The widespread use and storage of volatile organic compounds (VOCs) in the United States has led to releases of these chemicals into the environment, including groundwater sources of drinking water. Many of these VOCs are commonly found in public drinking water supplies across the nation and are considered by state or federal agencies to be potentially carcinogenic to humans. In this paper, we evaluate the detection frequencies, detected concentrations, and relative cancer risks of six VOCs in drinking water sources in California from 1995 to 2001. We find that, during this 7-year period, the most frequently detected VOCs in sampled drinking water sources were chloroform (12-14%), PCE (11-13%), and TCE (10-12%). Detection frequencies in water were lower for 1,1-DCE (3-6%), MTBE (1-3%), and benzene (<1%). Mean detected concentrations were also consistently above California's primary maximum contaminant level for some VOCs, including benzene, PCE, and TCE. Although none of the six VOCs necessarily poses a significant public health threat from drinking water exposures, 1,1-DCE and benzene were found to pose the greatest cancer risk relative to the other VOCs. However, after adjusting for the occurrence of each VOC in drinking water, chloroform and PCE were found to pose the greatest relative cancer risk. Despite media reports about significant MTBE contamination of drinking water supplies in California, MTBE detections were infrequent, and this chemical was found to pose the least cancer risk relative to the other VOCs.

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We analyzed cumulative lifetime exposure to chrysotile asbestos experienced by brake mechanics in the US during the period 1950-2000. Using Monte Carlo methods, cumulative exposures were calculated using the distribution of 8-h time-weighted average exposure concentrations for brake mechanics and the distribution of job tenure data for automobile mechanics. The median estimated cumulative exposures for these mechanics, as predicted by three probabilistic models, ranged from 0.16 to 0.41 fibers per cubic centimeter (f/cm 3 ) year for facilities with no dust-control procedures (1970s), and from 0.010 to 0.012 f/cm 3 year for those employing engineering controls (1980s). Upper-bound (95%) estimates for the 1970s and 1980s were 1.96 to 2.79 and 0.07-0.10 f/cm 3 year, respectively. These estimates for US brake mechanics are consistent with, but generally slightly lower than, those reported for European mechanics. The values are all substantially lower than the cumulative exposure of 4.5 f/cm 3 year associated with occupational exposure to 0.1 f/cm 3 of asbestos for 45 years that is currently permitted under the current occupational exposure limits in the US. Cumulative exposures were usually about 100-to 1,000-fold less than those of other occupational groups with asbestos exposure for similar time periods. The cumulative lifetime exposure estimates presented here, combined with the negative epidemiology data for brake mechanics, could be used to refine the risk assessments for chrysotileexposed populations.

The risk to adjacent aquatic systems posed by leachates from scrap tires used in engineering applications has not been characterized adequately. Toxicity testing, toxicity identification evaluation (TIE), and groundwater modeling were used to determine the circumstances under which tire shreds could be used as roadbed fill with negligible risk to aquatic organisms in adjacent water bodies. Elevated levels of iron, manganese, and several other chemicals were found in tire shred leachates. However, chronic toxicity tests with Ceriodaphnia dubia and fathead minnows (Pimephales promelas) showed no adverse effects caused by leachates collected from tire shreds installed above the water table. Exposure to leachates collected from tire shreds installed below the water table resulted in significant reductions to both survival and reproduction in C. dubia. The TIE results indicated that exposure to soluble metals (likely ferrous iron primarily) and the formation of iron hydroxide precipitates on this invertebrate species likely were the causes of the observed effects. The available chemistry data show that iron concentrations in the affected groundwater decreased substantially within a short distance (0.61 m) downgradient of tire shred fill. Based on geochemical modeling, the use of tire shreds in applications below the water table is appropriate in settings where dissolved oxygen is greater than 2.0 mg/L, pH is greater than 5.8, and a downgradient buffer of approximately 3.0 m exists between the fill and the surface water. For settings with lower dissolved oxygen concentrations or lower pH, results of groundwater modeling indicate that a greater buffer distance (approximately 11 m) is needed to dilute the leachate to nontoxic levels under various soil and groundwater conditions solely through advection and dispersion processes.

Beryllium manufacturing processes are associated with the immune-mediated chronic beryllium disease (CBO). Recent workplace epidemiological studies have been relatively unsuccessful in correlating disease with workplace air concentrations of beryllium, thereby failing to support the hypothesis that dose by the respiratory route determines the risk of disease. This has led to consideration of the hypotheses that dermal or oral exposures to beryllium can influence disease risk, either as a cause of sensitization or to induced tolerance to beryllium. If so, the control of dermal and/or ingestion exposure to beryllium, which has heretofore been widely disregarded in the United States, would be of practical importance. Most of the literature of the past 50 years indicates that ingestion and dermal uptake of beryllium are unimportant routes of exposures. The toxicology data generally support this position. However, research is under way to determine whether sensitization to beryllium may occur following exposure via routes other than inhalation, raising the question of whether this sensitization from other routes of exposure makes the lungs more susceptible to inflammation when inhaled doses are encountered. Using published data on other metals, this article describes the likely range of doses that a worker might incur in the workplace due to incidental exposure pathways (i.e., exposures not directly related to inhalation of workplace air), such as hand-to-mouth exposure, dermal contact, and resuspension following deposition of beryllium onto clothing. This analysis indicates that these incidental routes of exposure could contribute to total absorbed doses of beryllium that exceed simple airborne inhalation exposures. Because the doses presented by these alternative exposure pathways could be appreciable compared with the airborne inhaled dose, and could continue even when respirators are worn, these pathways may represent the primary routes of entry of beryllium into the body. We believe that the potential for exposure from these incidental exposure pathways merits additional study.