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UT ENS 112 - Chapter 10

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Environmental Science 112FALL SEMESTER 2018INSTRUCTOR: DR. Adrienne [email protected] 10Environmental Health● Environmental Health is a field that assesses environmental factors that can influence our health and quality of life○ These include both natural and anthropogenic factors● Environmental hazards are categorized into four types○ Physical Hazards■ Arise from natural environmental processes, such as UV radiation from sunlight and natural disasters● Reduced with protective measures, such as sunblock and disaster protection and warning systems○ Chemical Hazards■ Include synthetic chemicals such as pharmaceuticals, disinfectants, and pesticides, and natural toxins like venom○ Biological Hazards■ Result from interactions with other organisms, such as viruses, bacteria, insects, or parasites■ Infectious Disease: are illnesses that can be spread from person-to person■ Vectors are organisms that transfer diseases to their host○ Cultural Hazards■ Occur as the result of our place of residence, socioeconomic status, occupation, or behavioral choices1● Ex: smoking, poor diet, drug use, and workplace hazardsDisease is a major focus of environmental health● Infectious and noninfectious diseases cause the majority of human deaths worldwide● Noninfectious diseases develop without the action of a foreign organism● Infectious Diseases spreads when a pathogenic organism enters a host through the skin, via the respiratory system, or by the consumption of food or water○ Immunization, public sanitation, access to clean water, food security, and public education all help to reduce infectious disease○ Infectious diseases are the second-leading cause of death worldwideToxicology is the study of chemical hazards● Toxicology is the science of examining the effects of poisonous substances on humans and other organisms○ Toxicity is the degree of harm caused by a chemical substance called a toxicant● Any chemical has the potential to be a toxicant, depending on the dose and level of exposure● Environmental Toxicology is the study of anthropogenic chemicals released into the environment that have human health impactsMany Environmental health hazards exist indoors● Cigarette smoke and radon are leading indoor health hazards and the top two causes of lung cancer○ Radon is a radioactive gas that seeps up from certain types of bedrock. It is colorless and undetectable without specialized kits● Asbestos is a substance that was used in the past as insulation in walls and other products and is highly toxic when inhaled● Lead is a heavy metal that, when ingested, damages the brain, liver, kidney, and stomach2○ Lead poisoning has greatly declined since the phaseout of lead- based paint and leaded gasoline in the 1970’s● Polybrominated Diphenyl Ethers (PBDE’s) are compounds used as fire retardants in a variety of products, including electronica, plastics, and furniture○ Act as hormone disruptors, interfering with thyroid hormones○ European Union banned PBDE’s in 2003, but not the USToxic substances and their effects on organisms● The environment contains many natural toxic substances, such as petroleum, radongas, and toxins○ Toxins are toxic chemicals manufactured in the tissues of living organisms, often used as defense against other● We are also exposed to many synthetics chemical substancesSilent Spring began the public debate over synthetic chemicals● Prior to the 1960’s, pesticides were sprayed over residential neighborhoods and public areas, on an assumption that the chemical would not harm people● Rachel Carson published Silent Spring in 1962, using the scientific studies and case histories to demonstrate that pesticides like DDT were harmful to people○ Although the chemical industry challenged the book, public outcry led to the banning of DDT in the United States.● Synthetic Chemicals, such as DDT, take many routes traveling through the environmentNot all toxic substances are synthetic● Many toxic substances exist naturally in the environment and in the foods we eat○ It is a mistake to assume that all synthetics are bad and a natural are goodToxic Substances come in different types● Carcinogens are substances or types of radiation that cause cancer○ Cancer occurs when malignant cells grow uncontrollably, creating tumors and often leading to death3● Mutagens are substances that cause genetic mutations in the DNA of organisms○ Most mutations have little or no effect, but can lead to severe problems like cancer● Teratogens specifically cause birth defects● Neurotoxins such a heavy metals damage the nervous system● Allergens over-activate the immune system, causing an immune response when one is not necessary● Pathway inhibitors block one or more steps in important biochemical pathways○ Cyanide, for example, interrupts the chemical pathways that produce energy in the mitochondria● Endocrine disruptors interfere with the functions of body hormones, either by blocking them, accelerating their breakdown, or mimicking their effectsOrganisms have natural defenses against toxic substances● Organisms have evolved ways to tolerate harmful substances naturally present in the environment to gain an evolutionary advantage○ Skin, scales, and feathers resist uptake from the surrounding environmentIndividuals vary in their responses to hazards● An individual’s sensitivity to a given toxin will vary depending on genetics, overall health, gender, and age○ Those in poorer health, individuals of smaller size, and younger organisms with developing organ systems tend to be more sensitive○ The EPA extrapolates chemical exposure standards for adults down to infants and childrenThe risk of exposure can affect the response● The risk of a hazard also varies according to whether:○ A person experiences high exposure for short periods of time (acute exposure)○ Low exposure for long periods of time (chronic exposure)4Some toxicants persist in the environment● The rate at which a substance degrades in the environment depends on its chemistry and on external factors like temperature, moisture, and sun exposure● We have designed many chemicals, such as those in plastics, to be persistent and resist degradation○ Over time, most toxicants degrade into simpler compounds, called breakdown products, which may be less or equally harmful as the original substanceToxic substances may accumulate and move

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