Phthalates and Cumulative Risk Assessment The Tasks Ahead (2008) / Chapter Skim
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2 Phthalate Exposure Assessment in Humans
2 Phthalate Exposure Assessment in Humans
Pages 21-38
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From page 21... ...
Many questions remain unanswered about cumulative exposures to phthalates throughout the life span, relative contributions of various sources of exposure to the phthalate body burden over time, and mixed exposures that may include phthalates or other chemicals that may elicit common adverse outcomes. Despite those limitations, the existing information on human exposure to phthalates can be used to help determine whether cumulative risk assessment should be conducted for phthalates.
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From page 22... ...
The utility of other biologic matrices -- such as blood, breast milk, and seminal plasma -- for assessing human exposure remains largely unknown because there are few data. The incorporation of those novel matrices into human studies necessitates the measurement of oxidized metabolites to avoid problems with contamination by the ubiquitous parent diesters.
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From page 23... ...
2008) , urine samples from infants were found to have detectable concentrations of multiple urinary phthalate metabolites, which suggested that exposure to multiple phthalates is common even early in life.
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From page 24... ...
2007a NHANES, United States Germany United States 2001-2002 1988-2003 2003-2004 Spot Urine Sample 24-h Urine Sample Spot Urine Sample N = 1,647, over 20 y old N = 634, 20-29 y old N = 129, Adults Parent Compound Metabolite 50th % 95th % 50th % 95th % 50th % 95th % DMP MMP 1.40 9.10 – – – – DEP MEP 181 2,720 – – – – DBP MBP 19.1 95.4 112 604 – – DIBP MIBP 2.4 16.3 34.5 176 – – BBP MBZP 13.8 99.7 7.4 50.4 – – DCHP MCHP < LOD 0.500 – – – – DEHP MECPP – – 26.9 98.8 – – MEHHP 17.7 175 21.0 77.2 – – MEOHP 12.2 115 16.7 57.5 – – MEHP 4.10 39.5 7.6 33.6 – – DOP MCPP 2.60 12.0 – – – – MOP < LOD < LOD – – – – DINP MINP < LOD < LOD – – – – MHINP – – 2.0 11.9 MOINP – – 1.0 5.6 – –
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From page 25... ...
DIDP MCINP – – – – 4.4 104.4 MHIDP – – – – 4.9 70.6 MOIDP – – – – 1.2 15.0 MIDP – – – – < LOD < LOD a –, data not obtained; LOD, limit of detection. Note: LODs vary by study and by analyte but are generally less than 1 µg/L.
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From page 26... ...
Consequently, they may be especially vulnerable to phthalate exposures during critical stages of growth and development. Highly Exposed Populations Highly exposed people have urinary metabolite concentrations that often exceed those at the 95th percentile of the general population (Table 2-3)
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From page 27... ...
b MECPP 577 MECPP 26.9 [99] b Neonatal intensive care unit, 33 MEHP 129c MEHP 4.4 [30]
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From page 28... ...
. However, the low-molecular-weight phthalate metabolites, such as MEP and MBP, are eliminated quickly, yielding a large proportion of the free nonpolar monoesters, whereas the more polar oxidized metabolites have a greater proportion of conjugated monoesters (Silva et al.
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From page 29... ...
DEHP mono(2-ethyl-6-hydroxyhexyl) phthalate mono(2-ethyl-5-hydroxyhexyl)
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From page 30... ...
There are as yet unexplained interindividual differences in metabolic capacity at each step of phthalate metabolism, which may account for some of the differences seen in urinary metabolites by age, sex, race, and other demographic factors. Such differences may explain the observation that the urinary concentrations of oxidized metabolites are more prevalent in children than in adults (Koch et al.
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From page 31... ...
Thus, the model provides a means of extrapolating rat fetal dose from different phthalate exposure biomarkers in various compartments or biologic matrices. The DBP model has also been extrapolated for use in the human by adjusting the physiologic parameters and scaling chemical-specific parameters allometrically.
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From page 32... ...
Alternatively, it is possible that passive transfer of maternal oxidized metabolites across the placental barrier is not efficient or that they are excreted so rapidly that the resulting low serum concentrations lead to little transfer. Indeed, rat studies suggest that maternal DEHP dose is correlated with urinary and amniotic fluid concentrations of MEHP and MEHHP but that relationships are not linear (Calafat et al.
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From page 33... ...
CONCLUSIONS Our understanding of important sources of, routes of exposure to, and metabolism of phthalates in humans has increased over the last decade. Recent data have shown widespread human exposure to multiple phthalates from a multitude of sources.
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From page 34... ...
2003. Assessing human exposure to phthalates using monoesters and their oxidized metabolites as biomarkers.
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From page 35... ...
phthalate-containing medical products and uri nary levels of mono(2-ethylhexyl) phthalate in neonatal intensive care unit infants.
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From page 36... ...
phthalate and mono-(2-ethyl-5-oxohexyl) phthalate as biomarkers for human exposure assess ment to di-(2-ethylhexyl)
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From page 37... ...
2004. Detection of phthalate metabolites in human amniotic fluid.
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From page 38... ...
2007. Internal phthalate exposure over the last two decades -- a retrospective human biomonitoring study.
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