The primary health concern associated with chromite ore processing residues (COPR) at sites in Hudson County, NJ, is the inhalation of Cr(VI) suspended from surface soils. Since health-based soil standards for Cr(VI) will be derived using the inhalation pathway, soil suspension modeling will be necessary to estimate site-specific, health-based soil cleanup levels (HBSCLs). The purpose of this study was to identify the most appropriate particulate emission and air dispersion models for estimating soil suspension at these sites based on their theoretical underpinnings, scientific acceptability, and past performance. The identified modeling approach, the AP-42 particulate emission model and the fugitive dust model (FDM), was used to calculate concentrations of airborne Cr(VI) and TSP at two COPR sites. These estimated concentrations were then compared to concentrations measured at each site. The TSP concentrations calculated using the AP-42/FDM soil suspension modeling approach were all within a factor of 3 of the measured concentrations. The majority of the estimated air concentrations were greater than the measured, indicating that the AP-42/FDM approach tends to overestimate on-site concentrations. The site-specific Cr(VI) HBSCLs for these two sites calculated using this conservative soil suspension modeling approach ranged from 190 to 420 mg/kg.
Laboratory studies were conducted to evaluate airborne release of diacetyl from selected mixtures simulating butter flavorings added to foods. The test materials included diacetyl (97% purity); 0.015%, 0.15%, 1.5%, and 3.0% diacetyl in a water/propylene glycol mixture; 1.5% diacetyl in deionized water or soybean oil; and 3% or 6% diacetyl in a commercial steam distillate from milk fermentation known as “butter starter distillate.” Diacetyl was quantified by gas chromatography with flame ionization detection. Expected concentration-dependent emission patterns based on liquid diacetyl content were demonstrated, but were significantly altered by mixture composition. Soybean oil and deionized water more readily released diacetyl when compared with starter distillate, propylene glycol solutions, and pure diacetyl. Measured diacetyl concentrations under static headspace and dynamic flow-chamber conditions were compared to estimated concentrations utilizing Raoult's law with published and fitted activity coefficient corrections for each mixture, indicating that published coefficients often understated the measured concentrations. It is concluded that headspace (static) and small-chamber (dynamic) measurements of airborne diacetyl provide data to assist in validating model-estimated airborne diacetyl concentrations by using mixture-specific activity coefficients. Implications of these empirical data for validating exposure estimates for diacetyl based on near-field/far-field modeling in workplace settings are discussed.
Some of the most significant advances and refinements in human health risk assessments for environmental and occupational chemicals have come from investigations in the area of exposure assessment. This presentation summary describes three previously published examples of continuing advances in this process.
In recent decades, young men in some industrialized areas have reportedly experienced a decrease in semen quality.We examined effects of perinatal dioxin exposure on sperm quality and reproductive hormones.We investigated sperm quality and hormone concentrations in 39 sons (mean age, 22.5 years) born between 1977 and 1984 to mothers exposed to dioxin after the accident in Seveso, Italy (1976), and 58 comparisons (mean age, 24.6 years) born to mothers exposed only to background dioxin. Maternal dioxin levels at conception were extrapolated from the concentrations measured in 1976 serum samples.The 21 breast-fed sons whose exposed mothers had a median serum dioxin concentration as low as 19 ppt at conception had lower sperm concentration (36.3 vs. 86.3 million/mL; p = 0.002), total count (116.9 vs. 231.1; p = 0.02), progressive motility (35.8 vs. 44.2%; p = 0.03), and total motile count (38.7 vs. 98 million; p = 0.01) than did the 36 breast-fed comparisons. The 18 formula-fed exposed and the 22 formula-fed and 36 breast-fed comparisons (maternal dioxin background 10 ppt at conception) had no sperm-related differences. Follicle-stimulating hormone was higher in the breast-fed exposed group than in the breast-fed comparisons (4.1 vs. 2.63 IU/L; p = 0.03) or the formula-fed exposed (4.1 vs. 2.6 IU/L; p = 0.04), and inhibin B was lower (breast-fed exposed group, 70.2; breast-fed comparisons, 101.8 pg/mL, p = 0.01; formula-fed exposed, 99.9 pg/mL, p = 0.02).In utero and lactational exposure of children to relatively low dioxin doses can permanently reduce sperm quality.
Abstract Historical patch test data have been used to propose health‐based soil cleanup levels for Cr(VI) that are protective of eliciting allergic contact dermatitis (ACD) among previously sensitized individuals. Shortcomings regarding the use of these historical studies in the risk assessment of Cr(VI) have been identified and include the use of concentration as the dosimetric for ACD eiicitation rather than the mass per surface area. Information on the surface areas of the patches used by the authors of three of the historical studies have been made available recently, and their dose levels have been converted from units of concentration to mass per surface area. For this study, benchmark dose methods were used to estimate the 10% minimum eiicitation threshold (MET) based on the converted patch test data from these historical studies and from the data presented in a more recent patch test study by Nethercott et ah (1994). A truncated lognonmal model was fitted to the historical data from each individual historical patch test study, and to the data from the Nethercott et al. (1994) study using maximum likelihood methods. The 10% MET from the Nethercott et al. (1994) study is seven times lower than those from the historical studies. There are two primary reasons for this result. First, Nethercott et al. used a 0.25% potassium dichromate patch to screen study participants, whereas the historical studies used patches with up to 0.5%. Hence, individuals who were less senstive and those who had irritant, rather than allergic reactions.at the high doses, were excluded. Second, Nethercott et al. used a TRUE‐Test patch that is a more efficient and reliable allergen delivery device than those used in the historical studies. Assuming 100% bioavailability, the 10% MET from Nethercott et al. (1994) produces an ACD‐based soil standard of 445 mg/kg compared with the ACD‐based soil standards of 2,750 to 62,500 mg/kg calculated using the historical studies. The most recent patch study of Nethercott et al. (1994), which is based on modern patch testing methods and standardized diagnostic criteria, is the most scientifically appropriate for use in the risk assessment of Cr(VI) and produces the most conservative estimate of the 10% MET.
The objective of this study was to determine the valence state of chromium (Cr) in the blood of individuals with Cr-containing metal hip implants. Serum and red blood cell (RBC) Cr concentrations from 52 patients with Cr-containing total hip arthroplasties were measured preoperatively and at 3, 12, and 24 months postoperatively. Geometric mean and median pre-surgery serum Cr concentrations were consistently below 0.2 µg/L, while geometric mean and median pre-op RBC Cr concentrations were typically about four- to six-fold higher than the serum values. A significant 5- to 13-fold increase was found in the mean and median serum Cr concentrations three months post-surgery, with an 8- to 18-fold rise at 12 and 24 months, respectively. Steady-state serum concentrations were reached between 3 and 12 months. In contrast, there were no marked differences in mean and median RBC Cr concentrations pre- and post-surgery. Slope regression analysis for our data was similar to those reported for Cr(III) in spiked blood samples. The analysis showed that Cr released from hip implants preferentially distributed into serum and not RBC, indicating that the form of Cr present in blood of hip implant patients was in the form of non-toxic Cr(III). Our findings indicate that blood Cr concentrations Cr(III) associated with metal implants do not pose an adverse health risk to patients, which is in agreement with findings published by most investigators.
