Midterm Deck: Sessions 1-7 Flashcards
What is considered the purview of environmental epi?
Anything external to your skin about which you have no autonomous choice
Pros to dietary surveys (6)
- ecological overview of consumption vs. crop growth
- easy to do
- cheap to do
- individual level data
- culturally appropriate
- Can play with info over the life course
Cons to dietary surveys (3)
- Recall bias (cases and controls remember exposure differently)
- Measurement error
- Social desirability bias
Pros to crop sampling (4)
- Valid lab data
- Geographical breadth
- Cheap
- Easy
Cons to crop sampling (5)
- Lab Analyses can be expensive
- Could have lab error
- Timing Issues
- Can be ecologic and not specific
- Doesn’t take into account food prep or storage
Pros to Biomarkers (3)
- Know bioeffective does
- Gold standard for exposure
- Good quantitative data
Cons to Biomarkers (8)
- Expensive
- Complicated (logistically)
- Ethically questionable
- Invasive (may lead to participant selection bias)
- Timing may affect sampling (level of biomarker may shift in sample over time)
- Measurement Error
- Batch Effects/Freeze/Thaw bias
- Construct problem
What were the three primary exposure sampling methods used to deconstruct the afflatoxin story?
- food intake/dietary survey
- Biomarker Sampling
- Crop Sampling
How does afflatoxin cause cancer?
o Afflatoxin causes cancer by covalently binding to Guanine in DNA as it turns a nonwater soluble compound into a water soluble compound. → afflatoxin dna adduct → so afflatoxin causes cancer bc it damages dna and causes a mutation.
• Gene P53 is mutated in ½ of all cancer patients; it’s a key gene in cell replicatin. If P53 is damaged, it’s a key step in carcinogenesis
• Mutations in P53 and Mutations in guanine in codon 249 were often linked to afflatoxin contamination.
Construct Validity Problem - what is it, and where do we see it?
Construct validity is “the degree to which a test measures what it claims, or purports, to be measuring.”
So, for biomarker tests, you have to be careful that your test is actually measuring what you think it measures…ie. afflatoxin presence in urine may mean that u metabolize it better…not that you’ve eaten more of it… so you have to be careful about what your measurement is actually telling you in environmental epi.
Latency Period
Def: period of time between onset and diagnosis
o Can involve years or decades → must often assess historical exposures
o Exposures that occur during the latency period may not be relevant → is important to know the natural progression of disease
Name 4 nuances of exposure assessment
1) Latency
2) Incomplete Data
3) Exposure Metric
4) Interactions
Describe “Nuances of exposure assessment” # 1:
Latency: is the period of time between onset and diagnosis
• Can involve years or decades → must often assess historical exposures
• Exposures that occur during the latency period may not be relevant → is important to know the natural progression of disease
Describe “Nuances of exposure assessment” #2:
Incomplete Data
often individual level data is not available, must often work with indexes or exposure scales (job title; proximity to a source)
Describe “nuances of exposure assessment” #3
Exposure Metric Variation:
mean vs. cumulative (i.e. cig pack years over time) vs. peak (acute, when damage only happens above a certain threshold) vs. lagged (exposure today doesn’t impact disease risk tomorrow, it impacts disease risk years form now) exposure
Describe “nuances of exposure assessment” #4:
Interactions
Failure to consider interactions can hide relationships…as interactions can have effect modification on outcomes (ie a given level of exposure has a different effect if you do/do not have another issue). Interactions can take place amongst genetic susceptibility, age, and concurrent disease, etc.
Why is it key to take interactions into account when assessing exposure?
This is key because protections should be set up to help the most vulnerable (i.e. those impacted by interactions), not the average person (so if old people are impacted by an exposure more than young, that should be taken into account)
8 ways to assess exposure amounts
o 1) Environmental Monitoring o 2) Environmental Modeling o 3) Questionnaires and Job Records o 4) Biomarkers o 6) The Exposome o 7) Complex Mixtures o 8) Enviroment Wide Association Studies (EWAS)
Environmental Monitoring Represents & Requires…
• Represents exposure level but not dose absorbed by the individual
• Monitoring is expensive, and requires expert assistance in set-up, quality control, and analyses
* Must make sure the monitoring system is aesthetically and culturally appropriate for the study population.
Ambient Air monitoring is usually… ?
• Ambient is usually for a zone or room while micro-environments might be more important
Personal air monitoring can place ….?
• Personal monitoring can place a high burden on participants and is usually only a snap shot
Occupational routine air monitoring nuances
• In Occupational settings routine monitoring is often non-random & is only in “trouble spots” or “high” areas (so you don’t have a good idea of true exposure)
General Air monitoring stations can…?
• Air monitoring stations can provide ecological data but is often not sited randomly (or placed in the most useful spots)
4 Types of Environmental Modeling
Dispersion Models
Interpolation Models
Land Use Regression
Kriging