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Transcript
Chapter 17 Human Health and Environmental Risks Three categories of human health risks Physical – environmental factors (natural disasters) that cause injury and loss of life (Sunburn as well) Biological – associated with diseases Chemical – associated with chemicals and pesticides Biological Risks Infectious diseases- those caused by infectious agents, known as pathogens. Examples: pneumonia and venereal diseases Diseases not caused by pathogens include respiratory, digestive, and cancers Biological Risks Chronic disease- slowly impairs the functioning of a person’s body. Heart disease and most cancers Acute diseases- rapidly impair the functioning of a person’s body. Ebola Risk factors of chronic disease Low – income countries top risk factors for chronic disease are poverty, unsafe drinking water, poor sanitation, and malnutrition High –income countries increased availability of tobacco, combination of less active lifestyle, poor nutrition and overeating. Epidemic vs. Pandemic Epidemic – when a pathogen causes a rapid increase in disease Pandemic – when an epidemic occurs over a large geographic region such as an entire continent. Historical Diseases Plague – most familiar disease of human history (Black death) Caused by an infection from a bacterium that is carried in fleas. Mice and fleas.. Bad combination Killed nearly ¼ of the Eurpoean population in the 1300’s Last major pandemic was in Asia in the early 1900’s Historical Diseases Malaria – caused by infection from any one of several species of protist. Parasite spends one stage of its life inside a mosquito and anther stage inside a human Hits sub-Saharan Africa, Asia, middle east, and central and south America. Historical Diseases Tuberculosis – highly contagious diseases caused by a bacterium that primarily infects the lungs. Spread when a person coughs and expels the bacteria into the air Can be treated with antibiotics for a year. Emergent Diseases Emergent disease – defined as infectious diseases that were previously not describe or have not been common for at least the prior 20 years. HIV/AIDS Origin was mystery until 2006 – found in chimpanzees living in the African nation of Cameroon. Hunters exposed to virus when butchering or eating the chimps. More than 33 million people have died from AIDS related illness. Emergent Diseases Ebola Discovered in the Democratic Republic of Congo Death occurs within 2 weeks and there are no drugs available. Natural source remains unknown Emergent Diseases Mad Cow Disease Pathogens slowly damages a cow’s nervous system. Can be transmitted to humans who eat meat from infected cattle Emergent Diseases Bird Flu Also known as Spanish flu and caused by H1N1 Normally only infects birds H5N1 another strain that jumped from birds to people. More than 400 ppl had been infected by H5N1 nad half have died Emergent Diseases West Nile Virus Lives in hundreds of species of birds and transmitted among birds by mosquitos. First human case was in 1937 in the West Nile region of Uganda. In 1999 appeared in New York and quickly spread in the US. Chemical Risks Neurotoxins- chemicals that disrupt the nervous system Carcinogens- chemicals that cause cancer Ex. insecticides, lead, mercury Cause cell death, ex. asbestos, radon, and the chemical found in tobacco Teratogens- chemicals that interfere with the normal development of embryos or fetuses Ex. alcohol Allergens- chemicals that cause allergic reactions Endocrine disruptors- chemicals that interfere with the normal functioning of hormones in an animal’s body Dose-Response Studies Dose Response Study – expose animals or plants to different amounts of a chemical and then observe a variety of possible responses including mortality or changes in behavior or reproduction. Can be measured in concentration of chemical or dose of chemical. LD50- lethal dose that kills 50% of the individuals By quantifying the LD50 value, scientists can compare the value to thousands of previous tests. ED50- effective dose that causes 50% of the animals to display the harmful but nonlethal effect Retrospective versus Prospective Studies Retrospective studies monitor people who have been exposed to a chemical at some time in the past. Group that has been exposed to chemical and group that has not and observe the death rate in each group Prospective studies monitor people who might become exposed to harmful chemicals in the future. Ex. tobacco use Synergistic interactions- when two risks come together and cause more harm that one would. For example, the health impact of a carcinogen such as asbestos can be much higher if an individual also smokes tobacco. Routes of Exposure Bioaccumulation bioaccumulation- an increased concentration of a chemical within an organism over time Involves the biological sequestering of substances that enter the organism through respiration, food intake, or skin contact with the substance. Level at which a given substance is bioaccumulated depends on: Rate of uptake Mode of uptake Rate the substance is eliminated from the organism Transformation of the substance Fat content of the organism Environmental factors Biomagnification Biomagnification- the increase in a chemical concentration in animal tissues as the chemical moves up the food chain. Must be long-lived, mobile, soluble in fats, and biologically active. Bioaccumulation vs. Biomagnification Methylmercury taken up by bacteria and phytoplankton Small fish eat the bacteria and ACCUMULATE the mercury. Small fish are eaten by larger fish, which are then eaten by humans and animals resulting in the biomagnification of large concentration of mercury in human and animal tissue. The more fat-like a substance, the more likely it is to bioacculumate in organisms, such as fish. Persistence Persistence- how long a chemical remains in the environment Risk assessment Objective esstimation of risk. Includes indenfication of hazards, doseresponse assessment, exposure assessment, and risk characterization Risk acceptance The level of risk that can be tolerate 4 levels High risk – such as smoking or diriving while intoxicated Low risk – infrequent events that make have a large consequence, such as an earthquake Very low risk – events that occurred in recorded history, meteor striking NA Mixed risk – outcomes the increase the frequency against a background or occurrences, additional cases of caner beyond that normally expected Risk Management Process of determing what to do about risk. Includes risk identification and use of trying to reduce the risk. Risk Analysis Qualitative Risk Assessment Making a judgment of the relative risks of various decisions Probability- the statistical likelihood of an event occurring and the probability of that event causing harm Quantitative Risk Assessment The approach to conducting a quantitative risk assessment is: Risk= probability of being exposed to a hazard X probability of being harmed if exposed Stockholm Convention In 2001, a group of 127 nations gathered in Stockholm, Sweden, to reach an agreement on restricting the global use of some chemicals 12 chemicals were to be banned, phased out, or reduced These include DDT, PCBs, and certain chemicals that are by-products of manufacturing processes.
