Lecture 10 Thresholds and Risk Flashcards
What is risk?
Risk is the probability of an adverse outcome base on its exposure and severity of the hazardous event
Risk = exposure x hazard
What are people’s perception of risk?
Less control -> more fear Less knowledge (observable) -> more fear
What is risk analysis?
Uses qualitative (effect of toxicant, likelihood of event), and quantitative data (length of exposure, host susceptibility/biological variability) to help with rational decision making.
What is the Delaney Clause?
Clause prohibited adding chemicals that were found to be carcinogenic to lab animals or humans into foods.
What is risk assessment?
Systematic scientific evaluation of potential adverse health effects resulting from human exposures to hazardous agents or situations.
- Hazard identification
- Dose response
- Exposure - level, frequency, duration
- Risk characterisation
Why might we need to extrapolate from high doses?
Response from high doses may be what is available in terms of experimentally observed data. Not controversial that high doses causes adverse event
Why is extrapolation from high doses of carcinogens at times questionable?
High doses change toxicokinetics of carcinogen
May alter or overwhelm DNA repair mechanisms
Produce irritation/inflammation
What is NOAEL?
No Observed Adverse Effect Level
Highest dose that produced no significant adverse effect. Has to actually be a tested data point.
Often used as reference dose for risk assessment calculations
TRUE OR FALSE: NOAEL can be considered as risk-free?
FALSE! NOAEL still carries some risk.
What LOAEL?
Lowest Observed Adverse Effect Level
Lowest dose that still produced a significant adverse effect. Has to actually be a tested data point.
What is ADI and how is it calculated?
Acceptable daily intake of chemical which during an entire lifetime appears to be without appreciable risk.
ADI = NOAEL / (UF * MF)
UF = 10. Uncertainty factor, allows for interspecies differences (between animal model and human)
MF = 10. Modifying factor, allows for intraspecies differences (human-human)
What is Relative Risk Reduction?
1 - (event rate intervention group / event rate control group)
What is Absolute Risk Reduction?
Event rate control group - Event rate intervention group
Expressed as %
How do we calculate the Number Needed To Treat?
100/ARR
How many patients need to be exposed in order to prevent 1 event (extent of benefit)
How do we calculate the Number Needed To Harm?
100/Absolute Risk Increase %
How many patients need to be exposed for 1 adverse event to occur.
