Environmental Endocrine Disruptors: Persistence, Prevention, and Health Impacts, Slides of Public Health

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Environmental Endocrine Disruptors Part III: Persistence and Prevention Ovaries (women)Testicles (men) Pancreas Adrenal glands Hypothalamus Thyroid gland Parathyroid gland Pineal gland Pituitary gland docsity.com Course Objectives  Learn the terms pertaining to a chemical’s persistence properties, especially those of an environmental endocrine disruptor.  Recognize the science-based criteria and assessment models for the determination of persistence potential. Appreciate the cumulative effects due to a disruptor’s persistence properties.  Review the processes and strategies for prevention of persistent pollution. docsity.com Basics of Persistence (III)  Environmental persistence is much more dynamic, situational, and complex, when compared to persistence in a single medium. Many substances have properties that allow them to partition or dissolve in certain media, and even to speciate into a particular, irreversible form.  Environmental persistence thus should be evaluated on the basis of degradation rates, partitioning, speciation, and availability. docsity.com Long-Range Transport An important aspect of environmental persistence is its effects towards long-range transport (LRT) of the environmental contaminants.  Through LRT, persistent pesticides and other industrial chemicals can be present in remote regions such as the Arctic, where these substances have never been used.  The modes of LRT are not limited to atmo- spheric, oceanic, or terrestrial, but include cyclone activities and animal migration. docsity.com PBT Endocrine Disruptors  Pollutants that are persistent, bioaccumu- lative, and toxic (PBT), of which a good number are endocrine disruptors, are long- lasting and can build up in the food chain.  PBTs are of great ecological concern because they can induce severe adverse health effects, such as endocrine disruption.  Numerical criteria have been set up to identify the persistence and bioaccumulation potentials of toxic environmental pollutants. docsity.com Low Levels of PBTs  For certain types of adverse health effects such as endocrine disruption, even low levels of persistent and bioaccumulative toxicants (PBTs) in the environment collectively are still of global concern.  This is because, by comparison, inducibi- lity of environmental endocrine disruption is not chemical-selective. Yet more importantly, inducibilities of certain multiple PBTs for the same adverse effect are likely additive, if not synergistic. docsity.com Cumulative Effects (I)  Concurrent or subsequent exposures to persistent and bioaccumulative toxicants, of which many are environmental endocrine disruptors, are of global concern even when these pollutants are present at very low concentrations.  Synergism or additive effects have been observed between steroid hormones; between temperature and hormone response; between weakly estrogenic compounds; and between pesticides. docsity.com Cumulative Effects (II) More recently, additive effects have been observed from the combination of a strong estrogen 17β-estradiol and a weak estrogen such as bisphenol A, nonylphenol, phenyl salicylate, butylparaben, or genistein.  The natural estrogen estradiol is many thousand times more estrogenic than any of the weak xenoestrogens tested. Additive antiandrogenic effects also have been observed with the pesticides vinclozolin and procymidone. docsity.com Time of Exposure While exposure to environmental pollutants is mainly a function of their availability, time of exposure is equally a very crucial factor in the induction of endocrine disruption.  For example, estrogen levels in humans and rodents were seen to increase steadily through- out the pregnancy period, primarily due to a feed-forward mechanism of regulation; that is, any dose of a xenoestrogen would be additive with the endogenous level, due to the lack of feed-back control during this period. docsity.com Pollution Prevention (I)  The potency and toxicity of environmental endocrine disruptors (EEDs) are less critical.  The effects of an EED’s persistence and bioaccumulation are much more dynamic, more attenuable, and hence more critical.  One effective method of intervention is to divert the pollutant to an environment where its degradation half-life can be shortened considerably; in addition, chemical bioaccu- mulation can be intervened by segregation of relevant predators in the food chain. docsity.com Pollution Prevention (II) All processes and strategies for prevention and intervention of environmental pollution revolve around the principles of use reduction and source elimination. Modern methods tend to rely on integrated pest management and on chemical treatments for elimination and reduction of pollutants. A great deal of sewage sludge and other wastes also have been reduced considerably in the USA through regulatory statues, such as the Clean Water Act. docsity.com