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Lecture 4

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Environmental Science
Jovan Stefanovic

Lecture 4 Chemical Hazards Chemical Hazards – can also be found in soil, food, vegetation, air, basically everywhere Contaminants – any substance that MAY harm human health (but not necessarily) Pollutants – any substance that is MORE LIKELY to harm human health – toxic  People think that if something is synthetic, then it is dangerous  not necessarily true  some natural contaminants/pollutants are very dangerous to human health. - Endocrine disruptors o Chemicals that interfere with normal hormonal functions in our body – create adverse side effects eg. Cancers, birth defects, etc. - Chemical body burdens o Chemical pollutants are often called body burdens  mimic body hormones (same as endocrine disruptors)  they can accumulate in the body = body burdens  can also be from industrial wastes - Problem: o We don’t know enough about these chemicals and how they affect human health o Most studies and conclusions are based on animal studies that have similar physiologies as humans (eg. rats, pigs) Endocrine Disruptors - These chemicals disrupt the normal function of the endocrine system  pituitary, pineal, hypothalamus, etc…  all produce hormones (these are chemicals that regulate many important processes in our body) o  These disruptors bind to hormone receptors in the body (the body thinks this is acceptable because they mimic the appearance of these hormones).  Note: Hormones are produced in low amounts - Results? o Direct  alteration of genes (appearance and function) disrupt protein production (remember genes regulate proteins) o Indirect  alters hormone production, transportation, metabolism o These are very dangerous especially to fetuses since the thyroid hormone is primarily responsible for the brain development of fetuses in the womb. o In adults, health consequences is not permanent  recovery is possible. - DES (diethylstilbestrol) o During 1948-1971, this synthetic estrogen hormone was prescribed to prevent spontaneous abortion among expecting mothers  more than 1 million took this in a period of 10 years, 1960-1970  administered during the first 35 weeks of pregnancy.  However, the resulting children had a wide range of health problems when they reached 20-30 years of age.  During the 1980’s, problems started to show up in the offspring of the mothers who took the hormone:  Reproductive organ dysfunction  Abnormal pregnancies  Fertility problems in both sexes  Immune system disorders  Carcinoma (adenocarcinoma)  Cancers Endocrine Disruptors – Health Implications - Affect behaviours - feminization of males (also in roosters), abnormal sexual behaviours - Birth defects - Altered puberty process (very early or very late) - Cancers  mammary glands or testes - Thyroid dysfunction – PCB’s affect function of the thyroid gland o TSH produces T3 and T4 which regulates the normal function of a fetus’ brain and CNS development. o In adults, hypothyroidism can occur. - Neurobehavioural effects – mostly as a result from pre/post natal exposure to disruptors  affects mental development, decreases IQ, learning disabilities o Post natal – from breast milk and other types of exposure e.g. baby formula  PCB (polychlorinated biphenyl contaminants)  Impaired learning in nonhuman primates - poor IQ tests  Delayed psychomotor development (eg. 4 year old moving like a 2 year old) - distractibility  Organophosphates – affects brain development Chemical body burdens - Every year thousands of chemicals are released – research can take a long time so the adverse effects of these cannot be readily identified - Body burdens  endocrine disruptors are under this category  it is basically the number of chemicals accumulated inside the body or the total amount of all the chemicals in the body (humans accumulate these chemicals throughout their lives  since conception…through breast milk…etc.) o How much depends on location and mode of transmission. o These are hard to metabolize in the body so they accumulate in body tissues  They are not distributed homogenously in the body – some accumulate in hair, skin and some in livers or muscle  some chemicals concentrate in certain parts of the body.  E.g. Arsenic – accumulate mostly in hair - Monitoring body burdens o Computer modelling helps with predicting  levels in the body can change since they are excreted through sweat, urine, tears, etc.  they can also be degraded and changed to other forms  most are persistent (can accumulate) o Biomonitoring –  We try to monitor levels in the body; problem is that we don’t know the “normal levels”.  We don’t have a technique to detect these chemicals in low amounts, PPB (parts per billion).  Most techniques have detection levels – limitations  Researchers usually test two groups of people – those who are exposed to high concentrations and those who are exposed to “normal” concentrations.  They compare these groups and try to figure out the consequences of such exposure (health)  There are new chemicals as years go by and we have limited knowledge on them and therefore not have the ability to detect them. Organochlorine Substance - Most are organic substance – they have Hydrogen and Carbon e.g. fats – plus they have Chlorine - DDT: insecticides, Dioxins: by-product of many processes o Both are:  POP (persistent organic pollutants) – they don’t break down in the environment and stay there for a very long time  also stay in body for a very long time and don’t break down.  Bio accumulating – buildup in tissues of humans and/or other organism  Bio magnification – buildup within the food chain – lowest get less, and highest gets more (humans) Dioxins - These are group of chemicals with no usefulness and with similar chemical formula (characteristics) but differ in their toxicity.
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