Urine phthalate determinations as an index of occupational exposure to phthalic anhydride and di(2-ethylhexyl)phthalate

Human skin absorption of three phthalates

Population studies reveal widespread exposure to phthalates. Understanding their absorption, distribution, metabolism, and excretion is vital to reduce exposure. However, data on skin absorption remain limited. We thus aim to characterize the skin permeation of three phthalates in a mixture, neat or in emulsion; di(2-ethylhexyl) phthalate (d4-DEHP), dibutyl phthalate (d4-DBP), and diethyl phthalate (d4-DEP), by comparing in vitro human skin (800 µm) permeation (24 hours) results using flow-through diffusion cells with urine results obtained from volunteers exposed to the same mixture applied to a forearm (40 cm2). Metabolites were analyzed in receptor fluids and urine. Phthalates crossed the skin barrier and metabolized into monoesters before elimination. Increased permeation was observed for phthalates in emulsion compared to neat substances, with polyethylene glycol (PEG) in the receptor fluid enhancing emulsion permeation, but not affecting neat substances. In vitro results mirrored in vivo findings: DEP showed rapid permeation (J: ∼2 ug/cm2/h) and urinary excretion peaking at six hours post-application, whereas DBP exhibited slower kinetics (J: ∼0.1 ug/cm2/h), with a urinary peak at 15-17 hours post-application. DEHP had minimal permeation (J: ∼0.0002 ug/cm2/h) with no observable urinary peak. These findings underscore the importance of comprehending phthalate skin absorption for effective exposure mitigation strategies.

HBM4EU Occupational Biomonitoring Study on e-Waste-Study Protocol

Workers involved in the processing of electronic waste (e-waste) are potentially exposed to toxic chemicals. If exposure occurs, this may result in uptake and potential adverse health effects. Thus, exposure surveillance is an important requirement for health risk management and prevention of occupational disease. Human biomonitoring by measurement of specific biomarkers in body fluids is considered as an effective method of exposure surveillance. The aim of this study is to investigate the internal exposure of workers processing e-waste using a human biomonitoring approach, which will stimulate improved work practices and contribute to raising awareness of potential hazards. This exploratory study in occupational exposures in e-waste processing is part of the European Human Biomonitoring Initiative (HBM4EU). Here we present a study protocol using a cross sectional survey design to study worker’s exposures and compare these to the exposure of subjects preferably employed in the same company but with no known exposure to industrial recycling of e-waste. The present study protocol will be applied in six to eight European countries to ensure standardised data collection. The target population size is 300 exposed and 150 controls. Biomarkers of exposure for the following chemicals will be used: chromium, cadmium and lead in blood and urine; brominated flame retardants and polychlorobiphenyls in blood; mercury, organophosphate flame retardants and phthalates in urine, and chromium, cadmium, lead and mercury in hair. In addition, the following effect biomarkers will be studied: micronuclei, epigenetic, oxidative stress, inflammatory markers and telomere length in blood and metabolomics in urine. Occupational hygiene sampling methods (airborne and settled dust, silicon wristbands and handwipes) and contextual information will be collected to facilitate the interpretation of the biomarker results and discuss exposure mitigating interventions to further reduce exposures if needed. This study protocol can be adapted to future European-wide occupational studies.

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).

Lifetime cancer risk assessment for inhalation exposure to di(2-ethylhexyl) phthalate (DEHP)

The plasticizer di(2-ethylhexyl) phthalate (DEHP) is ubiquitous in the environment and considered as carcinogen; however, the carcinogenic risk of human exposure to DEHP in the air via inhalation is lacking. A probabilistic incremental lifetime cancer risk (ILCR) model was implemented to quantitatively estimate the potential cancer risk of DEHP via human inhalation by using Monte Carlo simulation. We assessed the cancer risk in different age groups (children, adolescents, and adults) exposed to different DEHP concentrations (background low, indoor moderate, and occupational high) for different durations (2, 8, and 20 years). Results showed that the cancer risk of exposure to DEHP was below the acceptable limit (10^-6) in the ambient air but was serious in indoor and occupational environments even at short exposure duration (2 years). The cancer risk of DEHP via inhalation in children was lower than that in adolescents and adults, but the risk in children via dermal and oral exposure to indoor dust and soft PVC toys should be considered. Sensitivity analysis indicated that the exposure concentration of DEHP was the strongest factor that influenced ILCR. Our work provides the evidence of cancer risk of DEHP via inhalation and highlights the risk in indoor and occupational environments.

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.

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.

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.

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.

Reproductive and developmental toxicity of phthalates

The purposes of this review are to (1) evaluate human and experimental evidence for adverse effects on reproduction and development in humans, produced by exposure to phthalates, and (2) identify knowledge gaps as for future studies. The widespread use of phthalates in consumer products leads to ubiquitous and constant exposure of humans to these chemicals. Phthalates were postulated to produce endocrine-disrupting effects in rodents, where fetal exposure to these compounds was found to induce developmental and reproductive toxicity. The adverse effects observed in rodent models raised concerns as to whether exposure to phthalates represents a potential health risk to humans. At present, di(2-ethylhexyl) phthalate (DEHP), di-n-butyl phthalate (DBP), and butyl benzyl phthalate (BBP) have been demonstrated to produce reproductive and developmental toxicity; thus, this review focuses on these chemicals. For the general population, DEHP exposure is predominantly via food. The average concentrations of phthalates are highest in children and decrease with age. At present, DEHP exposures in the general population appear to be close to the tolerable daily intake (TDI), suggesting that at least some individuals exceed the TDI. In addition, specific high-risk groups exist with internal levels that are several orders of magnitude above average. Urinary metabolites used as biomarkers for the internal levels provide additional means to determine more specifically phthalate exposure levels in both general and high-risk populations. However, exposure data are not consistent and there are indications that secondary metabolites may be more accurate indicators of the internal exposure compared to primary metabolites. The present human toxicity data are not sufficient for evaluating the occurrence of reproductive effects following phthalate exposure in humans, based on existing relevant animal data. This is especially the case for data on female reproductive toxicity, which are scarce. Therefore, future research needs to focus on developmental and reproductive endpoints in humans. It should be noted that phthalates occur in mixtures but most toxicological information is based on single compounds. Thus, it is concluded that it is important to improve the knowledge of toxic interactions among the different chemicals and to develop measures for combined exposure to various groups of phthalates.

Non-invasive matrices in human biomonitoring: a review

Humans and other living organisms are exposed to a variety of chemical pollutants that are released into the environment as a consequence of anthropogenic activities. Environmental pollutants are incorporated into the organism by different routes and can then be stored and distributed in different tissues, which leads to an internal concentration that can induce different alterations, adverse effects and/or diseases. Control measures should be taken to avoid these effects and human biomonitoring is a very useful tool that can contribute to this aim. Human biomonitoring uses different matrices to measure the target chemicals depending on the chemical, the amount of matrix necessary for the analysis and the detection limit (LOD) of the analytical technique. Blood is the ideal matrix for most chemicals due to its contact with the whole organism and its equilibrium with organs and tissues where chemicals are stored. However, it has an important disadvantage of being an invasive matrix. The development of new methodology and modern analytical techniques has allowed the use of other matrices that are less or non-invasive, such as saliva, urine, meconium, nails, hair, and semen or breast milk. The presence of a chemical in these matrices reflects an exposure, but correlations between levels in non-invasive matrices and blood must be established to ensure that these levels are related to the total body burden. The development of new biomarkers that are measurable in these matrices will improve non-invasive biomonitoring. This paper reviews studies that measure Cd, Pb, Hg, polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polycyclic aromatic hydrocarbons (PAHs), polybrominated diphenyl ethers (PBDEs), organochlorine pesticides and phthalates in non-invasive matrices, the most used techniques for measurements and what alternative techniques are available.

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.

Early pre-pubertal exposure to low-dose oral di(2-ethylhexyl) phthalate does not affect sperm plasma membrane stability, acrosomal integrity or chromatin structure in the post-pubertal boar

This study aimed to determine whether pre-pubertal exposure in boars to di(2-ethylhexyl) phthalate (DEHP), a plasticizer reported to have toxic effects on rodent reproduction, would affect the sperm ability to undergo capacitation and acrosome reaction (AR) in vitro or give rise to a higher degree of chromatin instability associated with acid-induced denaturation. Spermatozoa were collected from 16 boars (n=8/group) 8-9 months of age, exposed to 300mg/kg body weight of DEHP or placebo per os three times a week, from 3 to 7 weeks of age. The spermatozoa were cryopreserved and examined post-thaw by flow cytometry for their ability to capacitate in vitro when exposed to the effector bicarbonate and to acrosome-react when exposed to calcium ionophores, using the lipid stain Merocyanine-540 (m-540), and peanut agglutinin-fluorescein isothiocyanate, respectively, as probes. The ability of the DNA to sustain denaturation in vitro was tested using a sperm chromatin structure assay (SCSA). No significant differences between the DEHP-exposed group and controls were found for any of the sperm attributes examined. Frozen-thawed spermatozoa showed similar rates of non-capacitated cells between groups, and were capacitated at similar rates. Rates of induced ARs were also similar. Values of DNA denaturation were low and showed no differences between groups. In conclusion, pre-pubertal exposure to DEHP does not seem, under the conditions of the present experiment, to affect the ability of frozen-thawed spermatozoa collected post-puberty to capacitate or acrosome-react (the main requisites for fertilization) or to present damage in their nuclear genome.

Does exposure to di(2-ethylhexyl) phthalate in pre-pubertal boars affect semen quality post-puberty?

Di(2-ethylhexyl) phthalate (DEHP), a plastic softener used in polyvinyl chloride (PVC) products, has been ascribed to have toxic effects on animal reproduction. The present study aimed at determining potential late effects of pre-pubertal oral exposure to DEHP on semen quality in young pigs. Ten pairs of cross-bred male siblings were used. One brother in each pair became, at random, the test animal while the other acted as control. Test males were exposed to 300 mg/kg body weight (bw) of DEHP administered orally three times a week from 3 to 7 weeks of age. The control group was given placebo (water). Semen analyses started when the boars reached 6 months of age, with semen collected twice weekly, until animals were 9 months of age. Semen was evaluated for ejaculate volume, sperm concentration, total sperm count, sperm motility, sperm morphology (including presence of cells other than spermatozoa) and sperm plasma membrane integrity. Total sperm motility tended to be lower while local motility was higher in the DEHP-exposed group compared with controls (p = 0.07) when assessed by computer-assisted sperm analysis. The DEHP-exposed group had a significantly (p < 0.05) lower percentage of spermatozoa with tailless, defective heads (at 7-8 months of age) and double-folded tails (at 6-7, 7-8 and 6-9 months of age), compared with controls (albeit always under 5%). In summary, there were no obvious adverse effects of early oral exposure to 300 mg/kg bw of DEHP on sperm output and sperm quality in post-pubertal young boars.

Effects of exposure of pre-pubertal boars to di(2-ethylhexyl) phthalate on their frozen-thawed sperm viability post-puberty

Late effects of pre-pubertal oral exposure to di(2-ethylhexyl) phthalate (DEHP), a plastic softener used in, for example, polyvinyl chloride-products, on semen quality in young boars have not been clear-cut. The aim of this study was to determine whether stress imposed on spermatozoa would reveal such effects. Semen was collected from post-pubertal boars (8-9 months of age), which had been exposed to 300 mg kg(-1) body weight of DEHP per os three times a week from 3 to 7 weeks of age and from control siblings given placebo (water). The semen was cryopreserved and examined for plasma membrane integrity post-thaw using the short hypo-osmotic swelling test and flow cytometry (propidium iodide /SYBR-14). Sperm motility was assessed by computer-assisted sperm analysis. No significant difference in plasma membrane integrity could be found between the groups. The DEHP-exposed group had a significantly lower percentage of linearly motile spermatozoa at 30 min (P < 0.05) and 120 min (P < 0.001) after thawing, and a larger amplitude of lateral displacement of the head 120 min after thawing (P < 0.05), compared with controls. In summary, spermatozoa from boars pre-pubertally exposed to low doses of DEHP, showed kinematic deviations post-thaw that could be related to DEHP exposure.

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.

Human monitoring of phthalates and risk assessment

Some phthalates, such as di(2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP), and their metabolites are suspected of producing teratogenic and endocrino-disrupting effects. In this study, urinary levels of phthalates (DEHP, DBP, diethyl phthalate (DEP), butylbenzyl phthalate BBP), and monoethylhexyl phthalate (MEHP, a major metabolite of DEHP) were measured by high performance liquid chromatography (HPLC) in human populations (women [hospital visitors], n = 150, and children, n = 150). Daily exposure level of DEHP in children was estimated to be 12.4 microg/kg body weight/d (male 9.9 microg/kg body weight/d, female 17.8 microg/kg body weight/d), but, in women was estimated to be 41.7 microg/kg body weight/d, which exceeded the tolerable daily intake (TDI, 37 microg/kg body weight/day) level established by the European Union (EU) Scientific Committee for Toxicity, Ecotoxicity, and the Environment (SCTEE) based on reproductive toxicity. Based on these data, hazard indices (HIs) were calculated to be 1.12 (41.7/37 TDI) for women and 0.33 (12.4/37 TDI) for children, respectively. These data suggest that Koreans (women and children) were exposed to significant levels of phthalates, which should be reduced to as low a level as technologically feasible to protect Koreans from the exposure to toxic phthalates.

Synthesis of DEHP metabolites as biomarkers for GC–MS evaluation of phthalates as endocrine disrupters

Phthalates are used primarily as plasticizers to make polyvinyl chloride (PVC) soft and flexible. In recent years the phthalate esters have attracted increasing attention as environmental and biomedical pollutants and, because of their toxicological characteristics. In particular, they are more and more recognized as endocrine disrupters. In this context, we describe herein an efficient synthetic pathway leading to a series of metabolites of di(2-ethylhexyl) phthalate (DEHP). Mono(2-ethylhexenyl) phthalate was used as starting material to obtain these products in good yield, large scale and GC-MS purity. The metabolites of DEHP were synthesized, for the first time, as biomarkers to verify their quantitative determination in human urine and serum by GC-MS analysis for studying the exposure to phthalates and establishing reference values.

Immunotoxicology of organic acid anhydrides (OAAs)

Organic acid anhydrides (OAAs) have considerable economic importance due to their extensive use in the production of alkyd, epoxy, and polyester resins. Occupational exposure to OAAs has been associated with a variety of health effects, which may be classified into two major categories of direct toxicity/irritant and hypersensitivity. The hypersensitivity diseases associated with OAA exposure are thought to be related to the reactivity of these chemicals and in particular their ability to form protein conjugates that may be recognized as neo-antigens by the immune system. This review will present a brief discussion of the basic chemistry of these compounds and the environmental and biological monitoring methods used for exposure measurements. The clinical syndromes associated with exposure to these compounds will be discussed along with factors that may affect disease susceptibility. Finally, animal models that have been developed to examine the mechanisms of disease will be discussed.

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.

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

Little is known about occupational exposure to the plasticizer di(2-ethylhexyl)phthalate (CAS number 117-81-7), a compound widely used in polyvinylchloride (PVC) plastics. We have studied the uptake of DEHP in workers by determining the concentrations of four metabolites of DEHP in urine samples, i.e., mono(2-ethylhexyl)phthalate (MEHP), mono(5-carboxy-2-ethylpentyl)phthalate, mono(2-ethyl-5-oxohexyl)phthalate, and mono(2-ethyl-5-hydroxyhexyl)phthalate. In addition DEHP concentrations in the air were determined by personal air sampling. Nine workers in a PVC boot factory exposed to a maximum of 1.2 mg/m3 DEHP showed an increase in the urinary concentrations of all four metabolites over the workshift. These results were obtained on both the first and the last day of the workweek. With the exception of MEHP, the increases in the concentrations of the metabolites during a workday were statistically significant. Six workers from a PVC cable factory exposed to a maximum of 1.2 mg/m3 DEHP showed a one- to fourfold increase in the concentrations of the four metabolites over the workshift, but these increases were not statistically significant. These results indicate that measurement of DEHP metabolites in urine samples may be of use for monitoring the occupational exposure to DEHP.

Determination of four metabolites of the plasticizer di(2-ethylhexyl)phthalate in human urine samples

A method for biological monitoring of exposure to the plasticizer di(2-ethylhexyl)phthalate (DEHP) is described. In this method the four main metabolites of DEHP [i.e., mono(2-ethylhexyl)phthalate (MEHP), mono(5-carboxy-2-ethylpentyl)phthalate, mono(2-ethyl-5-oxohexyl)phthalate, and mono(2-ethyl-5-hydroxyhexyl)-phthalate] are determined in urine samples. The procedure includes enzymatic hydrolysis, ether extraction, and derivatization with triethyloxonium tetrafluoroborate. Analysis is performed by gas chromatography-electron impact mass spectrometry. The detection limit for all four metabolites is less than 25 micrograms/l urine. The coefficient of variation based on duplicate determinations of urine samples of workers occupationally exposed to DEHP was 16% for MEHP (mean concentration 0.157 mg/l) and 6%-9% for the other three metabolites (mean concentrations 0.130-0.175 mg/l). The method described here was used to study DEHP metabolism in man. Most persons excrete mono(2-ethyl-5-oxohexyl)-phthalate and mono(2-ethyl-5-hydroxyhexyl)phthalate as a (glucuronide) conjugate. Mono(5-carboxy-2-ethylpentyl)phthalate is mainly excreted in free form, while for MEHP a large interindividual variation in conjugation status was observed. Of the four metabolites quantified, 52% are products of a (omega-1)-hydroxylation reaction of MEHP [i.e., mono(2-ethyl-5-oxohexyl)phthalate and mono(2-ethyl-5-hydroxylation reaction of MEHP [i.e., mono(5-carboxy-2-ethylpentyl)phthalate], and 26% is not oxidized further (i.e., MEHP). A good correlation is obtained when the amount of MEHP omega-hydroxylation products is compared with the amount of MEHP (omega-1)-hydroxylation products in urine samples. When the internal dose of DEHP has to be established we recommend that the levels of all four metabolites of DEHP be studied in urine samples.