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Rats were nose-exposed to an atmosphere containing gaseous [11C]acrylic acid for 1 min and sacrificed 1.5 and 65 min later. At 1.5 min 28% of the administered radiolabel was associated with the snout of the exposed animal. The biodistribution data indicated the gastrointestinal tract as the major site of absorption of acrylic acid after inhalation exposure. Therefore, rats were also stomach intubated with an aqueous solution of [11C]acrylic acid and sacrificed at 1.5, 10, 20, 40, and 65 min after intubation. The absorption of acrylic acid from the stomach was rapid, as was its subsequent metabolism. Carbon-11 was rapidly eliminated from both nose-exposed and stomach-intubated animals as 11CO2, with about 60% of the administered dose eliminated 1 h after administration. A portion of the radiolabel was also eliminated via the renal system.

The consideration of multiple or cumulative sources of exposure to a chemical is important for adequately protecting human health. This assessment demonstrates one way to consider multiple or cumulative sources through the development of a relative source contribution (RSC) factor for the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), using the Exposure Decision Tree approach (subtraction method) recommended by the U.S. Environmental Protection Agency. The RSC factor is used to ensure that the concentration of a chemical allowed by a regulatory criterion or multiple criteria, when combined with other identified sources of exposure common to the population of concern, will not result in unacceptable exposures. An exposure model was used to identify relevant potential sources for receptors. Potential exposure pathways include ingestion of soil, water, contaminated local crops and fish, and dermal contact with soil and water. These pathways are applicable only to areas that are in close proximity to current or former military bases where RDX may have been released into the environment. Given the physical/chemical properties and the available environmental occurrence data on RDX, there are adequate data to support a chemical-specific RSC factor for RDX of 50% for drinking water ingestion.

Fischer-344 rats were exposed to 0.0, 0.3, 1.0, or 2.0 mg Cd/m3 as CdCl2 aerosol for 6 h/d, 5 d/wk, for 62 exposure days. Exposure to 2.0 mg Cd/m3 resulted in rapid weight loss, and all of the animals died within the first 45 exposure days. As a group, female rats survived significantly longer than the males. Exposure to Cd resulted in dose-dependent increases in lung weight. The increased weight was the result of additional tissue mass rather than edema. Both connective-tissue components, elastin and collagen, were significantly increased in the 1.0-mg/m3 group when these components were expressed on the basis of dry weight. Dose-dependent changes at the terminal bronchioles consisted of hyperplasia and flattening of type II cells, inflammation, and the proliferation of fibroblasts. Exposure to Cd also resulted in the development of intralymphatic microgranulomas in the perivascular and peribronchiolar lymphoid tissues.