MPH 6010 Exam 1 Flashcards
Environmental health
Prevention of illness, disability, and premature death from interactions between people and the environment- addresses all the physical, chemical, & biological factors external to a person, & all the related factors impacting behaviors. It encompasses the assessment & control of those environmental factors that can potentially affect health
Risk
Probability of an unwanted occurrence and uncertainty about when/where Hazard might occur
Public health
The art and science of protecting and improving the health of a community through an organized and systematic effort that includes education, assurance of provisions of health services and protection of the public from exposures that may cause harm
What other sciences does environmental health “borrow” from?
*Epi
*Toxicology
*Chem & physics
*Micro
*Engineering
*Climatology
Name some reasons that health has improved in the US because of environmental health
*Basic sanitation
*Water treatment
*Waste treatment
*Food quality protection & nutrition
Environmental media
Areas in which pollutants or other substances may appear
Examples of environmental media
*Air
*Water
*Soil
*Sediment
*Biota
Physical environment
Environment made up of those parts of nature which would exist regardless of human activity
Social environment
Enterprises initiated by humans that generate the pollutants and microbes that potentially affect human health
Examples of the social environment
*Housing
*Transportation
*Urban development
*Land use
*Industry
*Ag
Principal determinants of health worldwide (3 ps)
*Pollution
*Poverty
*Population
Environmental epidemiology
The study of diseases and health conditions (occurring in the population) that are linked to environmental factors- think the study of the distribution & determinants of health & diseases, morbidity, injuries, disability & mortality in populations
Sir Percival Pott
A London surgeon thought to be the first individual to describe an environmental cause of cancer. THINK Chimney sweeps had high incidence of scrotal cancer due to contact with soot.
John Snow
An English anesthesiologist who linked a cholera outbreak in London to contaminated water from the Thames River in the mid-1800s.
Snow employed a “natural experiment,” a methodology used currently in studies of environmental health problems.
Examples of epidemiology’s contributions to environmental health
*Concern with populations
*Use of observational data
*Methodology for study designs
*Descriptive and analytic studies
Environmentally associated morbidity
Acute and chronic conditions, allergic responses, & disability
Environmentally hazardous agents
Microbes, toxic chemicals & metals, pesticides, and ionizing radiation
Most vulnerable subgroups to environmental hazards
The elderly, persons with disabilities & chronic diseases, pregnant women, & children
Environmental risk transition
Used to characterize changes in environmental risks that happen as a consequence of economic development in the less-developed regions of the world
What factors characterize the environmental risk transition
*Poor food
*Poor air
*Poor water
*Diarrhea due to poor sanitation and hygiene
*Acute respiratory diseases due to poor housing and indoor air pollution from poor quality household fuels
*Malaria due to poor housing quality
*Long -range pollutants such as acid rain precursors, ozone-depleting chemicals, & greenhouse gasses
Urbanization
Linked to numerous adverse implications for the health of populations including high rates of morbidity & mortality, environmental changes, scarcities of food, water & other resources, energy consumption, and production of large quantities of toxic wastes
Population dynamics
Ever-changing interrelationships among the set of variables that influence the demographic makeup of populations as well as the variables that influence the growth & decline of population sizes
Factors that relate to the size, age & sex composition of populations
Fertility, death rates, & migration
Completed fertility rate (total fertility rate)
Number of children a woman has given birth to when she completes childbearing
Burden of disease
The impact of disease in a population - an approach to the analysis of health problems, including loss of healthy years of life- think DALYs
Life expectancy (expectation of life)
Average number of years an individual is expected to live if current mortality rates continue to apply
Life expectancy at birth-
Average number of years a newborn baby can be expected to live if current mortality trends continue
Disability-adjusted life years (DALYs)
Adjustment of life expectancy to allow for long-term disability as estimated from official statistics- a DALY lost is a measure of the burden of disease on a population
Forced migration
Forcible displacement of persons- a means of escaping from persecution for religious & political reasons & to obtain relief from unstable conditions in one’s home country
Demographic transition
Alteration over time in a population’s fertility, mortality & makeup- Does NOT include the effects of migration upon the age & sex composition of a population
Demographic transition stage 1
Most of the population is young and fertility & mortality rates are high- small population
Demographic transition stage 2
Drop in the mortality rates with high fertility & rapid increase in the population
Demographic transition stage 3
Dropping fertility rates that cause a more even distribution of the population according to sex & age
Epidemiologic transition
Shift in the pattern of morbidity & mortality from causes related primarily to infectious & communicable diseases to causes associated with chronic, degenerative diseases. Accompanies the demographic transition.
Effects of rapid growth in the world’s population
*Urbanization
*Overtaxing carrying capacity
*Food insecurity
*Loss of biodiversity
Factors that lead to urbanization
*Industrialization
*Availability of food
*Employment opportunities
*Lifestyle considerations
*Escape from political conflict
Hazards associated with the urban environment
*Biological pathogens or pollutants within the human environment that impair human health-Think pathogenic agents & their vectors & reservoirs
*Chemical pollutants within the human environment
*Availability, cost & quality of natural resources on which human health depends- think food, water, fuel
*Physical hazards
*Aspects of the built environment with negative consequences on physical or psychosocial health
*Overcrowding
*Natural resource degradation
*National/global environmental degradation
Carrying capacity
The maximum number of individuals that can be supported sustainably by a given environment
Thomas Malthus
First essay on population- said population would outstrip available resources, and positive checks for excessive population growth rates were epidemics of disease, starvation, & population reduction through warfare. Also said the growth of the population could be constrained through “preventive checks”- think not allowing people to marry
Food insecurity
Supplies of wholesome foods are uncertain or may have limited availability
Food insecurity & famine may occur when the carrying capacity in a particular geographic area is exceeded
Biodiversity
The different types & variability of animal & plant species & ecosystems in which they live- involves diversity in the genes of a population, diversity in the number of species, and diversity in habitats & is an essential dimension of human health
Environment
Complex of physical, chemical, & biotic factors that act upon an organism or an ecological community & ultimately determine its form & survival
Ecological model
Determinants of health (environmental, biological, & behavioral) interact & are interlinked over the life course of individuals
Ecosystem
Dynamic complex of plant, animal & microorganism communities and the nonliving environment interacting as a functional unit- Health of ecosystem is associated with the health of human beings, animals, & wildlife
Hippocrates
Noted the role of environment as an influence on disease
3 eras of environmental health
*First wave- hazardous working conditions & unsanitary conditions
*Second wave- environmental issues at forefront, air pollution, toxic chemical awareness, EPA founded
*Third wave- high population growth, industrialization, & urbanization with focus on greenhouse gasses & global warming
What does environmental epidemiology do
Studies a population in relation to morbidity and mortality- uses OBSERVATIONAL DATA
List study designs common in environmental epidemiology
*Cohort
*Cross-sectional
*Case-Control
*Case series
*Ecologic
*Experimental
Descriptive epidemiologic studies
Depiction of the occurrence of disease in populations according to classification by person, place, and time variables
*Regarded as a fundamental approach to delineate the patterns & manner in which disease occurs in populations
*Think disease clustering
Analytic epidemiologic studies
Examines causal (etiologic) hypotheses regarding the association between exposures and health conditions
Epidemiologic triangle
Used for describing the causality of infectious diseases- provides a framework for organizing the causality of other types of environmental problems
3 parts of the epidemiologic triangle
Host, Agent, Environment
Environment in the epi triangle
The domain in which disease-causing agents may exist, survive, or originate; it consists of “All that which is external to the individual human host”
Host in the epi triangle
A person or other living animal, including birds and arthropods, that affords subsistence or lodgment to an infectious agent under natural conditions
Agent in the epi triangle
A factor, such as a microorganism, chemical substance, or form of radiation, whose presence, excessive presence, or (in deficiency diseases) relative absence is essential for the occurrence of a disease
List Hill’s criteria of causality
*Strength
*Consistency
*Specificity
*Temporality
*Biological gradient
*Plausibility
*Coherence
Bias
Systematic deviation of results or inferences from the truth. Processes leading to such deviation. An error in the conception and design of a study—or in the collection, analysis, interpretation, reporting, publication, or review of data—leading to results or conclusions that are systematically (as opposed to randomly) different from the truth
What bias does the healthy worker effect introduce
Selection bias (in occupational mortality studies)
Healthy worker effect
Refers to the observation that employed populations tend to have a lower mortality experience than the general population
Confounding
The distortion of a measure of the effect of an exposure on an outcome due to the association of the exposure with other factors that influence the occurrence of the outcome
Limitations of epidemiologic studies
*Long latency periods
*Low incidence and prevalence
*Difficulties in exposure assessment
*Nonspecific effects
*Uncertainty with pathways of exposure
Prevalence
Refers to the number of existing cases of a disease, health condition, or deaths in a population at some designated time
Point prevalence
Refers to all cases of a disease, health condition, or deaths that exist at a particular point in time relative to a specific population from which the cases are derived
Equation for point prevalence
Number of persons ill/
Total number in group
* At a point in time
Incidence
The occurrence of new disease or mortality within a defined period of observation (e.g., week, month, year, or other time period) in a specific population
Equation for incidence rate
Number of new cases over a time period/
Total population at risk
*Times a specific multiplier
Case fatality rate
Provides a measure of the lethality of a disease
Equation for case fatality rate
Number of deaths due to disease/
number of cases of disease
*Times 100 during a time period
Odds ratio
The ratio of odds in favor of exposure among the cases [A/C] to the odds in favor of exposure among the non-cases [the controls, B/D]
*Think case-control study
Relative risk
The ratio of the incidence rate of a disease or health outcome in an exposed group to the incidence rate of the disease or condition in a non-exposed group (A/A=B)/(C/C+D)
RR > 1
Indicates that the risk of disease is greater in the exposed group than in the nonexposed group
RR < 1
Indicates possible protective effect
Examples of study endpoints
*Self-reported symptom rates
*Physiologic or clinical examinations
*Mortality
List some environmental epidemiology activities
*Identification of previously unrecognized exposures to known hazardous agents & the quantification of such risks
*Estimation of the amount of exposures that individuals have to environmental hazards
*Assessments of risks associated with exposures
*Evaluation of procedures to prevent exposure
For an environmentally associated health outcome to be considered a topic of environmental epidemiology…
Exposure factors must lie outside the individual’s immediate control- traditionally focuses on the air we breathe, the water we drink, & the food we eat
Goals of epidemiologic research
*Description of exposure-response gradients
*Discovery of how occupational hazards may cause harmful effects
*Characterization of vulnerable workers
*Input into programs for the prevention of occupationally related diseases
Epidemiology is important to environmental health because…
*Many exposures & health effects associated with the environment occur at the population level
*The epidemiologic methods of natural experiments & observational techniques are appropriate
*The study designs used in epidemiologic research can be applied directly to the study of environmental health issues
*Epidemiology aids in the development of hypotheses & the study of causal relationships
Epidemiology aids environmental health through…
Concerns with populations
Use of observational data
Methodology for study designs
OVERALL- epidemiologic input to environmental risk assessment involves the interpretation of epidemiological studies & their application to estimating the potential health risks to populations from known or estimated environmental exposures
Disease clustering
Aggregation of relatively uncommon events or diseases that may suggest common exposure to an environmental hazard
Natural experiments
Naturally occurring circumstances in which subsets of the population have different levels of exposure to a hypothesized causal factor in a situation resembling an actual experiment
Prevalence measures uses
Describe the scope & distribution of health outcomes in the population & assist with assessing variations in the occurrence of disease & development of etiologic hypotheses
Standardized mortality ratio-
Ratio of the number of deaths observed in the study group/population to the number that would be expected if the study population had the same specific rates as the standard population
3 requirements for the successful epidemiologic investigation of environmental exposures
*Direct & accurate estimates of the exposures
*Direct & accurate determination of the disease status of study population
*Appropriate statistical summarization & analysis of data pertaining to disease & exposure
Latency period
Time interval between initial exposure to a disease-causing agent & the appearance of a disease or symptoms
Advantages of enriovnmental epidemiology
*Engages the real world
*Shows a unique perspective on disease/health
*Basis for action despite ignorance of mechanism
Toxicology
The study/science of poisons- the study of the adverse effects of chemicals on living organisms (multidisciplinary art)
Think- toxicology studying dose-response relationships & mechanisms of action to understand adverse health effects linked to chemicals
399 BC Death of Socrates by Hemlock
Socrates was charged with religious heresy and corrupting the morals of local youth. The active chemical used was the alkaloid Coniine which, when ingested causes paralysis, convulsion and potentially death
Paracelsus
Said all substances are poisons; there is none which is not a poison. The right dose differentiates a poison from a remedy
Toxicant
A toxic substance that is man-made or results from human (anthropogenic) activity- has the ability to cause harm to organs or biochemical processes in areas beyond the site of exposure
Toxin
A toxic substance produced by a living organism- e.g., snake venom, bacterial toxins
Poison
A chemical/compound that produces adverse effects (illness, disability, death) at a low dose
Hazard
Anything that has potential to cause harm to human health and properties
Toxicity
Degree to which a substance is able to damage an exposed organism (is poisonous)- related to the physical & chemical properties
Characteristics of toxicants (5)
*Must be in the environment
*Must be bioavailable and bioaccumulated
*Must interact at a molecular site
*Must cause metabolic dysfunction
*Must decrease the fitness of an individual organism
Risk equation
hazard x exposure
Importance of toxicology
Safeguarding public health by identifying what the effects of these chemicals are & at what levels of exposure they may become hazardous to humans (understanding their toxicology)
Exposure
Proximity & or contact with a source of a disease agent in such a manner that effective transmission of the agent or harmful effects of the agent may occur
Toxicologist
Scientist who has received extensive training in order to investigate in living organisms “the adverse effects of chemicals (including their cellular, biochemical & molecular mechanisms of action) and assess the probability of their occurrence”
Environmental toxicology
The study of the impacts of pollutants upon the structure & function of ecological systems- examines how environmental exposures to chemical pollutants may present risks to biological organisms
Ecotoxicology
Studies the effects of pollutants on ecosystems & investigates dispersion of pollutants into the physical environment, their impact upon biological chains, such as food chains, & their toxic effects within ecosystems
Developmental toxicology
Researches the effects of natural & man-made chemicals on prenatal development
Teratogens
Substances that cause birth defects
Xenobiotics
Chemicals that are foreign to the biological system that can produce developmental toxicity
Poison
An agent that produces immediate effects such as lethality or sickness even when present in small doses- any agent capable of producing a deleterious response in a biological system
Toxic agent
Material or factor that can be harmful to biological systems
*Physical energy (heat, radiation)
*Substances derived from biological sources (venom)
*Almost all chemicals
Systemic toxins
Those that affect the entire body or multiple organ systems
Target organ toxins
Affect specific parts of the body
Dose
The amount of a substance administered at one time
Exposure dose
The amount of a xenobiotic encountered in the environment
External dose
A dose that results from contact with environmental sources, e.g., environmental contamination
Absorbed dose
The actual amount of the exposed dose that enters the body (AKA internal dose)
Administered dose
Indicates the effectiveness of a substance. Normally, effective dose refers to a beneficial effect such as relief of pain. It may also stand for a harmful effect such as paralysis
Dose-response curve
graph that is used to describe the effect of exposure to a chemical or toxic substance upon an organism
*X-axis- dose
*Y-axis- response
Dose-response relationship
The relationship of observed responses or outcomes in a population to varying levels of a beneficial or harmful agent- type of correlative relationship between the characteristics of exposure to a chemical & the spectrum of effects caused by the chemical
Uses of dose-response relationship
*Causal association between toxin & biological effects
*Minimum dosages needed to produce a biological effect
*Rate of accumulation of harmful effects
LD50 (lethal dose)
dosage (mg/kg body weight) causing death in 50% of exposed animals- can also be LD10 or LD90
Nature of toxic effects depends on…
*Innate toxicity of the chemical
*Whether it is in sufficient concentration
*How it impinges upon a somatic location as a consequence of the route & site of exposure
*Exposure needs to take place for sufficient time duration & frequency
*One’s ability to metabolize the chemical
Concentration & toxicity of chemicals affected by…
*Route of entry into the body
*Received dose of the chemical
**Duration of exposure
**Interactions among multiple chemicals
**Individual sensitivity
Most frequent sites of exposure to environmental chemicals
GI tract
Respiratory tract
Skin
Acute exposure
Usually a single exposure for less than 24 hours
Subacute exposure
Repeated exposure for 1 month or less
Subchronic exposure
Repeated exposure for 1-3 months
Chronic exposure
Repeated exposure for more than 3 months
Additive
The combination of 2 chemicals produces an effect that is equal to their individual effects added together
Synergism
The combined effect of exposures to 2 or more chemicals is greater than the sum of their individual effects
Potentiation
One chemical that is not toxic causes another chemical to become more toxic
Coalitive interaction
Several agents that have no known toxic effects interact to produce a toxic effect
Antagonism
2 chemicals administered together interfere with each other’s actions or one interferes with the action of the other
Chemical allergy
An immunologically mediated adverse reaction to a chemical resulting from previous sensitization to that chemical or to a structurally similar one
Chemical idiosyncrasy
When someone has either extreme sensitivity to low doses or insensitivity to high doses of a chemical
Direct effect
Denotes an immediate impact upon the cells & tissues of the body or upon specific target organs
Local effects
Damage at the site where a chemical first comes into contact with the body (think skin redness)
Systemic effects
Adverse effects associated with generalized distribution of the chemical throughout the body by the bloodstream to internal organs
Indirect effect
Change in the function of the body’s biochemical processes
Risk assessment
A process for identifying adverse consequences and their associated probability - the process of determining risks to health attributable to environmental or other hazards- provides an estimation of the likelihood of adverse effects
4 steps of a risk assessment
*Hazard identification
*Dose-response assessment
*Exposure assessment
*Risk characterization
Hazard identification
Examines the evidence that associates exposure to an agent with its toxicity & produces a qualitative judgment about the strength of that evidence, whether it is derived from human epidemiology or extrapolated from lab animal data
Dose-response assessment
The measurement of the relationship between the amount of exposure & the occurrence of the unwanted health effects
Exposure assessment
The procedure that identifies populations exposed to the toxicant, describes their composition & size, & examines the roots, magnitudes, frequencies & duration of such exposures
*Characterize the point of exposure setting & scenario
*ID exposure pathways
*Quantify the exposure
Exposure pathways
How does the agent move from its source to the individual- the processes for movement of substances from their sources to the people who are exposed
Exposure routes
Modes of entry into the body
Risk characterization
Estimates of the number of excess unwarranted health events expected at different time intervals at each level of exposure- yields a synthesis & summary of information about a hazard that addresses the needs & interests of decision makers & of interested & affected parties
Risk management
Actions taken to control exposures to toxic chemicals in the environment
List factors that influence exposure
*Exposure pathways
*Intensity/concentration
*Duration
*Frequency (think # of times and time in between)
*Intake variables
Examples of intake variables
Types of food, nutrition, starvation, etc.
Factors influencing toxicity
*Intake variables
*Physiological differences
*Genetic variability
*Chemical effects
*Environmental effects
Bioaccumulation
The process by which organism accumulates chemicals both directly from abiotic environment (water, soil, air) and dietary sources (trophic transfer)
Bioaccumulation factor
Toxicant concentration in organism /
Toxicant concentration in the media (think water, soil, etc.)
Bioconcentration factor
The ratio of the toxicant concentration in organism tissue to its equilibrium concentration in water expressed in equivalent units
Bioconcentration factor equation
Toxicant concentration in tissue/
Toxicant concentration in water
Biomagnification
The process whereby toxicants are passed from one trophic level to another & exhibit increased concentrations with the increase in trophic levels
