Environmental health
assesses environmental factors that influence our health & quality of life
Hazard
something that poses a risk of being harmful
Physical Hazards (1/4 types of environmental hazards)
- arise from processes that occur naturally in our environment & pose risks to human life or health
- some are ongoing: ultraviolet radiation from sunlight
- discrete events: earthquakes, volcanic eruptions, fires, floods, blizzards, landslides, hurricane
Chemical Hazards (2/4 types of environmental hazards)
- include many of the synthetic chemicals that our society manufactures: pharmaceuticals, disinfectants, and pesticides
- Some are substances that are naturally made by organisms (venoms) also can be hazardous, as can many substances that we find in natur
Biological Hazards (3/4 types of environmental hazards)
- result from ecological interactions among organisms
- when we become sick from a virus, bacterial infection, or other pathogen � parasitism by other species that are simply fulfilling their ecological roles � infectious disease � can be spread when path
Cultural Hazards (4/4 types of environmental hazards)
- Hazard that result from our place of residence, our socioeconomic status, our occupation, or our behavioral choices � lifestyle hazards
- can minimize or prevent (choosing to smoke), some can be out of our control (exposure to secondhand smoke)
- drug u
Many environmental health hazards exist indoors
- Cigarette smoke & radon are leading indoor hazards & are the top two causes of lung cancer in developed nations
- asbestos, lead poisoning, PBDEs
Radon
is a highly toxic radioactive gas that is colorless and undetectable w/o specialized kits � seeps up form the ground in areas w/ certain types of bedroom and can accumulate in basements and homes w/ poor circulation
Asbestos
there are several types � each of which is a mineral that forms long, thin, microscopic fibers � allows asbestos to try heat, muffle sound, and resits fire � was used widely as insulation in building and many products � its fibrous structure makes asbesto
Lead Poisoning
when ingested, lead can cause damage to the brain, liver, kidney, and stomach; learning problems and behavioral abnormalities; anemia; hearing loss; and even death � can result from drinking water that has passed through the lead pipes common in older hom
PBDEs
group of chemicals � provide fire-retardant properties and are used in diverse array of consumer products, including computers, televisions, plastics, and furniture � are released during production and disposal of products and may also evaporate at very s
Disease is a major focus of environmental health.
- Major killers: cancer, heart disease, and respiratory disorders � have some genetic basis, but they are influenced by environmental factors
- Infectious disease is a greater problem in developing countries, where it access for close to half of all death
Infectious disease interacts w/ social and environmental influences
- many disease are spreading b/c we are so mobile in our modern era of globalization � a pathogen can now hope continents in a matter of hours by airplane in its human host
- In our world of global mobility and dense human populations, novel disease that
Health workers are fighting disease in many ways
- such efforts are being spearheaded internationally by the United Nations, the WHO, the U.S. Agency for International Development, and nongovernmental organizations and funding agencies
- education, expand health care, ensure safe drinking water, food se
Toxicology
is the science that examines the effects of poisonous substances on humans and other organisms � assess and compare substances to determine their toxicity
Toxicity
the degree of harm a chemical substance can inflict
toxicant
A toxic substance; "The dose makes the poison" � a substance's toxicity depends not only on its chemical identity, but also on its quantity
environmental toxicology
deals with toxic substances that come from or are discharged into the environment � studies health effects on humans, other animals, and ecosystems, and it represents one approach within the broader scope of environmental health � general focus on human h
Risks must be balanced against rewards
- with most hazards, there is some tradeoff between risk and reward, and we out judge as best we can how these compare
- Example: BPA
- these chemicals have helped create the industrial agriculture that produced our food, the medical advances that protect
Toxic Substances in the Environment
our environment contains countless natural substances that may pose health risks � include oil oozing naturally from the ground; radon gas seeping up from bedrock; and toxins
toxins
toxic chemicals manufactured in the tissues of living organisms
Synthetic chemicals are all around us
- synthetic chemicals surround us in our daily lives
- many of these substances find their way into soil, air, and water
Synthetic chemicals are in all our bodies
- every one of us carries a of hundred of industrial chemicals in our bodies - among these were several toxic persistent organic pollutants restricted by international treaty
- Our exposure to synthetic chemicals begins in the womb, as substances our moth
Silent Spring began the public debate over synthetic chemicals
- Rachel Carson was a naturalist, author, and government scientist
- she brought together a diverse collection of scientists studies, medical cases histories, and other data that no one had previously synthesized and presented to the general public � her
Toxicants come in different types
- Carcinogens, Mutagens, Teratogens, Neurotoxins, Endocrine Disruptors, allergens
- the human immune system protects our bodies from disease � some toxicants weaken the immune system, reducing the body's ability to defend itself against bacteria, viruses,
Carcinogens
- substances or types of radiation that case cancer
- malignant cells grow uncontrollably, creating tumors, damaging the body, and often leading to death
- frequently has a genetic component, but a wide variety of environmental factors are thought to rais
Mutagens
substances that cause genetic mutations in the DNA of organisms � most mutations have little to no effect, but some lead to severe problems (cancer and other disorders)
Teratogens
cause harm to the unborn � affect the development of human embryos in the womb can cause birth defects
Neurotoxins
assault the nervous system � include venom
allergens
over-activate the immune system, causing an immune response when one is not necessary � one hypothesis for the increase in asthma in recent years is that allergenic synthetic chemicals are more prevalent in our environment � allergens are not universally
Endocrine Disruptors
- toxicants that interfere with the endocrine system, or hormone system � consists of chemicals messengers that travel through the blood-stream at extremely low concentrations and have many vital functions � stimulate growth, development, and sexual matur
Toxicants may concentrate in water
- small aquatic systems can be affected more easily than large aquatic systems b/c of size
- Water running off from land often transports toxicants from large areas and concentrates them in small volumes of surface water � if chemical persist in soil, the
Airborne substances can travel widely
- Airborne transport of pesticides is sometimes called pesticide drift
- because so many substances are carried by the wind, synthetic chemicals are ubiquitous worldwide � Earth's polar regions are particularly contaminated because natural patterns of glo
Some toxicants persist
- once a toxic substance arrives somewhere, it may degrade quickly and become harmless, or it may remain unaltered and permit for many months, years, or decades � the rate at which a given substance degrades depends on its chemistry and on factors such as
Toxic substances may accumulate and move up the food chain
- some toxic substances are quickly excreted and some are degraded into harmless breakdown products � others persist intact in the body
- Substances at are fat-soluble or oil-soluble are absorbed and stored in fatty tissues
- as you go higher in the troph
bioaccumulation
Such persistent toxicants accumulate in an animal's body in this process -- which results in the animal's having a greater concentration of the substance than exists in the surrounding environment
biomagnification
Toxic substances that bioaccumulate in an organism's tissues may be transferred to other organisms as predators consume pretty � then one organism consumes another, the predator takes in any stored toxicants and stores them itself � bioaccumulation takes
Not all toxicants are synthetic, and not all synthetic chemicals are toxic
- it would be a mistake to assume that all artificial substances are unhealthy and that all natural substances are healthy
- the amount of synthetic chemicals in our food from pesticide residues are dwarfed by the quantities of natural toxicants
- f fears
Wildlife studies integrate work in the field and lab
- studying how wild animals response to pollution and other hazards can help us detect environmental health threats before they do us too much harm
- often wildlife toxicologists work in the field w/ animals to take measurements, document patterns, and ge
Human studies rely on case histories, epidemiology, and animal testing
- case histories: study of individual patients
- epidemiological studies: large-scale comparisons of groups of people...these measure a statistical association between a health hazard and an effect, but they DO NOT confirm that the hazard causes the effec
Case History
- process of observation and analysis of individual patients
- have advanced our understanding of human illness, but they do not always help us infer the effects of rare hazards, new hazards, or chemicals that exist at low environmental concentrations and
epidemiological studies
- epidemiological process is akin to a natural experiment -- Epidemiological studies measure a statistical association between a health hazard and an effect, but they do not confirm that the hazard causes the effect
- To establish causation � manipulative
Dose-response analysis
- the standard method of testing with lab animals in toxicology
- quantify the toxicity of a substance by measuring the strength of its effect or the number of animals affected at different doses
Dose
the amount of substance the test animal receives
Response
the type or magnitude of negative effects the animal exhibits as a result � generally quantified by measuring the proportion of animals exhibiting negative effects
Dose-Response Curve
The data on a graph: x-axis: the dose; y-axis: response; toxicologists can calculate a convenient shorthand gauge of a substance's toxicity
LD50
lethal dose for 50% of individuals to die; a high LD50 indicates low toxicity, and low LD50 indicates high toxicity
ED50
If the experimenter is interest in nonlethal health effects � may want to document the level of toxicant at which 50% of a population of test animals is affected in some other way � effective-dose-50%
threshold
- Some substances can elicit effects at any concentration, but for others � responses may occur only above a certain dose, or threshold
- might be expected if the body's organs can fully metabolize or excrete a toxicant at low doses but become overwhelmed
Endocrine disruption poses challenges for toxicology
- emerging understanding of endocrine disruption leads toxicologist to question their assumptions, unconventional dose-response curves are presenting challenges for scientists studying toxic substances and for policymakers trying to set safety standards f
Individuals vary in their responses to hazards
- Different individuals may respond quite differently to identical exposures to hazards
- Sensitivity varies with a variety of factors: age, sex, weight, genetics, current condition, socioeconomic status � poorer people are more susceptible b/c they can n
The type of exposure can affect the response
- acute exposure: high exposure for short periods of time; easier to recognize; nuclear accidents, chemical spill, oil spill, accidental ingestion
- chronic exposure: low exposure long periods of time; harder to recognize; smoking, alcohol abuse
Synergistic Effects
- interactive impacts that are greater than the simple sum of their constituent effects
- Chemical substances, when mixed, may act together in ways that cannot be predicted from the effects of each in isolation � mixed toxicants may sum each other's effec
We express risk in terms of probability
Exposure to an environmental health threat does not invariably produce some give effects � causes some probability of harm, some statistical chance that damage will result � a scientists must know more than just its identity and strength � also known the
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 posed by that phenomenon
Our perception of risk may not match reality
- Every action we take and every decision we make involves some element of risk, some probability that things will go wrong � we try everyday to minimize the risk, but our perception of risk do not always match statistical reality; People often worry abou
Risk Assessment
the quantitative measurement of risk and the comparison of risks involved in different activities or substances together � is way to identify and outline problems � in environmental health, it helps ascertain which substances and activities suppose health
risk management
which consists of decisions and strategies to minimize risk; in most nations, risk management is handled largely by federal agencies � in the U.S.: EPA, CDC, and FDA
Risk management combines science and other social factors
- scientific assessments of risk are considered in light of economic, social, and political needs and values � risk managers assess costs and benefits of addressing risk in various ways w/ regard to both scientific and nonscientific concerns before making
Two Approaches Exist for Determining Safety
- Innocent-until-proven guilty � to assume that substances are harmless until shown to be harmful. pro: virtue of facilitating technological innovation and economic activity; con: wide use of substances that may be dangerous; test subject: human
- Precaut
Philosophical approaches are reflected in policy
- nations vary in how they blend the two approaches when it comes to regulating synthetic substances
- Europe: precautionary principle; U.S.: innocent-until-proven-guilty
- The FDA, under the Food, Drug, and Cosmetic Act of 1938 and its subsequent amendme
The Toxic Substances Control Act
- directs EPA to monitor thousands of industrial chemicals manufactured in or imported into the U.S. � gives the agency power to regulate these substances and ban them if they are found to pose excessive risk
- Many public advocates view TSCA as being far
2007 � Reach (Europe)
REACH program (registration, evaluation, authorization, and restriction of chemicals)
- use precautionary principle
- shifts burden of proof to industries, rather than governments
- if more than 1 metric ton imported, must be registered with a European Ch