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 that could 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

Risk Assessment 4 steps 1. Identification of the hazard 2. Dose-Response assessment 3. Exposure assessment 4. Risk characterization

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

Toxic Heavy Metals Travel through toxic pathways Biomagnifications: the accumulation or increase in concentration of a substance in living tissue as it moves through a food web.

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

General Effects of Pollutants - 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 Individuals differ in their response to chemicals Dose-Response Curve: - LD-50 - ED-50 - TD-50 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 Acute and Chronic Effects

Precautionary Principle The idea that in spit 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

Risks and Hazards Risk in a PRA (probablistic risk assessment) is defined as a feasible detrimental outcome of an activity or action. In a PRA, risk is characterized by two quantities: the magnitude (severity) of the possible adverse consequence(s), and the likelihood (probability) of occurrence of each consequence.

In the estimation of the risks, three or more steps are involved, requiring the inputs of different disciplines: Hazard Identification, aims to determine the qualitative nature of the potential adverse consequences of the contaminant (chemical, radiation, noise, etc.) and the strength of the evidence it can have that effect Dose-Response Analysis, is determining the relationship between dose and the probability or the incidence of effect (dose-response assessment). Exposure Quantification, aims to determine the amount of a contaminant (dose) that individuals and populations will receive. This is done by examining the results of the discipline of exposure assessment. As different location, lifestyles and other factors likely influence the amount of contaminant that is received, a range or distribution of possible values is generated in this step.exposure assessment Finally, the results of the three steps above are then combined to produce an estimate of risk. Because of the different susceptibilities and exposures, this risk will vary within a population.