Chapter 2

Environmental epidemiology- The study of diseases and health conditions occurring in the population that are linked to environmental factors.

Hippocrates- stated water quality and air had a role in causing disease.

Pott- Observed at chimney sweeps had a high incidence of scrotal cancer and suggested they bathe her weekly.

Snow- determined cholera was more likely obtained from water downstream. Snow removed the water pump handle to stop the outbreak.

How does epidemiology aid environmental health? It deals with the concerns with population, uses observational data, uses methodology for study designs, and uses descriptive and analytics studies.

Prevalence- total number of existing cases of a disease, health condition or deaths in a population at some designated time.

Point Prevalence- is prevalence measured at a particular point in time.

Point prevalence formula- # of people ill divided by the total number in the group. Take your answer X 100 to get the %.

How prevalence measure is used- all numbers of existing cases of a disease, health condition, or deaths in a population at some designated time.

Incidence- occurrence of new diseases or mortality in a defined period of observation in a specific population.

Incidence formula- Period of time (ie 5 years) X multiplier (ie 100,000) divided by the total population at risk.

Population at risk definition- members of the population who are capable of developing the disease or condition being studied.

Case Fatality Rate- A measure of lethality of a disease.

Identify the formula for case fatality rate- # of deaths due to disease DIVIDED BY number of cases of disease X period of time X 100

What is a cross- sectional study? Examines the relationship between disease or other health related characteristics and other variables of interest as they exist in a defined population at one particular time.

How is data gathered for a cross-sectional study? - A Questionare is used to collect data.

Why does a cross-sectional study not prove a causal relationship? Because it identifies exposure and effect at the same time, but justifies further studies to be done.

 What is a case-control study? Study in which subjects who participate are defined on the basis of Presence (cases) or absence (controls) of outcomes of interest.

Identify the odds ratio formula?

What does the odds ratio measure? A measure of association for case control studies.

 Odds ratio if > 1.0- exposure is more likely associated with cases than controls, so exposure is more likely associated with disease.

Odds ratio if < 1.0- The disease is not likely associated with exposure.

What is a cohort study? An identified group/population at risk is followed over a period of time to determine the exposure that causes disease.

Prospective- collect data as the group is followed forward in time.

Retrospective- if data has been collected on the group in the past. (Historical).

What is the best measure of association for a cohort study?Risk Ration or Relative Risk.

А Identify the formula for a risk ratio. (A) DIVIDED BY (A+B) DIVIDED BY (C) DIVIDED BY (C+D)

What determines risk in the risk ratio? IF RR= 1.0, then risk is same for exposed and unexposed. IF RR IS < 1.0, the exposure is protective of health.

What is the 2X2 table formula for a risk ratio?

How do cohort studies and case control studies differ in regard to knowing the population at risk? Cohort study is a group of individuals with exposure and a group without exposure followed over time to compare disease occurance. Case control is individuals with a disease compared with similar individuals with disease to determine Association of disease with prior exposure.

How is the risk ratio interpreted  if > 1.0 or if 1.0 or if < 1.0?IF RR is> 1.0, then the risk of disease is greater in the exposed group than the non- exposed group (the > RR, the > risk the disease is associated with the exposure). IF RR= 1.0= RISK is the same for exposed AND unexposed. IF RR < 1.0 = The exposure is protected by health.

What is an ecological study? The incidence of a disease in one geographical area is compared to that of another area. ex CA mortality rate In areas with hazardous waste sites versus areas without hazardous waste sites.

Identify and understand the example of an ecological study of perchlorate. Group of people= ADHD/Autism diagnosis studied with drinking water exposed to perchlorate vrs drinking water without exposure = No greater outcome of ADHA/Autism.

5 What is perchlorate and the hazards associated with it? A Chemical salt- it is associated with production of rocket Propellant, Fire works motches, explosives.

Identify the formula for standardized mortality ratio? Deaths observed DIVIDED BY deaths expected X 100

How is the SMR used? Used to compare the mortality of a smaller group to the maternal mortality of the larger group that includes it.

Identify and explain the epidemiologic triangle model of causality. HOST, AGENT, ENVIRONMENT TRIANGLE. It is used for describing the casualty of infectious diseases.

AGENT- could be biological chemical radiation or radioactive particle.

ENVIRONMENT- allows the agent to move to the host. Examples are air, water, soil, and fomite which is an in animate object.

HOST- Must be susceptible to the agent. May be any living organism that allows subsistence of an infectious agent. A human host is usually afflicted by the agent.

Identify and explain the 7 criteria of causality. 1. strength strong associations support casual Relationships. Examples are heavy cigarette smokers are up to 30 times more likely to die from lung cancer than non-smokers. 2. Consistency- Association is observed repeatedly. The relationship between smoking and lung cancer has been found repeatedly in many studies.. 3. Specificity- A specific association is one that has a specific exposure that causes a specific disease. ex- Sufficient exposure to Vibrio cholerae in food or water causes cholera.

Temporality- Cause always occurs before effect 

Biological Gradient- A dose-response relationship exists, greater dose = greater response. ex more cigs smoked= more likely of lung cancer mortality.

Biological Plausibility- The association agrees with the current understanding of pathological processes. ex Animals studies agree with human studies that lead is neurotoxicity (damages nervous system)

Coherence- It is compatible and does not seriously conflict with current scientific knowledge.