Oral and Dermal Bioavailability Studies of Polycyclic Aromatic Hydrocarbons from Soils Containing Weathered Fragments of Clay Shooting Targets.

The relative oral bioavailability and dermal absorption of chemical substances from environmental media are key factors that are needed to accurately estimate site-specific risks and manage human exposures. This study evaluated the relative oral bioavailability and dermal absorption of several polycyclic aromatic hydrocarbons (PAHs) found in soils collected from two formerly used Department of Defense sites impacted by weathered fragments of clay shooting targets. Concentrations of individual carcinogenic PAHs in the ≤250 μm fraction of soil ranged from approximately 0.

Risk assessment implications of site-specific oral relative bioavailability factors and dermal absorption fractions for polycyclic aromatic hydrocarbons in surface soils impacted by clay skeet target fragments.

Risk assessment conclusions for a site may differ when using site-specific versus default values for the relative bioavailability factor (RBAF) and dermal absorption fraction (ABS.d), because these inputs affect both surface soil screening levels and risk/hazard estimates. Indeed, our case study demonstrates that different conclusions may be reached as to regulatory need for remedial action to protect human health when evaluating soil sampling data for seven carcinogenic polycyclic aromatic hydrocarbons (PAHs) using site-specific versus default TCEQ and USEPA residential soil screening levels.

Development of an inhalation reference concentration for diethanolamine.

An inhalation reference concentration (RfC) was developed for diethanolamine (DEA), based principally on evaluation of three animal studies (Gamer et al., 1993, 1996, 2008). The RfC (25 μg/m) was based on statistically significantly increased relative liver weight in female rats in Gamer et al.

The perpetuation of the misconception that rats receive a 3-5 times lower lung tissue dose than humans at the same ozone concentration.

This paper highlights the pervasive misconception concerning 1994 findings from Hatch et al. about ozone (O) tissue dose in humans versus rats. That study exposed humans to 0.

Development of an inhalation unit risk factor for isoprene.

A unit risk factor (URF) was developed for isoprene based on evaluation of three animal studies with adequate data to perform dose-response modeling (NTP, 1994, 1999; Placke et al., 1996). Ultimately, the URF of 6.

Development of an inhalation unit risk factor for hexavalent chromium.

A unit risk factor (URF) was developed for hexavalent chromium (CrVI). The URF is based on excess lung cancer mortality in two key epidemiological studies of chromate production workers. The Crump et al.

Development of a cancer-based chronic inhalation reference value for hexavalent chromium based on a nonlinear-threshold carcinogenic assessment.

The carcinogenicity of hexavalent chromium(CrVI) is of significant interest to regulatory agencies for the protection of public health and to industry. Additionally, the mode of action (MOA) and conditions under which CrVI may induce carcinogenicity (e.g.

Development of a unit risk factor for nickel and inorganic nickel compounds based on an updated carcinogenic toxicity assessment.

The TCEQ has developed a URF for nickel based on excess lung cancer in two epidemiological studies of nickel refinery workers with nickel species exposure profiles most similar to emissions expected in Texas (i.e., low in sulfidic nickel).

A chronic reference value for 1,3-butadiene based on an updated noncancer toxicity assessment.

A chronic noncancer toxicity assessment for 1,3-butadiene (BD) has been conducted by the Texas Commission on Environmental Quality (TCEQ) using information not available to the U.S. Environmental Protection Agency (U.

Development of a unit risk factor for 1,3-butadiene based on an updated carcinogenic toxicity assessment.

The Texas Commission on Environmental Quality (TCEQ) has developed an inhalation unit risk factor (URF) for 1,3-butadiene based on leukemia mortality in an updated epidemiological study on styrene-butadiene rubber production workers conducted by researchers at the University of Alabama at Birmingham. Exposure estimates were updated and an exposure estimate validation study as well as dose-response modeling were conducted by these researchers. This information was not available to the U.