatocarcinogenic in rats and mice. DEHP is potentially set free from objects made of synthetic materials (e.g., those used in medicine). Chronically, the greatest amounts are transferred to persons undergoing hemodialysis (up to 3.1 mg/kg b.w. per day) who would thus be considered the individuals most endangered by tumorigenesis. Although toxicokinetics seem to play a certain unclear role in the course of DEHP-related toxicity, toxicodynamic factors appear more decisive. DEHP is a representative of "peroxisome proliferators" (PP), a distinct group of substances that, in rodents, do not only induce peroxisomes but also specific enzymes in other organelles, organ growth, and DNA synthesis. The cluster of the characteristic effects of PP is generally, although perhaps not quite appropriately summarized as "peroxisome proliferation," and is strongest in the liver. The lowest observed effect level (LOEL) and the no observed effect level (NOEL) of peroxisome proliferation in the rat, as determined by the induction of specific enzymes (peroxisomal beta-oxidation, carnitine-acetyl-transferase, cytochrome P-452), DNA synthesis, and hepatomegaly, may be assumed as 50 and 25 mg/kg b.w. per day, respectively. DEHP and other carcinogenic PP are neither genotoxic nor tumor initiators, but they appear to be tumor promoters, also implicating a threshold level for the carcinogenic effect. Although a causal relationship between a particular effect of peroxisome proliferation and hepatocarcinogenesis is as yet unknown, peroxisome proliferation as a whole phenomenon appears to be associated with the potential of tumor induction, as shown by comparison of the relative strength of individual PP and by comparison of species and organ specificities. Likewise, LOEL and NOEL of rodent carcinogenesis, that is, 300 and 50 to 100 mg/kg b.w. per day, respectively, are above but not too far from the corresponding values for the investigated parameters of peroxisome proliferation. Thus, with respect to dose alone, worst-case exposure in hemodialysis patients is at least 16-fold below the LOEL of any characterized PP-specific effect of DEHP and approximately 100-fold below that of DEHP-related tumorigenesis. Also, primates are less responsive to PP than rats with respect to the investigated biochemical and morphological parameters. If this lower primate responsiveness is extrapolated to estimate carcinogenicity in humans, we might thus arrive at an even larger safety margin than when based on exposure alone. Doses of PP hypolipidemics that had clearly induced several indicators of peroxisome proliferation in rats did not cause any clear-cut enhancements in the peroxisomes of patients, even though most of these hypolipidemics were considerably stronger PP than DEHP. Thus, an actual threat to humans by DEHP seems rather unlikely. Accordingly, hepatocarcinogenesis was neither enhanced in workers exposed to DEHP nor in patients treated with hypolipidemics.

Pancreatic cancer among workers processing synthetic resins

A nested case-control study was conducted to investigate whether an excess of pancreatic cancer, identified in a cohort mortality study with follow-up from 1946 through 1988, was associated with potential workplace exposures at a New Jersey plastics manufacturing and research and development facility. The study population included 28 male pancreatic cancer cases and 140 randomly selected controls, matched on year of birth and at risk (alive) at the time of the case death. Using plant work history records, department assignments for the two groups were compared according to duration and time since first assignment. Workers assigned to a work area that processed vinyl resins and polyethylene (PE) were shown to be at increased risk. Men assigned more than 16 years to this department had a significantly increased risk ratio of 7.15 (95% confidence intervals [CI]: 1.28-40.1). No excess was seen with shorter duration assignments. Seven of the nine cases began working in this area in the 1940s. Average latency was 32 years, and all but three cases worked 20 years or more in this unit. Over the study period, significant exposure-related process changes occurred, in addition to the use of numerous chemical additives. Although vinyl and PE processing operations could not be analyzed separately, the pancreatic cancer excess is more likely to be related to vinyl processing. Identification of a causative agent or combination of agents would require investigations with more detailed exposure information.

Evaluation of di(2-ethylhexyl)phthalate-induced embryotoxicity in rodent whole-embryo culture

Di(2-ethylhexyl)phthalate (DEHP) is a commonly used plasticizer. Human exposure has been documented, and therefore it is important to investigate the toxic potential of this compound. When DEHP was administered in vivo, it was found to be a developmental toxicant in rodents. The purpose of this investigation was to determine if DEHP was directly embryotoxic to rat embryos. Embryos were cultured for 44 h beginning on gestational d 10. Embryos were cultured in rat serum to which DEHP was added to attain final concentrations within the 0.01-2.0% range. DEHP decreased growth and development at all tested concentrations higher than 0.5%. These results suggest that the parent compound itself is able to alter normal embryonic growth and development; however the high embryotoxic concentrations are unlikely to be attained in vivo.