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PH Enviromental > Wk 1 Exposure Assess/toxicol/epi > Flashcards

Wk 1 Exposure Assess/toxicol/epi Flashcards

0
Q

Define exposure assessment

A
  • Determination or estimation-of the magnitude, frequency, duration, and route of exposure
  • Characterization of the exposed population
  • Characterization of uncertainty
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1
Q

Define exposure science

A

The study of human contact with chemical, physical, or biological agents occurring in their environments.

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2
Q

List goals of an exposure assessment

A
  • Understand the role of environmental exposures in the etiology of disease
  • Support risk assessment (do those with higher exposure have greater disease)
  • identifying characterize susceptible populations (children, those that live near a factory/chemical plant)
  • tracking of environmental exposures
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3
Q

Define exposure

A

Concentration of an agent at the external boundary of the human system (levels before entering body)

Examples: concentration of lead in air, concentration of benzo[a]pyrene in grilled steak

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4
Q

Define dose

A

Amount of chemical that crosses barrier and is deposited in the body.
(Inside body)

Examples: blood level, benzoapyrene-albumin adduct, concentration of dioxin in breast milk

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5
Q

Define agent

A

Any chemical, biological, or physical material capable of eliciting a biological response (radon, pesticide)

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6
Q

Define vector and give examples

A

Medium in which agent is found (air, soil, water, food)

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7
Q

Define route

A

Path by which chemical crosses the barrier between external and internal to the body-goes from an exposure to a dose (ingestion, inhalation, Dermal)

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8
Q

Important questions to ask when assessing exposure?

A

Who’s exposed? (workers, elderly, children)

What is the route of exposure? Exposure curve breaking hair, drinking water, dermal contact, congestion?

What is the magnitude of exposure?

What is the frequency and duration of exposure?

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9
Q

Populations at higher risk when exposed?

A

Workers

Child

Infant

Elderly

Someone with underlying disease

Pregnant women

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10
Q

Vectors in routes of exposure for human being?

A

Air-lungs

Food-G.I. tract

Soil-G.I. tract, skin

Water-G.I. tract, skin

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11
Q

List exposure assessment methods

A

Questionnaires

Interviews

Time activity diaries

Environmental measures-air monitoring, drinking water measurements, soil samples, duplicate diet

Biological monitoring

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12
Q

Describe the advantages and disadvantages of different exposure assessment methods

A

Questionnairs-can introduce recall bias, but the low-cost

Interviewers-sometimes recall bias, if well-trained can eliminate a lot of recall bias

Time-activity diaries-in accurate reporting, greater detail

Environmental measures-more accurate, but uncertainty of how much each person was exposed

Biological monitoring-accurate, people and willing to give sample- privacy , things may shop in the blood that they were exposed to from a different source

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13
Q

Explain “the dose makes the poison”

A

“I’ll substances are poisons; there is none that is not a poison. The right dose differentiates between the poison and remedy.” -Paracelsus

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14
Q

Define toxicology

A

The study of adverse effects of agents on living organisms

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15
Q

Define environmental toxicology

A

Study of how environmental exposures present risks to humans and ecosystems

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16
Q

Define dose

A

The amount of agent actually deposited within the body

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17
Q

Define response

A

Reaction or health effect occurring in an organism after exposure to environmental agent

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18
Q

Define a Xenobiotic

A

Foreign material

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19
Q

Define endogenous

A

Produced within an organism, naturally occurring

20
Q

What is toxicokinetics

A

(What your body does to a chemical)

processes of absorption, distribution, metabolism and excretion( ADME )that govern the fate of a Xenobiotic

21
Q

What is toxicodynamics

A

(what a chemical does your body)

Processes of interaction of chemical substances with target sites and the subsequent reactions leading to adverse effects

22
Q

Define each:

Absorption

Distribution

Metabolism

Excretion

A

Absorption; cross barrier between external and internal
(eg air- lungs-alveoli,
food/H2O-G.I. tract-epithelial lining, skin-epithelial cells)

Distribution; circulation via bloodstream

Metabolism; physical and chemical changes of a Xenobiotic within an organism

Excretion; elimination of a compound via urine, feces, sweat, milk, saliva

23
Q

What is LD50?

And is a low LD50 good?

A

LD50-lethal dose that kills 50% of the animals in a trial

The lower the LD50 the more toxic the chemical is (because it kills at a lower dose)

24
What factors affect absorption (in humans)?
Lipid soluble-more easily absorbed Size-smaller or easily absorbed Structural similarity to endogenous molecules Charge/polarity
25
What can cross the blood brain barrier?
Lipid solubile
26
Can toxins cross the placental barrier?
Layers impede distribution of some toxins to fetus
27
Metabolism equals ?
Biotransformation
28
What is Biotransformation's purpose & how is it accomplished?
Purpose: to convert lipid soluble molecules to water soluble molecules Accomplished: through the activity of cellular enzymes
29
Explain phase 1 and phase 2 of biotransformation
Phase 1: add or exposure a functional group (like adding a hitch) Phase 2: conjunction with water-soluble molecule (like adding a trailer)
30
Define bioactivation
The generation of biologically reactive intermediates that may occur during biotransformation. The toxicity of most organic molecules is due to bioactivation. (your body inadvertently makes a chemical harmful)
31
List to reactive intermediates inside the body that are dangerous
Electrophiles (electron deficient)-have a positive charge: look for negative charge DNA and glutathione: have a negative charge ``` Free radicals (Odd or unpaired electrons) can act as a electrophiles-covalently binding ``` Can abstract hydrogen from target molecules Can activate molecular oxygen
32
How did chemicals cause toxicity? There are two toxicology principles name and explain both?
Molecular targets concept -The toxic action of the chemical is a consequence of the physical/chemical interaction of the active form of that chemical with a molecular target with in the living organism Post-response concept -The magnitude of the toxic effect is the function of the concentration of altered molecular targets which, in turn, is related to the concentration of the active form of the toxicant (biological effective dose) at the site where the molecular targets are located
33
Define epidemiology
The study of the distribution and determinants of health, disease, or injury in human populations
34
Define environmental epidemiology
The study of diseases and health conditions occurring in the populations that are linked to environmental factors
35
Examples of environmental epidemiological studies
John snow/ cholera/broad Street Pump
36
Two classes of epidemiological studies and descriptions of each
Descriptive-describes occurrences of disease with respect to persons, place, and time variables Analytic/inferential--examines casual (ideological) hypothesis regarding the association between exposures and health conditions
37
List the three kinds of analytic epidemiological study designs
Cross-sectional Case-control Cohort
38
Explain: a case-control study
Had to disease case is different from nondisease (controls) with respect to prior exposure history? Compare frequencies of exposure among cases and controls Start with one sick population and one healthy population
39
Pros and cons of case-control study
Pros: good for Rare diseases Quicker Less expensive than cohort Can examine multiple exposures for a single outcome Cons; BUT...Not good for rare EXPOSURE Can't be sure of temporal relationship between exposure and disease
40
Pros and cons of cohort study
Pro: Strongest study design Multiple outcomes for a single exposure Good for rare exposures no temporal ambiguity Cons: Expensive May require a large population and long follow-up period
41
Explain a cohort study
- Investigators record who is exposed and who isn't and record who develops disease - Can establish that the exposure proceeds the disease-no temporal ambiguity - Expensive, may require a large population and along follow-up.
42
Define causality.
A causal association must exist between an agent factor and disease in the host for there to be causality.
43
What is the criteria that needs to be taken into account in the assessment of a causal relationship between factor A and disease B
Hills criteria of causality: Strength Consistency-consistently seen in multiple kinds of studies? Specificity-alternative explanations? Temporality-exposure proceed disease? Or vice versa? Biological gradient-dose response(high, med, low) Plausibility-is a plausible? Coherence- do we see similar results in lab or an animal studies?
44
Define and give an example of bias
Deviation of results or inferences from the truth, or processes leading to such deviation. -Trending collection, analysis, interpretation, publication, or review of data that can lead to the conclusion that are systematically different from the truth. Example: recall bias in pesticide use in parents of children with leukemia-parents with kids who were sick will remember info about exposure differently
45
What is a confounder?
"A hidden variable" that could mistakenly lead you to believe that an exposure is associated with the outcome. It is associated with the exposure It is associated with the outcome It is NOT a result of exposure
46
An example of a confounder
Observational studies show a positive association between ice cream sales and the level of violent crimes. does that mean ice cream causes crime? Ice cream is a compounder - violent crime increases when the weather warms up - people also want to eat ice cream when the weather warms up Remember correlation is not causation
47
Limitations of epidemiological studies
Long latency. Infrequent occurrence of certain diseases Difficulties in exposure assessment Nonspecific FX Co-exposures
48
Strength of epidemiological studies
Direct relevance to the human population Includes genetic diversity and variability in other endogenous factors inherent human populations Can identify etiologic agents Can identify areas for control and prevention

PH Enviromental (10 decks)

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