Environmental Health and Toxicology

Environmental Health, Pollution, and Toxicology

• People often believe that natural soil, water, and air are good, but human activities can contaminate them.
• An example of a natural disaster is the Lake Nyos tragedy in Cameroon in 1986, where a massive release of CO2 from the lake killed animals and 1800 people.

Basic Concepts

• Disease: An impairment of an individual's well-being and ability to function due to a poor adjustment between the individual and the environment.
• Pollution: An unwanted change in the environment caused by the introduction of harmful materials or production of harmful conditions.
• Contamination: Making something unfit for a particular use by introducing undesirable materials.
• Toxin: A substance that is poisonous to living things.
• Toxicology: The science that studies toxins or suspected toxins.

Carcinogens and Synergism

• Carcinogen: A toxin that increases the risk of cancer.
• Synergism: The interaction of different substances resulting in a total effect that is greater than the sum of the effects of the different substances.
• Examples of synergism include the combination of sulfur dioxide and coal dust particles, which causes greater damage to the lungs when inhaled together.

Measuring Pollution

• Units used to express the abundance of pollutants/toxins in the environment differ widely, including ppm (parts per million), ppb (parts per billion), mg/L (milligrams per litre), and µg/L (micrograms per litre).

Categories of Pollutants

• Environmentally Transmitted Infectious Diseases (e.g., Legionnaires' disease, Salmonella, Cholera, Malaria, Anthrax)
• Toxic Heavy Metals (e.g., Mercury, Lead, Cadmium, Nickel, Gold, Platinum, Silver, Bismuth, Arsenic, Selenium, Vanadium, Chromium, Thallium)
• Organic Compounds (e.g., Synthetic organic compounds used for pest control, pharmaceuticals, food additives)
• Persistent Organic Pollutants (POPs) (e.g., DDT, Atrazine, Dioxins)
• Hormonally Active Agents (HAAs) (e.g., Atrazine)
• Nuclear Radiation
• Thermal Pollution
• Particulates (e.g., dust, asbestos)
• Noise Pollution

Toxic Heavy Metals

• Biomagnification: The accumulation or increasing concentration of a substance in living tissue as it moves through the food web.
• Body Burden: The amount of concentration of a toxic chemical, especially radionuclides, in an individual.
• Examples of toxic heavy metals include Cadmium, Lead, Mercury, which can accumulate in fatty body tissue and cause health hazards.

Dose-Response and Toxic Pathways

• Dose-response: The principle that the effect of a chemical on an individual depends on the dose or concentration of that chemical.
• ED-50: The effective dose that causes an effect in 50% of the population on exposure to a particular toxicant.
• TD-50: The toxic dose defined as the dose that is toxic to 50% of the population exposed to a toxin.
• LD-50: A crude approximation of a chemical's toxicity defined as the dose at which 50% of the population dies on exposure.

General Effects of Pollutants

• Threshold Effects: A level below which effects are not observable and above which effects become apparent.
• Acute and Chronic effects:
  • Acute effect: One that occurs soon after exposure, usually to large amounts of pollution.
  • Chronic effect: Occurs over a long period, often from exposure to low levels of a pollutant.
• Tolerance: The ability to withstand stress resulting from exposure to a pollutant or other harmful condition, including behavioural, physiological, and genetic tolerance.

This quiz covers environmental health, pollution, and toxicology, including human activities and their impact on the environment, as well as natural events like the Lake Nyos disaster.