John Schaum
United States Environmental Protection Agency
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Environmental Science & Technology | 2010
John Schaum; Mark Cohen; Steven G. Perry; Richard Artz; Roland R. Draxler; Jeffrey B. Frithsen; David K. Heist; Matthew Lorber; Linda Phillips
Between April 28 and July 19 of 2010, the U.S. Coast Guard conducted in situ oil burns as one approach used for the management of oil spilled after the explosion and subsequent sinking of the BP Deepwater Horizon platform in the Gulf of Mexico. The purpose of this paper is to describe a screening level assessment of the exposures and risks posed by the dioxin emissions from these fires. Using upper estimates for the oil burn emission factor, modeled air and fish concentrations, and conservative exposure assumptions, the potential cancer risk was estimated for three scenarios: inhalation exposure to workers, inhalation exposure to residents on the mainland, and fish ingestion exposures to residents. U.S. EPAs AERMOD model was used to estimate air concentrations in the immediate vicinity of the oil burns and NOAAs HYSPLIT model was used to estimate more distant air concentrations and deposition rates. The lifetime incremental cancer risks were estimated as 6 × 10(-8) for inhalation by workers, 6 × 10(-12) for inhalation by onshore residents, and 6 × 10(-8) for fish consumption by residents. For all scenarios, the risk estimates represent upper bounds and actual risks would be expected to be less.
Science of The Total Environment | 1994
Matthew Lorber; David H. Cleverly; John Schaum; Linda Phillips; Greg Schweer; Timothy M. Leighton
A model for predicting concentrations of dioxin-like compounds in beef is developed and tested. The key premise of the model is that concentrations of these compounds in air are the source term, or starting point, for estimating beef concentrations. Vapor-phase concentrations transfer to vegetations that cattle consume, and particle-bound concentrations deposit onto soils and these vegetations as well. Congener-specific bioconcentration parameters, coupled with assumptions on cattle diet, transform soil and vegetative concentrations into beef fat concentrations. The premise of the validation exercise is that a profile of typical air concentrations of dioxin-like compounds in a United States rural environment is an appropriate observed independent data set, and that a representative profile of United States beef concentrations of dioxin-like compounds is an appropriate observed dependent result. These data were developed for the validation exercise. An observed concentration of dioxin toxic equivalents in whole beef of 0.48 ng/kg is compared with a predicted 0.36 ng/kg. Principal uncertainties in the approach are identified and discussed. A major finding of this exercise was that vapor phase transfers of dioxin-like compounds to vegetations that cattle consume dominate the estimation of final beef concentrations: over 80% of the modeled beef concentration was attributed to such transfers.
Journal of Exposure Science and Environmental Epidemiology | 2003
John Schaum; Laurie Schuda; Chieh Wu; Rhonda Sears; Joseph Ferrario; Kimberlea Andrews
This study measured 21 persistent, bioaccumulative, and toxic (PBT) pollutants in the US milk supply. Since milk fat is likely to be among the highest dietary sources of exposure to PBTs, it is important to understand their levels in this food. Nationwide samples were collected from 45 dairy plants in July of 2000 and again in January 2001. The levels of all chemicals in the chlorobenzene, pesticide and other halogenated organic groups were determined to be below their detection limits in all samples. National averages were computed for 11 chemicals or chemical groups found above the detection limits. The national average CDD/CDF and PCB TEQ concentrations were 14.30 and 8.64 pg/l, respectively, for a total of 22.94 pg/l. These levels are about half the values found in a similar study conducted in 1996. If this difference is in fact indicative of declining milk levels and assuming exposure levels from nondairy pathways have remained the same over this time period, this would result in an overall decrease in adult background dioxin exposure of 14%. Six PAHs were detected with national averages ranging from 40 to 777 ng/l. Cadmium concentrations ranged from 150 to 870 ng/l with a national average of 360 ng/l. Lead concentrations were consistently higher than those of cadmium, ranging from 630 to 1950 ng/l with a national average of 830 ng/l. PAHs showed the strongest seasonal/geographic differences, with higher levels in winter than summer, north than south and east than west. Average adult daily intakes from total milk fat ingestion were computed for all detected compounds and compared to total intakes from all pathways: CDD/CDF/PCB TEQs: 8 vs. 55 pg/day, PAHs: 0.6 vs. 3 μg/day, lead: 0.14 vs. 4–6 μg/day, and cadmium: 0.06 vs. 30 μg/day.
Chemosphere | 1996
Dwain Winters; David H. Cleverly; Kristen Meier; Aubry Dupuy; Christian Byrne; Cindy L Deyrup; Richard Ellis; Joseph Ferrario; Robert Harless; William Leese; Matthew Lorber; Danny McDaniel; John Schaum; Jim Walcott
The USEPA and the USDA have completed the first statistically designed survey of the occurrence and concentration of CDDs and CDFs in the fat of beef animals raised for human consumption in the United States. Back fat was sampled from 63 carcasses at federally inspected slaughter establishments nationwide. The sample design called for sampling beef animal classes in proportion to national annual slaughter statistics. All samples were analyzed using a modification of EPA method 1613, using isotope dilution, High Resolution GC/MS to determine the rate of occurrence of 2,3,7,8-substituted CDDs/CDFS. The whole weight method detection limits ranged from 0.05 ng kg-1 for TCDD to 3 ng kg-1 for OCDD. The results of this survey showed a mean concentration (reported as I-TEQ, lipid adjusted) in U.S. beef animals of 0.35 ng kg-1 and 0.89 ng kg-1 when either non-detects are treated as 0 value or assigned a value of 1/2 the detection limit, respectively.
Chemosphere | 1989
G.A. Kew; John Schaum; P. White; T.T. Evans
Volatilization of 2,3,7,8-TCDD from soil and resorption on foliage represents a significant route of contamination. Some studies indicate low-level uptake, translocation from roots to foliage and transpiration from foliage, while one shows more than 95% of 2,3,7,8-TCDD associated with edible fruits and with tubers is found in peels. Differences in bioavailability from different soils might account for some inconsistencies between existing studies, suggesting additional information useful in reporting future work.
Soil & Sediment Contamination | 2005
M. B. Shoaf; Jeffry H. Shirai; Golan Kedan; John Schaum; John C. Kissel
Sediment contamination is common and assessment of potential dermal exposure to sediments is of interest to risk assessors. However, few measurements of coastal sediment (as opposed to terrestrial soil) adherence to skin have been reported in the literature. Results are reported here for sediment loads on the skin of 18 adults engaged in clam digging for periods of up to 90 minutes in a tide flat in Rhode Island. Post-activity geometric mean loads were 0.02, 0.12, 0.16, 0.58 and 0.88 mg/cm2 on faces, forearms, lower legs, feet and hands, respectively. Pre-activity loadings were less than 0.01 mg/cm2 on all body parts except feet. These results are similar to very limited previously reported data obtained from four persons gathering reeds for basketry in a tide flat in Washington State.
Chemosphere | 1987
C.H. Nauman; John Schaum
Abstract Exposure assessment procedures have been developed using relevant and likely scenarios through which humans could be exposed to dioxin-contaminated soil. Five exposure pathways were chosen for analysis: dust inhalation, fish ingestion, dermal absorption, soil ingestion, and beef/dairy product ingestion. Equations for calculating exposure levels and associated cancer risks are presented, and factors describing contact rate, exposure duration, absorbed fraction and miscellaneous parameters for each pathway are discussed.
Journal of Toxicology and Environmental Health | 2009
Timothy A. Roy; Karen Hammerstrom; John Schaum
Six dermal absorption experiments (one in vivo, five in vitro) were conducted using 3,3′,4,4′-tetrachlorobiphenyl (TCB) either neat at 141 μg/cm2 or sorbed on a low organic (LOS) or high organic (HOS) soil at 6–10 μg/cm2. All soil experiments were conducted at 1000 ppm and soil loads of 6–10 mg soil/cm2. After 96 h the percentage of applied dose absorbed (PADA) for TCB sorbed on LOS was 49.7 (rat, in vivo), 31.9 (rat, in vitro), and 7.4 (human, in vitro). The 96-h PADA for TCB sorbed on HOS was 9.6% (rat, in vitro). Generally, rat skin was observed to be four- to ninefold more permeable to TCB than human skin (in vitro). At steady state, the dermal flux of TCB on LOS at 1000 ppm and on HOS at 1000 ppm (both in vitro, rat) was 33 and 10 ng/cm2/h, respectively (ratio = 3.3).
Journal of Toxicology and Environmental Health | 2008
Timothy A. Roy; Karen Hammerstrom; John Schaum
Eight dermal absorption experiments (two in vivo; six in vitro) and one intravenous experiment were conducted using 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) either neat (high dose at ∼250 μg/cm2 and low dose at 10 ng/cm2) or sorbed on a low organic soil (LOS) or high organic soil (HOS) at 1 ppm (10 ng TCDD/10 mg soil/cm2). After 96 h the percent of applied dose absorbed (PADA) for the neat low dose was 78% in vivo (rat) and 76% in vitro (rat). PADA for the equivalent TCDD dose sorbed on LOS were 16.3% (rat in vivo), 7.7% (rat in vitro) and 2.4% (human in vitro). The PADA for TCDD sorbed on HOS (1 ppm) was 1.0% (rat in vitro). Generally, rat skin was observed to be three to four times more permeable to TCDD than human skin. At steady state, the dermal flux of TCDD in neat form, sorbed on LOS at 1 ppm, and sorbed on HOS at 1 ppm (all in vitro, rat) was 120, 0.007, and 0.0007 ng/cm2/h, respectively (ratio = 1.7 × 105:10:1). Making adjustments to account for differences between in vitro and in vivo results and adjusting for application to monolayer loads, the 24-h TCDD absorption for human skin is estimated as 1.9% from LOS (1 ppm) and 0.24% from HOS (1 ppm).
Chemosphere | 1986
Debdas Mukerjee; Jerry Stara; John Schaum
Abstract The human health risk assessment is supported by methodology for utilizing toxic effects in animals consisting of carcinogenic and noncarcinogenic responses as a result of chronic, subchronic and acute exposures. One of the initial steps in a risk assessment activity involves the estimation of exposure levels. These estimates are typically based on either direct environmental measurements or predictions obtained from fate and transport models. The decision to develop assessment of risk from chronic exposure based on a nonthreshold model is made if a chemical demonstrates carcinogenic activity in animal bioassays and/or in human epidemiological studies. In the absence of any positive human epidemiologic data, it is assumed that a substance which induces a statistically significant carcinogenic response in animals has the probability to cause cancer in humans. The carcinogenic potential of 2,3,7,8-TCDD has been established based on chronic exposure in rodents. In addition, 2,3,7,8-TCDD has also been shown to be a liver cancer promoter in rodents. In the risk assessment on dioxins based on chronic exposure in experimental animals, 2,3,7,8-TCDD is regarded as a carcinogenic substance. Carcinogenic data from animal bioassays are utilized for the assessment of risk for the purpose of estimating the likelihood of 2,3,7,8-TCDD being carcinogenic for humans and to determine the magnitude of the potential impact on public health.