Lecture note 9

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Department
Environmental Science
Course
EESA10H3
Professor
Jovan Stefanovic
Semester
Winter

Description
Lecture 9 During the lecturre we will come on formulas and everything needed on questions 1. Todays topic is TOXICOLOGY and RISK ASSESMENT Very basic What is Toxicology? Science that studies poisons. How they are produced? How they are removed from the environment? Where can they be find? How they affect the organism? That’s the study of poison . Tocicisty of some chemicals basically depends on 1) Chemical characteristics of the poison that are: • Polarity Electronegativity • Oxidation state: When we talked about arsenic 3 and 5 are different • Molecular weight • Dissociation • Solubility – Water soluble toxins: Inorganic chemical dissolve in water, difficult for them human cell. They surround the cell but they don’t enter – Fat soluble toxins: Organic chemical are dissolved in fats. Fat soluble cell easily enter the cell, that’s why they bioaccumalate. • Persistence of chemical: Some chemicals can break down easily, some stay persistence for years without much change. • Bioaccumulation • Biomagnification • Chemical interaction – Antagonistic effect: One chemical reduces the toxicity of another chemical eg. Vitamin A and E might reduce cacogenic effect for some chemicals. – Synergistic: 2 different chemicals taken up at the same time by a person increase the risk of a disease eg. Smoking and • Multiple chemicals – food additives, pesticides, air pollution Very rare human is exposed to one chemical, usually exposed to multiple chemicals. • Receptor: Anybody can be the receptor, any organisms that receive exposure or dose, this course focoused on human. Frequency of the exposure is important to know Age: Child or elder person www.notesolution.com General Health: can be more prone for some respeonses, even some people of same age or same general health can have different effect. • Dose: Amount of chemical that person takes up or been exposed too. Three major routes for exposure: Ingestion through food, water etc, greatest exposure 95% going through ingestion Inhalation about 10% Transfer through the skin: Industrial chemicals could be absobs through the skin 5% Three different types of doses: Acute Dose: one single dose, usually high dose received in short time Chronic Dose: continuous dose but low dose Long term dose: low dose but receive for long time. • Response Syptoms that can be measured Response can be divided into 2 groups: Non specific: No certain tissue is attacked, the whole system is attacked. Eg. Burning, everything is destroyed and also when Narcosis(drunk) effects nervous system, vision, liver or some other organs. No specific tissue that is effected Specific: We know the tissue. Two different type of responses: Acute: Rapid response or death Chronic : Delay response Every chemical is harmful at some level, Water is poison if u drink 3 litters or more at once, can cause every serious health effects. About 100 cups of coffee for some people can cause death. Or 100 pills of aspirin. Question is How much can cause harmful effect. Its really hard from where to start measuring toxicology, if we measure right after we are exposed then there will be no good result Measurement endpoint is easier to measure, we measure biomarkers such as hormones and protein marker thats tells about enzyme induction. www.notesolution.com Scientists usually do experiments on animals. These experiments help scientists to determine lethal dose ( LD 50). Lethal dose is amount of the chemical received as a single dose that will cause mortality of the 50% percent of the experimental animals in a period of 14 days. Case reports: Some family physician make reports about what sypotoms are noted, what are possible complications or suicide reports etc. Epidemiological studies compare control group of individuals and other group is exposed to chemicals. Computer stimulation: very peopular, to stimulate real life Tissues: cultures of cells and bacteria its is really hard to compare animal studies to humans, but these studies are really helpful to determine dose response occurrence. How much and how the response will change if dose increases, for this purpose acute toxicology tests are used. On the grapgh, A Non Threshold chemicals is carcinogens and B Threshold chemicals - None carcinogens. Dose should reach a certain number to see response. Risk Assessment Risk is a possibility of something happens or not happen. Risk for us is suffering harm from a hazard. We have to use probabilyt ti know how big risk is. Probability is something that defines the risk. Eg smoking has a risk of getting lung cancer. But if someone is a smoker that person 1 in 250 people who smoke will get a cancer Risk assessment is the scientific process to estimate that how much harm will a chemical give. Usually a group of scientists from different groups do these studies. Benefits of Risk Assessment It helps to establish the risk, to know how big the risk is of certain chemical and to compare the risk of different chemicals • When agent suspected of causing diseases or testing new chemical • Help rank contribution to overall risk www.notesolution.com • Help identify risk that are easily reduced or eliminated • Help clarified what is known and not known about situation • Can provide quantitative information for decision making • Health Canada – regulations for foods and drags • Canada Council of Ministers of the Environment – National Contaminated Sites Program – Canada-Wide Environmental Standards (CWES) • Ontario Ministry of Environment – Site-specific clan-up guidelines for contaminated soils • CEPA (Canadian Environmental Protection Agency) – 23 000 substances currently in use Stages of Risk Assessment Stage 1 Problem Definition What we want to achieve? who will do that? You are going check everything policies etc Who is the receptor, who is going to read your risk assessment and use it. What is the chemical and how much money you have. Stage 2 Identify contaminant Single compound or mixture It is important to know what is contaminated. Soil water stc Stage 3 Receptor Analysis Who is the organism • Organism, species or groups of species exposed to stressor • Define scenario: – Length of exposure (life time, 20 years – latency for cancer) Acute, chronic. – Incremental or total exposure – Define routes of exposure (ingestion, inhalation, dermal) – Determine rate of exposure from each route. Amount per day etc. – Characterized activity pattern that result in exposure. What does a person do. – Human: who? average person, age, gender Women are sometimes more vulnerable to some chemicals then men – Average & worst case – Sensitive subpopulation – Resent interest in children www.notesolution.com Stage 4 Pathway Analysis Each chemical has different pathway based on its chemical characteristics. Where will we find this chemical according to characteristics. Evaluate routes of exposures, how much is in soil air water etc. Also how much is ingested or inhaled Quantify amount of Exposure. How much the dose is. Imaginary scenario Method or technique we going to use How to do measurements. How much the measurement represent the situation and also take in mind the natural variability. Stage 5 Exposure Assessment • Multiple routes of exposure • Quantify exposure from: – Air (indoor/outdoor) – Water (drinking, showering) – Soil – Sediments – Diet (many varieties) How to calculate exposure? Multiply concentration X intake Rate Stage 6 Toxicity assessment www.notesolution.comLecture 9 During the lecturre we will come on formulas and everything needed on questions 1. Todays topic is TOXICOLOGY and RISK ASSESMENT Very basic What is Toxicology? Science that studies poisons. How they are produced? How they are removed from the environment? Where can they be find? How they affect the organism? Thats the study of poison . Tocicisty of some chemicals basically depends on 1) Chemical characteristics of the poison that are: Polarity Electronegativity Oxidation state: When we talked about arsenic 3 and 5 are different Molecular weight Dissociation Solubility Water soluble toxins: Inorganic chemical dissolve in water, difficult for them human cell. They surround the cell but they dont enter Fat soluble toxins: Organic chemical are dissolved in fats. Fat soluble cell easily enter the cell, thats why they bioaccumalate. Persistence of chemical: Some chemicals can break down easily, some stay persistence for years without much change. Bioaccumulation Biomagnification Chemical interaction Antagonistic effect: One chemical reduces the toxicity of another chemical eg. Vitamin A and E might reduce cacogenic effect for some chemicals. Synergistic: 2 different chemicals taken up at the same time by a person increase the risk of a disease eg. Smoking and Multiple chemicals food additives, pesticides, air pollution Very rare human is exposed to one chemical, usually exposed to multiple chemicals. Receptor: Anybody can be the receptor, any organisms that receive exposure or dose, this course focoused on human. Frequency of the exposure is important to know Age: Child or elder person www.notesolution.com
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