The Food Quality Protection Act of 1996 (FQPA) requires the EPA to consider "available information concerning the cumulative effects of such residues and other substances that have a common mechanism of toxicity ... in establishing, modifying, leaving in effect, or revoking a tolerance for a pesticide chemical residue." This directive raises a number of scientific questions to be answered before the FQPA can be implemented. Among these questions is: What constitutes a common mechanism of toxicity? The ILSI Risk Science Institute (RSI) convened a group of experts to examine this and other scientific questions using the organophosphorus (OP) pesticides as the case study. OP pesticides share some characteristics attributed to compounds that act by a common mechanism, but produce a variety of clinical signs of toxicity not identical for all OP pesticides. The Working Group generated a testable hypothesis, anticholinesterase OP pesticides act by a common mechanism of toxicity, and generated alternative hypotheses that, if true, would cause rejection of the initial hypothesis and provide criteria for subgrouping OP compounds. Some of the alternative hypotheses were rejected outright and the rest were not supported by adequate data. The Working Group concluded that OP pesticides act by a common mechanism of toxicity if they inhibit acetylcholinesterase by phosphorylation and elicit any spectrum of cholinergic effects. An approach similar to that developed for OP pesticides could be used to determine if other classes or groups of pesticides that share structural and toxicological characteristics act by a common mechanism of toxicity or by distinct mechanisms.

In this 2-year study, the suitability of the Hsd:Sprague-Dawley SD (SD) as a replacement for the Crl:CD BR (CD) rat was assessed by comparing survival rates, palpable mass incidence, body weights, food consumption, clinical laboratory parameters, and necropsy and histopathology observations. At week 104, survival rates in the CD and SD males were 29 and 49%, respectively. Corresponding survival rates in females were 44 and 63%. The total numbers of animals with palpable masses and animals with neoplasms were similar in the CD and SD rats; however, the total numbers of palpable masses and neoplasms were higher in the CD rats. The incidence of corneal lesions was higher in the SD rats, whereas the incidence of lenticular opacities was higher in the CD rats. Body weights, food and water consumption, and organ weights were significantly lower in the SD rats. In contrast, food intake per kilogram of body weight was slightly higher in the SD rats. Numerous differences in clinical laboratory parameters between the CD and SD rats were observed. Some of these were consistent with the increased prevalence of kidney disease and secondary sequelae in the SD rats. Taken together, the better survival, smaller size, and lower food consumption of the SD rat may make it a better model for chronic bioassays. However, the increased propensity for spontaneous renal disease may limit the utility of the SD rat for studying nephrotoxic compounds.

The article contains sections titled: 1. Introduction 2. Physical Properties 3. Chemical Properties 4. Production 4.1. Thermodynamics and Rates of Reaction 4.2. Production from Charcoal and Sulfur 4.3. Production from Methane and Sulfur 4.4. Other Processes 5. Environmental Aspects 6. Quality Specifications and Analytical Methods 7. Storage and Transportation 8. Uses and Economic Aspects 9. Toxicology and Occupational Health 10. Carbonyl Sulfide

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