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University of Toronto Scarborough
Environmental Science
Jovan Stefanovic

Lecture 4: Chemical Hazards and Human Health Chemical Hazards – spread everywhere in all mediums • Endocrine disruptors • Chemical body burdens Both are interconnected with each other. Endocrine problems can be a body burden and vice versa. Data mostly from animal studies, not much from human exposure. Animals have similar physiology to humans and scientists are working on it very hard to get better answers. Endocrine disruptors: organs that produce hormones which help in coordinate the body functions are disrupted in some way or the other: 1. Direct effects: - Bind to hormone receptors - Alter the appearance of some genes which can alter the appearance. - Changes in the level of produced proteins 2. Indirect effects: - Altering hormone production - Altering hormone transport - Altering hormone metabolism - Fetus more sensitive than adults DES (diethylstilbesteol) • Synthetic estrogen used by physicians to prevent spontaneous abortion (1948-1971) • Administered for early pregnancy until 35 weeks • > 1million women took it between 1960-1970 • Daughters whose mothers took DES have increased incidents of: – Reproductive organ dysfunction – Abnormal pregnancies – Reduction in fertility – Immune system disorders – Adenocarcinoma: Some type of carcinoma -- Mothers didn’t suffer as much as the kids did Endocrine disruptors – Health Implications • Feminization of males • Abnormal sexual behavior • Birth defects • Altered time to puberty www.notesolution.com • Cancer of mammary glands or testis • Thyroid dysfunction (especially by PCB’s) Endocrine disruptors – neurobehavioral effects • Prenatal and early postnatal exposures (mostly through the breast milk) • PCBs: – Impaired learning in nonhuman primates – Delayed psychomotor development – Distractibility – Poor IQ tests brain defects caused by lowering TSH – Organophosphates - directly Brain development Chemical body burdens: mainly industrial chemicals • Quantity of chemicals accumulated in the body are called body burdens – Not stable over time – they can be excreted too – Not distributed homogeneously in a body: some accumulated in liver, skin, hair etc – Not possible to detect if present in very low concentrations: techniques such as calorimetric methods or ICP (induct copper plasma) - to detect levels of metals (not organics). – Biomonitoring – monitoring people exposed to “normal level” to “very high concentrations” Monitoring also depends on what chemical is being exposed. Organochlorine Substances • Dioxins • DDT Dioxins They are a group of chemicals similar in characteristics but different in toxicity. They are associated with furans. • Dioxins have no commercial usefulness by themselves • Formed during – Combustion process such as waste incineration, forest fires and backyard trash burning – Manufacturing processes such as herbicide manufacture and paper manufacture Dioxins • Group of chemical compounds with similar chemical structure. Very persistent chemical. • One of the most toxic and very persistent and most studied is 2,3,7,8- tetrachlorodibenzo-p- dioxin (TCDD): Important to remember that this chemical has 4 Cl atoms. The higher the Cl level in a compound the more toxic the chemical is. Major source of dioxin contamination: Food: plants
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