Lect 4 Risk Assessment - ENSC

Environmental Toxicology and Chemical Risks

• Lecture 4: Risk Assessment and Regulation

• Instructor: Louise M. Winn, Ph.D.

• Location: Botterell Hall RM 557

• Contact: winnl@queensu.ca

The Environmental Movement

• Rachel Carson's "Silent Spring" (1962)

  • Exposed hazards of pesticide DDT.

  • Catalyzed public rejection of DDT.

• Impacts:

  • Regulation of acceptance of chemicals.

  • Environmental assessment of potential damage.

Regulatory Response

• Definition: Regulation is a principle, rule, or condition that governs behavior of citizens and organizations.

  • Used by governments to achieve public policy objectives.

  • Serves as a form of law with general applicability.

• Importance of Regulation:

  • Impacts virtually every aspect of life including toxic substances.

  • Ideally guided by scientific research.

  • Influenced by social and economic factors.

  • Goal: Establish safe limits.

Federal Acts and Regulations

• At least 31 Federal Acts concerning:

  • Pest control products.

  • Radioactive materials/nuclear waste.

  • Hazardous material transportation.

  • Environmental protection.

  • Environmental assessments.

  • Fisheries.

• Notable Legislation: CEPA, 1999 - Protection of human health and the environment.

Understanding Risk

• Components:

  • Hazard: The ability to cause adverse effects.

  • Receptor: The entity exposed to the hazard.

  • Exposure: Interaction/contact with the hazard.

• Risk: The probability that the hazard will result in adverse effects.

Risk Assessment

• An established process, originally created for insurance claims and now widely used by various professions (e.g., firefighters, economists).

• Purpose: Establish a degree of safety, ideally in quantitative terms.

Risk Assessment for Toxic Substances

• Focuses on estimating the probability of adverse events and effects.

Methods of Assessing Risk

• Human Health Risk Assessment (HHRA)

• Environmental Risk Assessment (ERA)

• Risk Assessments can be:

  • Predictive (planned release)

  • Retroactive (existing condition)

• Key Differences between HHRA and ERA:

  • Scope

  • Assessment endpoints

  • Receptors

  • Toxicological data

Environmental Risk Assessment

• Evaluates likelihood of harmful effects from exposure to a substance.

• Considers direct and indirect effects based on scientific measurements and judgments.

Environmental Risk Assessment Framework

• Key Components:

  1. Problem formulation

  2. Exposure assessment

  3. Exposure-response assessment

  4. Risk characterization

• Involves multiple parties:

  • Risk assessors

  • Risk managers

  • Stakeholders

1. Problem Formulation

• Initial planning and scope definition through:

  • Collection of information

  • Hazard identification

  • Substance characterization

  • Structure-activity relationship (SAR) analysis

  • Toxicity and epidemiology evidence

  • Identification of sensitive receptors

  • Conceptual model

2. Exposure Assessment

• Necessary to quantify or estimate exposure levels:

  • Properties of the substance

  • Fate and transformation

  • Spatial and temporal dimensions

  • Duration and frequency of exposure

  • Measurement in environmental compartments

  • Body burden and tissue residues

3. Exposure-Response Assessment

• Examines dose/concentration versus response:

  • Utilizes toxicological data

  • Employs experimental methods

  • Considers species, life stages, and endpoints

4. Risk Characterization

• Evaluates toxicity and potential adverse effects:

  • Summary of methodologies, data, and assumptions

  • Estimates the likelihood of adverse effects as a ratio.

  • Example ratio interpretation:

    • 
      

      1 indicates adverse effects expected.

    • < 1 indicates no expected adverse effects.

Uncertainty in Evaluations

• Identifies sources of uncertainty:

  • Information gaps

  • Extrapolations and assumptions

• Recommended approach: Set a 100x fold safety factor for human risk assessments.

Addressing Uncertainty

• Approaches include:

  • Safety factors

  • Precautionary principle

  • Weight of evidence

  • Professional judgement

Post-Risk Assessment Actions

• Risk Management/Decision:

  • Risk communication with risk managers post-assessment.

  • Types of decision outcomes:

    • Insufficient information: no risk estimation.

    • Low risk: generally no action required.

    • Moderate/high risk: necessary actions to manage risk.

Implementation of Risk Management

• Management methods must consider:

  • Economic factors

  • Public health implications

  • Social/political context.

• Management options to reduce risk:

  • Control measures

  • Substitution of materials

  • Informing stakeholders

• Examples:

  • Containment

  • Product reformulation

  • In situ treatment

  • Active monitoring

Uses of Environmental Risk Assessment

• Applicable for:

  • Regulation of releases

  • Restoration of contaminated sites

  • Management of past releases

  • Permitting processes

  • Setting monetary damages under "polluter pays" principle.