Evaluation of potential human health effects associated with the agricultural uses of 1,3-D: Spatial and temporal stochastic risk analysis.

Dow AgroSciences (DAS) markets and sells 1,3-Dichloropropene (1,3-D), the active ingredient in Telone®, which is used as a pre-plant soil fumigant nematicide in economically important crops in California. 1,3-D has been regulated as a "probable human carcinogen" and the California Department of Pesticide Regulation limits use of 1,3-D based on human health risk assessments for bystanders. This paper presents a risk characterization for bystanders based on advances in the assessment of both exposure and hazard.

Cyphenothrin Flea and Tick Squeeze-On for Dogs: Evaluation of Potential Health Risks Based on the Results of Observational Biological Monitoring.

An observational biomonitoring study was conducted involving adults and children in households that purchased and applied a cyphenothrin-containing spot-on product for dogs as part of their normal pet care practices. The 3- to 6-yr-old children had greater exposure than the adult applicators in the same house, 3.8 and 0.

Effects of 17 beta-estradiol exposure on Xenopus laevis gonadal histopathology.

The natural estrogen 17 beta-estradiol (E2) is a potential environmental contaminant commonly employed as a positive control substance in bioassays involving estrogenic effects. The aquatic anuran Xenopus laevis is a frequent subject of reproductive endocrine disruptor research; however, histopathological investigations have tended to be less than comprehensive. Consequently, a study was designed to characterize gross and microscopic changes in the gonads of X.

Development, standardization and refinement of procedures for evaluating effects of endocrine active compounds on development and sexual differentiation of Xenopus laevis.

Xenopus laevis has been introduced as a model to study effects of endocrine-active compounds (EAC) on development and sexual differentiation. However, variable and inconsistent data have raised questions about the reliability of the test methods applied. The current study was conducted in two laboratories to develop, refine, and standardize procedures and protocols.

Mortality partitions and their relevance to research on senescence.

The reasons for classifying causes of death into aggregate groups are discussed and the impact of mortality partitions on analyses of mortality is described. Special emphasis is given to a mortality partition that distinguishes between intrinsic causes of death that arise primarily from the failure of biological processes that originate within an organism, and extrinsic causes of death that are primarily imposed on the organism by outside forces. Examples involving mortality data for mice, dogs, and humans are used to illustrate how this mortality partition infuses biological reasoning into mathematical models used to analyze and predict senescent-determined mortality, enhances the information content of the mortality schedules generated from these models, improves mortality comparisons between populations within species separated by time or geographic location, and provides a logical pathology endpoint for making interspecies comparisons of mortality.

Statistical inferences about the mechanism of action in carcinogenicity studies.

An innovative approach to dose-response modeling provides statistical insight into the relative likelihood of different mechanisms of action in cancer dose-response studies. Two illustrative examples are given based on time-to-tumor data on mammary fibroadenoma and adenocarcinoma in female Sprague-Dawley rats using 34 different dose metrics. The likelihood for the study outcome was calculated for each dose metric and compared with the background likelihood using a likelihood-ratio test.