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Boulder City, CO, United States

E Risk science

Boulder City, CO, United States
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Williams P.R.D.,E Risk science | Sahmel J.,ChemRisk | Knutsen J.,Colorado School of Mines | Spencer J.,Environmental Profiles Inc. | Bunge A.L.,Colorado School of Mines
Critical Reviews in Toxicology | Year: 2011

There is growing emphasis in the United States and Europe regarding the quantification of dermal exposures to chemical mixtures and other substances. In this paper, we determine the dermal flux of benzene in neat form, in organic solvents, and in aqueous solutions based on a critical review and analysis of the published literature, and discuss appropriate applications for using benzene dermal absorption data in occupational risk assessment. As part of this effort, we synthesize and analyze data for 77 experimental results taken from 16 studies of benzene skin absorption. We also assess the chemical activity of benzene in simple hydrocarbon solvent mixtures using a thermodynamic modeling software tool. Based on the collective human in vivo, human in vitro, and animal in vitro data sets, we find that the steady-state dermal flux for neat benzene (and benzene-saturated aqueous solutions) ranges from 0.2 to 0.4 mg/(cm 2•h). Observed outlier values for some of the animal in vivo data sets are possibly due to the use of test species that have more permeable skin than humans or study conditions that resulted in damage to the skin barrier. Because relatively few dermal absorption studies have been conducted on benzene-containing organic solvents, and available test results may be influenced by study design or vehicle effects, it is not possible to use these data to quantify the dermal flux of benzene for other types of solvent mixtures. However, depending on the application, we describe several potential approaches that can be used to derive a rough approximation of the steady-state benzene dermal flux for these mixtures. Important limitations with respect to quantifying and evaluating the significance of dermal exposures to benzene in occupational settings include a lack of data on (1) factors that affect the dermal uptake of benzene, (2) the dermal flux of benzene for different organic solvent mixtures, (3) meaningful metrics for evaluating the dermal uptake of benzene, (4) steady-state versus non-steady-state dermal flux values for benzene, (5) the effect of skin damage on the dermal flux of benzene, (6) standardized test methods for estimating the dermal flux of benzene, and (7) robust estimates of the evaporation rate of benzene from different liquid vehicles. © 2011 Informa Healthcare USA, Inc.


Von Stackelberg K.,E Risk science | Von Stackelberg K.,Harvard University
Journal of Toxicology | Year: 2013

Chlorophenoxy compounds, particularly 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxy)acetic acid (MCPA), are amongst the most widely used herbicides in the United States for both agricultural and residential applications. Epidemiologic studies suggest that exposure to 2,4-D and MCPA may be associated with increased risk non-Hodgkins lymphoma (NHL), Hodgkin's disease (HD), leukemia, and soft-tissue sarcoma (STS). Toxicological studies in rodents show no evidence of carcinogenicity, and regulatory agencies worldwide consider chlorophenoxies as not likely to be carcinogenic or unclassifiable as to carcinogenicity. This systematic review assembles the available data to evaluate epidemiologic, toxicological, pharmacokinetic, exposure, and biomonitoring studies with respect to key cellular events noted in disease etiology and how those relate to hypothesized modes of action for these constituents to determine the plausibility of an association between exposure to environmentally relevant concentrations of 2,4-D and MCPA and lymphohematopoietic cancers. The combined evidence does not support a genotoxic mode of action. Although plausible hypotheses for other carcinogenic modes of action exist, a comparison of biomonitoring data to oral equivalent doses calculated from bioassay data shows that environmental exposures are not sufficient to support a causal relationship. Genetic polymorphisms exist that are known to increase the risk of developing NHL. The potential interaction between these polymorphisms and exposures to chlorophenoxy compounds, particularly in occupational settings, is largely unknown. © 2013 Katherine von Stackelberg.


Williams P.R.D.,E Risk science
Journal of Toxicology and Environmental Health - Part B: Critical Reviews | Year: 2014

The Occupational Safety and Health Administration (OSHA), which was formed by the Occupational Safety and Health Act of 1970 (OSH Act), establishes enforceable health and safety standards in the workplace and issues violations and penalties for non-compliance with these standards. The purpose of the current study was to evaluate the number and type of violations of the OSHA (1987) Occupational Exposure to Benzene Standard. Violations of the OSHA Hazard Communication Standard (HCS), particularly those that may pertain to specific provisions of the benzene standard, were also assessed. All analyses were based on OSHA inspection data that have been collected since the early 1970s and that are publicly available from the U.S. Department of Labor enforcement website. Analysis of these data shows that fewer than a thousand OSHA violations of the benzene standard have been issued over the last 25+ years. The results for benzene are in contrast to those for some other toxic and hazardous substances that are regulated by OSHA, such as blood-borne pathogens, lead, and asbestos, for which there have been issued tens of thousands of OSHA violations. The number of benzene standard violations also varies by time period, standard provision, industry sector, and other factors. In particular, the greatest number of benzene standard violations occurred during the late 1980s to early/mid 1990s, soon after the 1987 final benzene rule was promulgated. The majority of benzene standard violations also pertain to noncompliance with specific provisions and subprovisions of the standard dealing with initial exposure monitoring requirements, the communication of hazards to employees, and medical surveillance programs. Only a small fraction of HCS violations are attributed, at least in part, to potential benzene hazards in the workplace. In addition, most benzene standard violations are associated with specific industries within the manufacturing sector where benzene or benzene-containing products may be used or produced during production processes, such as petroleum refineries, metal industries, and chemical companies. Not surprisingly, the greatest number of benzene standard violations have been issued to private facility owners (rather than government entities), given that the OSH Act primarily covers private sector employers. More violations have also been issued during inspections where union representation was present and from complaint-driven (vs. planned or other) inspections, which is consistent with OSHA inspection priorities. Violations of the benzene standard have typically involved a single instance per facility and 10 or fewer exposed employees. Because the OSH Act prescribes penalty caps for citations, initial penalties issued for noncompliance with the benzene standard have generally been less than 5,000 per violation. Despite some potential limitations, the OSHA inspection database contains the best available data for assessing historical and current violations of the benzene standard. These data, which have not been previously analyzed or published for benzene, may be of interest to professionals and practitioners involved in benzene risk assessment, risk management, and/or public policy issues. © 2014 Taylor & Francis Group, LLC.


Potential threats to drinking water and water quality continue to be a major concern in many regions of the United States. New Jersey, in particular, has been at the forefront of assessing and managing potential contamination of its drinking water supplies from hazardous substances. The purpose of the current analysis is to provide an up-to-date evaluation of the occurrence and detected concentrations of methyl tertiary butyl ether (MTBE) and several other volatile organic compounds (VOCs) in public water systems, private wells, and ambient groundwater wells in New Jersey based on the best available data, and to put these results into context with federal and state regulatory and human-health benchmarks. Analyses are based on the following three databases that contain water quality monitoring data for New Jersey: Safe Drinking Water Information System (SDWIS), Private Well Testing Act (PWTA), and National Water Information System (NWIS). For public water systems served by groundwater in New Jersey, MTBE was detected at a concentration ≥10 μg/L, ≥20 μg/L, and ≥70 μg/L at least once in 30 (2%), 21 (1.4%), and five (0.3%) of sampled systems from 1997 to 2011, respectively. For private wells in New Jersey, MTBE was detected at a concentration ≥10 μg/L, ≥20 μg/L, and ≥70 μg/L at least once in 385 (0.5%), 183 (0.2%), and 46 (0.05%) of sampled wells from 2001 to 2011, respectively. For ambient groundwater wells in New Jersey, MTBE was detected at a concentration ≥10 μg/L, ≥20 μg/L, and ≥70 μg/L at least once in 14 (2.1%), 9 (1.3%), and 4 (0.6%) of sampled wells from 1993 to 2012, respectively. Average detected concentrations of MTBE, as well as detected concentrations at upper-end percentiles, were less than corresponding benchmarks for all three datasets. The available data show that MTBE is rarely detected in various source waters in New Jersey at a concentration that exceeds the State's health-based drinking water standard or other published benchmarks, and there is no evidence of an increasing trend in the detection frequency of MTBE. Other VOCs, such as tetrachloroethylene (PCE), trichloroethylene (TCE), and benzene, are detected more often above corresponding regulatory or human-health benchmarks due to their higher detected concentrations in water and/or greater toxicity values. The current analysis provides useful data for evaluating the nature and extent of historical and current contamination of water supplies in New Jersey and potential opportunities for public exposures and health risks due to MTBE and other VOCs on a statewide basis. Additional forensic or forecasting analyses are required to identify the sources or timing of releases of individual contaminants at specific locations or to predict potential future water contamination in New Jersey. © 2014 Copyright Taylor and Francis Group, LLC.


Williams P.R.D.,E Risk science | Mani A.,University of Cincinnati
Journal of Toxicology and Environmental Health - Part B: Critical Reviews | Year: 2015

Benzene exposures among vehicle mechanics in the United States and abroad were characterized using available data from published and unpublished studies. In the United States, the time-weighted-average (TWA) airborne concentration of benzene for vehicle mechanics averaged 0.01-0.05 ppm since at least the late 1970s, with maximal TWA concentrations ranging from 0.03 to 0.38 ppm. Benzene exposures were notably lower in the summer than winter and in the Southwest compared to other geographic regions, but significantly higher during known gasoline-related tasks such as draining a gas tank or changing a fuel pump or fuel filter. Measured airborne concentrations of benzene were also generally greater for vehicle mechanics in other countries, likely due to the higher benzene content of gasoline and other factors. Short-term airborne concentrations of benzene frequently exceeded 1 ppm during gasoline-related tasks, but remained below 0.2 ppm for tasks involving other petroleum-derived products such as carburetor and brake cleaner or parts washer solvent. Application of a two-zone mathematical model using reasonable input values from the literature yielded predicted task-based benzene concentrations during gasoline and aerosol spray cleaner scenarios similar to those measured for vehicle mechanics during these types of tasks. When evaluated using appropriate biomarkers, dermal exposures were found to contribute little to total benzene exposures for this occupational group. Available data suggest that vehicle mechanics have not experienced significant exposures to benzene in the workplace, except perhaps during short-duration gasoline-related tasks, and full-shift benzene exposures have remained well below current and contemporaneous occupational exposure limits. These findings are consistent with epidemiology studies of vehicle mechanics, which have not demonstrated an increased risk of benzene-induced health effects in this cohort of workers. Data and information presented here may be used to assess past, current, or future exposures and risks to benzene for vehicle mechanics who may be exposed to gasoline or other petroleum-derived products. © Taylor & Francis Group, LLC.


Williams P.R.D.,E Risk science | Unice K.,Cardo ChemRisk LLC
Environmental Forensics | Year: 2013

Indoor air quality is a growing area of public health concern worldwide, particularly in less developed countries. Although one of the key factors that can affect indoor exposure levels is the air exchange rate (AER), few AER measurements are available for the range of housing types and conditions found in most developing countries. The current paper provides a review of the sparse literature on reported AERs in developing countries, and presents the results of a field study in which AERs were measured under varying conditions in two rural village homes in the Northern Highlands of Peru. AER measurements were collected using a well established and rigorous tracer gas technique. Measured AERs based on 19 tests of discrete interior spaces in the two exemplar homes typically ranged from 2 to 20 h-1 when all windows and doors were closed or with 1 to 2 apertures, but values as low as 0.5 to 1 h-1 were measured in tightly constructed spaces. Although limited in size and scope, our test results illustrate how AERs can vary between disconnected spaces within a home or among different housing units in the same general region, depending on the building construction and degree of ventilation. Our findings are generally consistent with reported AER values in other developing countries, but provide important region-specific data and represent the only known AER values for rural village homes in Peru. These data can be used to support broader efforts aimed at assessing and reducing air pollution exposures and risks worldwide. © 2013 Taylor and Francis Group, LLC.


Williams P.R.D.,E Risk science | Dotson G.S.,CDC NIOSH | Maier A.,Toxicology Excellence for Risk Assessment TERA and NIOSH
Environmental Science and Technology | Year: 2012

Uman health risk assessments continue to evolve and now focus on the need for cumulative risk assessment (CRA). CRA involves assessing the combined risk from coexposure to multiple chemical and nonchemical stressors for varying health effects. CRAs are broader in scope than traditional chemical risk assessments because they allow for a more comprehensive evaluation of the interaction between different stressors and their combined impact on human health. Future directions of CRA include greater emphasis on local-level community-based assessments; integrating environmental, occupational, community, and individual risk factors; and identifying and implementing common frameworks and risk metrics for incorporating multiple stressors.


von Stackelberg K.E.,E Risk science
Integrated Environmental Assessment and Management | Year: 2013

Ecosystem services as a concept and guiding principle are enjoying wide popularity and endorsement from high-level policy thinkers to industry as support for sustainability goals continue to grow. However, explicit incorporation of ecosystem services into decision making still lacks practical implementation at more local scales and faces significant regulatory and technical constraints. Risk assessment represents an example of a regulatory process for which guidance exists that makes it challenging to incorporate ecosystem service endpoints. Technical constraints exist in the quantification of the relationships between ecological functions and services and endpoints valued by humans, and the complexity of those interactions with respect to bundling and stacking. In addition, ecosystem services, by their very definition, represent an anthropogenic construct with no inherent ecological value, which, in practical terms, requires a far more inclusionary decision making process explicitly incorporating a greater diversity of stakeholder values. Despite these constraints, it is possible, given a commitment to sustainable decision making, to simplify the process based on strategic outcomes (e.g., identifying desired end-states in general terms). Decision analytic techniques provide a mechanism for evaluating tradeoffs across key ecosystem services valued by stakeholders and to develop criteria drawn from the entire spectrum of stakeholders in evaluating potential alternatives. This article highlights several examples of ways in which ecosystem service endpoints can be incorporated into the decision-making process. © 2013 SETAC.


Williams P.R.D.,E Risk science
Environmental Forensics | Year: 2011

Extensive water quality monitoring data in California are now available for methyl tertiary butyl ether (MTBE) that span the past 16 years. The statewide database includes most of the active (and some inactive) public drinking water wells in the state, most of which have been repeatedly sampled for MTBE during 1995 to 2010. The cumulative detection frequency of MTBE in public drinking water wells in California at any concentration level is approximately 1.6% and 0.9% based on a one-detection criterion and two-detection criterion, respectively. The detection frequency of MTBE is approximately two to three times lower at concentrations above the state drinking water standards. Since 1996, the annual detection frequency of MTBE at any concentration level has ranged from 0.4 to 0.9% (one-detection criterion) and 0.2% to 0.7% (two-detection criterion). Despite repeated sampling, MTBE has been detected in only 1 or 2 years for most public drinking water wells that have ever been found to contain MTBE at any concentration level. The annual average detected concentration of MTBE has ranged from 5 to 16 μg/L (arithmetic mean) and 2 to 5.5 μg/L (median), excluding two outlier samples. MTBE detections are more prevalent in select geographic locations, rather than widespread across the entire state. The cumulative detection frequency for MTBE is approximately 1% for wells that belong to very small and small public drinking water systems (i.e., that serve between 25 and 3,300 people) and is approximately 2% for wells that belong to large and very large public drinking water systems (i.e., that serve >10,000 people). No detections of tertiary butyl alcohol (TBA) were found from 1996 to 2000, although few samples of TBA were collected during this time period. From 2001 to 2010, the cumulative detection frequency of TBA in public drinking water wells in California at any concentration level was approximately 1.4% and 0.2% based on a one-detection criterion and two-detection criterion, respectively. The cumulative detection frequency of tetrachloroethylene (PCE) in public drinking water wells in California is at least six times greater than that of MTBE and TBA, and unlike the trends observed for MTBE and TBA, PCE is often consistently detected in the same wells over time. The results of this analysis can be used to assess historical and current detections of MTBE in public drinking water wells in California. Also, if coupled with other chemical and site-specific information, the results can be used to assess potential future impacts of MTBE on drinking water supplies. © Taylor & Francis Group, LLC.


PubMed | E Risk science
Type: Journal Article | Journal: Environmental science & technology | Year: 2012

Human health risk assessments continue to evolve and now focus on the need for cumulative risk assessment (CRA). CRA involves assessing the combined risk from coexposure to multiple chemical and nonchemical stressors for varying health effects. CRAs are broader in scope than traditional chemical risk assessments because they allow for a more comprehensive evaluation of the interaction between different stressors and their combined impact on human health. Future directions of CRA include greater emphasis on local-level community-based assessments; integrating environmental, occupational, community, and individual risk factors; and identifying and implementing common frameworks and risk metrics for incorporating multiple stressors.

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