Lecture 4: Chemical Hazards and Human Health

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Environmental Science
Jovan Stefanovic

Human Health and the Environment Lecture 4: Chemical Hazards and Human Health Chemical Hazards • Why chemical hazards all contaminants all pollutants that we discussed until now are basically chemical hazards – in water, in air • This lecture will be about the chemical hazards that are spread everywhere – in every medium be soil, food, plants, meat, water, even in air • Endocrine disruptors • Chemical body burdens of industrial chemicals • Some chemicals that are body burdens are also endocrine disruptors and on the other hand endocrine disruptors can accumulate in the body and we call them body burdens and they also do the same in industrial because endocrine disruptors can be industrial • What is the biggest problem with these chemicals? We don’t know much about it especially not how these chemicals affect human health • Most of our conclusions are assumptions or they are based on animal studies – many experimental animals have a similar physiology with humans but not the same and who knows • That is what we have right now and science is working on that very hard so soon we will have some better answers What are Endocrine disruptors? • First you have to know what endocrine glands are • Picture posted to show what are the endocrine glands – these organs in our body produce hormones • What are the hormones? Chemicals that regulate many different processes that are very important processes in our body and they regulate the processes in very tiny amounts • What do endocrine disruptors do to these functions? Hormones are carried through our body by some receptor also some chemical that carry the hormone • Because of the similarity between the hormone and our pollutant our endocrine disruptor receptor is confused • What is happening? Some genes can be altered because these receptors bind with DNA and alter the appearance of the gene • What the genes do is regulate the production of different proteins and as a result of their changes and alterations so changes are reliable to produce proteins are seen in a body – that is all about direct effects • Also there are many types of indirect affects – production of the hormones, metabolism of the hormones, transport of the hormones through the body • What is specific for endocrine disruptors? Adults are not that sensitive (adverse affects are not very visible on adults), fetuses are much more sensitive • Fetuses are more sensitive on the changes of the hormones than adults • Thyroid hormone affects mental brain development of fetuses DES (diethylstilbestrol) • Problems are not seen if a pregnant mother is exposed to endocrine disruptor – not much problems can be seen to your health Life Support EESA10H3 • But the problem is changes in health and life of daughters and sons – we have to wait 20 to 30 years to see this adverse affect until the daughter or son reach maturity to have own kids • An example of this is DES, a synthetic estrogen hormone that physicians prescribe to prevent spontaneous abortion • Lasted for almost 30 years from 1948 to 1971 • More than one million women took this in a period of ten years from 1960 to 1970 • During the 1980s started facing significant increases in some health problems such as reproduction organ dysfunction, abnormal pregnancies in daughters, reduction in fertility when daughters and sons try to have their own kids, immune system disorders, and some type of carcinoma (adenocarcinoma) • This is lack of knowledge in a time when some medication is prescribed (when we discuss risk assessment later we will come back to this problem again) • Mothers didn’t suffer that much but kids did Endocrine disruptors – Health Implications • Other problems with the endocrine disruptors affects our health – feminization of the males, some strange abnormal sexual behaviour, birth defects, cancer, altered time to puberty, and thyroid dysfunction especially PCBs affect function of the thyroid gland Endocrine disruptors – neurobehavioural effects • Besides these factors, affects on a sexual behaviour and sexual problems neural behavioural affects are also seen • As a result of prenatal or postnatal exposure • What is the postnatal exposure? Mostly from the breast milk and other exposures • Gave example of PCBs – PCBs can greatly affect thyroid function but later as a neural behaviour affect can be some problem with mental developments of the kids, learning disabilities, some poor IQ tests later in life • In animal studies some impaired learning in non-human primates seen • Organophosphates affect directly brain development Chemical body burdens • What are these chemicals – industrial chemicals many of them called body burdens because during the time they accumulate in the body • Quantity of these chemicals accumulated in the body are called body burdens • Why is it difficult to do research in this area and to solve some of these problems? • These chemicals are not stable over time inside our body – partially they can be metabolized, changed into other forms, degraded (but not much), most of them are very persistent, and some of them can be execrated through the urine or other forms of execration • They are not distributed evenly through our body – some are accumulated in the liver, some can be accumulated in the nails or skin, hair (arsenic particularly accumulates in the hair) • Because of that more organs are exposed and the concentration is higher • The big problem is the detection of these chemicals, still do not have a specific technique to detect these chemicals in very low concentrations such as PPB or even less Life Support EESA10H3 • PPB means part per billion or even in lower concentrations • Techniques such as chlordane methods or ICP (induct coupled plasma) very good to detect the level of different metals • All of these techniques have a detection limit – below that detection limit these techniques simply can’t detect such lower levels, that is the limitation we just can’t do it • But still government provides money for monitoring of all these chemicals in population • Researchers monitor usually two groups of people – one that are exposed to very high concentrations of certain chemicals and another one that we call normal exposure (not very high exposure) • Something with or without normal chemical exposure • They compare these two groups and try to figure out what is normal and can cause health and adverse affects or what can’t • We’ll also talk about threshold levels when we discuss risk assessments in a couple of weeks because all of these depends on the types of chemicals Organochlorine Substances • Are two different chemicals – will talk about dioxins and DDT (are not in the textbook) • Found this very intriguing and very important subject of big concerns right now Dioxins • What are dioxins? First you have to know that dioxins are not one chemical , it is a group of chemicals similar in their chemical characteristics (chemical formula) but very different in their toxicity • These chemicals are actually not produced in any kind of industry for themselves – they don’t have any implication (no commercial usefulness) • They are produced during some other processes such as combustion (in any kind of combustion) dioxins are produced • We are most concerned about the incineration of different wastes – doesn’t mean that it is not produced in other types of combustion • Even if you burn the trash in your backyard you produce some dioxins • In car exhaust you also can find dioxins • Dioxins are always associated with furans but we won’t talk about furans today only dioxins • Also dioxins are produced during the manufacturing processes – herbicide manufacture and paper manufacture Dioxins • Group of chemical compounds with similar chemical structure • One of the most toxic and most studied is 2, 3, 7, 8 – tetrachlorodibenzo-p-dioxin (TCDD) • What you need to definitely remember is that this chemical has 4 chlorine atoms and we try to remember their position • Only such a position of chlorine caus
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