Lisa J. Yost

A market basket survey of inorganic arsenic in food.

Dietary arsenic intake estimates based on surveys of total arsenic concentrations appear to be dominated by intake of the relatively non-toxic, organic arsenic forms found in seafood. Concentrations of inorganic arsenic in food have not been not well characterized. Accurate dietary intake estimates for inorganic arsenic are needed to support studies of arsenics status as an essential nutrient, and to establish background levels of exposure to inorganic arsenic. In the market basket survey reported here, 40 commodities anticipated to provide at least 90% of dietary inorganic arsenic intake were identified. Four samples of each commodity were collected. Total arsenic was analysed using an NaOH digestion and inductively coupled plasma-mass spectrometry. Separate aliquots were analysed for arsenic species using an HCl digestion and hydride atomic absorption spectroscopy. Consistent with earlier studies, total arsenic concentrations (all concentrations reported as elemental arsenic per tissue wet weight) were highest in the seafoods sampled (ranging from 160 ng/g in freshwater fish to 2360 ng/g in saltwater fish). In contrast, average inorganic arsenic in seafood ranged from less than 1 ng/g to 2 ng/g. The highest inorganic arsenic values were found in raw rice (74 ng/g), followed by flour (11 ng/g), grape juice (9 ng/g) and cooked spinach (6 ng/g). Thus, grains and produce are expected to be significant contributors to dietary inorganic arsenic intake.

Estimation of Multimedia Inorganic Arsenic Intake in the U.S. Population

Arsenic is widely distributed in the environment by natural and human means. The potential for adverse health effects from inorganic arsenic depends on the level and route of exposure. To estimate potential health risks of inorganic arsenic, the apportionment of exposure among sources of inorganic arsenic is critical. In this study, daily inorganic arsenic intake of U.S. adults from food, water, and soil ingestion and from airborne particle inhalation was estimated. To account for variations in exposure across the U.S., a Monte Carlo approach was taken using simulations for 100,000 individuals representing the age, gender, and county of residence of the U.S. population based on census data. Our analysis found that food is the greatest source of inorganic arsenic intake and that drinking water is the next highest contributor. Inhalation of airborne arsenic-containing particles and ingestion of arsenic-containing soils were negligible contributors. The exposure is best represented by the ranges of inorganic arsenic intake (at the 10th and 90th percentiles), which were 1.8 to 11.4 µg/day for males and 1.3 to 9.4 µg/day for females. Regional differences in inorganic arsenic exposure were due mostly to consumption of drinking water containing differing inorganic arsenic content rather than to food preferences.

Estimation of Dietary Intake of Inorganic Arsenic in U.S. Children

ABSTRACT Arsenic is a natural component of the environment and is ubiquitous in soils, water, and the diet. Because dietary intake can be a significant source of background exposure to inorganic arsenic (the most toxicologically significant form), accurate intake estimates are needed to provide a context for risk management of arsenic exposure. Intake of inorganic arsenic by adults is fairly well characterized, but previous estimates of childhood intake were based on inorganic arsenic analyses in a limited number of foods (13 food types). This article estimates dietary intake for U.S. children (1 to 6 years of age) based on reported inorganic arsenic concentrations in 38 foods and in water used in cooking those foods (inorganic arsenic concentration of 0.8 μg/L), and U.S. Department of Agriculture food consumption data. This information is combined using a probabilistic software model to extract food consumption patterns and compute exposure distributions. The mean childhood dietary intake estimate for inorganic arsenic was 3.2 μg/day with a range of 1.6 to 6.2 μg/day for the 10th and 95th percentiles, respectively. For both the mean and 95th percentile inorganic arsenic intake rates, intake was predominantly contributed by grain and grain products, fruits and fruit juices, rice and rice products, and milk.

Occupational trichloroethylene exposure and non-Hodgkin's lymphoma: a meta-analysis and review.

Methods: Meta-analysis and review of 14 occupational cohort and four case-control studies of workers exposed to trichloroethylene (TCE) to investigate the relation between TCE exposure and the risk of non-Hodgkin’s lymphoma (NHL). Studies were selected and categorised based on a priori criteria, and results from random effects meta-analyses are presented. Results: The summary relative risk estimates (SRRE) for the group of cohort studies that had more detailed information on TCE exposure was 1.29 (95% CI 1.00 to 1.66) for the total cohort and 1.59 (95% CI 1.21 to 2.08) for the seven studies that identified a specific TCE exposed sub-cohort. SRREs for three studies with cumulative exposure information were 1.8 (95% CI 0.62 to 5.26) for the lowest exposure category and 1.41 (95% CI 0.61 to 3.23) for the highest category. Comparison of SRREs by levels of TCE exposure did not indicate exposure-response trends. The remaining cohort studies that identified TCE exposure but lacked detailed exposure information had an SRRE of 0.843 (95% CI 0.72 to 0.98). Case-control studies had an SRRE of 1.39 (95% CI 0.62 to 3.10). Statistically significant findings for the Group 1 studies were driven by the results from the subgroup of multiple industry cohort studies (conducted in Europe) (SRRE = 1.86; 95% CI 1.27 to 2.71). The SRRE for single industry cohort studies was not significantly elevated (SRRE = 1.25; 95% CI 0.87 to 1.79). Conclusions: Interpretation of overall findings is hampered by variability in results across the Group 1 studies, limited exposure assessments, lack of evidence of exposure response trends, lack of supportive information from toxicological and mechanistic data, and absence of consistent findings in epidemiologic studies of exposure and NHL. Although a modest positive association was found in the TCE sub-cohort analysis, a finding attributable to studies that included workers from multiple industries, there is insufficient evidence to suggest a causal link between TCE exposure and NHL.

Importance of Considering the Framework Principles in Risk Assessment for Metals

The recent EPA Framework for Metals Risk Assessment provides the opportunity for contextual risk assessment for sites impacted by metals (such as the depicted Dauntless Mine in Colorado).

Issues in arsenic cancer risk assessment.

Efforts to develop effective therapeutic treatments for promoting fast wound healing after injury to the epidermis are hindered by a lack of understanding of the factors involved. Re-epithelialization is an essential step of wound healing involving the migration of epidermal keratinocytes over the wound site. Here, we examine genetic variants in the keratin-1 (KRT1) locus for association with migration rates of human epidermal keratinocytes (HEK) isolated from different individuals. Although the role of intermediate filament genes, including KRT1, in wound activated keratinocytes is well established, this is the first study to examine if genetic variants in humans contribute to differences in the migration rates of these cells. Using an in vitro scratch wound assay we observe quantifiable variation in HEK migration rates in two independent sets of samples; 24 samples in the first set and 17 samples in the second set. We analyze genetic variants in the KRT1 interval and identify SNPs significantly associated with HEK migration rates in both samples sets. Additionally, we show in the first set of samples that the average migration rate of HEK cells homozygous for one common haplotype pattern in the KRT1 interval is significantly faster than that of HEK cells homozygous for a second common haplotype pattern. Our study demonstrates that genetic variants in the KRT1 interval contribute to quantifiable differences in the migration rates of keratinocytes isolated from different individuals. Furthermore we show that in vitro cell assays can successfully be used to deconstruct complex traits into simple biological model systems for genetic association studies.

Derivation of Soil Clean-Up Levels for 2,3,7,8-Tetrachloro-dibenzo-p-dioxin (TCDD) Toxicity Equivalence (TEQD/F) in Soil Through Deterministic and Probabilistic Risk Assessment of Exposure and Toxicity

ABSTRACT While risk assessments are extensively used for guiding critical and resource intensive decisions, assessments that rigorously integrate key exposure and toxicity terms are less often published. This article derives residential soil clean-up levels accounting for ingestion and dermal contact (direct contact criteria [DCC]) for a chlorinated dibenzo-p-dioxin and furan (PCDD/F as toxicity equivalence TEQD/F) impacted site using site-specific information and deterministic and probabilistic methods. In addition, TEQD/F risk assessment has been the subject of extensive scientific and regulatory debate including in-depth comments from two USEPA Science Advisory Boards and the National Academy of Sciences (NAS) on the proposed USEPA Draft Dioxin Risk Assessment. This article presents and applies toxicity values seeking to address the NAS recommendations regarding cancer risk assessment. Deterministic DCC estimates ranged from 19 to 250 ppb through application of linear and nonlinear cancer toxicity values, and a DCC of 5.3 ppb was estimated based on the World Health Organizations Joint Exposure Committee on Food Additives assessment value for noncancer and cancer endpoints. A wide range of DCC estimates were calculated using probabilistic methods, with the prior USEPA 1 ppb clean-up value falling below the first percentile of estimates, suggesting that the 1 ppb value is health protective.

Lack of Complete Exposure Pathways for Metals in Natural and FGD Gypsum

ABSTRACT Use of wallboard made from synthetic gypsum generated via flue-gas desulfurization (FGD) by coal-fired power plants (FGD gypsum) raised questions concerning the potential for exposure to residual trace metals. Because gypsum is widely used (e.g., in wallboard), any issue with metals could have far-reaching implications. A conceptual site model evaluated potential human health exposure pathways for metals in gypsum, through consideration of data for 21 metals including samples of natural (mined) gypsum, and of FGD gypsum. Because there are no screening values for gypsum, comparisons were made to background soil concentrations and to risk-based concentrations for metals in soil termed preliminary remedial action goals (PRGs), which assume more frequent and prolonged contact with particulate soil than would be likely for gypsum, and thus provide a health protective means for evaluation of exposure. Additional screenings evaluated occupational exposure and agricultural use of gypsum. Maximum metal concentrations in natural and FGD gypsum samples were either consistent with background concentrations or much lower than PRGs for residential or agricultural soil, or workplace air, and thus exposure pathways for these media were considered incomplete. Separate analyses of mercury volatilization were conducted, and this pathway was also found to be incomplete.

Risk Assessment as a Decision-Making Tool for Treatment of Emissions at a New Aluminum Smelter in Iceland: 1. Background and Introduction

ABSTRACT Protection of human health and ecosystems is gaining importance in corporate decision- making regarding industrial development. During the design phase for an aluminum smelter in East Iceland, it became necessary to determine whether a wet scrubber system should be installed to reduce sulfur dioxide emissions. Predictive risk assessment was used to determine whether there would be a consequential difference in the level of risk to human and ecological receptors from constituents in air emissions from the aluminum smelter, either with or without wet scrubbers. Benchmark exposure concentrations were established for avian, mammalian, and plant receptors and were compared to air modeling predictions to develop risk estimates. Benchmark concentrations were derived using plant uptake models for fluoride and polycyclic aromatic hydrocarbons (PAHs), and food-web modeling for birds and mammals. Exposure models were developed for all receptors, and population-level effects were modeled for plant, bird, and mammal receptors. Results indicated that exposures under both scenarios are lower than risk thresholds, and overall risk was lower for a smelter without wet scrubbers. Thus, although mass loading of sulfur dioxide (and other constituents) would be reduced using wet scrubbers, the corresponding risk to ecological receptors would actually be higher because of higher exposure-point concentrations in air.

Risk Assessment as a Decision-Making Tool for Treatment of Emissions at a New Aluminum Smelter in Iceland: 2. Human Health Risk Assessment

ABSTRACT Alcoa recently constructed the Fjarðaál aluminum smelter in Reyðarfjörður, East Iceland. The smelter is designed to produce a maximum of 346,000 metric tons per year of aluminum. A risk assessment was conducted to evaluate the differential human health risk related to estimated potential air emissions from the planned Fjarðaál smelter with and without seawater scrubbers. Air-dispersion modeling results provided for particulate matter (PM10), sulfur dioxide (SO2), hydrogen fluoride (HF), and polycyclic aromatic hydrocarbons (PAHs) were compared to ambient air standards or air quality guidelines from Norway, Iceland, or European directives and from the U.S. Environmental Protection Agency. Risk estimates were calculated for PAHs. Modeled air estimates were mapped geospatially, to identify potential receptors, including onsite outdoor worker, seagoing worker, hypothetical fence-line resident, future hypothetical resident, closest current resident, residents in neighboring villages, closest farmer, and a visitor to the nearby Holmanes Nature Reserve. Both with and without seawater scrubbers, the predicted exceedances of standards per year for SO2 were well below the maximum number allowed. Use of seawater scrubbers was predicted to decrease average SO2 air concentration estimates in the short term; however, annual estimates were lower without seawater scrubbers. Risk estimates for carcinogenic and non-carcinogenic PAHs, and modeled air concentrations of HF and PM10, were well within acceptable levels.