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Exposure assessment issues in epidemiology studies of phthalates.

ABSTRACT: The purpose of this paper is to review exposure assessment issues that need to be addressed in designing and interpreting epidemiology studies of phthalates, a class of chemicals commonly used in consumer and personal care products. Specific issues include population trends in exposure, temporal reliability of a urinary metabolite measurement, and how well a single urine sample may represent longer-term exposure. The focus of this review is on seven specific phthalates: diethyl phthalate (DEP); di-n-butyl phthalate (DBP); diisobutyl phthalate (DiBP); butyl benzyl phthalate (BBzP); di(2-ethylhexyl) phthalate (DEHP); diisononyl phthalate (DiNP); and diisodecyl phthalate (DiDP).Comprehensive literature search using multiple search strategies.Since 2001, declines in population exposure to DEP, BBzP, DBP, and DEHP have been reported in the United States and Germany, but DEHP exposure has increased in China. Although the half-lives of various phthalate metabolites are relatively short (3 to 18h), the intraclass correlation coefficients (ICCs) for phthalate metabolites, based on spot and first morning urine samples collected over a week to several months, range from weak to moderate, with a tendency toward higher ICCs (greater temporal stability) for metabolites of the shorter-chained (DEP, DBP, DiBP and BBzP, ICCs generally 0.3 to 0.6) compared with those of the longer-chained (DEHP, DiNP, DiDP, ICCs generally 0.1 to 0.3) phthalates. Additional research on optimal approaches to addressing the issue of urine dilution in studies of associations between biomarkers and different type of health effects is needed.In conclusion, the measurement of urinary metabolite concentrations in urine could serve as a valuable approach to estimating exposure to phthalates in environmental epidemiology studies. Careful consideration of the strengths and limitations of this approach when interpreting study results is required.

SUBMITTER: Johns LE

PROVIDER: S-EPMC4648682 | biostudies-literature | 2015 Dec

REPOSITORIES: biostudies-literature

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Exposure assessment issues in epidemiology studies of phthalates.

Johns Lauren E LE Cooper Glinda S GS Galizia Audrey A Meeker John D JD

Environment international 20150824

<h4>Purpose</h4>The purpose of this paper is to review exposure assessment issues that need to be addressed in designing and interpreting epidemiology studies of phthalates, a class of chemicals commonly used in consumer and personal care products. Specific issues include population trends in exposure, temporal reliability of a urinary metabolite measurement, and how well a single urine sample may represent longer-term exposure. The focus of this review is on seven specific phthalates: diethyl p ...[more]

PMID: 26313703

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Project description:BackgroundThe association between environmental chemical exposures and chronic diseases is of increasing concern. Chemical risk assessment relies heavily on pre-market toxicity testing to identify safe levels of exposure, often known as reference doses (RfD), expected to be protective of human health. Although some RfDs have been reassessed in light of new hazard information, it is not a common practice. Continuous surveillance of animal and human data, both in terms of exposures and associated health outcomes, could provide valuable information to risk assessors and regulators. Using ortho-phthalates as case study, we asked whether RfDs deduced from male reproductive toxicity studies and set by traditional regulatory toxicology approaches sufficiently protect the population for other health outcomes.MethodsWe searched for epidemiological studies on benzyl butyl phthalate (BBP), diisobutyl phthalate (DIBP), dibutyl phthalate (DBP), dicyclohexyl phthalate (DCHP), and bis(2-ethylhexyl) phthalate (DEHP). Data were extracted from studies where any of the five chemicals or their metabolites were measured and showed a statistically significant association with a health outcome; 38 studies met the criteria. We estimated intake for each phthalate from urinary metabolite concentration and compared estimated intake ranges associated with health endpoints to each phthalate's RfD.ResultFor DBP, DIBP, and BBP, the estimated intake ranges significantly associated with health endpoints were all below their individual RfDs. For DEHP, the intake range included associations at levels both below and above its RfD. For DCHP, no relevant studies could be identified. The significantly affected endpoints revealed by our analysis include metabolic, neurodevelopmental and behavioral disorders, obesity, and changes in hormone levels. Most of these conditions are not routinely evaluated in animal testing employed in regulatory toxicology.ConclusionWe conclude that for DBP, DIBP, BBP, and DEHP current RfDs estimated based on male reproductive toxicity may not be sufficiently protective of other health effects. Thus, a new approach is needed where post-market exposures, epidemiological and clinical data are systematically reviewed to ensure adequate health protection.

Project description:BackgroundSchool-aged children living near plastics-producing factories may have higher risk of exposure to phthalates released during the manufacturing processes.ObjectivesWe aimed to investigate the urinary concentrations of phthalate metabolites in school-aged children living near a petrochemical complex and estimate the cumulative risk of phthalate exposure.MethodsWe used a well-established cohort (Taiwan Petrochemical Complex Cohort for Children, TPE3C) of school-aged children (6-13 years old) living near polyvinyl chloride (PVC) and vinyl chloride monomer (VCM) factories in central Taiwan from October 2013 to September 2014. A total of 257 children were included from five elementary schools: Syu-Cuo Branch (n = 58, school A, ~0.9 km), Feng-An (n = 40, school B, ~2.7 km), Ciao-Tou (n = 58, school C, ~5.5 km), Mai-Liao (n = 37, school D, ~6.9 km), and Lung-Feng (n = 57, school E, ~8.6 km). We analyzed 11 metabolites of seven phthalates (including di-2-ethylhexyl phthalate (DEHP) and di-n-butyl phthalate (DnBP)) in urine. Daily intakes (DIs) were compared with acceptable intake levels to calculate the hazard quotient (HQ) for individual phthalates, and the cumulative risk for each child was assessed using a hazard index (HI), which was the sum of the the individual HQs.ResultsThe geometric mean and proportion of participants with HIs exceeding one for hepatic (HIhep) and reproductive (HIrep) effects were 0.33 (13.2%) and 0.24 (7.8%), respectively. The major contributors to phthalate exposure risk were DEHP, di-iso-butyl phthalate (DiBP) and DnBP in all children. Moreover, we observed a U shaped distribution of DEHP exposure by school distance from the PVC and VCM factories (school A: 7.48 μg/kg/day and school E: 80.44 μg/kg/day). This may be due to emissions (closest) and and being located downwind of PVC scrap incineration (farthest).ConclusionsOur findings suggest that children living near a petrochemical complex were at a greater risk of phthalate exposure than normal school-aged children and that phthalate exposure was mainly attributed to DEHP, DiBP and DnBP. In addition, inhalation may have been a risk factor for people living near to PVC and VCM factories.

Project description:We performed personal PM2.5 monitoring involving 56 adult residents in Hong Kong. Additionally, paired personal and residential indoor fine particle (PM2.5) samples were collected from 26 homes and from 3 fixed monitoring locations (i.e., outdoor samples). Six PM2.5-bound phthalate esters (PAEs)-including dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DnBP), butyl benzyl phthalate (BBP), di(2-ethylhexyl) phthalate (DEHP), and di-n-octyl phthalate (DnOP)-were measured using a thermal desorption-gas chromatography/mass spectrometer method. Average ∑6PAEs (i.e., summation of six PAE congeners) concentrations in personal PM2.5 exposure (699.4 ng/m3) were comparable with those in residential indoors (646.9 ng/m3), and both were slightly lower than the outdoor levels. DEHP was the most abundant PAE congener (80.3%-85.0%) and found at the highest levels in different exposure categories, followed by BBP, DnBP, and DnOP. Strong correlations were observed between DEHP with DnBP (rs: 0.81-0.90; p < 0.01), BBP (rs: 0.81-0.90; p < 0.01), and DnOP (rs: 0.87-0.93; p < 0.01) in each exposure category. However, no apparent intercorrelations were shown for PAE congeners. Higher indoor concentrations and a stronger correlation between DMP and DEP were found compared with outdoor concentrations. Principal component analysis affirmed heterogeneous distribution and notable variations in PAE sources across different exposure categories. The average daily intakes of ∑6PAEs and DEHP via inhalation were 0.14-0.17 and 0.12-0.16 μg/kg-day for adults in Hong Kong. A time-weighted model was used to estimate PAE exposures incorporating residential indoor and outdoor exposure and time activities. The inhalation cancer risks attributable to measured and estimated personal exposure to DEHP exceeded the U.S. EPA's benchmark (1 × 10-6). The results provide critical information for mitigation strategies, suggesting that PAEs from both ambient and indoor sources should be considered when exploring the inhalation health risks of PAEs exposure.

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Exposure assessment issues in epidemiology studies of phthalates.

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Exposure assessment issues in epidemiology studies of phthalates.

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