Critical Aspects of EPA's IRIS Assessment of Inorganic Arsenic Interim Report (2013) / Chapter Skim
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2 Exposure Considerations
2 Exposure Considerations
Pages 11-17
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From page 11... ...
Probabilistic exposure modeling that used NHANES dietary data from 2003– 2004 coupled with duplicate diet and biomarker measurements estimated that the major contributors to dietary inorganic arsenic intake are vegetables (24%) , fruit juices and fruits (18%)
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From page 12... ...
The mean urinary excretion fraction was about 58% in one subject and 63% in the other -- indicating that a substantial fraction of the rice arsenic was absorbed. Several studies have identified increased concentrations of urinary arsenic metabolites after ingestion of rice, and studies that used more sensitive arsenic speciation methods have found elevated concentrations of urinary inorganic arsenic and DMA in people for whom rice is a dietary staple (e.g., Cascio et al.
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From page 13... ...
Predictions of tissue concentrations of inorganic arsenic and its metabolites may be obtained by using physiologically based pharmacokinetic models, although human data to parameterize such models is limited (El-Masri and Kenyon 2008)
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From page 14... ...
14 F FIGURE 2 Arseni metabolism: Inor ic rganic arsenate (AsV) can be reduced by glutathione (G d GSH)
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From page 15... ...
. There is consistent evidence from epidemiologic studies in populations exposed to high arsenic concentrations in drinking water that people who can efficiently convert inorganic arsenic to DMA are at lower risk for arsenic-induced disease than those who are "poor methylators", who have higher proportions of MMA and inorganic arsenic in urine.
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From page 16... ...
Arsenic measured in urine is derived from recent exposures, largely the previous day, so consideration of whether exposures are constant or changing over longer durations involved in the development of arsenic-induced toxicities is needed. Total arsenic includes some forms of organic arsenic commonly occurring in various seafoods, such as arsenobetaine, that have short half-lives and little or no toxicity.
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From page 17... ...
Arsenic metabolites in blood differs from those in urine in that there is a substantially lower proportion of DMA (because of its shorter circulating half-life) and relatively more inorganic arsenic and MMA (Hall et al.
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