Environmental Neuroscience Advancing the Understanding of How Chemical Exposures Impact Brain Health and Disease: Proceedings of a Workshop (2020) / Chapter Skim
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2 Neurotoxicants and Their Risks to Human Health
2 Neurotoxicants and Their Risks to Human Health
Pages 5-16
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From page 5... ...
. • The combination of three environmental chemical exposures -- lead, organophosphate pesticides, and methyl mercury -- are responsible for greater IQ loss than medical conditions such as preterm birth, neurodevelopmental disorders, and socioeco nomic and nutrition-related factors (Bellinger)
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From page 6... ...
With regard to genetics, she pointed out that in the 1990s, prominent biologists predicted that mapping of the entire human genome would reveal the causes of common and debilitating diseases, including common psychiatric disorders. However, what genetics has shown instead is that these disorders are usually caused by either rare mutations; interactions of multiple genes; or interactions with epigenetic, environmental, and microbial factors that exert their effects as early as during fetal development and across the entire life span (Berkowitz, 2020)
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From page 7... ...
Jennifer McPartland, senior scientist in the Health Program at the Environmental Defense Fund, added that for most chemicals in commerce, little information exists regarding potential hazards and extent of exposure, particularly as these factors relate to effects on the brain. Yet, she noted that new tools are available with the potential to fill these massive data gaps and complement some of the more traditional methods such as animal and epidemiological studies.
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From page 8... ...
, hydroxylated BDEs (OH-BDEs) , polychlorinated biphenyls (PCBs)
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From page 9... ...
has been documenting human exposure levels to pesticides and other environmental chemicals, said Beate Ritz, professor of epidemiology, environmental health sciences, and neurology at the University of California, Los Angeles. The NHANES 1999–2000 reported the presence of metabolites of organophosphate pesticides in more than half of the urine samples collected and chorpyrifos in more than 90 percent (Barr et al., 2004)
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From page 10... ...
10 ENVIRONMENTAL NEUROSCIENCE FIGURE 2-2 Human exposure to agricultural chemicals. Three common agricultural chemicals -- atrazine, glyphosate, and 2-4-D -- are widely used in the United States, with the use of glyphosate increasing dramatically to about 250 million pounds per year.
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NEUROTOXICANTS AND THEIR RISKS TO HUMAN HEALTH 11 FIGURE 2-2 Continued continued
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From page 12... ...
Among the chemicals being produced at these high rates are industrial chemicals including perfluorinated chemicals such as Teflon, flame retardants used in consumer products such as mattresses and couches, plasticizers like phthalates, and chemicals used in food packaging, such as bisphenol A
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From page 13... ...
Chan School of Public Health, and colleagues estimated the contribution of several risk factors to IQ loss in a population of 25.5 million children. They concluded that just three environmental chemical exposures -- lead, organophosphate pesticides, and methyl mercury -- are together responsible for greater IQ loss than medical conditions such as preterm birth, neurodevelopmental disorders such as autism and ADHD, and socioeconomic and nutrition-related factors such as iron deficiency and non-organic failure to thrive (Bellinger, 2012)
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From page 14... ...
ASSESSING THE RISK OF EXPOSURES Regulatory agencies have developed risk assessment paradigms such as the four-step risk assessment process used by EPA, which characterizes the risk posed by a certain chemical by first identifying health problems caused by the particular pollutant and then assessing dose–response and extent of exposure over time, said Cory-Slechta (see Figure 2-3)
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From page 15... ...
The EPA risk assessment paradigm is used by EPA and other regulatory agencies to characterize the level of risk to a population posed by individual chemicals based on health problems associated with the chemical, the dose and timing of exposure, and the number of people exposed. SOURCES: Presented by Deborah Cory-Slechta, June 25, 2020; EPA, 2020; NRC, 1983.
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