Environmental Health, Pollution and Toxicology Chapter 15 Environmental Health, Pollution and Toxicology

Terminology Pollution: introduces harmful materials or produces harmful conditions to the environment - introduced through a) Point Sources: b) Area Sources: c) Mobile Sources: Contamination: making something unfit for a particular use through the introduction of undesirable material Toxicology: the science that studies chemicals known to be toxic Carcinogen: a type of toxin that increases the risk of cancer Synergism: the interaction of different substances resulting in a total effect greater than the sum of the effects of the separate sources

Measuring Pollutants Measuring depends on the substance Common Units ppm: Parts per million ppb: Parts per billion Micrograms per cubicle meter (measures air)

Categories of Pollutants Infectious Agents Toxic Heavy Metals Organic Compounds Radiation Thermal Pollution Particulates Asbestos Electromagnetic Fields Noise Pollution Voluntary Exposure

Infectious Agents Spread from the interactions between individuals and food, water, air, or soil Greatest mortality in developing countries Examples: Legionnaires' disease Giardiasis Salmonella Malaria

Toxic Heavy Metals Mercury, lead, cadmium, nickel, arsenic... Travel through toxic pathways Biomagnification: the accumulation or increase in concentration of a substance in living tissue as it moves through a food web. “Body burden”: accumulation of heavy metals in the body

Mercury and Minamata, Japan Vinyl chloride factory Mercury released in waste (inorganic) Bacteria converted to organic compound absorbed faster and retained longer (fish)

Mercury and Minamata, Japan Illustrates four major factors that must be considered in evaluating and treating toxic environmental problems: individual responses pollutant may have a threshold effects may be reversible ecological and biological processes can alter pollutant

Organic Compounds Organic Compounds: composed of carbon Synthetic Organic Compounds: used in industrial processes Persistent Organic Pollutants: Synthetic organic compounds often containing chlorine, that do not easily break down in the environment. Hormonally Active Agents: Chemicals in the environment able to cause reproductive and developmental abnormalities in animals

Thermal Pollution Heat released into water or air that produces undesirable effects Sudden to long-term Natural and human induced (electric power plants – major source) Impacts: DO concentrations, spawning; disease susceptibility; physical stress Cooling towers, artificial lagoons

Particulates Dust, soot, asbestos fibers Natural dust storms; fires; volcanic eruptions Human activities farming; oil and coal combustion

Asbestos Term for several minerals that take the form of small, elongated particles or fibers Industrial use fire prevention; insulation

Electromagnetic Fields (EMF) Electric motors, transmission lines; appliances Fields drop off quickly with distance Some indication that MF may cause problems

Noise Pollution increases exponentially as a power of 10 Unwanted sound Travels as waves Logarithmic increases exponentially as a power of 10 Pitch, frequency and length determine environmental effects

Voluntary Exposure Tobacco, alcohol and drugs Various results, but end result is the degradation of mind and body

General Effects of Pollutants on Wildlife Populations - Changes in Abundance - Changes in Distribution - Changes in Birth Rates - Changes in Death Rates - Changes in Growth Rates

Concept of Dose and Response The effect of a certain chemical on an individual depends on the dose (dose response) Individuals differ in their response to chemicals Dose-Response Curve: - LD-50 (Lethal) - ED-50 (Effective) - TD-50 (Toxic) Threshold Effects: - the level below which effects are not observable and above which effects become apparent

Ecological Gradients Changes in vegetation with distance from a toxic source Tolerance: The ability to resist or withstand stress resulting from exposure to a pollutant or harmful condition - Behavior vs. Physiological - Genetic Acute and Chronic Effects

Risk Assessment Four steps: 1. Identification of the hazard Investigate the population; test on animals; study at molecular level on cells 2. Dose-Response assessment Relationship between dose and effect 3. Exposure assessment Evaluate the intensity, duration and frequency of human exposure 4. Risk characterization Rank risks in terms of magnitude of the potential environmental health problem that might result from exposure

Precautionary Principle The idea that in spite of the fact that full scientific certainty is often not available to prove cause and effect, we should still take cost-effective precautions to solve environmental problems where there exists a threat of potentially serious and/ or irreversible environmental damage