Aquatic and Terrestrial Pollution Notes - 8.12 to 8.15

LD50 and Dose Response Curve

Studies that expose an organism to different doses of concentrations of a chemical in order to measure the response (effect) of the organism

• independent variable - the concentration of the chemical added to food, water, or air

• dependant variable = the response measured in the organizam (usually death or impairment)

LD50

stands for "lethal dose 50" and refers to the amount of a substance that is estimated to be lethal to 50% of the test population in order to determine the toxicity level of a substance.

Data is usually expressed as:

• mass/body unit mass

• ppm (parts per million) in air

• mass/volume (in water or blood)

Dose Response Curve

illustrates the relationship between the dosage or concentration of a substance and its effect on an organism, population, or ecosystem.

Graphed with percent mortality or after effect on y axi and dose concentration of chemical on x axis

Dose Response Studies

scientific investigations that assess the relationship between the dose of a substance and the extent of the biological response it produces

• not tested on humans, as data from other mammals are used to simulate human toxicity

• LD50 or ED50 ÷ 1000 = max allowable level for humans

Threshold or Toxicity Threshold

The threshold level refers to the lowest dose or concentration at which an adverse effect begins to occur. Below this level, there may be no observable impact on organisms.

• effects includes paralysis, cancer, or death

ED50

Stands for “effective dose 50” and refers to he dose concentration of a toxin or chemical that causes a non-lethal effect in 50% of the population being tested

• effects include infertility, paralysis, and cancer

Routes of Exposure

Ways that pollutants get exposed to or enter the human body.

• Lead - water pipes and paint chips

• mercury - seafood (tuna)

• CO - indoor biomass combustion

• PM - pollen, dust, ash, etc

• Arsenic - rice and groundwater

Synergism

The interaction of two or more substances to the cause and effect greater than each of them individually

• ex. Lung cancer from asbestos with lung damage from smoking

• makes it especially hard to pinpoint exact effects of a specific pollutant on humans

Pathogens

microorganisms, such as viruses and bacteria, that take advantage of humans as hosts and can lead to disease. They invade the body and disrupt normal bodily functions, leading to illness.

• virus, bacteria, fungus, protists, or worms

• ex. HIV, Ebola, COVID-19

Vectors

Organisms, often mosquitoes and ticks, that transmit pathogens from one host to another.

• ex. malaria, lyme disease, bubonic plague

Infectious Disease and Development

Less developed, poorer countries typically have higher rates of infectious diseases due to

• less sanitary waste disposal

• less access to healthcare

• lack of water treatment and filtration