Tag Archives: exposure assessment

Mulitmedia Modeling of Children’s Lead Exposure

Zartarian V, Xue J, Tornero-Velez R, Brown J. Children’s Lead Exposure: A Multimedia Modeling Analysis to Guide Public Health Decision-Making. Environmental health perspectives 2017 Sep 12;125(9):097009. doi: 10.1289/EHP1605.

BACKGROUND: Drinking water and other sources for lead are the subject of public health concerns around the Flint, Michigan, drinking water and East Chicago, Indiana, lead in soil crises. In 2015, the U.S. Environmental Protection Agency (EPA)’s National Drinking Water Advisory Council (NDWAC) recommended establishment of a “health-based, household action level” for lead in drinking water based on children’s exposure.

OBJECTIVES: The primary objective was to develop a coupled exposure-dose modeling approach that can be used to determine what drinking water lead concentrations keep children’s blood lead levels (BLLs) below specified values, considering exposures from water, soil, dust, food, and air. Related objectives were to evaluate the coupled model estimates using real-world blood lead data, to quantify relative contributions by the various media, and to identify key model inputs.

METHODS: A modeling approach using the EPA’s Stochastic Human Exposure and Dose Simulation (SHEDS)-Multimedia and Integrated Exposure Uptake and Biokinetic (IEUBK) models was developed using available data. This analysis for the U.S. population of young children probabilistically simulated multimedia exposures and estimated relative contributions of media to BLLs across all population percentiles for several age groups.

RESULTS: Modeled BLLs compared well with nationally representative BLLs (0-23% relative error). Analyses revealed relative importance of soil and dust ingestion exposure pathways and associated Pb intake rates; water ingestion was also a main pathway, especially for infants.

CONCLUSIONS: This methodology advances scientific understanding of the relationship between lead concentrations in drinking water and BLLs in children. It can guide national health-based benchmarks for lead and related community public health decisions.

Human Exposure to Perfluorochemicals

Jian JM, Guo Y, Zeng L, Liang-Ying L, Lu X, Wang F, Zeng EY. Global distribution of perfluorochemicals (PFCs) in potential human exposure source-A review. Environ Int. 2017 Aug 8;108:51-62. doi: 10.1016/j.envint.2017.07.024.

Human exposure to perfluorochemicals (PFCs) has attracted mounting attention due to their potential harmful effects. Breathing, dietary intake, and drinking are believed to be the main routes for PFC entering into human body. Thus, we profiled PFC compositions and concentrations in indoor air and dust, food, and drinking water with detailed analysis of literature data published after 2010. Concentrations of PFCs in air and dust samples collected from home, office, and vehicle were outlined. The results showed that neutral PFCs (e.g., fluorotelomer alcohols (FTOHs) and perfluorooctane sulfonamide ethanols (FOSEs)) should be given attention in addition to PFOS and PFOA. We summarized PFC concentrations in various food items, including vegetables, dairy products, beverages, eggs, meat products, fish, and shellfish. We showed that humans are subject to the dietary PFC exposure mostly through fish and shellfish consumption. Concentrations of PFCs in different drinking water samples collected from various countries were analyzed. Well water and tap water contained relatively higher PFC concentrations than other types of drinking water. Furthermore, PFC contamination in drinking water was influenced by the techniques for drinking water treatment and bottle-originating pollution.

TOX in Urine as an Exposure Surrogate, China

Y Kimura S, Zheng W, N Hipp T, M Allen J, D Richardson S. Total organic halogen (TOX) in human urine: A halogen-specific method for human exposure studies. Journal of environmental sciences (China). 2017 Aug;58:285-295. doi: 10.1016/j.jes.2017.04.008.

Disinfection by-products (DBPs) are a complex mixture of compounds unintentionally formed as a result of disinfection processes used to treat drinking water. Effects of long-term exposure to DBPs are mostly unknown and were the subject of recent epidemiological studies. However, most bioanalytical methods focus on a select few DBPs. In this study, a new comprehensive bioanalytical method has been developed that can quantify mixtures of organic halogenated compounds, including DBPs, in human urine as total organic chlorine (TOCl), total organic bromine (TOBr), and total organic iodine (TOI). The optimized method consists of urine dilution, adsorption to activated carbon, pyrolysis of activated carbon, absorption of gases in an aqueous solution, and halide analysis with ion chromatography and inductively coupled plasma-mass spectrometry. Spike recoveries for TOCl, TOBr, and TOI measurements ranged between 78% and 99%. Average TOCl, TOBr, and TOI concentrations in five urine samples from volunteers who consumed tap water were 1850, 82, and 21.0μg/L as X, respectively. Volunteers who consumed spring water (control) had TOCl, TOBr, and TOI average concentrations in urine of 1090, 88, and 10.3μg/L as X, respectively. TOCl and TOI in the urine samples from tap water consumers were higher than the control. However, TOBr was slightly lower in tap water urine samples compared to mineral water urine samples, indicating other sources of environmental exposure other than drinking water. A larger sample population that consumes tap water from different cities and mineral water is needed to determine TOCl, TOBr, and TOI exposure from drinking water.

DBP Compliance Data are Poor Proxies for Short-Term Exposure

Parvez S, Frost K, Sundararajan M. Evaluation of Drinking Water Disinfectant Byproducts Compliance Data as an Indirect Measure for Short-Term Exposure in Humans. Int J Environ Res Public Health. 2017 May 20;14(5). pii: E548. doi: 10.3390/ijerph14050548.

In the absence of shorter term disinfectant byproducts (DBPs) data on regulated Trihalomethanes (THMs) and Haloacetic acids (HAAs), epidemiologists and risk assessors have used long-term annual compliance (LRAA) or quarterly (QA) data to evaluate the association between DBP exposure and adverse birth outcomes, which resulted in inconclusive findings. Therefore, we evaluated the reliability of using long-term LRAA and QA data as an indirect measure for short-term exposure. Short-term residential tap water samples were collected in peak DBP months (May-August) in a community water system with five separate treatment stations and were sourced from surface or groundwater. Samples were analyzed for THMs and HAAs per the EPA (U.S. Environmental Protection Agency) standard methods (524.2 and 552.2). The measured levels of total THMs and HAAs were compared temporally and spatially with LRAA and QA data, which showed significant differences (p < 0.05). Most samples from surface water stations showed higher levels than LRAA or QA. Significant numbers of samples in surface water stations exceeded regulatory permissible limits: 27% had excessive THMs and 35% had excessive HAAs. Trichloromethane, trichloroacetic acid, and dichloroacetic acid were the major drivers of variability. This study suggests that LRAA and QA data are not good proxies of short-term exposure. Further investigation is needed to determine if other drinking water systems show consistent findings for improved regulation.

Evaluating bias in lead sampling, Flint, Michigan

Sampling for lead in drinking is easier said than done. There are scientific and technical issues that complicate sampling and interpretation of testing results. It is important to understand that the purpose of sampling for lead under the USEPA lead rule is not exposure assessment. The primary goal is to confirm whether or not the water system is practicing optimal corrosion control. Seems to me that we are at a critical juncture in regulating lead in drinking water and some innovative thinking is needed to develop and move forward with a regulatory approach that will be effective in reducing lead exposure.

Goovaerts P. Monitoring the aftermath of Flint drinking water contamination crisis: Another case of sampling bias? Sci Total Environ. 2017 Mar 2. pii: S0048-9697(17)30440-0. doi: 10.1016/j.scitotenv.2017.02.183.

The delay in reporting high levels of lead in Flint drinking water, following the city’s switch to the Flint River as its water supply, was partially caused by the biased selection of sampling sites away from the lead pipe network. Since Flint returned to its pre-crisis source of drinking water, the State has been monitoring water lead levels (WLL) at selected “sentinel” sites. In a first phase that lasted two months, 739 residences were sampled, most of them bi-weekly, to determine the general health of the distribution system and to track temporal changes in lead levels. During the same period, water samples were also collected through a voluntary program whereby concerned citizens received free testing kits and conducted sampling on their own. State officials relied on the former data to demonstrate the steady improvement in water quality. A recent analysis of data collected by voluntary sampling revealed, however, an opposite trend with lead levels increasing over time. This paper looks at potential sampling bias to explain such differences. Although houses with higher WLL were more likely to be sampled repeatedly, voluntary sampling turned out to reproduce fairly well the main characteristics (i.e. presence of lead service lines (LSL), construction year) of Flint housing stock. State-controlled sampling was less representative; e.g., sentinel sites with LSL were mostly built between 1935 and 1950 in lower poverty areas, which might hamper our ability to disentangle the effects of LSL and premise plumbing (lead fixtures and pipes present within old houses) on WLL. Also, there was no sentinel site with LSL in two of the most impoverished wards, including where the percentage of children with elevated blood lead levels tripled following the switch in water supply. Correcting for sampling bias narrowed the gap between sampling programs, yet overall temporal trends are still opposite.

Human exposure to arsenic in household water, Pakistan

Rasheed H, Kay P, Slack R, Gong YY, Carter A. Human exposure assessment of different arsenic species in household water sources in a high risk arsenic area. The Science of the total environment. 2017 Jan 25. pii: S0048-9697(17)30098-0. doi: 10.1016/j.scitotenv.2017.01.089.

Understanding arsenic speciation in water is important for managing the potential health risks associated with chronic arsenic exposure. Most arsenic monitoring studies to date have only measured total arsenic, with few looking at arsenic species. This study assessed 228 ground water sources in six unstudied villages in Pakistan for total, inorganic and organic arsenic species using ion chromatography inductively coupled plasma collision reaction cell mass spectrometry. The concentration levels approached 3090μgL-1 (95% CI, 130.31, 253.06) for total arsenic with a median of 57.55μgL-1, 3430μgL-1 (median=52) for arsenate (As+5) and 100μgL-1 (median=0.37) for arsenite (As+3). Exceedance of the WHO provisional guideline value for arsenic in drinking water (10μgL-1) occurred in 89% of water sources. Arsenic was present mainly as arsenate (As+5). Average daily intake of total arsenic for 398 residents living in the sampled houses was found up to 236.51μgkg-1day-1. This exposure estimate has indicated that 63% of rural residents exceeded the World Health Organization’s provisional tolerable daily intake (PTDI) of 2.1μgkg-1day-1 body weight. Average daily intake of As+5 was found to be 15.63μgkg-1day-1 (95% CI, 5.53, 25.73) for children ≤16 and 15.07μgkg-1day-1 (95% CI, 10.33, 18.02) for adults. A mean daily intake of 0.09μgkg-1day-1 was determined for As+3 for children and 0.26μgkg-1day-1 for adults. Organic arsenic species such as monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and Arsenobetaine (AsB) were found to be below their method detection limits (MDLs).

Uranium Exposure from Drinking Water, Rajasthan, India

Jakhu R, Mehra R, Mittal HM. Exposure assessment of natural uranium from drinking water. Environmental Science: Process Impacts. Nov 2016 

The uranium concentration in the drinking water of the residents of the Jaipur and Ajmer districts of Rajasthan has been measured for exposure assessment. The daily intake of uranium from the drinking water for the residents of the study area is found to vary from 0.4 to 123.9 μg per day. For the average uranium ingestion rate of 35.2 μg per day for a long term exposure period of 60 years, estimations have been made for the retention of uranium in different body organs and its excretion with time using ICRP’s biokinetic model of uranium. Radioactive and chemical toxicity of uranium has been reported and discussed in detail in the present manuscript.