APES Chapter 17

Hormonally Active Agents (HAAs)
-pesticides/synthetic chem’s that can act as hormone impostors
-can impair reproductive syst/sexual devel’ment or cause physical/behavioral disorders
-includes hormone mimics
-hormone blockers can disrupt system by preventing natural hormones from attaching to receptors
-concern about some HAAs that act as thyroid disrupters and can cause growth or weight-control problems and brain or behavioral disorders
-i.e. DDT, PCBs, mercury

Bisphenol A (BPA)
-chemical building block in hardened plastics used in bottles and food storage containers
-is a hormone mimic
-BPA can stay in syst for up to 24 hrs after being ingested
-most Americans have trace levels over current threshold level, more in children/adolescents than adults

Risk
-probability of suffering harm from a hazard that can cause injury, disease, death, econ loss, or damage
-expressed as mathematical statement about likelihood

Risk Assessment
-use statistical methods to estimate how much harm a particular hazard can cause to human health/enviro
-helps estimate probability of risk, compare it with probability of other risks, and establish priorities for avoiding/managing risks

Risk Management
-involves deciding whether/how to reduce particular risk to a certain level and at what cost

Pathogen
-organism that can cause disease in another organism

Biological Hazard
-from pathogens that can infect humans

Chemical Hazard
-from harmful chemicals in air, water, soil, food, and human-made products

Physical/Natural Hazard
-includes fire, quakes, volcanic eruptions, floods, and storms

Cultural Hazard
-includes unsafe working conditions, unsafe highways, criminal assault, and poverty

Lifestyle Choices
-includes smoking, food choices, alcohol consumption, sexual responsibility

Infectious Disease
-caused when pathogen invades the body and multiplies in cells and tissues
-includes flu, malaria, TB, measles

Bacterial Disease
-spreads as bacteria multiply
-i.e. TB

Viral Disease
-spreads as virus takes over cell’s genetic mechanisms to copy selves
-i.e. flu, HIV

Transmissible Disease
-infectious disease that can be transmitted from one person to another
-i.e. flu, TB, measles

Nontransmissible Disease
-caused by something other than a living organism
-doesn’t spread from person to person
-tends to develop slowly and have multiple causes
-as life expectancy increases, more people will suffer/die from these
-i.e. cardiovascular diseases, cancer, asthma, diabetes

Four Most Serious Infectious Diseases
-pneumonia/flu, HIV/AIDS, TB, diarrheal diseases

How Infectious Diseases Enter Body
-human to human contact
-human to fetus or baby
-pets, livestock, wild animals, insects, food, water, or air to humans

Epidemic
-large-scale outbreak of an infectious disease in an area or country

Pandemic
-global outbreak of an infectious disease

Increased Genetic Resistance to Antibiotics
-spread of bacteria around world from human travel and international trade
-overuse of pesticides that increase populations of pesticide-resistant insects and other carriers of bacterial diseases
-some drug-resistant bacteria can quickly transfer resistance to other bacteria by exchanging genetic material
-overuse of antibiotics and growing use of antibacterial hand soaps and cleaners promotes resistance
-every major disease-causing bacterium is resistant to at least 1 of the 160 antibiotics in use for bacterial infections

Tuberculosis (TB)
-extremely contagious bacterial infection of lungs
-many people don’t appear to be sick while infected, and only 1/2 know they’re infected
-one person can infect many if unaware of illness
-without treatment about 1/2 the people with active TB die from bacterial destruction of lung tissue
-multi-drug resistant TB is on the rise, can’t be treated with antibiotics

Factors Accounting for Spread of TB
-too few screenings and control programs
-most strains have developed genetic resistance to the majority of effective antibiotics
-population growth, urbanization, and air travel have increased person-to-person contact
-people in poor countries often have to wait months to hear diagnosis, so often spread disease and/or die in this time
-diagnosis methods are outdated and inadequate
-most cases are in poor countries, so little incentive for large drug companies to invest in developing new drugs to treat it

Flu
-biggest viral disease killer
-easily transmitted by body fluids and airborne emissions of infected person

Hepatitis B
-third largest viral killer
-damages liver
-transmitted through unsafe sex, sharing hypodermic needles, infected mothers passing onto child, or exposure to infected blood

Emergent Disease
-virus that’s adapted and emerged as a new disease or pathogenic strain

West Nile Virus
-transmitted to humans through mosquito bites that were infected by feeding on birds with virus
-caused severe illnesses in many cases since emerging in US in 1992, i.e. viral encephalitis or viral meningitis (both deal with brain and spinal cord)
-chance of being infected and killed is low

HIV/AIDS
-HIV isn’t deadly, but AIDS cripples immune system and leaves the body vulnerable to infections
-transmitted by unsafe sex, sharing hypodermic needles, infected mothers passing onto child, or exposure to infected blood
-most people with HIV are living in sub-Saharan Africa
-AIDS is #1 killer of women btwn 15 and 49 globally
-has affected pop age structures, lead to diminished education and health care, decreased food production and economic devel’ment, and disintegration of families

Treatment of HIV/AIDS
-combinations of expensive antiviral drugs can slow progress of AIDS and person could live up to 24 years after being infected, but very expensive
-cost is too high for less devel’d countries
-without treatment, takes 10-11 yrs for HIV to become AIDS

Malaria
-no vaccine for prevention
-caused by parasite spread by certain mosquitoes, contaminated blood transfusions, sharing hypodermic needles
-infects and destroys red blood cells
-causes intense fever, chills, drenching sweats, severe abdominal pain, vomiting, headaches, and increased susceptibility to other diseases
-most common in children under 5
-survivors often suffer brain damage and impaired learning ability
-parasite has become resistant to common antimalarial drugs

Prevention of Malaria
-working to develop new antimalarial drugs, vaccines, and biological controls for mosquitoes
-developing mosquitoes resistant to malaria parasite
-outbreeding malaria-carrying mosquitoes through genetic engineering
-killing mosquitoes through dehydration
-providing poor people with free or inexpensive long-lasting insecticide-treated bed nets and window screens
-give children zinc and Vitamin A supplements
-spray insides of homes with low amounts of DDT 2 times per yr

Ecological Medicine
-new interdisciplinary field devoted to tracking down unwanted connections spreading diseases from animals to humans
-have identified human practices encouraging this spread of disease, i.e. clearing forests, expanding suburbs, and hunting

Reduce Spread of Infectious Disease
-increase research on tropical diseases/vaccines
-reduce poverty and decrease malnutrition
-improve water quality, reduce unnecessary antibiotics use
-educate people to take all of antibiotic prescription
-reduce antibiotics to promote livestock growth
-require careful hand washing by medical personnel
-immunize children against major viral disease
-provide oral rehydration for diarrhea victims
-conduct global campaign to reduce HIV/AIDS

Toxic Chemical
-chemical that can cause temporary or permanent harm or death to humans and animals
-top five toxic substances are arsenic, lead, mercury, vinyl chloride, and polychlorinated biphenyls (PCBs)

PCBs
-chlorine-containing organic compounds
-very stable, nonflammable, exist as oily liquids or solids that enter air as vapor under certain conditions
-used to be used as lubricants, hydraulic fluids, and insulators of electrical transformers and capacitators
-US Congress banned domestic production in 1977
-proven to cause liver and other cancers in test animals and probably humans, now banned in most countries
-break down slowly in enviro
-fat soluble so can be biomagnified

Mutagens
-chemicals and forms of radiation that cause of increase the frequency of mutations in DNA
-most cause no harm but some lead to cancer or other disorders

Teratogens
-chemicals that cause harm and birth defects to a fetus or embryo
-i.e. ethyl alcohol–why drinking while pregnant can cause low birth weight or various physical/mental problems
-also includes benzene, formaldehyde, lead, mercury

Carcinogens
-chemicals, types of radiation, or certain viruses that can cause or promote cancer
-cancer is when malignant cells multiply uncontrollably creating tumors that can damage the body and lead to premature death
-i.e. arsenic, formaldehyde, PCBs, UV radiation

Human Immune System
-consists of specialized cells and tissues to protect body agst disease and harmful substances by forming antibodies that render invading agents harmless
-some chemicals (i.e. arsenic) can weaken immune system and leave body vulnerable to attacks by allergens and infectious bacteria or viruses

Human Nervous System
-includes brain, spinal cord, and peripheral nerves
-neurotoxins (natural or synthetic chemicals in environment, i.e. PCBs, arsenic, lead) can harm it
-can lead to behavioral changes, learning disabilities, retardation, ADD, paralysis, death

Human Endocrine System
-complex network of glands that release tiny amounts of hormones into bloodstreams
-low levels of hormones regulate bodily systems that control sexual reproduction, growth, development, learning ability, and behavior
-each type of hormone has a unique shape so it can attach to receptors on cells and transmit messages

Mercury
-mercury and compounds are all toxic
-long-term exposure can permanently damage nervous system, kidneys, and lungs
-low levels can harm fetuses or cause birth defects
-released into air from rocks, soil, volcanoes, and ocean vapor
-2/3 of it in atmosphere is from human activities
-rain washes these emissions out of atmosphere and onto soil or into water
-can’t be broken down or degraded, biomagnifies

Ways Humans Are Exposed to Mercury
-inhale vaporized elemental mercury or particles of inorganic mercury salts
-can eat fish contaminated with methylmercury
-consumption of high-fructose corn syrup

Methylmercury
-especially dangerous neurotoxin
-is very persistent in enviro so can be biomagnified in food chains or webs
-can cause brain damage in fetuses/children and can harm heart, kidneys, or immune system of adults

Toxicology
-study of harmful effects of chemicals on humans and other organisms

Toxicity
-measure of the harmfulness of a substance
-its ability to cause injury, illness, or death in a living organism

Dose
-amount of a harmful chemical a person has ingested, inhaled, or absorbed through skin

Response
-damage to health resulting from exposure to a chemical

Variables Affecting Toxicity
-dose, age of person, genetic makeup
-how well body’s detoxification systems work
-solubility, substance’s persistence, biomagnification

Children Are More Vulnerable Than Adults
-infants and young children breathe more air, drink more water, and eat more food per unit of body weight
-exposed to toxins in dust and soil when they put dirty fingers or toys in their mouths
-immune system isn’t fully developed

Dose-Response Curve
-scientists estimate toxicity of chemicals by determining effects of various doses of the chemical on test organisms and plotting results on these curves
-can determine lethal dose (kills one) and median lethal does (kills 50% test population)
-nonthreshold dose-response model–any dosage of a toxic chemical causes harm that increases with dosage
-threshold dose-response model–certain level of chemical must be reached for detectable harmful effects

Case Reports
-provide info about people suffering an adverse health effect or dying after exposure to chemical
-often involves accidental/deliberate poisonings, overdoses, homicides, suicide attempts
-aren’t reliable sources for estimating toxicity but can provide clues about environmental hazards and suggest a need for lab investigations

Lab Animals to Test Toxicity
-most widely used method
-often use lab-bred mice or rats because systems are fairly similar to those of humans and are small and able to reproduce quickly
-can take many years, many animals, and lots of money to complete

Epidemiological Studies
-compare health of people exposed to a chemical (experimental group) to health of an unexposed group (control)
-goal is to determine if statistical association between exposure to a toxic chemical and a health problem is strong, moderate, weak, or undetectable

Four Factors Limiting Epidemiological Studies
-often too few people have been exposed to high enough levels of toxic agent to detect significant differences
-studies take a long time
-closely linking observed effect with exposure to chemical is different because people are exposed to many toxic agents
-can’t use these to evaluate hazards from new technologies or chemicals to which people haven’t been exposed

Pollution Prevention
-supporters say we shouldn’t release chemicals that we know or suspect could cause harm into environment
-need to find harmless or less harmful substitutes for toxic and hazardous chemicals or recycle them within production processes

Precautionary Principle
-when there’s substantial prelim evidence that something harms humans or the environment, we should take precautionary measure to prevent or reduce such harm
-can use pollution prevention to implement this, but would require assuming that new chemicals and technologies are harmful until proven otherwise

Risk Analysis
-identifying hazards and evaluating their associated risks (risk assessment), ranking risks (comparative risk analysis), determining options and making decisions about reducing or eliminating risks (risk management), and informing decision makers and the public about risks (risk communication)

Three Greatest Threats to Humans of Premature Deaths
-poverty
-born male
-smoking
-rest are primarily lifestyle choices

Cigarette Smoking
-most preventable major cause of suffering and premature death among adults
-causes heart disease, stroke, lung and other cancers, bronchitis, and emphysema
-could also be linked to various mental illnesses
-secondhand smoke is also health hazard

Reduce Threats from Cigarette Smoking
-quit smoking by age 30
-add federal tax on price of cigarettes
-classify and regulate tobacco as a drug
-enact smoking bans
-media coverage about harmful effects
-mandatory health warnings on cigarette packs

Factors Causing People to Misjudge Risks
-fear
-degree of control one has in a situation
-whether a risk is catastrophic vs. chronic
-optimism bias or belief that risks apply to others but not them
-many risky things are highly pleasurable or give instant gratification

Four Principles to Evaluate and Reduce Risks
-compare risks
-determine how much of a risk you are willing to accept
-determine actual risk involved
-concentrate on evaluating and carefully making important lifestyle choices