Toxicology

• Risks of exposure to toxins:
• Toxins can have ecological, environmental, or human health impacts
• Chemicals or radiation that cause DNA mutations
• Can cause cancer or birth defects
• Organisms that cause disease can be bacterial (TB) or viral (Covid)
• Commonly referred to as "infectious diseases" that can spread easily in a population (epidemics or pandemics)
• Many are "vector borne" because they are spread by insects like mosquitoes (malaria) or plague (fleas)
• Viral treatments: vaccines, Bacterial treatments: antibiotics or vector control
• Carcinogens:
• Chemicals, radiation, or viruses that cause cancer
• Course Connections: UV Rays (depletion of ozone layer), HPV causes cervical cancer, Benzene from gasoline, Smoking/Indoor fires
• Endocrine Disrupters:
• Chemicals that disrupt the function of hormones, leading to reproductive harm
• Course Connections: Pesticides (DDT), Plastics (BPA)
• Neurotoxins (Brain Damage):
• Heavy metals like Lead and Mercury can cause brain damage
• Hg from burning coal, Pb from gas additives, paints, and lead pipes
• Methyl-Mercury (Hg) damages the nervous system, including coordination and the senses of touch
• Lead (Pb) causes development issues and kidney damage, especially dangerous for kids
• Persistent Toxins (Forever Chemicals):
• Chemicals that do not biodegrade in living systems like DDT, Mercury, and BPA's
• These chemicals "bioaccumulate" in living tissue and "biomagnify" in food webs
• Top predators get the highest dose and see the main physiological harm
• Measuring Toxicity:
• Threshold Level of Toxicity - "Dose" at which the first "response" is detected
• Response can be higher heart rate, body temperature, or anything physiological
• Measuring Toxicity LD-50:
• LD50 is the amount of a chemical that is required in one dose to kill 50% of the test population in 14 days
• The smaller the LD50, the more toxic the chemical
• LD-50 of 10mg per kilogram of body weight is more toxic than LD-50 of 50mg per kilogram of body weight
• Chemicals (poisons) are rated according to their Lethal Dose Value
• Physiology is the study of how organisms function and respond to changes in their environment
• Different organisms have different physiologies, but all living organisms have a "Range of Physiological Tolerance" for environmental factors
• The range of tolerance describes how much environmental change can occur before the organism becomes stressed and dies
• Biological hazards are generally pathogens or vectors that cause or spread disease
• Chemical hazards include indoor air pollutants like cigarette smoke and substances like Benzene, a known human carcinogen
• Physical hazards include radiation, nuclear materials, earthquakes, and tidal waves (tsunamis)
• Risk Assessment involves 4 steps:

  • Hazard Identification: Determines if the hazard is chemical, physical, or biological and its potential to cause cancer or illness
  • Dose-Response: Determines at what dose a physiological response occurs, such as neurological damage from Mercury (Hg)
  • Exposure Assessment: Determines if exposure to an environmental hazard will be acute or chronic
  • Risk Analysis: Evaluates the risks vs benefits in terms of human health and the economy
• The Precautionary Principle suggests assuming a large risk until all risks associated with exposure to something are known