MIDTERM1 Flashcards
Epidemiology
is the study and analysis of the distribution, patterns and determinants of health and
disease. It is a cornerstone of public health, and shapes policy decisions by identifying risk factors for disease and targets for preventive healthcare.
Environmental Risk
arises from environmental hazards or environmental issues…..aims to assess the effects of stressors, often chemicals, on the local
environment
Hazard
Something that has the potential to harm you.
Risk
likelihood of a hazard causing harm.
Natural Environment
Consists of those parts of the earth – living or non-living – that are not a product of human activity. This includes living organisms, ecosystems, climate, weather, minerals, soil, air,
and water. The implication, of course, is that humans are not part of the natural system, which is clearly wrong; but it is reasonable to distinguish natural from man-made change
Built Environment
Consists of everything constructed by humans,
including buildings, towns, cities, roads,
infrastructure, water and energy supply systems, and perhaps even cultivated forests, urban parks, botanic gardens, and reservoirs.
The Three P’s
Pollution, Population, Poverty
Epidemiologic transition
Shift in the pattern of morbidity and mortality
– Before shift: causes primarily related to infectious and
communicable diseases
– After shift: causes associated with chronic, degenerative
diseases
hazardous agents
Account for many of the forms of environmentally associated
morbidity and mortality
* Examples
– Microbes
– Toxic chemicals and metals
– Pesticides
– Ionizing radiation
Prevalence
Number of existing cases of or deaths
from a disease or health condition in a
population at some designated time
Point prevalence =
Number of persons ill / Total number in the group
at a point in time
Incidence
Occurrence of new disease or mortality
within a defined period of observation
(e.g., a week, month, year, or other time
period) in a specified population………….
Incidence rate = Number of new cases over a time period / Average population at risk during the same time period x multiplier (e.g., 100,000)
Cross-sectional study
Different groups compared at the same time
Case Fatality Rate (CFR)
CFR(%) =
Number of deaths due to disease “X” /
Number of cases of disease “X”
x 100 during a time period
Longitudinal study
same group compared over time.
Odds Ratio (OR)
Measure of association between exposure and
outcome— Used in case-control studies
What Is the Epidemiologic Triangle?
Used to describe causality of infectious diseases
* Provides framework for organizing the causality
of other types of environmental problems
Environment in the “Triangle
Domain in which disease-causing agents
may exist, survive, or originate
* Consists of “All that which is external to
the individual human host.”
Host in the “Triangle”
“person or other living animal, including
birds and arthropods, that affords
subsistence or lodgment to an
INFECTIOUS AGENT under natural
conditions”
Agent in the “Triangle”
“factor (e.g., a microorganism, chemical substance, form of radiation, mechanical, behavioral, social agent or process) whose presence, excessive presence, or (in deficiency diseases) relative absence is essential for the occurrence of a disease”
Limitations of Epidemiologic Studies
- Long latency periods
- Low incidence and prevalence
- Difficulties in exposure assessment
- Nonspecific effects
What Is Environmental Epidemiology?
- Study of diseases and health conditions
(occurring in the population) linked to
environmental factors - Exposures usually involuntary
Carcinogen
- Chemical (or substance) that causes or is
suspected of causing cancer, a disease associated
with unregulated proliferation of cells in the body
Latency
- Time period between initial exposure and
a measurable response - Can range from a few seconds (in the case of acutely toxic agents) to several
decades for agents that may be
carcinogenic
Biomagnification
(Toxic Pathways) (Bioaccumulation)
– the accumulation or increase in concentration of a
substance in living tissue as it moves through the food
chain.
– e.g. Cadmium, mercury are biomagnified
Bioaccumulation
Toxins that bioaccumulate in the tissues of one organisms may be transferred to other organisms as predators consume
prey. * With each step up the food chain, concentrations of the toxin can be magnified
* This is called Biomagnification
▪ Heavy metals
▪ Chlorinated hydrocarbons
Persistent Organic Pollutants (POPs)
- Persistence of the chemical
– How long it can remain in the environment. – Chemicals have half lives - (POPs) are extremely
dangerous due to their ability to be biomagnified.
– For example, phthalates found in polyvinyl chloride plastic & some deodorants & cosmetics have been shown to be toxic to lab animals - Nearly everyone in the U.S. has phthalates in their tissues because these chemicals are highly persistent
types of hazards
-Chemical hazards— from harmful chemicals in
air, water, soil, food, and human-made
products.
* Natural hazards– such as fire, earthquakes,
volcanic eruptions, floods, and storms.
* Cultural hazards– such as unsafe working
conditions, unsafe highways, criminal assault,
and poverty.
* Lifestyle choices– such as smoking, making
poor food choices, drinking too much alcohol,
and having unsafe sex.
pathogen
an organism that can
cause disease in another organism.
– Bacteria.
– Viruses.
– Parasites.
– Protozoa.
– Fungi.
Risk Assessment
Provides a qualitative or quantitative estimation
of the likelihood of adverse effects that may
result from exposure to specified health hazards
or from the absence of beneficial influences
* Hazard identification
* Dose–response assessment
* Exposure assessment
* Risk characterization
Exposure Assessment
Procedure that “identifies populations exposed
to the toxicant, describes their composition and
size, and examines the roots, magnitudes,
frequencies, and durations of such exposures”
* One of the weakest aspects of risk assessment
* Takes into account the following:
– Where the exposure occurs
– How much exposure occurs
– How a toxic substance is absorbed by the body
Zoonosis
An infection or infectious disease
transmissible under natural conditions
from vertebrate animals to humans”
Methods for Transmission of Zoonoses
* Contact with the skin
* Bite or scratch of an animal
* Direct inhalation or ingestion
* Bite of an arthropod vector
Vector
An insect or any living carrier that transports an
infectious agent from an infected individual or its
wastes to a susceptible individual or its food or
immediate surroundings”
* Various species of rodents
– Rats and mice
* Arthropods
– Mosquitoes
– Ticks
– Sand flies
– Biting midges
DDT (dichloro-diphenyl-trichloroethane)
It was initially used with great effect to combat malaria, typhus, and the other insect-borne human diseases among both military and civilian populations
Exposure Source
origin of environmental contamination ex. Industrial releases, consumer product chemicals, combustion byproducts(car pollutants)
Exposure Route
Contact, ingestion, inhalation ex food, dust, drinking water,
Exposure pathway
Exposure Pathway Categories.
Element 1: Contamination Sources.
Element 2: Environmental Fate and Transport.
Element 3: Exposure Points.
Element 4: Exposure Routes.
Element 5: Potentially Exposed Populations.
Risk assessments
Risk assessment is the process
of using statistical methods to
estimate how much harm a
particular hazard can cause to
human health or to the
environment.
- It helps us to establish priorities
for avoiding or managing risks.
- It involves deciding whether or
how to reduce a particular risk
to a certain degree
ex. cooking an egg lowers the risk of food poisoning
Dose-Response Assessment
Estimates how much of the chemical it would take to cause varying degree of health effects that could lead to illness. What is the relationship between dose and incidence of the adverse effect in humans?————–How the proportion of responding individuals in a population or the severity of the toxic response within an
individual increases with dose is investigated.
Hazard Identification
Identifies any potential health problems that a chemical can cause. Does the agent cause an
adverse effect?
Exposure Assessment
Determines the amount, duration, and pattern of exposure to the chemical
Risk Characterization
Assesses the risk for the chemical to cause illness in the general population. What is the
estimated incidence of the effect in a given population?
NOAEL
NOAEL: no-observed-adverse-effect-level ….. is defined as the highest dose where the effects observed in the treated group do NOT imply an adverse effect to the subject.
LOAEL
LOAEL: lowest-observed-adverse-effect-level…. Lowest dose at which there WAS an observed toxic or adverse effect.
DNEL
DNEL: Derived No-Effect Level
EDI
Estimated daily intake (mg/kg/day)
