ENS-112 Environmental Science Chapter 10 PDF

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Chapter 1 notes from Dr. Adrienne George's lectures for ENS-112 Environmental Science at The University of Tampa...

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Environmental Science 112 FALL SEMESTER 2018 INSTRUCTOR: DR. Adrienne George [email protected]

Chapter 10 Environmental 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 choices

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● Ex: smoking, poor diet, drug use, and workplace hazards

Disease 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 worldwide

Toxicology 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 impacts

Many 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 stomach

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○ 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 US

Toxic substances and their effects on organisms ● The environment contains many natural toxic substances, such as petroleum, radon gas, 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 substances

Silent 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 environment

Not 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 good

Toxic 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 death

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● 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 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

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 ○ 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 children

The 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)

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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

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 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 different trophic levels ● 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 1950’s to the 1970’s

Studying Effects of Hazards ● DEtermining the health effects of a hazard is complex ● Wildlife toxicologists take measurements, document patterns, and generate hypotheses

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 ● Epidemiological studies are large scale comparisons among grounds of people ○ Tracking groups of people for a long period of time

Dose-Response analysis is a mainstay of toxicology

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● A dose-response analysis involves quantifying the toxicity of a substance by measuring its effects on animals at different doses ○ The dose is the amount of the substance the animal receives ○ The response is the type of magnitude of toxic effects the animal exhibits as a result of the dose ● Data from this analys… ● The amount of substance needed to kill half the population of study animals,

LD 50 , is determined by the curve ○ A high LD 50 indicates low toxicity ○ A low

LD 50 indicates high toxicity

● For a nonlethal toxicant, and effective dose - 50% or

ED 50

- may be measured

instead ● Responses to some toxicants only occur above a certain dose, or threshhold. ○ This is called a threshold dose and is observed when the body’s organs can metabolize or excrete a toxicant at low doses but get overwhelmed at high doses

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 …

The probability of risk may not match reality ● The probability that some harmful outcome will result from a given action, event, or substance expresses the risk. ● Figure 10.10

Risk assessment analyzes risk quantitatively ● The quantitative measurement of risk and the comparison of risks involved in different activities and substances are termed risk assessment ● Assessing risk involves:

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○ Determining whether a substance has toxic effects ○ ..

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 ● Figure 10.11 ● 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

Two approaches exist for testing the safety of a new product ● The “innocent until proven guilty” approach assumes that substances are harmless until shown to be harmful ● The precautionary principle approach assumes substances are harmful until proven harmless ● Table 10.12

Governments regulate industrial chemicals ● In the united states, the FDA monitors foods, food additives, cosmetics, drugs, and medical devices ● In 2007, the European Union's REACH program went into effect ○ Registration, Evaluation, Authorization, and Restriction of Chemicals

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