Terrestrial Pollution/Human Health

Human Health and the Environment

  • Pollutants can have both direct and indirect impacts on the health of organisms, including humans.

  • It can be difficult to establish a cause and effect between pollutants and human health issues because humans experience exposure to a variety of chemicals and pollutants.

  • Dysentery is caused by untreated sewage in streams and rivers.

  • Mesothelioma is a type of cancer caused mainly by exposure to asbestos.

    1. What are the types and characteristics of major groups of pollutants in environmental toxicology?

    2. Why is there controversy and concern about synthetic organic compounds such as dioxin?

Bioaccumulation and Biomagnification

  • Bioaccumulation is the selective absorption and concentration of elements or compounds by cells in a living organism, most commonly fat-soluble compounds.

  • Biomagnification is the increase in concentration of substances per unit of body tissue that occurs in successively higher trophic levels of a food chain or in a food web.

  • Some effects that can occur in an ecosystem when a persistent substance is biomagnified in a food chain include eggshell thinning and developmental deformities in top carnivores of the higher trophic levels.

  • Humans also experience harmful effects from biomagnification, including issues with the reproductive, nervous, and circulatory systems.

  • DDT, mercury, and PCBs are substances that bioaccumulate and have significant environmental impacts.

    1. How do the processes of bioaccumulation and biomagnification work and why are they important in toxicology?

    2. How is bioaccumulation different from biomagnification?

    3. How did Rachel Carson contribute to the study of toxicology?

    4. Why did Rachel Carson title her book Silent Spring?

    5. What are some environmental effects of bioaccumulation and biomagnification?


  • Lethal dose 50% (LD50) is the dose of a chemical that is lethal to 50% of the population of a particular species.

  • A dose response curve describes the effect on an organism or mortality rate in a population based on the dose of a particular toxin or drug.

  1. What is LD50? Why is LD50 important to toxicology?

  2. What is the dose-response concept and how does it relate to LD-50, TD-50, LC-50, ED-50, ecological gradients, and tolerance?

  3. What is the importance of the threshold effect of environmental toxins?

Infectious Disease

  • Pathogens adapt to take advantage of new opportunities to infect and spread through human populations.

  • Specific pathogens can occur in many environments regardless of the appearance of sanitary conditions.

  • As equatorial-type climate zones spread north and south in to what are currently subtropical and temperate climate zones, pathogens, infectious diseases, and any associated vectors are spreading into these areas where the disease has not previously been known to occur.

  • Poverty-stricken, low-income areas often lack sanitary waste disposal and have contaminated drinking water supplies, leading to havens
    and opportunities for the spread of infectious diseases.

    1. Why are infectious diseases more prevalent/problematic in developing countries?

    2. How can climate change increase the range of infectious diseases?

  • Plague is a disease carried by organisms infected with the plague bacteria. It is transferred to humans via the bite of an infected organism or through contact with contaminated fluids or tissues.

  • Tuberculosis is a bacterial infection that typically attacks the lungs. It is spread by breathing in the bacteria from the bodily fluids of an infected person.

  • Malaria is a parasitic disease caused by bites from infected mosquitoes. It is most often found in sub-Saharan Africa.

  • West Nile virus is transmitted to humans via bites from infected mosquitoes.

  • Severe acute respiratory syndrome (SARS) is a form of pneumonia. It is transferred by inhaling or touching infected fluids.

  • Middle East Respiratory Syndrome (MERS) is a viral respiratory illness that is transferred from animals to humans.

  • Zika is a virus caused by bites from infected mosquitoes. It can be transmitted through sexual contact.

  • Cholera is a bacterial disease that is contracted from infected water.