environmental health Flashcards
What is environmental health?
- The branch of public health that focuses on all aspects of the natural and built environment that may affect human health.
- Field of EH tends to focus on man-made (anthropogenic) environmental hazards that lie outside of an individual’s immediate control (involuntary)
why is environmental health important?
Globally, nearly 25 percent of all deaths and the total disease burden can be attributed to environmental factors
Environmental Factors affecting health
Exposure to hazardous substances in the air, water, soil & food Natural and technological disasters Physical hazards Nutritional deficiencies The built environment
environmental quality and health impact
Poor environmental quality has its greatest impact on people whose health status is already at risk. Therefore, environmental health must address the societal and environmental factors that increase the likelihood of exposure and disease.
Environmental health on a global scale
Note that environmental exposures and their effects on human health vary across the globe.
With economic development and population change, there introduces the potential for Environmental Risk Transmission
Three demographic transition stages
Stage 1 → most of the population is young; fertility and mortality rates are high; the population remains small
Stage 2 → drop in mortality rate; fertility remains high; rapid increase in population
Stage 3 → drops in fertility rates causing a more even distribution of the population according to age and sex
Environmental Risk Transition
Changes in environmental risks that happen as a consequence of economic development in the less developed regions of the world
Environmental Risk Transition in less and more developed countries
Less developed countries
—Risks due to poor housing, unsafe food and water (i.e. diarrhea, malaria)
More developed countries
—-New set of environmental problems— Risks due to long-term exposure to pollution, chemical exposures (i.e. cancer, developmental disabilities)
Epidemiologic Transition
Shift in pattern of morbidity and mortality
TOP TEN LEADING CAUSES OF DEATH
What is epidemiology
The study of the distribution and determinants of disease frequency in human populations……and the application of this study to control health problems; “population medicine”
What is environmental epidemiology
- Focuses on diseases linked to environmental exposures/hazards
- Usually focuses on factors that are beyond a persons control
Descriptive epidemiology
- includes surveillance
- Track and compare disease rates in populations across place or time
- Provides info for understanding risk factors for disease
Analytical epidemiology
- epidemiological research/studies
- Document link between exposure and disease
Descriptive epidemiology: Measures of disease frequency
Prevalence
incidence
prevalence
- Number of existing cases of a disease in a population at a certain point in time
- # of existing cases of disease / total # of people in population
- Provides a snapshot of disease occurrence in the population
- used to:
- —Assess variation in disease occurrence
- —Estimating needs of medical facilities and for allocating resources for treating people who already have a disease
- —Aid in the development of hypotheses
incidence
- Different from prevalence because it focuses on the number of NEW cases of a disease that develop in a population at risk during a certain period of time
- # of NEW cases of disease / total # of people at risk (during a given period of time)
- used to:
- —Estimate the probability of someone developing a disease during a certain period of time
- —evaluate effectiveness of programs that try to prevent disease from occurring
- —demonstrate causality between an exposure and a health outcome
types of study design
experimental and observational studies
types of experimental studies
clinical trial/Randomized control trials
types of observational studies
cohort cross-sectional case-control ecological case series
cohort studies
Classify participants based on exposure status, then observe them over time to determine incidence of disease
Prospective - Outcome has not yet occurred
enroll now and follow in the future
Retrospective — outcome has already occurred
use historical records to assess health outcome
Good for identifying multiple outcomes
Not good for identifying multiple exposures
case-control studies
Classify participants based on presence or absence of disease
Cases — have the disease
Controls — sample of pop. that produced the cases and do not have the disease
Determine exposure retrospectively
Good for studying rare outcomes (can only examine one or a few outcomes)
Good for identifying multiple exposures
cross-sectional studies
Assess exposure and disease status at the same point in time
Unable to tell which came first — exposure or disease
Not good for testing hypotheses
Good for generating hypotheses
ecological studies
Evaluates an association between disease and exposure on the population level
Individual data are not used
Ecological Fallacy — Unknown if people with disease are the same people that have been exposed
Good for looking at association and generating hypotheses
case series
Collect information about people who all have the same disease
Not good for finding causal associations
Good for developing hypotheses
identification of vulnerable populations
children
elderly
pregnant women
people with disabilities / chronic diseases
occupation (increased vulnerability/exposure w specific jobs
limitations of environmental epidemiology
Long latency periods
low incidence and prevalence
recall bias
recall bias
People with disease may be more likely to recall an exposure than people without a disease
Reduced reliability of exposure information from control group
difficulties in exposure assessment
- Need accurate exposure assessment
- Exposure often misclassified
- Challenging to measure exposure to a chemical mixture
- Challenging to monitor low-level environmental exposures
- Lack of individual exposure measurements - ambient measurements do not provide direct information about an individual’s exposure
Hills criteria of causality
strength, consistency, specificity, temporality, biological gradient, plausibility, coherence
