EESA10 Complete Textbook Notes.pdf

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University of Toronto Scarborough
Environmental Science
Jovan Stefanovic

Life Support: The Environment and Human Health Chapter 1: Environment, Health, and Risk - Improved water, food, sanitation = improved nutrition, cleaner fuels - We have many global problems o Global warming, population growth, habitat destruction, resource depletion The Environmental Crisis - Human beings are changing the earth’s atmosphere, geosphere, and biosphere o Between 1/3 and 1/2 of earths surface was changed by humans o Carbon dioxide levels increased 30% since industrial revolution o Atmospheric nitrogen mostly caused by humanity and not by natural terrestrial sources o Health reproductions of amphibians are damaged by ultraviolet light o The declining of various amphibians and animals should be a clear indication of environmental threats to human health - Today’s environmental degradation is rapidly an unprecedented global crisis o Caused by population growth and industrialization - In the past 100 years... o Manufacturing increased o Use of fossil fuels increased o Number of automobiles o Production of synthetic chemicals - In 150 years... o We have 30% concentration of carbon dioxide o Ozone destroying chlorofluorocarbons - Human made emissions have led us to acid rain Human and Ecosystem Health Life Support: The Environment and Human Health - Biologists and ecologists have an idea where the human health reflects the health of a complex ecosystem - Some believe humans dominate nature - Some believe that the harmful things humans do to the environment can undo itself with the help of technology - We avoid talking about the global change we are experiencing because it may be too frightening or overwhelming - Some believe we are experiencing global warming’s effects as we speak - Science has proven that the earth is warming, and GHG are part of the cause - Political leadership have begun to seek solutions to the global issues of climate change Health and the Environment - New health effects are arising and could possibly be directly from climate change or indirectly o Prevalence of malaria has increased worldwide, but no link to climate change was made o Funding the science to see whether certain health effects are caused by climate change can be quite costly - Environmental Degradation o Imbalance between population and resources o Increases cost and development o Extends prolonged poverty - Some poor people are forced out of their lands to country sides where they suffer from natural causes such as droughts and floods. - Serious environmental problems are often unknown or unrecognized - Change in natural systems may be sudden and nonlinear - Medical waste incineration is a major source of dioxin and mercury released into the environment Page 10 – 12 Physicians and Public Health Professionals Life Support: The Environment and Human Health - Physicians need to look at a number of things when a patient exposed to toxic exposure... o Nature/duration of patients exposure o Degree of potential health threat it poses o Extent of the risk to the patient/community o Even though these skills are important, many medical students lack in studying them - We need to change our way of thinking toward creating health, not curing disease - We need to learn the connections between health and environment Solutions - How can we promote health? o Stop further environmental degradation, by... Change policies that control pollution Prevent generation of pollution and environmental damage in the first place o Change relationship between developed and developing countries, by... New strategies for transferring technologies while minimizing the destruction of resources and the generation of pollutants o Promoting the education of environment and promotion of health No matter what occupation, you must understand the environmental issues in relation to health and the quality of life Chapter 2: Urban and Transboundary Air Pollution - Recognition of the relationship between exposure to air pollutants and respiratory illness dates back to the sixteenth century and description of respiratory disease in miners - Much of what we currently understand about environmental lung disease derives from the study of exposed workers since the Industrial Revolution - Later in the industrial nations of Europe and North America, whole communities were engulfed in air pollutants, resulting in serious illness and death among individuals with cardiopulmonary disease Life Support: The Environment and Human Health - These air pollution emergencies were caused by air stagnation, which resulted in greatly increased concentrations of atmospheric pollutants, especially sulfur dioxide and suspended particulates - After these air pollution problems, more attention has been placed on the health effects of air pollution. We face a crisis in worldwide air pollution today because of a few reasons. - First, since the atmosphere is dynamic and always changing, contaminants are transported (sometimes over thousands of miles), diluted, precipitated, and transformed. Air pollution therefore knows no boundaries or national borders - Second, many cities in developing nations and in Eastern Europe are experiencing uncontrolled industrial expansion, increasing motor vehicle numbers and congestion, and pollution caused by fuels used for cooking and heating - A 1988 study between air pollution and wealth reported that poorer countries (relying heavily on coal) had significantly higher levels of total suspended particulates (TSPs) than wealthier nations - Third, in nations that have reduced the primary emissions from heavy industry, power plants, and automobiles, new problems have arisen from pollution by newer industries and from air pollution caused by secondary formation of acids and ozone - Finally damage to ecosystems and agriculture from acid rain, damage to building and artwork, and reduced visibility are all attributable to air pollution Defining Adverse Health Effects - Any effect that results in altered structure or impaired function or that represents the beginning of a sequence of events leading to altered structure or function is considered an “adverse health effect” Sulfur Dioxide and Acidic Aerosols - Sulfur dioxide (SO2) is produced by the combustion of sulfur contained in fossil fuels, such as coal and crude oil - The sulfur dioxide released into the atmosphere does not remain gaseous. It undergoes chemical reaction with water, metals, and other pollutants to form aerosols - Sulfur dioxide and other products of fossil fuel combustion forms the heavy urban pollution in many cities in developing nations today by mainly burning coal - Smog – a descriptive term generically referring to the visibly cloudy combination of smoke and fog - Two measures of air acidity showered significant effects: o Higher particle acidity was significantly associated with an increased risk of bronchitis o Higher levels of gaseous acids were significantly associated with the risk of asthma - Acidic aerosols result in “acid rain” which may threaten aquatic life - Patients with asthma are very sensitive to the bronchoconstrictive effects of SO2 and react to much lower levels compared to normal people Particulates Life Support: The Environment and Human Health - Particulate air pollution is closely related to SO2 and aerosols - The term usually refers to particles suspended in the air after various forms of combustion or other industrial activity - Particles < 2.5 microns in diameter are called PM2.5 or “fine” particles - Heart-rate Variability (HRV) – a measure of the cyclic variations of beat-to-beat intervals and of the instantaneous heart rate Photochemical Oxidants - The other two most commonly generated industrial and urban pollutants are ozone and oxides of nitrogen - In contrast to sulfur dioxide, ozone and oxides of nitrogen are produced not so much by heavy industry but by the action of sunlight on the waste products of the internal combustion engine - The two most important of theses products are unburned hydrocarbons and nitrogen dioxide (NO2), a product of the interaction of atmospheric nitrogen with oxygen during high temperature combustion - Ultraviolet irradiation by sunlight of this mixture results in chemical reactions of compounds that appear in both gaseous and particulate aerosols. This mixture of pollutants is the smog that is found in cities with lots of sunlight (Los Angeles, Mexico City, and Taipei) - Ozone and nitrogen dioxide are relatively water insoluble and reach lower into the respiratory tract. Therefore these gases can cause damage at any site from the upper airways to the alveoli. Exposure to Ozone and Nitrogen Dioxide - Animal studies have clearly documented severe damage to the lower respiratory tract after high exposure, even briefly, to ozone - High concentrations of ozone are most often observed in the summertime, when sunlight is most intense and temperatures are highest. These are conditions that increase the rate of photochemical formation - Ozone levels generally lowest in the morning hours, accumulating through midday, and decreasing rapidly after sunset - Ozone concentrations are higher in outdoor air than in indoor air - Staying indoors, closing car windows, and using air-conditioning are generally recommended as protecting against exposure to ambient ozone Carbon Monoxide (CO) - Carbon monoxide is emitted mainly from internal combustion engines used in motor vehicles - Exposure can also occur after the burning of coal, paper, wood, oil, gas, or any other carbonaceous material - Carbon monoxide is an odourless, colourless gas produced by incomplete combustion of carbonaceous fuels such as wood, gasoline, and natural gas Life Support: The Environment and Human Health - Because of its marked affinity for haemoglobin, CO impairs oxygen transport, and poisoning often manifests as adverse effects - Fetuses and children are more susceptible than adults to CO poisoning Indoor Air Pollution - The term indoor air pollution refer to homes and non-factory public buildings - Pollution can come from heating and cooking combustion, pesticides, tobacco emissions, abrasion of surfaces, evaporation of vapours and gases, radon, and microbiological material from people and animals - Indoor air pollution is a particular problem in poor communities in developing countries - Indoor air pollution is associated with acute respiratory infection in infants and children under five and a large number of children die in developing countries Current Regulation of Air Pollution - Air pollution is a growing, global problem. Only global approaches will succeed in controlling it. Chapter 3: Water Quality and Water Resources - Water is essential to human life, and it is needed to be plentiful for human to survive. - Industrial wastes and climate change pose both new and old threats to our water supply - The next info is going to be about how to maintain quality and water quantity... Introduction - We endure the potential diseases in contaminated water since the 19 century o Some diseases include diarrheal diseases which kill 2 million annually - Even though we have improved our ways of water sanitation, it still leaves 20% without improved drinking supplies - Evidence have shown that changing the means of human waste disposal is much better than purifying your water supplies Sources of Water - There’s also surface water, and there’s ground water o Surface water is Streams, lakes, and rivers Life Support: The Environment and Human Health most contaminated because it’s on the surface...being prone to chemicals and microbial pathogens from waste runoff from nearby land o Ground water is... Artesian or other types of wells Not as contaminated because its beneath the soil which act as filters for the water... However, ground water can be contaminated if waste on top seeps through...such as a landfill. Once ground water is contaminated, the water stays contaminated for a long time Uses of Water - Water isn’t only to be consumed. It’s actually the least we do with water... - 70% of water is used for agriculture o 88% in Africa (highest), and 31% in Europe (lowest) o US and Europe use 55% of their water for industries o In industries, water is used for cooling or flushing equipment, which then leads to rivers, streams, etc. (contaminated water) o Home wise... Most is used for toilet flushing, then clothes washers, and then faucets Sources of Contamination - Chemicals can enter into water through a number of ways... o Fertilizers and pesticides are washed away from land and brought to streams, lakes, and rivers (surface water) o This can happen to animal waste in the similar fashion o Heavy landfills can have their chemicals seep through into ground water o Even Earth’s crust contaminates the water with arsenic and radon when water is in contact with it o Also, treating water with chemicals and disinfectants have a chance for it to be still present in our drinking water Life Support: The Environment and Human Health - Sources of contaminants that discharge into receiving waters from a pipe or other identifiable device are called “point sources”. o These include industrial wastes, and sewage treatment plants - The sources of contaminants that don’t use visible pipes are called ``non-point sources” o Including agricultural run off, oil run off, chemicals from streets, etc, etc - Acts such as the “US Clean water act” and the “safe water drinking act” has tremendously reduced the amount of point source contaminants o Even though we reduced point source contaminants, water is still vulnerable to non-point source contaminants Water Treatment Process - Even though we have been treating water for a long time, the water treatment process changes very little - The Water Process o Water is pumped from source o Held in settling tanks, where water is treated with chlorine to get rid of microbial pathogens and sediments o Coagulant is then added. This makes small particles (organic matter/microbes) stick together in water o Then flocculation happens, when they stir the water so the particles stick together, being heavier and larger, they’ll sink to the bottom - Since the above steps are just to get rid of small particles, it is not chemical free. - Treating the water with chlorine, or other forms such as ultra violet light or ozone, is needed to disinfect the water before it gets distributed - Reverse osmosis and other filtration techniques are becoming more common with the demand for higher water quality. - In developing worlds, is kind of hard to have such a complex water treatment process. - Even though boiling water can take away chemicals, it requires that they don’t have. o Alternatives have been on arise Black water bottles to collect solar energy to heat up the water inside, disinfecting the water!?!?! Who would want to do that Life Support: The Environment and Human Health Biological Threats to our Water Quality - WHO (World health Org.) says there are 5 ways water can be associated with human disease... o Waterborne: diseases transmitted from microorganisms that survive in water and are ingested. o Water washed: diseases such as trachoma and skin/eye infections that are from inadequate washing of hands/food o Water based: diseases such as schistosomiasis that form in fresh water and can come in contact through bathing/digesting and dracunculiasis o Water related: diseases such as dengue fever and malaria, organisms that breed/spend a part of their lifecycle in water. They don’t actually come in contact with human host... o Water dispersed infections: caused by microorganisms such as legionella, that reproduce in water supplies, and then transmitted to humans by air - Most of the above diseases/infections infect the gastrointestinal tract - They enter water from human/animal poop - Microbial pathogens have different categories: bacterial, viral, or protozoal o Different categories are caused by the difference in life cycle, hosts, survival in environment, and their removal by water treatment Protozoa - Since 1970, there have been an increasing number of Giardia Lamblia, Cryptospordium parvum, and other infections due to protozoal pathogens - Both can cause severe chronic diarrhea o People with C Parvum in particular, can cause severe fatal diarrhea if they also have aids or a cancer chemotherapy patient (immunocompromised) - Protozoal pathogens appear to be a very tiny, encapsulated cyst or oocyst, in humans - They can live through very harsh environments, and live through chlorination treatments - Just a small ingestion can cause severe infections, posing a great threat Chemical Threats to Water Quality - Common toxic chemicals found in drinking water... Life Support: The Environment and Human Health Nitrates - Can accumulate in ground/surface water via fertilizer/runoff and from septic tanks and other waste systems - After digested, the nitrates become more toxic nitrates by colonizing the gastrointestinal tract - Nitrates oxidize the haemoglobin in red blood cells, which can lead to methemoglobinemia, which holds back red blood cells ability to send oxygen to the body - Methemoglobinemia is the lack of oxygen, turning your skin blue! (cyanosis), and on severe cases, brain damage and death - Those severe cases only happens in agricultural/rural areas where they use private wells - Studies say that north America and Europe have a high nitrate contamination level - Nitrate may also cause reproductive problems Pesticides - Because of agricultural purposes, pesticides are both in surface and ground water - More herbicides are used in developed countries, that’s why they find it more in the water supply - Developing countries don’t have the necessary resources for herbicides, so there would be less chemical pesticides but an increase in insecticides - Harmful pesticides have been banned from United States...but some can still be in drinking water and/or humans. - Even though there haven’t been any actual acute pesticide poisoning due to drinking water contamination, if there was one it could lead to severe wide spread contamination. - Also, pesticides can have a long term affect on humans due to prolonged exposure - Since we use herbicides, there is a very little affect on humans - Bad pesticides that can potentially cause cancer include things like herbicide 2, 4-D and organchlorine insecticides such as DDT and dielhdrin Industrial Discharge - The clean water act that was posed in 1972 helped reduce the levels of industrial discharge. - Underground water tanks have chemicals seeping out of it, old hazardous waste sites and contaminated sediments have a great amount of chemicals as well Life Support: The Environment and Human Health - Underground storage tanks leave chemicals such as methyl-tertiary-butyl-ether (MTBE) contaminating water o This was used as an additive in gasoline to lower emissions, but has moved through the soil into ground water and led to the contamination of wells Radon - Occurs when there are uranium deposits in earth’s crust - It dissolves in water as it seeps through earth’s crust - Dissipates when the water comes in contact in air, so its only usually found where there’s high concentrations of it and groundwater is encased in rock or clay - Radon emits alpha particles that alter DNA once exposed - Areas with high levels of radon include the Appalachian regions, new England, and some of the rocky mountain and southwest regions - These high levels increase the risk of lung cancer from inhaling the aerosolized water Arsenic - Appears in local water supplies because it leaches onto arsenic deposits in the earth’s crust - This is also a by product of several industries, including pesticides, wood preservatives, and mining - Some health effects include skin, lung, and bladder cancer, skin hyperpigmentation, keratosis, vascular disease, and neurotoxicity - Places with the highest amount of arsenic include India, Bangladesh, Taiwan, Argentina, and Chile - In 1950 – 1970, India and Bangladesh has promoted tube pipe wells to be installed because their surface water was too contaminated. - The tube wells were used to supply for irrigation where areas needed water. - They soon found out that the water was contaminated with arsenic and everyone started getting skin manifestations of arsenic poisoning - With them stopping the use of the wells, they lost economically due to the lost crop yields that needed the water Lead - As early as the 1800’s, we used lead pipes to transfer water Life Support: The Environment and Human Health - Hot water would dissolve the lead from the pipes quicker than cold water would have - If we have a tap with water sitting in it for a long time, it is good to let the tap run a bit before actually using it for consumption - Water that is just sitting in the taps is more likely to accumulate lead - Even though lead exposure through water is only 20%, only a little bit of poisoning can lower IQ scores, and cause behavioural problems in infants and children, and also cause hypertension for adults - These pipes are still used, and are in homes rather than at the distribution. Thus, checking for lead levels requires people to check individual homes Disinfectant By-Products - Formed by the reaction of dissolved hydrocarbons with chlorine - Trihalomethanes and haloacetic acids are the most common DBP - They cause cancer in the bladder and colon Threats to Water Quantity or Availability - They say that in the future, availability of water is going to become critical along with water quality and purity - Only 0.007% of earth’s water is pure - With growing populations, it would only decrease - During the next century, changes in global climate are likely to have a profound effect on water supplies in certain regions such as central asia where there are areas that are water stressed - There is going to be a lot less stream run off from mountains and cliffs - Places that use these runoffs as a main source of water will have to adapt to the changes - Even though we are running into tough times, we usually lead to an innovative and cooperative solution Solutions for Water Quality - To improve quality of water, we can either find a way to better way of cleaning the water or we can find a way of not even having contaminated water in the first place - Just because we treat the water does not mean we are getting rid of chemicals and stopping diseases from happening Life Support: The Environment and Human Health - There are such technologies that are able to get rid of such chemicals but still have its setbacks such as not being able to get rid of lead, nitrates or other charged molecules. These forms of treatment are also very expensive - Different treatments are used in order to perform different treatments - New York used to get their water from an unfiltered source, but soon changed their ways by managing their watershed where they get their water, more frequently - Safe drinking water act has put the US in greater protection for their watersheds - We should look at where were getting the water from and not too much on the technological parts that treat the water Solutions for Water Quantity - Adequate clean water depends on the increase of water quantity and quality - As we begin to lose less and less water available for human beings, we will have to change ways in order to conserve water - Reusing of wastewater for specific uses, and altered demands for water are some ways we can help preserve water - Even though we think water is an endless resource, we tend to waste lots of water through leakage, using too much, etc - Since irrigation uses the most amount of water, we should try and find a better and more efficient solution for irrigation to save water - Even though there are ways out there that can help make sprinkling the crops efficiently by 70%, only 10-15% use it - We can lessen the water toilets and showers use - Instead of standard toilet flues of 6 gallons of water, we can use 1.6 gallons per flush - Even leaking pipes can lose almost 20% of the water being distributed - Most home water such as toilet flushing, car washing, and other stuff do not need water fit for drinking - Also, the way we grow crops use tons of water. - 100 – 250 gallons of water is used to produce a pound of corn - 2000 – 8500 gallons are used to grow grain and to product a pound of beef - We take water for granted while other parts are struggling to find new ways to get water Life Support: The Environment and Human Health - Lots of innovation, money, and determination is needed to change our way of water. Chapter 4: Human Health and Heavy Metals Exposure • Metals, a major category of globally distributed pollutants, are natural elements that have been extracted from the earth and harnessed from human industry and products for millennia • Metals are notable for their wide environmental dispersion from such activity; • Their tendency to accumulate in select tissues of the body • Their overall potential to be toxic even at relatively minor levels of exposure o In case of lead and mercury, may be toxic even at trace levels of exposure • Even metals that are essential have the potential to become harmful at high levels of exposure, a reflection of a basic tenet of toxiocology – “the dose makes the poison” • US. Agency for Toxic Substances and Disease Registry (ATSDR) o Rankings of metals as potential hazards The first, second, third, and sixth hazards are heavy metals: lead, mercury, arsenic, and cadmium • Exposure to metals can occur through a variety of routes o Metals may be inhaled as dust or fume Tiny particulate matter, such as the lead oxide particles produced by the combustion of leaded gasoline) o Some can be vaporized and inhaled o Metals may also be ingested involuntarily through food and drink Amount absorbed from the digestive tract can vary widely, depending on the chemical form of the metal and the age and nutritional status of the individual o Once a metal is absorbed, it distributes in tissues and organs Metals tend to persist in some storage sites, like the liver, bones, and kidneys, for years or decades • Toxicity of metals most commonly involves the brain and the kidney, but other manifestations occur, and some metals, such as arsenic are clearly capable of causing cancer • Difficult in diagnosis o Because an individual with metals toxicity, even if high dose and acute, typically has very general symptoms such as weakness or headache • Chronic Exposure to metals at a high enough level to cause chronic toxicity effects o Such as hypertension in individuals exposed to lead and renal toxicity in individuals exposed to cadmium Mercury Life Support: The Environment and Human Health • Mercury comes in a number of different chemical forms • Metallic mercury (Hg) is used in thermometers, dental amalgams, and some batteries Exposure • In its pure form, metallic mercury is a liquid, • Contrary to popular opinion, it is not hazardous if ingested (because it is not significantly absorbed in this form). • However, it left standing, or if aerosolized – for example, through attempted vaccum cleaning – metallic mercury will volatilize into a vapor that is well absorbed by the lungs • Mercurous and mercuric mercury (Hg+ and Hg 2+) are encountered in some chemical, metal processing, electrical equipment, automotive and building industries and in medical and dental services o Mercurous and mercuric mercury from inorganic and organic compounds with other chemicals that can be readily absorbed through ingestion o All three forms of mercury are toxic to various degrees • From a global perspective, mercury has been increasing in importance as a widespread contaminant o About half of the National Priority List toxic waste sites in the US contain mercury o Through waste incineration The medical industry is one of the largest contributors to mercury pollution in this fashion o Brazil Have seen widespread mercury contamination (and resultant health effects) through a combination of its indiscriminate use in gold mining and deforestation • When deposited in soil, organic mercury compounds are slowly broken down into inorganic compounds; o Conversely, inorganic mercury can be converted by microorganisms in soil and water into the organic compound methyl mercury, which is then bioconcentrated up the food chain o Fish, particularly tuna, king mackerel and swordfish, can concentrate methyl mercury at high levels Consumption, should be limited in frequency And entirely avoided by women during pregnancy Toxicity Life Support: The Environment and Human Health • High levels of mercury exposure that occur through, for example, inhalation of mercury vapors generated by thermal volatilization can lead to life threatening injuries to the lungs and neurological system o At lower but more chronic levels of exposure Erethism with tremor of the hands, excitability, memory loss, insomnia, timidity and sometimes delirium • Was once commonly seen in workers exposed to mercury in the felt hat industry o Dentists Have been associated with measurable declines in performance on neurobehavioural tests of motor speed, visual scanning, verbal and visual memory and visuomotor coordination Contrary to some opinions expressed in the popular media, however, evidence from well conducted studies is lacking that the small amount of mercury released from dental amalgams during chewing is capable of causing significant illnesses, such as multiple sclerosis, systemic lupus, or chronic fatigue syndrome • Dimethylmercury o A “supertoxic, superdangerous” compound that can penetrate through latex gloves as well as skin This compound does not occur naturally; rather it is synthesized for use as a standard in nuclear magnetic resonance spectroscopy of mercury compounds and for heavy atom labeling of biomolecules for x ray structure determination Following a recent fatality in which exposure to only a few drops spilled on a latex gloved hand resulted in systematic absorption of the compound, central nervous system degeneration, and the death of a prominent environmental chemist, it is likely that the continued use of dimethylmercury for even these few specialized applications will be curtailed • Sensitivity of the fetal and infant nervous system to low level mercury toxicity o Mothers exposed to mercury in the 1955 diaster in Minamata Bay, Japan, gave birth to infants with mental retardation, retention of primitive reflexes, cerebellar symptoms and other abnormalities o Recent research in the Faroe Islands has demonstrated that, even at much lower levels, mercury exposure on the part of pregnant women through dietary intake of fish and whale meat, an important regional food staple, is associated with decrements in motor function, language, memory and neural transmission in their offspring • Organic mercury, o Form of mercury bioconcentrated in fish and whale meat, readily crosses the placenta and appears in breast milk Life Support: The Environment and Human Health Arsenic • Arsenic is a toxic and carcinogenic heavy metal, and human exposures are common. • Scientists and regulators are debating safe exposure standards Exposure • Significant exposure to arsenic occurs through both anthropogenic and natural sources • Occupational and community exposure to arsenic form the activities of humans occur through the smelting industry, the use of gallium arsenide in the microelectronics industry, and the use of arsenic in common products such as wood preservatives, pesticides, herbicides, fungicides and paints • Widespread dispersion of arsenic is a by product of the combustion of fossil fuels in which arsenic is a common contaminant • In some counties, arsenic is also a natural contaminant of wells o Deep water wells in parts of Taiwan and Chile are now well known to be contaminated with arsenic, giving rise to chronic manifestations of toxicity discussed below o Water from relatively shallow tube wells that were placed in areas of Bangladesh, West Bengal, and other parts of the subcontinent has also been found to be heavily contaminated with arsenic o Water is some parts of the US, such as areas of the Southwest, also carry a significant risk of arsenic contamination Toxicity • The toxicity of an arsenic containing compound depends on its valence state (zero- valent, trivalent, or pentavalent), its form (inorganic or organic), and factors that modify its absorption and elimination. • Inorganic arsenic is generally more toxic than organic arsenic • And trivalent arsenite is more toxic than pentavalent and zero valent arsenic o Testing individual with suspected toxicity must be done more than 48 hours after the individual abstains from eating seafood • Once absorbed into the body, arsenic undergoes some accumulation in soft tissue organs such as the liver, spleen, kidneys, and lungs, but the major long term storage site for arsenic is keratin- rich tissues, such as skin, hair and nails – making the measurement of arsenic in these biological specimens useful for estimating total arsenic burden and long term exposure under certain circumstances • Acute Arsenic Poisoning o Lethality o Stems from arsenic’s destruction of the integrity of blood vessels and gastrointestinal tissue and its effect on the heart and brain • Chronic arsenic Exposure to lower levels of arsenic results o in somewhat unusual patterns of skin hyperpigmentation, o peripheral nerve damge manifesting as numbness, Life Support: The Environment and Human Health o tingling and weakness in the hands and feet, o diabetes o blood vessel damage resulting in a gangrenous condition affecting the extremities • Chronic Arsenic Exposure o Causes elevated risk of developing a number of cancers, most notably skin cancer, cancers of the liver, lung, bladder, and possibly the kidneys and colon • The dose necessary to increase the risk for cancer has become the focus of particularly intense scrutiny in the US because of proposed efforts to lower standards governing general population exposures to arsenic • Among environmental scientists studying this problem, the most common view is that the current standard for the allowable amount of arsenic in US drinking water – 50 ug/ liter is probably not adequate to sufficiently safeguard the general population from arsenic’s cancer risk Chapter 9: Endocrine Disruption - Tens of thousands of synthetic chemicals have been synthesized and released into our environment for the past 50 years - These chemicals can interfere with hormone function - There is debate whether there are evidence of significant health risks to human population from exposure to these chemicals - There is research for the past few years demonstrating how chemicals in environment can interfere with endocrine function o For adults, there is the ability to recover o In the fetus though, even minor changes in hormone levels can lead to lifelong effects - Endocrine disruption is gaining public attention and many public policy decisions today involve chemicals known or suspected to interfere with hormone function. Historical Background - Endocrine disruption is not a new phenomenon o Eg. 1930 test on animals demonstrated estrogenic properties of a number of industrial chemicals (eg. Bisphenol A – used in many plastics) o Eg. 1950s studied feminizing effect of DDT in roosters - In 1971, a synthetic estrogen diethylstilbestrol (DES) was used for pregnant women o Linked to epidemic of vaginal clear cell carcinoma to young pregnant women in use o DES daughters had higher risk of reproductive and immunological abnormalities o Sons were at risk of genital anomalities and abnormal spermatogenesis o In animals (and possibly humans) it alters male/female typical behaviour patterns o Fetus is most at risk, not the adult Life Support: The Environment and Human Health Mechanisms of Action and Fetal Vulnerability - Some pesticides and other industrial chemicals directly bind to or block hormone receptors, therefore initiating or blocking receptor-activated gene transcription (production of proteins) - Other chemicals act indirectly by altering hormone production, hormone transport on binding proteins, receptor numbers on target organs, or hormone metabolism. - Polychlorinated biphenyls (PCBs) o Interferes with thyroid hormone T by4increasing metabolism of T , inte4fering with T 4elivery or interfering with conversion of T to4T 3 - Fetus more sensitive to low level exposures. o Eg. Mild hypothyroidism in adult does not have long term effects but subtle hypothyroidism during fetal and neonatal life causes disruption of neurotransmitters, growth and development Potential Health Implications - Abnormalities in animals exposed to endocrine disrupting chemicals include feminization, abnormal sexual behaviour, birth defects, altered sex ratio, low sperm density, decreased testis size, etc.... - Pesticides and industrial chemicals linked to thyroid stimulating hormone, testosterone, prolactin levels in adults. - Population-based epidemiologic studies are weak because of o time lag between exposure of chemical and clinical disease o Also difficulty defining exposed and control populations o Poor assessment of exposure during prenatal period o Limited understanding of gene-environment interactions Hormones and Neurobehavioral Effects - Certain environmental pollutants associated with learning and behavioural abnormalities after prenatal or early postnatal exposures due to endocrine mechanisms o Eg. Low dose of dioxin during development of rats produce feminizing effects (altered sexual differentiation of brain) - Thyroid disruption linked to developmental effects of fetal brain o Wildlife and lab animals eating contaminated food from the Great Lakes are affected o Eg. PCBs cause impaired learning in nonhuman primates o Higher levels of PCBs in breast milk correlate with high TSH levels in nursing infants o PCB affects brain development by suppressing thyroid hormone Beyond Endocrine Disruption: Other Signaling Pathways Life Support: The Environment and Human Health - Some chemical interfere with neurotransmitter levels and binding o Eg. Organophosphates Reversible for adults but permanent for a developing brain Rodents exposed to single dose of organophosphates during neonatal life have permanent decreased brain density and hyperactive behaviour as adults - In the developing brain, neurotransmitters perform growth-regulatory functions Policy Implications - Some argue there isn’t conclusive proof of human health effects - Others point to suggestive evidence to take action - Detecting health effects from endocrine disrupters is difficult o Hormones act at low levels so even low-level exposures to hormonally active agents may be of concern o Effects may be subtle and often delayed so its hard to link early life exposures to illnesses o Adverse impacts may manifest primarily in populations rather than individuals so surveillance systems that focus on individuals rather than populations fail to detect early evidence - Low-level exposures to endocrine disrupters are everywhere in today’s environment o Persistent chemicals such as DDT, PCBs and dioxins detected in nearly 100% samples of human blood The International Joint Commission and the POPs Treaty - International Joint Commission (IJC) created by a treaty between US and Canada in 1909 a group that aims to detect a “persistent toxic substance” (some are endocrine disruptors) and eliminate it o Linked toxic substances (mostly organochlorines) to injury, disease, and death in a variety of forms, including humans o SAB (science Advisory Board) said that how the IJC are testing these chemicals are impractical and unscientific Treat them as a class not individually Individual – doesn’t threaten health/ecosystems o IJC said all parties should take note of chlorine and chlorine containing compounds as industrial feedstock’s (reduce or eliminate other uses) - Proof of casual links between individual chemicals and effects is not a reasonable assumption since the substances exist in the environment Life Support: The Environment and Human Health - The Stockholm Convention – effort to reduce human exposures to endocrine disrupting chemicals o Fights the 12 POPs, chemicals that are environmentally persistent, bioaccumulate, and affects the future generation Screening, Testing, and Tracking - The OECD (Organization for Economic Cooperation and Development) o Initiating screening and testing programs - How can we help improve screening, testing, and tracking? - + monitoring and tracking = way to track subtle trends - Active reporting in birth defects instead of passive reporting - Accurate biological monitoring of blood and urine for chemical toxicants - Medical community can evaluate the science and educating the public - International perspective since it can travel great distances over water/air Chapter 10: Body Burdens of Industrial Chemicals in the General Population - Body burden is defined as the quantity of an exogenous substance or its metabolites that has accumulated in an individual or population - Focus on the class of organochlorines because there is ample data on their presence in human tissues and considerable concern about their global accumulation, toxicity, and impact on human and wildlife health Body-Burden Estimation - An individual’s body burden of a pollutant is estimated by measuring the concentration of that substance in one or more tissues, usually by gas chromatography/mass spectrometry (GC/MS) - Chemical body burdens are complex and dynamic in a number of ways, and these characteristics make a full characterization of the general public’s body burden exceedingly difficult: o First, the body burden of a pollutant is not stable over time. It reflects a dynamic balance between the amount taken in and the amount excreted or metabolized into another material o Chemicals that are persistent are those that resist metabolic alteration and excretion and/or are tightly bound to the tissues in which they are stored o Second, body burdens are not distributed homogeneously within an individual: the partitioning of a pollutant among various tissues and fluids reflects the Life Support: The Environment and Human Health substance’s degradability and affinity for fats, minerals, and other endogenous materials o Third, the body burden of an individual in today’s environment consists of hundreds of synthetic substances o The ability of chemical analyses based on GC/MS to characterize the full range of contaminants is limited in a number of ways o Compounds can be identified only if they are present in concentrations above a detection level (usually in parts per trillion or billion) o Substances present in very low quantities will not be detected, but if there are hundreds or thousands of them, together they may make up the bulk of the total chemical burden o Routine analyses can identify only compounds that can be matched against a reference database of chemical signatures, so substances that are not yet in the database go uncharacterized o Thus, novel or exotic compounds, such as many industrial by-products, environmental breakdown products, and metabolic products, will remain unidentified in even the most rigorous analysis Biomonitoring Programs in the United States - Public health officials and scientists use biomonitoring information for surveillance, control, and treatment - The purpose of many biomonitoring programs has been to assess the health risks of occupationally or environmentally exposed individuals This chapter is very short and there is a table that lists the chemicals in the tissues of the general North American population that covers about 3-5 pages of the chapter Chapter 12: Radiation and Health - Concern about Radiation: Is exposure generated by nuclear-power-plant accidents or by contamination from nuclear facilities during normal operation? - 3 major nuclear-reactor accidents have occurred since the creation of nuclear power: 1. Windscale, England in 1957 2. Three Mile Island plant in Pennsylvannia in 1979 3. Chernobyl in the former Soviet Union in 1986 - Radon gas emanating from underlying geological formations or building materials in homes is a far more common and significant source of public exposure to ionizing radiation than emissions from nuclear plants - Epidemiologic science (study of populations) that tries to relate very low radiation exposures to cancer is still unproven – lack of scientific certainty fuels public controversy: o What level is acceptable? - Recent Years: nonionizing radiation public attention Life Support: The Environment and Human Health - Radiation inspires a special dread - Many radiation scientists believe that ppl don’t understand that smoking and driving are much more dangerous than exposure to low levels of radiation Types of Radiation - Ionizing and nonionizing radiation - Ionizing portion of the spectrum includes gamma rays and ultraviolet radiation - The distinguishing feature of ionizing radiation is that it has a photon or particle sufficiently energetic to break chemical bonds damaging the DNA of an atom or molecule in tissue carcinogenic - Nonionizing radiation is not energetic enough to disrupt electrons and hence is not thought to be genotoxic But it can heat tissue - Electromagnetic fields (EMFs) initially believed to be biologically inactive, but proposed otherwise - Melatonin (biological clock hormone made by pineal gland)hypothesis: o Reduction in the pineal gland’s nocturnal production of melatonin cause increase susceptibility to DNA damage through a reduction of melatonin’s antioxidant action Health Effects of Ionizing Radiation - Sources of radiation health effects come from: o Long-term follow-up of the survivors of the atomic bombings Hiroshima and Nagasaki o Studies of patients receiving diagnostic and therapeutic radiation o Studies of occupational cohorts (groups) with prolonged exposures - Ionizing radiation produces 2 kinds of cell injury: immediate and delayed - High level doses: skin burns, hair loss, damage to intestinal lining - Low level doses: less predictable because they involve the cancerous transformation of cells - Linear, No-threshold Hypothesis: all exposure to radiation presents some risk to human health - Relation between very low doses of radiation and cancer is unresolved - Little argument about the effects of high and moderately high doses of radiation - Exposures to levels of 10-50 rem have an increased likelihood of developing cancer Exposure Standards - 1980s: Scientists observed more cancer deaths among the bomb victims than had been predicted Life Support: The Environment and Human Health - Turns out, less radiation had produced more cancer Atomic Bomb Survivors - Few large populations that have been exposed to known levels of radiation survivors of Hiroshima and Kagaski are best known and studied - Leukemia, thyroid and breast cancer appearing to be most radiosensitive sites - The highest radiation-related increase in breast cancer is in women less than age 10 at the time of the bombing Epidemiologists’ Problem with Cancer Studies - These people study the cause of disease in groups rather than individuals - Proving causation involves many steps before judgement is made Fallout from Nuclear Testing - 1950s: radioactive fallout from the Nevada Test site in Utah was studied - Reported striking increase in deaths from leukemia from 19 year olds Accidents at Nuclear Plants - 1979: Three Mile Island nuclear plant in Pennsylvania accident – study undertaken - Exposure from the accident was low influenced some risks of cancers for those exposed - 1986: Accident at Chernobyl in former Soviet Union effected much of Northern Europe receiving a dose of 5-10 mSv o Beginning 1992, have been reports of an extremely large increase in thyroid cancer in children Routine Nuclear-Power-Plant Operations - Several reports of increases in leukemia among children living near certain nuclear facilities in Great Britain Environmental Contamination from Nuclear Plants Nuclear-Waste Containment - Production of radioactive waste from nuclear plants = bad main component is uranium - Low-level wastes and high level wastes - Low level wastes: include materials are intensely radioactive and stored in waste dumps - Concern about the longevity of many of the wastes’ isotopes and toxicity Radon - Accumulate to high levels in enclosed spaces such as basements - Radon Progeny: decay products of radon attach to dust particles - If inhaled, further decay occurs and can expose the lining of the lung to alpha radiation = cancerous Life Support: The Environment and Human Health Health Effects of Nonionizing Radiation Power Lines - Some stupid study again, does power lines’ EMF cause cancer? Conflicting answers! - If EMFs are carcinogenic, it is a promoter, not an initiator Household Appliances - WOW ... one report linking maternal use of electric blankets during pregnancy with birth weight and fetal development, but number of exposed cases too small to produce a stable result Cellular (Mobile) Telephones - Reports with brain cancer in a frequent user on the same side of his head on which he used the phone - Only a few studies have been conducted - Most frequent human radiation exposure is to radon - Can be easily measured and easily mitigated by increasing ventilation in enclosed spaces where radon accumulates - Nonionizing radiation is also common: power lines, mobile phones etc - Tip from the book: - Use cell phones less frequently! Prescriptions Editor’s Note - Greatest danger posed by nuclear power: its central role in the proliferation of nuclear weapons! Chapter 1 (pg.6 – 10) Risk and Caution: Some Definitions - A risk is a potential threat to health and life - How we assess, perceive, communicate, and manage risks is termed risk analysis - Risk analysis is a substantive, changing, and controversial field o It is quantitative and produces numerical estimates of exposure, dose, and effect - Patients worried about exposure to environmental or occupational agents often want to know what their risk of developing disease will be Satisfactory answers are difficult to establish - Risk assessment provides probability figures that apply to populations, not to individuals, - The term exposure refers to the intensity and duration of contact with a substance or with a physical agent such as ultraviolet, x ray or microwave radiation - Inhalation, skin absorption, and ingestion are the possible routes of exposure Life Support: The Environment and Human Health - How much a person really actually absorbs exposure constitutes the dose, the most important determinant in clinical disease o What does someone was exposed to depends on the amount, route, and duration of exposure and on the concentration and chemistry of the substance or the intensity of the physical agent o The biological effect depends on the substance’s chemistry or a physical agent’s type, on the dose and on the patient’s susceptibility to disease - One of the challenges in assessing an environmental exposure is getting some idea of the actual dose the patient received o The exposure disease model involves four elements: The exposure to the substance The does the patient actually absorbed The biological effect of the absorbed dose The clinical disease that results - Risk Assessment o 1) Hazard Identification Which involves identifying health hazards in the environment and characterizing their physical and chemical properties, their environmental and biological fates, and their abilities to cause disease o 2) Exposure Assessment Which involves estimating human exposure from air, water, food or skin contact with the hazardous agent o 3) Dose Response Assessment Which involves characterizing the potential of a substance to cause disease as a function of the exposure or dose o 4) Risk Characterization Which integrates information on the agent’s toxicity, likely routes of exposure and dose response assessment into an estimate of the agent’s probable effect on the health of the population Animal studies - Clinical and epidemiological studies offer the most direct means of assessing human health risks associated with hazardous exposures - Data from laboratory studies usually form the backbone of risk assessment - Toxicologists readily admit that laboratory animals differ from humans in a variety of ways: humans are larger; live longer; frequently suffer from two or more diseases at a time; may receive different exposures than lab animals do; may metabolize more, store, or excrete the agent differently; and as a species, are more genetically heterogeneious Extrapolating Results to Humans Life Support: The Environment and Human Health - One objection to the use of animal data is that lab experiments typically use high doses so that the test will be sensitive and unlikely to give a false negative result; the risk estimate is then extrapolated from results seen at high experimental doses to the much lower levels – often 1000 to 10000 times lower – that are typical of environmental exposures - Many risk estimators prefer to use mathematical models to characterize the underlying dose response curve - Three classes of models o 1) Tolerance Distribution Models assume that each individual in a population has a threshold below which he or she will not respond, and that thresholds vary among in
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