Reproductive toxicity environmental exposures

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. 

EPA. 1989c. Delayed reproductive effects following exposure to toxic chemicals during critical developmental periods. Research Triangel park, NC U.S. Environmental Protection Agency. NTIS PB90-112830.->c... 

Develop more accurate and efficient methods of measuring human exposure to environmental chemicals with potential reproductive toxicity. 

Numerous diagnostic methods have been developed to evaluate female reproductive dysfunction. Although these methods have rarely been used for occupational or environmental toxicological evaluations, they may be helpful in defining biological parameters and mechanisms related to female reproductive toxicity. If clinical observations link exposure to the reproductive effect of concern, these data will aid the assessment of adverse female reproductive toxicity. The following clinical observations include end-points that may be reported in case reports or epidemiological research studies. 

The human reproductive process does not fit perfectly into the animal model of reproductive and developmental toxicity. Conditions of the fetal-maternal unit that affect both mother and child have not been adequately addressed in this monograph, although there is some evidence that some of these adverse outcomes, such as pregnancy-induced hypertension, may be related to environmental exposure (Tabacova et al., 1998 Dawson et al., 1999). This is a promising frontier for new research. We have also not dealt with genetic susceptibility to developmental toxicants. Advances in this field may illuminate many of the mysteries of how toxicants act, and on whom. Limited data are available on mechanisms of action (see section 5.2.4). The work on oxidative stress in pregnancy (Tabacova et al., 1998 Hubei,... 

The hazard classification should lead directly to labelling of acute health effects, environmental and physical hazards. The labelling approach that involves a risk assessment should only be applied to chronic health hazards, e.g. carcinogenicity, reproductive toxicity, or target organ systemic toxicity based on repeated exposure. The only chemicals it may be applied to are those in the consumer product setting where consumer exposures are generally limited in quantity and duration ... 

Reproductive failure can be induced by environmental hazards at any level, although most types of infertility have not been linked to environmental factors. Since it is not ethically possible to observe or impose reproductive toxic exposures on human subjects, much of what we believe about the effects of putative toxins are based on the assumption that well-defined spontaneous reproductive failures are accurate surrogates for environmentally induced defects. Spontaneous reproductive failures, together with results from animal experiments, are used as models to predict or to understand the impact of reproductive toxicants on the human system. 

Currently, there are a limited number of chemicals classified as male reproductive toxicants. As scientific, public, and regulatory interest in this field increases, the result will most certainly be an increased knowledge base of the type and number of chemicals that can adversely affect the male reproductive tract. Once a chemical is considered a potential reproductive toxicant, there are measures in place to protect humans from occupational and environmental exposure. For example, when the results from a risk assessment indicate that the potential exists for adverse reproductive effects in humans, a regulatory agency such as the US EPA may impose restrictions on the availability or uses of certain compounds. Reproductive toxicity testing is fundamental to this type of risk-based decision-making, and will hopefully lead to the development of safer chemicals and drugs. 

Even as the route of exposure and the molecular interactions that cause the toxic effects are delineated, that is not the entire story. Chapter 6, Factors Modifying the Activity of Toxicants, describes the myriad physiological and environmental factors that can alter the exposure of the organism to the toxicant and also the response to the compound. Nutritional status, complexing elements in the environment, as well as the organism and reproductive status can all drastically affect the response of an organism to environmental exposure. 

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