Session Schedule & Abstracts
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|Chair(s): Amina Wilkins Wilkins.Amina@epa.gov
Sponsored by Exposure Assessment SG
1:30 pm A Systematic Review on Bioaccessibility of Arsenic in Rice. Zhou Zheng*, Shao Kan; Indiana University email@example.com
Abstract: In order to more accurately estimate arsenic exposure from rice consumption, it is critical to consider bioaccessibility of arsenic in rice, which refers to the fraction of arsenic that is soluble and ready for absorption in GI tract. The concentration of arsenic in rice could be enormously different from the concentration that is bioaccessible in the GI tract. In FDAâ€™s 2016 Arsenic in Rice and Rice Products Risk Assessment Report, an estimate of 63%~99% was used as the bioaccessibility of total arsenic in rice. In our study, we performed a systematic review to summarize the current state of knowledge of the bioaccessibility of arsenic in rice, and a meta-analysis to provide a more robust probabilistic estimation of arsenic bioaccessibility. 143 articles were extracted from the PubMed and Toxline online database by using the key keywords of arsenic, rice, bioaccessibility, and bioavailability. Among these 143 studies, eight publications, which provided high-quality and primary experimental data on the bioaccessibility of arsenic in rice, were included in our review. Results of our meta-analysis show that the median (with 5th and 95th percentile) of bioaccessibility estimate was 75.5% (45.0- 94.4%) and 90.4% (72.2- 98.4%) for total and inorganic arsenic, respectively. In addition, we employed a generalized linear regression analysis to explore the correlations between arsenic bioaccessibility and various factors that could potentially influence the bioaccessibility, such as rice genotypes and cooking methods. Our preliminary results suggest that short-grain genotype and unmilled rice were significantly correlated with lower bioaccessibility of total arsenic (but not necessarily low total arsenic concentrations) while controlling for other factors.
1:50 pm Estimating Water Age and its Effects on Water Quality in a Full-Scale Green Home. Julien R*, Mitchell J; Michigan State University firstname.lastname@example.org
Abstract: Green building practices are focused on the efficient use of water, energy, and materials. These design elements such as low-flow fixtures and high-efficiency appliances continue to gain popularity. For example, the percentage of homes with an average toilet flush volume less than two gallons has increased from 8.5% in 1999 to 37% in 2016. Adoption of these and other water efficient technologies has dramatically reduced the quantity of water consumed in the United States. However, plumbing system design has not adequately kept pace to address the changing demand. As a result, increased hydraulic retention time or water age occurs and can have an adverse effect on water quality including the reduction of disinfectant residual, increased leaching of pipe materials into the bulk water, and the promotion of opportunistic pathogens such as Legionella spp., Mycobacterium spp., and P. aeruginosa. Opportunistic pathogens in drinking water plumbing are the primary cause of waterborne disease in developed countries. The incidence of Legionella spp. increased from 0.39 cases per 100,000 in 200 to 1.15 in 2009. Unfortunately, quantifying health risks associated with water usage patterns is not well studied. This study aims to estimate water age within the premise plumbing of a full-scale residential net-zero building to evaluate health risks. Water age will be estimated based on data collected from flow meters that are installed at several fixtures within the home. Multiple flow regimes will be evaluated and compared to analytical water quality data collected from the home to characterize potential risks.
2:10 pm Risk Assessment of Benzo[a]pyrene in Heat-processed Meat in Denmark: A Probabilistic Approach. Georgiadis S*, Jakobsen LS, Nielsen BF, Nauta MJ, Pires SM; Technical University of Denmark email@example.com
Abstract: Heat-processed meat may contain high concentrations of polycyclic aromatic hydrocarbons, a class of chemical components including benzo[a]pyrene (BaP) that is classified as group 1 human carcinogen by IARC. To minimize risk due to dietary exposure to these contaminants, food and health authorities may advise the population to limit certain preparation practices such as barbecuing. Assessment of the health risk given specific food preparation practices may direct food-safety strategies to those consumer-groups that are at higher risk. Our objective was to estimate the extra lifetime risk of cancer due to exposure to BaP through barbecued meat in Denmark, both for the overall population and for subgroups. The probabilistic risk model consists of two parts; exposure assessment and cancer risk estimation. The first part focuses on modelling human exposure to BaP, taking into account the variability among individuals and between population subgroups. Consumption of various meat types and concentration of BaP in barbecued meat types are described by probability distributions. In the second part, human exposure is converted to an equivalent animal exposure to allow the usage of an animal dose-response model. The variability in individuals' sensitivity to BaP and uncertainty in interspecies differences are quantified. The extra lifetime risk of cancer due to BaP is calculated through a dose-response model whose parameters are uncertain. To derive population-level results, the frequency of consumption of barbecued meat in Denmark is assessed, while for population subgroups, model outputs are presented as a function of the number of barbecued meat servings. An event-based Monte Carlo simulation scheme is built to perform the calculations and separate uncertainty and variability. The findings of this study highlight that uncertainties induced in the cancer risk assessment module overshadow any variations within population or between population subgroups.
2:30 pm Determing the Relationship Between Drinking Private Well Water and Children's Blood Lead Levels. Komandur AR*, Stillo FJ, Gibson JM; University of North Carolina at Chapel Hill firstname.lastname@example.org
Abstract: Over the past 50 years, the U.S. Environmental Protection Agency and other governmental organizations have been passing regulations to decrease the populationâ€™s exposure to lead, which is a potent neurotoxin. However, as recent events in Flint, Michigan and other areas have demonstrated, lead exposure through drinking water is still a prominent concern. Lead adversely impacts health when consumed through drinking water, but no research has yet been done to investigate the relationship between drinking water contaminated with lead from private wells and human health outcomes. To better understand this relationship, we are conducting a study to determine the relationship between lead contamination in private wells in North Carolina and childrenâ€™s blood lead levels. Sixty children under the age of 7 were recruited from households relying on private wells for their water in Wake and Gaston counties. Throughout summer 2018, we are collecting blood samples from each child, along with water and dust samples from their respective households. We will use regression models and Bayesian networks to explore the relationship between water lead and blood lead, controlling for other lead sources and potential confounders. After controlling for background lead exposure, we anticipate that water lead levels will have a direct effect on blood lead levels. Although prior studies have shown elevated risks of exposure to lead in water from private wells, compared to in treated municipal water, this study is the first of its kind to investigate the health risks to children of drinking private well water that is contaminated with lead.
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