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.