Developmental hazards

Case Studies in Environmental Medicine Taking an Exposure History—The importance of taking an exposure history and how to conduct one are described, and an example of a thorough exposure history is provided. Other case studies of interest include Reproductive and Developmental Hazards Skin Lesions and Environmental Exposures Cholinesterase-Inhibiting Pesticide Toxicity and numerous chemical-specific case studies. 

Regulatory guidelines require that there be maternal toxicity at the highest dosage level in embryo-fetal developmental toxicity studies. It is important to avoid excessive toxicity in these studies since it is known that marked maternal toxicity can cause secondary developmental toxicity (see discussion in Section 8.4.3, Association between Developmental and Maternal Toxicity ). This secondary developmental toxicity is irrelevant to the assessment of the developmental hazard of the test agent and thus simply confounds the interpretation of the data. 

Welch LW. 1998. Reproductive and developmental hazards - an overview for occupational and environmental health nurses. AAOHN J 46(2) 57-65. 

Fu, L.-J., Staples, R E. and Stahl Jr, R.G. (1991) Application of the Hydra attenuata assay for identifying developmental hazards among natural waters and wastewaters, Ecotoxicology and Environmental Safety 22(3), 309-319. 

The sufficient evidence category includes data that collectively provide enough information to judge whether or not a human developmental hazard could exist within the context of dose, duration, timing, and route of exposure. This category may include both human and experimental animal evidence. 

The United States Navy has been concerned for some time with protecting its military and civilian personnel from reproductive and developmental hazards in the workplace. As part of its efforts to reduce or eliminate exposure of Naval personnel and their families to reproductive and developmental toxicants, the Navy requested that the National Research Council (NRC) recommend an approach that can be used to evaluate chemicals and physical agents for their potential to cause reproductive and developmental toxicity. The NRC assigned this project to the Committee on Toxicology, which convened the Subcommittee on Reproductive and Developmental Toxicology, to prepare this report. In this report, the subcommittee recommends an approach for evaluating agents for potential reproductive and developmental toxicity and demonstrates how that approach can be used by the Navy. 

The use of a template (Box 3-1) for summarizing the available data is advised as a guide for ensuring consistency in the characterization of reproductive and developmental hazards. 

In vivo Maternal toxicity Embryo toxicity Structural/ functional deficits Determination of developmental hazard... 

The normal sex organ histopathology noted in animals combined with the occurrence of rat feto-toxicity only in the presence of maternal toxicity suggests that ethyl acrylate does not pose a significant reproductive and developmental hazard to humans. 

The proposed US EPA weight-of-evidence (WOE) scheme for suspect developmental toxicants defines three levels of confidence for data used to identify developmental hazards and to assess the risk of human developmental toxicity (1) definitive evidence for human developmental toxicity or for no apparent human developmental toxicity, (2) adequate evidence for potential human developmental toxicity or no apparent potential human developmental toxicity, and (3) inadequate evidence for determining potential human developmental toxicity. The scheme may require scientific judgment based on experience to weigh the implications of study design, statistical analyses, and biological significance of the data. 

Over 80 000 chemicals are listed in the TSCA registry, with 1500-2500 new chemicals added each year 20 000 chemicals are commonly found in the workplace (NIOSH list) with <1% tested for reproductive and developmental hazard potential. It is therefore necessary and appropriate to develop fast, inexpensive, sensitive, and accurate methods to prescreen the plethora of chemicals and concentrate resources on those identified by the screening test(s) as potential human health hazards. However, the mechanisms of action of developmental toxicants appear numerous and frustratingly difficult to identify (see section Mechanisms). 

Developmental Hazards (Effects). Over the last few years our... 

Developmental hazards may be expressed as death of conceptus, live malformed offspring, developmental ly delayed/runted offspring, and functionally impaired offspring. Death and altered development may be the results of a poor environment presented by the dam or a direct effect upon organogenesis and development of the conceptus/offspring. 

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