Ch 14 Environmental Health & Toxicology Lecture Outlines PDF

ENVIRONMENT the science behind the stories Lecture Outlines Chapter 14 Environmental Health and Toxicology Withgott | Laposat...

ENVIRONMENT the science behind the stories Lecture Outlines Chapter 14 Environmental Health and Toxicology Withgott | Laposata Sixth Edition Lecture Outlines by James Dauray, College of Lake County © 2018 Pearson Education, Inc. Poison in the Bottle: How Safe is Bisphenol A? § The chemical Bisphenol A (BPA) is in hundreds of everyday products, yet it has been linked to breast cancer, prostate cancer, heart disease, and many other health risks. § BPA is an additive used to make the coatings of metal cans, dental sealants, and the polycarbonate plastic found in water bottles, toys, and electronics. § 93% of Americans have detectable amounts in their urine § Hundreds of studies on mice, rats, and other animals have shown many apparent effects of BPA. § BPA is structurally similar to the hormone estrogen and can induce some of its effects in animals. Environmental Health § Environmental health: a field that assesses environmental factors that can influence our health and quality of life § These include both natural and anthropogenic (man-made) factors. We face four types of environmental hazards § Physical hazards: arise from natural environmental processes, such as UV radiation from sunlight and natural disasters § These risks can be reduced with protective measures, such as sunblock, and disaster detection 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 diseases: illnesses that can be spread from person-to-person § Vectors: organisms that transfer diseases to their host § Cultural hazards: occur as the result of our place of residence, socioeconomic status, occupation, or behavioral choices § Choosing to smoke, accompanying people who smoke, diet, drug use, and workplace hazards are all examples. Noninfectious disease is affected by genes, environment, and lifestyle § Infectious and noninfectious diseases cause the majority of human deaths worldwide. § Noninfectious diseases: develop without the action of a foreign organism § Noninfectious diseases can be lessened or increased through changing lifestyles.  Infectious disease has long plagued humanity § Infectious diseases spread when a pathogenic (disease-causing) organism or agent enters a host through the skin, via the respiratory system, or by the consumption of food or water. § The pathogen uses conditions inside the body to reproduce, then induces the host to expel its offspring through coughing, sneezing, vomiting or diarrhea. © 2018 Pearson Education, Inc. We fight infectious disease with diverse approaches § Scientists did not establish the connection between disease and microorganisms until the late 1800s. § This discovery led to antibiotics and many societal approaches that help minimize the spread of disease. § Sterilizing drinking water § Providing sanitary facilities (e.g., indoor plumbing) § Ensuring nutritious diets § Treatment, quarantining, and early intervention help to break the cycle of infection that caused historical disease outbreaks, such as cholera in London in the 19th century. Infectious disease remains a concern § Potential epidemics can still emerge, such as the outbreak of Ebola in West Africa in 2014. § Diseases like this are caused by pathogens that mutate readily, giving rise to strains with slightly different genetics. § Diseases can also be spread more easily than in the past, due to worldwide travel and the spread of vector insects through global warming.  Toxicology is the study of chemical hazards § Toxicology: the science of examining the effects of poisonous substances on humans and other organisms § Toxicity: the degree of harm caused by a chemical substance called a toxicant § Any chemical has the potential to be a toxicant, depending on the chemical properties and the dose § Environmental toxicology: the study of anthropogenic chemicals released into the environment that have human health effects © 2018 Pearson Education, Inc. Many environmental health hazards exist indoors § Cigarette smoke and radon are major indoor health hazards, and the top two causes of lung cancer. § Radon: a radioactive gas that seeps up from certain types of bedrock § It is colorless and undetectable without specialized kits. § Asbestos: a substance that was used in the past as insulation in walls and other products § Scars and impairs lung function when inhaled, causing a disorder called asbestosis. § Lead: a heavy metal that, when ingested, damages the brain (nervous system), liver, kidney, and stomach § This condition is called lead poisoning, and has greatly declined since the phaseout of lead-based paint and leaded gasoline in the 1970s.  § Polybrominated diphenyl ethers (PBDEs): are compounds used as fire retardants in a variety of products, including electronics, plastics, and furniture § Similar to BPA, PBDEs act as hormone disruptors, interfering with thyroid hormones. § The European Union banned PBDEs in 2003, but they have not yet been addressed in the United States. © 2018 Pearson Education, Inc.  Toxic Substances and Their Effects on Organisms § The environment contains many natural toxic substances such as petroleum, radon gas, or toxins. § Toxins: toxic chemicals manufactured in the tissues of living organisms, often used as defense against others § We are also exposed to many synthetic (artificial, man-made) chemical substances. © 2018 Pearson Education, Inc. Synthetic chemicals are all around us § Tens of thousands of synthetic chemicals have been manufactured for various industries. § Many of these find their way into the environment. § A 2002 study found that 80% of U.S. streams contained trace amounts of antibiotics, detergents, solvents, perfumes, and other substances. § Pesticides used on lawns and farms are some of the most widespread chemicals. § Concentrations are rarely enough to harm people, but often harm aquatic life. § Contamination is the most severe in the farming states of the Midwest and Great Plains.  Silent Spring began the public debate over synthetic chemicals § Prior to the 1960s, pesticides were indiscriminately sprayed over residential neighborhoods and public areas, on an assumption that the chemicals would not harm people. § Rachel Carson published Silent Spring in 1962, using scientific studies and case histories to demonstrate that chemicals or 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. © 2018 Pearson Education, Inc.  Toxic substances come in different types § Carcinogens: substances or types of radiation that cause cancer § Cancer occurs when DNA mutates damaging cell cycle proteins; malignant cells grow uncontrollably creating tumors § polycyclic aromatic hydrocarbons (PAHs): make up some of the carcinogens found in cigarette smoke, charred meat, and the emissions of fossil fuel (coil, oil, or natural gas) combustion § Carcinogens are difficult to detect because there may be a long lag time between exposure and the onset of the disease. § 2 of every 5 Americans are diagnosed with some form of cancer in their lives © 2018 Pearson Education, Inc.  § Mutagens: substances that cause genetic mutations in the DNA of organisms § Most mutations have little or no effect, but some can lead to severe problems like cancer. § Teratogens: specifically cause birth defects § examples include using alcohol and smoking while pregnant © 2018 Pearson Education, Inc.  § Neurotoxins: chemicals that damage the nervous system § nervous system: consists of the brain, spinal cord, and neurons (nerve cells) § Allergens: over-activate the immune system, causing an immune response when one is not necessary § immune system: consist of white blood cells, antibodies, lymph nodes, spleen, bone marrow, and thymus § Pathway inhibitors: block one or more steps in important biochemical pathways § cyanide interrupts the chemical pathways that produce energy (cellular respiration) in mitochondria leading to death © 2018 Pearson Education, Inc. § Endocrine disruptors: chemicals that interfere with the functions of body hormones, either by blocking them, accelerating their breakdown, or mimicking their effects § endocrine system: consists of the body’s chemical messengers (hormones) that control many vital functions and the glands that produce them § glands of endocrine system: hypothalamus, pituitary, thyroid, adrenals, ovaries, testes § BPA is one example of an endocrine disruptor that mimics the female hormone estrogen. § Phthalates: chemicals used as softeners in plastics and fragrance enhancers in some perfumes and cosmetics § These are also endocrine disruptors, and are linked to birth defects, breast cancer, low sperm counts, and other reproductive effects. Organisms 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 environment. § Metabolic pathways can break down toxic substances or make them water soluble so they can be excreted through the kidneys. § Substances that cannot be metabolized are sequestered by the body in fatty tissues to protect vital organs.  Individuals vary in their responses to hazards § An individual’s sensitivity to a given toxin will vary depending on genetics, overall health, gender, and age. § The risk of a hazard also varies according to whether a person experiences high exposure for short periods of time (acute exposure) or low exposure for long periods of time (chronic exposure). © 2018 Pearson Education, Inc.  Airborne substances can travel widely § Toxic substances are released around the world from agricultural, industrial, and domestic activities and may sometimes be redistributed by air currents, exerting impacts on ecosystems far from their site of release § Earth’s polar regions are contaminated due toxicants moving as a result of the global distillation effect (aka the grasshopper effect). § Pesticide drift takes place when winds blow airborne pesticide long distances. © 2018 Pearson Education, Inc.  Toxic substances may concentrate in water § Toxic substances are not evenly distributed in the environment and move about in specific ways. § Water running off from land often transports toxicants from large areas and concentrates them in surface water. § Wastewater treatment plants add toxins, pharmaceuticals, and detoxification products to waterways. § Chemicals in soil can leach into groundwater and contaminate drinking water supplies. © 2018 Pearson Education, Inc.  Some 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 substance. © 2018 Pearson Education, Inc.  Toxic substances may accumulate and move up the food chain § Substances that are fat or oil soluble are absorbed and stored in body tissues. § Given enough time and exposure, bioaccumulation (gradual buildup of substances/chemicals/pesticides) will occur, and the concentration of the substance in the animal’s tissues will exceed that of the environment. § Toxic substances that bioaccumulate will be transferred to other organisms as predators consume prey. © 2018 Pearson Education, Inc.  § As predators ingest more and more prey over time, biomagnification occurs, resulting in greater and greater concentrations of the toxin. § Biomagnification of DDT caused many North American birds of prey to decline from the 1950s through the 1970s due to a thinning of the shells of the eggs they would lay. © 2018 Pearson Education, Inc.  Toxic substances can threaten ecosystem services § Toxicants can alter the manner in which organisms interact, threatening ecosystem services. § Pesticide exposure is a factor in the recent decline of honeybee populations, affecting the ecosystem service of pollination they provide. § Pesticides and antifungal agents also harm decomposers and detritivores in soil, disrupting nutrient cycling services provided by them. © 2018 Pearson Education, Inc. Studying Effects of Hazards § Biologist Louis Guillette compared blood samples of alligators in lakes that received agricultural runoff with those in cleaner lakes, and found hormonal imbalances in those exposed to pesticides. § Males had low levels of testosterone, while females had elevated levels of estrogen. § He followed this up with lab experiments that atrazine, a commonly used herbicide, was inducing production of an enzyme that converts testosterone to estrogen. § Researcher Tyrone Hayes found similar reproductive problems in frogs, and attributed them to atrazine, as well. § Male frogs raised in contaminated water became feminized and hermaphroditic. § Field surveys confirmed that leopard frogs in areas of heavy atrazine usage had hormonal problems.  Human studies rely on case histories, epidemiology, and animal testing § The process of observation and analysis of individual patients is known as a case history approach. § Case histories help us understand disease, but tell little about probability, risk, and population-level effects. § Epidemiological studies: large-scale comparisons among groups of people that involves tracking groups of people for a long period of time and looking for observable differences in rates of deaths, cancer, and other health problems © 2018 Pearson Education, Inc. § The epidemiological process is akin to a natural experiment in which the experimenter studies groups of research participants made available by some event that has occurred. § Epidemiological studies yield relatively accurate predictions about risk, but often take a long time and do not address the effects of new, future hazards. § Additionally, due to the presence of many other external factors, these studies only measure a statistical association between a hazard and health effect. § They do not confirm that the hazard causes the effect. Dose-response analysis is a mainstay of toxicology § Dose-response analysis: involves quantifying the toxicity of a substance by measuring its effects on animals at different doses § Dose: the amount of substance the animal receives § Response: the type of magnitude of toxic effects the animal exhibits (such as death) as a result of the dose § Data from this analysis is plotted on a graph, with dose on the x-axis and response on the y-axis. § This generates a dose-response curve. § LD50 : the amount of substance needed to kill half the population § A high LD50 indicates low toxicity. § A low LD50 indicates high toxicity. § For a nonlethal toxicant, an effective dose-50% or ED50 may be measured instead. § Threshold dose: the dose at which a response to a toxicant begins to occur § It is observed when the body’s organs can metabolize or excrete a toxicant at low doses but gets overwhelmed at high doses. § Responses may decrease as a dose increases, producing U-shaped or J-shaped curves. § This type of curve is often the result of endocrine-hormone disruptors, as the body is geared to respond to minute doses. Chemical mixes may be more than the sum of their parts § Mixed toxicants may sum, cancel out, or multiply each other’s effects. § Synergistic effects: occur when the interactive impacts of chemicals are greater than the sum of their individual effects Risk Assessment and Risk Management § Exposure to an environmental health threat does not always produce a harmful effect; it produces a statistical chance that damage will result. § Risk is measured in terms of probability, a quantitative description of the likelihood of a certain outcome. § The probability that some harmful outcome will result from a given action, event, or substance expresses the risk. Risk assessment analyzes risk quantitatively § Risk assessment: the quantitative measurement of risk and the comparison of risks involved in different activities and substances § Assessing risk involves: § determining whether a substance has toxic effects § performing a dose-response analysis § assessing the individual’s or population’s likely extent of exposure Risk management combines science and other social factors § Risk management: consists of decisions and strategies to minimize risk based on comparisons of costs and benefits § In the United States, risk management is handled by the FDA, the EPA, and the CDC. § Comparing costs and benefits is difficult, because the benefits are economic, while the costs are usually health-related. § For example, finding a replacement for BPA would raise production costs, which would then be passed on to consumers. Philosophical and Policy Approaches § There are two basic philosophical approaches to categorizing substances as safe or dangerous. § The “innocent-until-proven-guilty” approach assumes that substances are harmless until shown to be harmful. § This approach hastens the development of new technologies (due to the absence of thorough testing), but may put dangerous substances into wide use. § The precautionary principle approach assumes substances are harmful until proven harmless. § This allows us to identify potentially harmful toxins before they are released, but significantly slows technological and economic advancement. Philosophical approaches are reflected in policy § European nations largely incorporate the precautionary principle in their policies. § The United States follows the innocent-until-proven-guilty approach, with several agencies in charge of tracking health issues. § The FDA monitors food and food additives, cosmetics, drugs, and medical devices. § The EPA regulates pesticides. § OSHA regulates workplace hazards.  EPA regulation is only partially effective § Toxic Substances Control Act (TSCA): directs the EPA to monitor thousands of industrial chemicals manufactured in or imported to the United States § Many believe the law is too weak. § There has been an increase of more than 22,000 new chemicals since the law was passed, but only 5 have been restricted. § The EPA must have proof of toxicity to compel agencies to perform more extensive testing of risk. § Only 10% of chemicals have been screened for toxicity. © 2018 Pearson Education, Inc.  § In its regulation of pesticides, the EPA is responsible for “registering” each new pesticide that manufacturers propose to bring to market. § The manufacturer first provides the results of safety assessments of the pesticide. § The EPA examines the ingredients and evaluates whether the chemical poses risk to people, other organisms, or water or air quality. § The EPA then approves, denies, or sets limits on the sale and use of the product, including labeling. § This process does take economic considerations into account. © 2018 Pearson Education, Inc. Toxicants are regulated internationally § In 2007, the European Union’s REACH program went into effect. § REACH stands for Registration, Evaluation, Authorization, and Restriction of Chemicals. § REACH requires industry to determine chemical safety and submit those results to national governments for approval. § REACH differs markedly from TSCA, reflecting the vast philosophical differences between the two governments. § The world’s nations have also sought to address chemical pollution with international treaties. § The Stockholm Convention on Persistent Organic Pollutants (POPs) came into force in 2004 and has been ratified by 172 nations. § POPs are toxic chemicals that persist in the environment, bioaccumulate, and biomagnify in the food chain, and travel long distances. § The Stockholm Convention aims first to end the use and release of the12 most dangerous POPs. LD50 Sample Questions 1) The LD50 of aflatoxin (mold in food) is 5 mg/kg rat. What is the LD50 for an average adult male (175 lbs.)? (conversion: 1 lb. = 0.454 kg) LD50 Sample Questions 1) The LD50 of aflatoxin (mold in food) is 5 mg/kg rat. What is the LD50 for an average adult male (175 lbs.)? (conversion: 1 lb. = 0.454 kg) 175 x 0.454 = 79.45 kg 5 mg poison X mg of poison = 1 kg lab rat 79.54 kg man X = 397.7 mg/person 2) The LD50 of DDT (insecticide) is 100 mg/kg rat. What is the LD50 for an 80 kg male? 2) The LD50 of DDT (insecticide) is 100 mg/kg rat. What is the LD50 for an 80 kg male? 100 mg poison X mg of poison = 1 kg lab rat 80 kg man X = 8,000 mg/person 3) The LD50 of sodium chloride (table salt) is 3,000 mg/kg rat. What is the LD50 in grams/person for an average American female (77 kg)? (conversion 1,000 mg = 1 g) 3) The LD50 of sodium chloride (table salt) is 3,000 mg/kg rat. What is the LD50 in grams/person for an average American female (77 kg)? (conversion 1,000 mg = 1 g) 3,000 mg poison X mg of poison = 1 kg lab rat 77 kg female X = 231,000 mg/female (must divide by 1,000 to get grams/female) So, 231 grams/female