Environmental Science Notes on Aquatic and Terrestrial Pollution

Learning Goals

  • LG 53-1: Explain how dose-response curves are used to estimate lethal doses of chemicals.

  • LG 53-2: Identify how we estimate potential harm of chemicals in the environment.

  • LG 53-3: Describe the major philosophies of regulating chemicals in the environment.

LG 53-1: Dose-Response Curves and Lethal Doses of Chemicals

  • Dose-Response Studies:

    • Evaluates how different concentrations of chemicals affect living organisms.

    • Include observations of various responses such as mortality, behavioral changes, and reproductive impacts.

  • Types of Studies:

    • Acute Studies: Examines effects of short-term exposure to a chemical.

    • Chronic Studies: Investigates effects of long-term exposure to a chemical.

  • Toxicity Measurement:

    • LD50 (Lethal Dose 50%): Quantity of a substance that kills 50% of a population; a key indicator of chemical toxicity.

    • Chemicals with lower LD50 values are more toxic.

  • Effectiveness and Safety Measurements:

    • ED50 (Effective Dose 50%): Dose that results in a harmful effect in 50% of the population, which is not lethal.

    • NOEL (No Observed Effect Level): Highest concentration of a chemical that shows no observed lethal or sublethal effects.

  • Safety Margin Calculation:

    • A safe concentration may be computed by dividing the LD50 by 10.

LG 53-2: Estimating Potential Harm of Chemicals

  • Risk Analysis Steps:

    1. Risk Assessment: Identifying the potential hazards and evaluating their risk.

    2. Risk Acceptance: Determining how much risk is acceptable, a subjective measure that can vary.

    3. Risk Management: Implementing strategies to minimize risks, involving trade-offs (e.g., energy production vs. radiation risks from nuclear energy).

  • Environmental Hazard:

    • Any entity in the environment that can potentially cause harm.

  • Risk Assessment Equation Insight:

    • The likelihood of rare high-risk events can be equivalent to frequent low-risk events in terms of potential harm.

LG 53-3: Major Philosophies of Regulating Chemicals

  • Innocent-until-Proven-Guilty Principle:

    • A potential hazard should not be regarded as active without sufficient scientific evidence of danger.

  • Precautionary Principle:

    • Advocates for preemptive action when a hazard's potential is plausible, even without conclusive evidence of harm.

  • International Agreements:

    • Stockholm Convention (2001):

    • 127 nations agreed to phase out or manage 12 harmful chemicals (the "dirty dozen"), including various pesticides (e.g., DDT) and industrial chemicals (e.g., PCBs).

    • REACH (2007):

    • The European Union established regulations on chemical safety involving registration, evaluation, authorization, and restrictions, following the precautionary principle.

    • The number of chemicals regulated under these agreements has increased over the years, emphasizing the evolving nature of chemical regulation.

  • sublethal effects: those that impair an organism’s behavior, physiology, or reproduction.