2CHEMICAL HAZARDSA toxic chemical can cause temporary or permanent harm or death.Mutagenschemicals or forms of radiation that cause or increase the frequency of mutations in DNA.Type of carcinogenCarcinogenschemicals or types of radiation that can cause or promote cancer.Teratogenschemicals that cause harm or birth defects to a fetus or embryo.AllergensChemicals that cause allergic reactions. Can cause abnormally high response of the immune system
4Mutagens Ionizing Radiation PAH – polycyclic aromatic hydrocarbons Gamma, X and UVRadioactive decayPAH – polycyclic aromatic hydrocarbonsPAH – mutagen and carcinogen - largest group of known carcinogens – major components in fossil fuel and released during fossil fuel combustionIf affect sperm/egg can be passed down to childrenCystic Fibrosis, Down Syndrome, Sickle CellBenzo[a]pyrene
5Carcinogen Asbestos (synergistic with smoking tobacco) Acrylamide (used as a polymer; plastics)Dioxins (herbicides & paper bleaching)BPA (bisphenol-A), PCBBPA found in plasticsPCB used to manufacture electronics (banned in 1979)Many chemicals in cigarette smokeViruses- HPVKey factors in cancer risk:#1 Smoking (30%)#2 Diet (30%)#3 Industrial Chemicals (30%)Occupational (15), Environmental (10)#4 Genetic (10%)
7Endocrine DisruptersChemicals that interfere with the normal functions of hormones.Found in drinking water from sewage, farming, & pesticides that mimic animal hormonesGrowth hormones in cattle etc., human birth control pillsMany male fish, amphibians, and reptiles becoming feminized:Low sperm countTestes that produce both egg and spermExamples: DDT, Atrazine (herbicide)
9Effects of Chemicals on the Immune, Nervous, and Endocrine Systems Endocrine Disruptorsp235Reduced penis size, female shellfish with male organs, decreased fertility rates, decreased sperm counts and endometirosis, early pubertyFigure 18-9
10CHEMICAL HAZARDSA hazardous chemical can harm humans or other animals because it:Is flammableIs explosiveAn irritantInterferes with oxygen uptakeInduce allergic reactions.
11Effects of Chemicals Immune, Nervous, and Endocrine Systems Chronic vs. AcuteLong-term exposure to some chemicals at low doses may disrupt the body’s:Immune system: affect cells and tissues that protect the body against disease and harmful substances. Synthetic Pesticides, PCBNervous system: brain, spinal cord, and peripheral nerves. DDT, Heavy Metals – Pb, Hg, CdEndocrine system: complex network of glands that release minute amounts of hormones into the bloodstream. DDT, BPA, PCB, Dioxin, Pthalates, diethylstilbestrol (DES)Epidemiological studies from Canada and the former Soviet Union find that children and adults exposed to pesticides suffer similar immune system alterations and higher rates of infectious disease. The risks of pesticide-induced immunosuppression are known to be greatest to infants and children, the aged, people malnourished or chronically ill.
12Industrial Disasters Bhopal, India – The world’s worst industrial accident occurred in 1984 at a pesticide plant in Bhopal, India.An explosion at Union Carbide pesticide plant in an underground storage tank released a large quantity of highly toxic methyl isocyanate (MIC) gas.15,000-22,000 people diedIndian officials claim that simple upgrades could have prevented the tragedy.Minamata, Japan – methylmercury, caused Minimata DiseaseLove Canal – Industrial Waste near town and site turned school. NIAGARA FALLS, N.Y.--Twenty five years after the Hooker Chemical Company stopped using the Love Canal here as an industrial dump, 82 different compounds, 11 of them suspected carcinogens, have been percolating upward through the soil, their drum containers rotting and leaching their contents into the backyards and basements of 100 homes and a public school built on the banks of the canal.
13Toxicity Measurement of how harmful a substance is Depends on Chemical or ionizing radiationDepends onDoseExposureAgeGenetic Make-up of IndividualDetoxification SystemSolubilityPersistenceBioaccumulationBiomagnificationChemical Interactions
14Dose-Response Studies Expose organism to different amounts of a chemical and observe a variety of responses to:Mortality (most common; i.e. LD-50)Changes in behaviorChanges in reproductionMeasured as a concentration of a chemical in air, water or food.Also measured as a dose – the amount of chemical absorbed/consumed by an organismBecause of their short duration (1-4 days) called acute studies.
15Dose-Response Studies Count how many die after exposure to each concentrationData usually exhibits an S-shaped curveLowest dose no mortalityThreshold – dose at which effect can be detectedLD50 – measurement useful in comparing harmful effects of different chemicalsImportant in assessing the toxicity of new chemicals to determine if the new chemical is more or less lethalLD50 can be different among species and rats and mice are usually used to test LD50 in humans. Extrapolate to account for mass differences.
16Testing Standards Chemicals are regulated by EPA as of 1976 Manufacturer of chemical must demonstrate that chemical will not cause adverse effects.Devised a system of testing a bird, mammal, fish & invert.Using LD50 values:Safe concentrations for animals are determined by taking the LD50 value/10For humans LD50 values determined for rats/mice are divided by 1000 to ensure an extra level of caution (very conservative).
17Toxicity - Dose LD50 Median lethal dose The amount of chemical in 1 dose that kills 50% of animals within a 14 day periodPoison - LD50 of 50mg/kg of body weight
19Toxicity - Dose “The dose makes the poison” Paracelsus, 1540 Supertoxic (dioxin, nerve gas and botulism toxin)Extremely toxic (nicotine)Very toxic (mercury salts, codeine)Toxic (lead salts, caffeine, DDT)Moderately Toxic (methyl alcohol, aspirin)Slightly Toxic (ethyl alcohol, soap)Essentially nontoxic (water)
20Toxicity - Exposure Methods of Exposure How often and for how long? IngestionInhalationThrough SkinHow often and for how long?Acute vs. ChronicFor example DDT was shown to be safe by spraying on children because it does not easily penetrate the skin, however it is eaten in food and inhaled as well.
21TOXICOLOGY: ExposureEstimating human exposure to chemicals and their effects is very difficult because of the many and often poorly understood variables involved.Figure 18-11
22Persistence Bioacculumlation and Biomagnification Lipid soluble POP – persistent organic pollutantsPCB, Dioxin, DDTHeavy Metals – methyl mercury, tetraethyl leadAlgal Blooms – “red tide” makes mussels toxic.
23DDT and Bioaccumulation(absorbed or stored in organs) and Biomagnification (through a food chain) Fig. 11-4p. 231
24TOXICOLOGY: genetic make-up Typical variations in sensitivity to a toxic chemical within a population, mostly because of genetic variation.Figure 18-10
25Other Studies Chronic Studies: Retrospective vs. Prospective Studies: Toxicology studies conducted over a long period of time.Goal is to examine the long-term effects of chemicals on survival and impacts on reproductionRetrospective vs. Prospective Studies:Epidemiology – understanding the causes of disease in humans & wildlifeRetrospective Studies – monitor people who have been exposed to a chemical in the past. Ex: Bhopal, India – still monitoring people who were exposed.Prospective Studies – monitor people who might be exposed to chemicals.