HSCI 204 MIDTERM EXAM QUESTIONS ANSWERED CORRECTLY LATEST UPDATE 2026
Definition of Environmental Health - Answers 1. Broad view of the environment: ex. physical, social,
etc
2. Goal is to minimize adverse health effects caused by environmental hazrads
Why is environmental health important? - Answers 1. There are enormous impacts at teh population
level
2. everyone is affected (widespread)
3. Inherently interdiscplinary
4. Overlaps with many fields
5. Small effects at the individual level
--> which makes it difficult
Historically, info about enviromental health came from 2 sources. - Answers 1. Anecdotal
occupational observations; workers would experience a rare disease with unexpected frequency
ex. Chimney workers would have hella lung cancer
2. Disasters/sudden unexpected events that would lead to a negative health impacts
ex. the Mimata disaster; mercury got thrown in the ocean and fish ate it- biomagnification, then
humans ate it and got mercury poisoning
Change in perception of environmental health - Answers in the 1970s:
Due to:
- Publication of Silent spring in 1962: Rachel Carson was a big environemntal health advocate and
wrote about how we need to be more cautious with using pesticides and this led to a global impact of
widespread recognition and concern
- Events at Love Canal: Love Canal was used as dumpster site and as trash accumulated there, toxic
chemicals also started to appear and with homes so close by, many ppl were affected and many had
to be evacuated- events were widely reported
Major Public Health Achievements - Answers 1. Mortality dropped due to better/cleaner drinking
water
2. Decrease in lead in our air
Environnmental risk transition - Answers As countries get more developed (wealth increase),
Household risks will fall (sanitation), community risks with rise then fall (urban pollution) and global
risks will rise (global warming)
Where should we intervene? The pyramid - Answers 1. Elimination: Physically remove hazard
2. Sublimation: Replace hazard
3. Engineering control: Make physical modifications to control hazard
4. Administrative control: Change the way ppl work
5. PPE: Personal Protective Gear (least effective)
Where should we intervene? 3 ways- ex air pollution - Answers 1. At the source: Reduce emissions
(less vehicle mileage)
2. Along the pathway: Move houses farther from roads
3. At the household level: Make ppl wear masks, keep windows closed
Environmental hazards are - Answers upstream forces
ex. transportation-> co2 emissions -> pollution
The Lancet commision on Pollution and health - Answers Ppl tend to only focus on acute/immediate
threats and don't seem to recognize chronic illnesses where the cause isn't as obvious
Leading of causes of Death graph: what doesn't it tell us? - Answers 1. When ppl are dying
2. Things other than death (quality of life) -How long have ppl been sick
3. Upstream causes
Key limitations of "how many ppl die of__?" - Answers Doesn't tell when ppl are dying ( child's death
is equal to an old persons)
Key limitations of "how many ppl die from__ and at what age?" - Answers Doesn't tell us how their
quality of life was; doesn't give any info on illnesses that affect us in ways other than death
Best graph: "How many ppl die from___, at what age, how long were they disabled by___ and how
severe was it?" - Answers Still limitations like upstream forces
DALY= YLL (years life lost)+ YDL (years lived w/ disability) - Answers Disability Adjusted Life Years:
Represents dying prematurely and living at a less ideal life
GBD - Answers Global burden of disease
,Counterfactual vs current exposure - Answers Counterfactual represents exposure at an alternate
situation whereas current is teh actual: this can help us imagine an alternate situation with less
exposure
The prevention paradox - Answers The highest risk ppl are a very small group that make up a small
amounts of death whereas the bigger majority have a smaller risk but most of our deaths come from
them
ex. 99% of ppl dont live in ideal air conditions; pollution only gives a small increase risk of death at teh
individual level but thats for teh entire 99%.
GBD still has many things to work on - Answers 1. Certain exposure-outcome relationships
2. Uncertainties in exposure assesments
3. 1-1 pairs don't work on climate change
4. The cut of on a continuous disease
5. Disability weights 9how to assign a proper number to a disability)
Exposure assesment asks - Answers Who's exposed? To what? To how much" for how long? when?
where? etc
Exposure routes: 4. - Answers The way a pollutant get's into us
1. Dermal: through the skin
2. Inhalation: Through respiratory tract
3. Ingestion: Through GI tract
4. Mother-fetus
Exposure pathways - Answers The path a pollutant takes from source to subject
ex. Pollutant emission, movement of pollutant- exposure- dose- effect
How to stop an exposure - Answers must look at pathway to know here to intervene:
ex. Pollutant emission (reduce emissions), Movement of pollutant (taller smoke stack to dilute
pollution), exposure (air cleaners), dose (wear masks), effect (medical intervention)
Purposes of Exposure Assesmnets: - Answers 1. Epidemiology
2. Impact assesmnent
3. Public Health surveillance
4. Evaluating the impact of policy changes or interventions
5. Comparison with exposure regulations or guidelines
3 key ideas in EXposure assesments - Answers 1. Concentrations vary from time to time (ex. day to
day): Temporal variation
2. Concentrations vary from place to place: Spacial variation
3. Ppl move around: Need to know WHERE ppl are at time in place
Why does health research need exposure variation? - Answers Without exposure variation, we won't
know if the exposure has a relationship with health effects-- we won't know the degree of influence of
he disease
Exposure assesments methods: - Answers 1. Direct methods Directly measures exposure
- EX. Personal measures like biomarkers: Organic samples that directly measures the amount of
pollutant (hair, nails, etc)
Trade offs and good: Gives us better estimates, but high demand on participant and costly
2. Indirect methods:
EX. Area measurements, questionaires, models
Trade offs and good: Not as good estimate but cheaper and can sue for a large population
3 keys ideas to epidemiology - Answers 1. Not everyone who's exposed will get the disease
2. Not everyone who has teh disease got it from teh same exposure of interest
3. Correlation isnt teh same as causation
Study designs - Answers Observational studies: Simply analyze and observe like
- cross sectional studies (snapshot studies, assess exposure at only one point in time), cohort studies
(get a group of ppl and follow them to see who get's disease), case-control (get cases and non cases
and go back to see who was exposed), and time
EXperimental studies: Actual experiments
- Natural experiments (take advantage of a natural event to study its effect, randomized control trial
(randomly assign ppl placebos and actual to figure out smth about the disease), Randomized
crossover design (Everyone get's intervention then stops getting it and compares with yourself)
Rekative Risk ratio - Answers Measures the risk of getting disease
, ex. select 102 ppl expose to chemical vs 198 not exposed. There are 27 cases in exposed group and 39
cases in nonexposed: whats RR
Risk in exposed: 27/102= 0.26
Risk in unexposed: 39/198= 0.20
RR is risk exposed/risk unexposed: 0.26/.20= 1.34
This means that there is a 1.34x increase in risk in the expsed group vs unexposed thus, this pollutant
is related to increase chance risk.
Population Attributable Fraction - Answers the proportional reduction in population disease or
mortality that would occur if exposure to a risk factor were reduced to an alternative ideal exposure
scenario
Shifting the Curve - Answers Refers to way we can account for may more people at the tail ends of a
curve that might have the disease if we shift it by a little bit. A small increase in exposure can account
for much more ppl with the disease which is why we need to shift the curve
Synergostic effect - Answers When 2 or more risk factors are together and magnify each other's
effects
ex. Lead and tobacco= way decrease in IQ
precaustionary principle vs Definitive causality - Answers 1. Lack of full scientific evidence won't be a
reason as to why we won't take action- Precautionary measures should be taken even if the exposure
outcome isn't 100%
2. Won'ttake action until there's a definitive relationship with full proof.
Toxicokinetics: ADME - Answers 1. Absorption: Pollutant is absorbed via route
2. Distribution: will be distrubuted in teh body
3. Metabolism: Body will try to break it down into smth more soluble so we can pee it out
4. Excretion: excrete it
Toxic effects - Answers Mortality, Teratogenecity (birth), Carcinogenity, Mutagenity (dna),
Neurotoxity
Dimensions of Toxicity - Answers 1. Target organ and pollutant: Hazardous substances can impact
more than 1 organ
2. The dose: How much have you taken: each substance is a poison at teh right dose, smth healthy
can be bad if taken too much
3. Route of exposure: Some routes are more deadly than others
4. Timing of exposure: timing matters ex ,pregnancy
5. Duration of exposure: chronic vs acute
Threshold and Shape of graph matters - Answers Threshold: Yes vs none is very important: If there is
a threshold then there's an amount that is harmless and we can continue to use substance without
getting bad effects, whiel if theres no threshold then any amount is bad
Shape: Linear vs Curve: if its linear then wherever in the grapgh will be the same severitywhile a curve
shows that the severity is different for where the dose is at
Supralinear Dose-response graph - Answers At low doses, there's a high increase in effects but as
doses continue to rise then effects start to even out. (the intensity of effects depends of where you
are)
- Also called deceleratung relationship where teh initial impact has hugfe health effects but as doses
increase the health risk decreases/slows down
LD50 - Answers Lethal dose 50: the dose that kills 50% of the population
NOAEL - Answers no-observed adverse effects level / highest dose administered that does not show
adverse effects
LOAEL - Answers Lowest Observed Adverse Effect Level, the lowest dose (or concentration) at which
you first start to see an adverse effect
RfD - Answers Reference dose: Usually the NOAEL/Uncertainty
this is the dose that is considered "okay"- we use uncertainty values to be completetly safe and to
have a margin of safety (we don't want to be just at the NOAEL)
4 steps to risk assesment - Answers 1. Hazard identification 2. Exposure assessment 3. Dose-response
assessment 4. Risk Categorization
risk assessment vs risk management - Answers 1. It's really just observing/analyzing and putting
together all teh information regarding risk
2. The action we take to control risk
Definition of Environmental Health - Answers 1. Broad view of the environment: ex. physical, social,
etc
2. Goal is to minimize adverse health effects caused by environmental hazrads
Why is environmental health important? - Answers 1. There are enormous impacts at teh population
level
2. everyone is affected (widespread)
3. Inherently interdiscplinary
4. Overlaps with many fields
5. Small effects at the individual level
--> which makes it difficult
Historically, info about enviromental health came from 2 sources. - Answers 1. Anecdotal
occupational observations; workers would experience a rare disease with unexpected frequency
ex. Chimney workers would have hella lung cancer
2. Disasters/sudden unexpected events that would lead to a negative health impacts
ex. the Mimata disaster; mercury got thrown in the ocean and fish ate it- biomagnification, then
humans ate it and got mercury poisoning
Change in perception of environmental health - Answers in the 1970s:
Due to:
- Publication of Silent spring in 1962: Rachel Carson was a big environemntal health advocate and
wrote about how we need to be more cautious with using pesticides and this led to a global impact of
widespread recognition and concern
- Events at Love Canal: Love Canal was used as dumpster site and as trash accumulated there, toxic
chemicals also started to appear and with homes so close by, many ppl were affected and many had
to be evacuated- events were widely reported
Major Public Health Achievements - Answers 1. Mortality dropped due to better/cleaner drinking
water
2. Decrease in lead in our air
Environnmental risk transition - Answers As countries get more developed (wealth increase),
Household risks will fall (sanitation), community risks with rise then fall (urban pollution) and global
risks will rise (global warming)
Where should we intervene? The pyramid - Answers 1. Elimination: Physically remove hazard
2. Sublimation: Replace hazard
3. Engineering control: Make physical modifications to control hazard
4. Administrative control: Change the way ppl work
5. PPE: Personal Protective Gear (least effective)
Where should we intervene? 3 ways- ex air pollution - Answers 1. At the source: Reduce emissions
(less vehicle mileage)
2. Along the pathway: Move houses farther from roads
3. At the household level: Make ppl wear masks, keep windows closed
Environmental hazards are - Answers upstream forces
ex. transportation-> co2 emissions -> pollution
The Lancet commision on Pollution and health - Answers Ppl tend to only focus on acute/immediate
threats and don't seem to recognize chronic illnesses where the cause isn't as obvious
Leading of causes of Death graph: what doesn't it tell us? - Answers 1. When ppl are dying
2. Things other than death (quality of life) -How long have ppl been sick
3. Upstream causes
Key limitations of "how many ppl die of__?" - Answers Doesn't tell when ppl are dying ( child's death
is equal to an old persons)
Key limitations of "how many ppl die from__ and at what age?" - Answers Doesn't tell us how their
quality of life was; doesn't give any info on illnesses that affect us in ways other than death
Best graph: "How many ppl die from___, at what age, how long were they disabled by___ and how
severe was it?" - Answers Still limitations like upstream forces
DALY= YLL (years life lost)+ YDL (years lived w/ disability) - Answers Disability Adjusted Life Years:
Represents dying prematurely and living at a less ideal life
GBD - Answers Global burden of disease
,Counterfactual vs current exposure - Answers Counterfactual represents exposure at an alternate
situation whereas current is teh actual: this can help us imagine an alternate situation with less
exposure
The prevention paradox - Answers The highest risk ppl are a very small group that make up a small
amounts of death whereas the bigger majority have a smaller risk but most of our deaths come from
them
ex. 99% of ppl dont live in ideal air conditions; pollution only gives a small increase risk of death at teh
individual level but thats for teh entire 99%.
GBD still has many things to work on - Answers 1. Certain exposure-outcome relationships
2. Uncertainties in exposure assesments
3. 1-1 pairs don't work on climate change
4. The cut of on a continuous disease
5. Disability weights 9how to assign a proper number to a disability)
Exposure assesment asks - Answers Who's exposed? To what? To how much" for how long? when?
where? etc
Exposure routes: 4. - Answers The way a pollutant get's into us
1. Dermal: through the skin
2. Inhalation: Through respiratory tract
3. Ingestion: Through GI tract
4. Mother-fetus
Exposure pathways - Answers The path a pollutant takes from source to subject
ex. Pollutant emission, movement of pollutant- exposure- dose- effect
How to stop an exposure - Answers must look at pathway to know here to intervene:
ex. Pollutant emission (reduce emissions), Movement of pollutant (taller smoke stack to dilute
pollution), exposure (air cleaners), dose (wear masks), effect (medical intervention)
Purposes of Exposure Assesmnets: - Answers 1. Epidemiology
2. Impact assesmnent
3. Public Health surveillance
4. Evaluating the impact of policy changes or interventions
5. Comparison with exposure regulations or guidelines
3 key ideas in EXposure assesments - Answers 1. Concentrations vary from time to time (ex. day to
day): Temporal variation
2. Concentrations vary from place to place: Spacial variation
3. Ppl move around: Need to know WHERE ppl are at time in place
Why does health research need exposure variation? - Answers Without exposure variation, we won't
know if the exposure has a relationship with health effects-- we won't know the degree of influence of
he disease
Exposure assesments methods: - Answers 1. Direct methods Directly measures exposure
- EX. Personal measures like biomarkers: Organic samples that directly measures the amount of
pollutant (hair, nails, etc)
Trade offs and good: Gives us better estimates, but high demand on participant and costly
2. Indirect methods:
EX. Area measurements, questionaires, models
Trade offs and good: Not as good estimate but cheaper and can sue for a large population
3 keys ideas to epidemiology - Answers 1. Not everyone who's exposed will get the disease
2. Not everyone who has teh disease got it from teh same exposure of interest
3. Correlation isnt teh same as causation
Study designs - Answers Observational studies: Simply analyze and observe like
- cross sectional studies (snapshot studies, assess exposure at only one point in time), cohort studies
(get a group of ppl and follow them to see who get's disease), case-control (get cases and non cases
and go back to see who was exposed), and time
EXperimental studies: Actual experiments
- Natural experiments (take advantage of a natural event to study its effect, randomized control trial
(randomly assign ppl placebos and actual to figure out smth about the disease), Randomized
crossover design (Everyone get's intervention then stops getting it and compares with yourself)
Rekative Risk ratio - Answers Measures the risk of getting disease
, ex. select 102 ppl expose to chemical vs 198 not exposed. There are 27 cases in exposed group and 39
cases in nonexposed: whats RR
Risk in exposed: 27/102= 0.26
Risk in unexposed: 39/198= 0.20
RR is risk exposed/risk unexposed: 0.26/.20= 1.34
This means that there is a 1.34x increase in risk in the expsed group vs unexposed thus, this pollutant
is related to increase chance risk.
Population Attributable Fraction - Answers the proportional reduction in population disease or
mortality that would occur if exposure to a risk factor were reduced to an alternative ideal exposure
scenario
Shifting the Curve - Answers Refers to way we can account for may more people at the tail ends of a
curve that might have the disease if we shift it by a little bit. A small increase in exposure can account
for much more ppl with the disease which is why we need to shift the curve
Synergostic effect - Answers When 2 or more risk factors are together and magnify each other's
effects
ex. Lead and tobacco= way decrease in IQ
precaustionary principle vs Definitive causality - Answers 1. Lack of full scientific evidence won't be a
reason as to why we won't take action- Precautionary measures should be taken even if the exposure
outcome isn't 100%
2. Won'ttake action until there's a definitive relationship with full proof.
Toxicokinetics: ADME - Answers 1. Absorption: Pollutant is absorbed via route
2. Distribution: will be distrubuted in teh body
3. Metabolism: Body will try to break it down into smth more soluble so we can pee it out
4. Excretion: excrete it
Toxic effects - Answers Mortality, Teratogenecity (birth), Carcinogenity, Mutagenity (dna),
Neurotoxity
Dimensions of Toxicity - Answers 1. Target organ and pollutant: Hazardous substances can impact
more than 1 organ
2. The dose: How much have you taken: each substance is a poison at teh right dose, smth healthy
can be bad if taken too much
3. Route of exposure: Some routes are more deadly than others
4. Timing of exposure: timing matters ex ,pregnancy
5. Duration of exposure: chronic vs acute
Threshold and Shape of graph matters - Answers Threshold: Yes vs none is very important: If there is
a threshold then there's an amount that is harmless and we can continue to use substance without
getting bad effects, whiel if theres no threshold then any amount is bad
Shape: Linear vs Curve: if its linear then wherever in the grapgh will be the same severitywhile a curve
shows that the severity is different for where the dose is at
Supralinear Dose-response graph - Answers At low doses, there's a high increase in effects but as
doses continue to rise then effects start to even out. (the intensity of effects depends of where you
are)
- Also called deceleratung relationship where teh initial impact has hugfe health effects but as doses
increase the health risk decreases/slows down
LD50 - Answers Lethal dose 50: the dose that kills 50% of the population
NOAEL - Answers no-observed adverse effects level / highest dose administered that does not show
adverse effects
LOAEL - Answers Lowest Observed Adverse Effect Level, the lowest dose (or concentration) at which
you first start to see an adverse effect
RfD - Answers Reference dose: Usually the NOAEL/Uncertainty
this is the dose that is considered "okay"- we use uncertainty values to be completetly safe and to
have a margin of safety (we don't want to be just at the NOAEL)
4 steps to risk assesment - Answers 1. Hazard identification 2. Exposure assessment 3. Dose-response
assessment 4. Risk Categorization
risk assessment vs risk management - Answers 1. It's really just observing/analyzing and putting
together all teh information regarding risk
2. The action we take to control risk
