Week 6: Risk Assessment and Management

Risk Assessment

1. Hazard Identification

2. Dose-assessment

3. Exposure assessment → risk characterization

…leads into risk management

Risk Management

5. Risk evaluation

6. Risk perception and communication

7. Control of exposure

8. Risk monitoring

Risk Analysis

• The process oof analyzing the possible health effects on people of exposure to substances and other potential hazards

• typically involves toxicology and/or epidemiology

Hazard Identification

Known substance: heavy use of toxicological and epidemiological evidence

unknown substance event: health hazard evaluation: (particular problem) or hazard audit (determine potential hazards)

General vs occupational environments: Former much harder to assess unless records of past (industrial activity)

eg. Love canal

Hazard Identification and Toxicology

• Determine dose-response relationship

• Threshold or non-threshold? (suspected carcinogens usually) assumed to have non-threshold curve

• hard to classify invisible hazards

NOAEL vs LOAEL

NOAEL: no observed adverse effect level

• Threshold dose

LOAEL: lowest observed adverse effect level

• How back-cast from actual doses administered?

• What are implications of choosing “C” as acceptable daily intake value

Acceptable Daily Intake (ADI)

ADI = NOAEL (or LOAEL) divided by UF

• eg. para-dichlorobenzene - tremors and liver effects

• NOAEL: 150mg/kg, 5 days a week sub chronic rat study

• Assume no human data (UF 100) and ADI based on acute (non chronic) toxicology study (UF 10)

• ADI (70kg per person) = (150mg/kg * 70kg)* (5 days divided 7 days/week) divided by (100* 10)

  = 7.5 mg/ person/day

What is ADI

the amount of a substance you can consume daily over your lifetime without a significant risk of harm. Its calculated using experimental data on animals or humans, with safety factors (uncertainty factors, UF) to account for differences between animals and humans

Uncertainty factor (uf)

• differences between animals and humans (eg. 10)

• variations among humans

Final ADI

ADI = 7.5mg/person/day meaning, a 70kg person can safely consume up to 7.5 mg of para-dichlorobenzene per day without adverse affects

• this process ensures safety with a large margin of error, accounting for both the differences between species and variability among humans

TDI values

Tolerable daily intakes of environmental chemicals

• values per kg

Why does lead have separate values for adult and child?

lead has a separate tolerable daily intake (TDI) values for adults and children because children are more sensitive to lead exposure than adults due to physiological and developmental differences

Why lead?

1. Body weight

   • children have lower body weight

2. Developing nervous system

3. Absorption differences

4. Increased vulnerability

total dose/ external dose

• total amount of substance through all routes of exposure

• amount to which body exposure

absorbed dose

• Amount that enters body

Target organ dose

• Amount that gets to specific (vulnerable) organ systems

• Most important, existing toxicological data needed

Traditional vs modern methods

Traditional

• drinking water to test it

• traditional methods are still being used

Modern

• Lab techniques

Why do many epidemiologic studies only measure environmental concentration instead of absorbed doses, and what are the implications of this approach?

• Many epidemiologic studies measure environmental concentrations (eg. level in air, water, or soil) instead of absorbed doses because measuring absorbed doses requires more complex, invasive, and expensive methods, such as biological sampling and detailed analysis.

• Measuring environmental concentrations is easier and provides a conservative estimate of exposure, ensuring risks are not underestimated

Exposure analysis… are direct methods better?

Direct: We can see direct results and evidence

• Gives more accurate measures

Indirect: Interviews will be subjective

Why direct methods are better:

1. accuracy

2. specificity

3. revelance to health

however…

• maybe be more costly, time-consuming and invasive

Exposure assessments

• In absence of local/survey based values, standard intake values may be used

• How/why might individual values vary substantially?

Daily routines are different etc.

Risk characterization/ Risk estimation

• based on lifetime exposure (70yrs)

  eg. 1.3 pCi/L of radon, lifetime 2 in 100 people could get lung cancer

• any regulation of radon should consider this the baseline risk

Risk Management: What is it, Why is it important?

• The process of taking action to reduce or eliminate hazards, or at least the harms they cause

Risk evaluation

• compare to standards (legally binding) or guidelines (not legally binding)

• eg., benzene: WHO drinking water standard is 0.01 mg/L health Canada estimates average Canadian water source has 0.001 mg/L

• absence of dose/response much more difficult

Risk perception

• Subjectively assessed threat of harm

• Individuals/groups often disagree about the threat of harm (e.g. experts vs laypeople)

• Precursor to good risk communication

• studied by social scientists - predictors of threat evaluations

Perception of risk

• Everyone is exposed to all hazards equally (but many are difficult to avoid entirely). People tend to feel others are more at risk than themselves across a range of hazards

• perceptions change considering public vs personal risk

  • also varies based on exposure and personal experience

  • eg. Flying may be more of a perceived risk, if you are a person that flys more

Risk perception and accountability

Hazard risks are more acceptable if they are perceived to:

• voluntary vs imposed

• control vs uncontrol