Toxicology and Human Health

1. Toxicology and Human Health Module 8 Lesson 5 Notes

2. Biological Risks • Infectious diseases – those caused by infections agents, called pathogens • Examples: pneumonia and venereal diseases • Chronic disease – slowly impairs the functioning of a person’s body • Examples: heart disease and most cancers • Acute diseases – rapidly impair the functioning of a person’s body • Example: Ebola hemorrhagic fever By Offiikart (Own work) [CC0], via Wikimedia Commons

3. Risk Factors for Chronic Diseases in Humans in Low- Income Countries -In low-income countries, the top 10 risk factors leading to chronic disease are associated with poverty, including unsafe drinking water, poor sanitation, and malnutrition. -Nearly half of the children under the age of 5 who die from pneumonia do so because they suffer from poor nutrition.

4. Risk Factors for Chronic Diseases in Humans in High - Income Countries -In high-income countries the people can afford better nutrition and proper sanitation so fewer young people die from diseases such as pneumonia and diarrhea. -Risk factors – increased tobacco use (#1), less active lifestyles, poor nutrition, overeating – leads to high blood pressure and obesity

5. What Are Non-transmissible Diseases? Non-transmissible disease: not caused by living organisms and does not spread from one person to another Example: heart and blood disorders, asthma, malnutrition Image from: https://www.cdc.gov/heartdisease/facts.htm

6. What Are Transmissible Diseases? • Transmissible Disease: caused by living organisms (bacteria, parasite, etc.) and can be spread from person to person • Pathogens: infectious agents-spread by air, water, food, body fluids, some insects, etc.

7. Top 7 Deadliest Infectious Diseases • Acute respiratory infection (pneumonia, flu) • AIDS (virus) • Diarrheal diseases (bacteria and virus) • Tuberculosis (bacteria) • Malaria (parasite) • Hepatitis B (virus) • Measles (virus)

8. What are Carcinogens? • Carcinogens: chemicals, radiation, or viruses that cause the growth of a cancerous (malignant) tumor—cells multiply uncontrollably and may spread by metastasis to other parts of the body • Cigarette smoke, occupational exposure, environmental pollutants, inheritance

9. What are Mutagens? • Mutagens: agents that cause random mutations (changes) in DNA. • Example: mutations in sperm or egg cells can be passed on and cause bipolar disorder, cancer, hemophilia, Down Syndrome, etc. Most mutations are harmless (DNA repair enzymes)

10. What are Teratogens? • Teratogens: chemicals, radiation, or viruses that cause birth defects during the first 3 months of pregnancy • Thalidomide – prescribed to women for morning sickness in the 1950s and 60s, resulted in birth defects. • Excessive alcohol consumption in during pregnancy results in fetal alcohol syndrome. Other examples: PCBs, steroid hormones, heavy metals (lead, mercury) Image from: Otis Historical Archives National Museum of Health and Medicine. (NCP14053) [CC BY 2.0

11. What are neurotoxins? • Chemicals that disrupt the nervous system of animals. • Insecticides are often neurotoxins that affect an insects ability to control nerve impulses. • Lead and mercury can damage a person’s brain and nervous system.

12. What Are Allergens? • Chemicals that cause an allergic response. • Examples include: • Some chemicals naturally found in peanuts and milk • Several drugs such as penicillin and codeine

13. What are Endocrine Disruptors? • Chemicals that interfere with the normal functioning of the hormones in an animals body. • Examples: pollution from animal rearing facilities, hormones from human birth control pills found in residential sewage, and some pesticides that mimic animal hormones. • Endocrine disruptors are leading to the increasing number of fish, reptiles, and amphibians that have males with low sperm counts or have testes that produce eggs. • In humans endocrine disruptors affect production of testosterone in males and can lead to low sperm counts. In women they increase risk of breast cancer.

14. Dose-Response Studies • Expose animals or plants to different amounts of a chemical and then observe a variety of possible responses including mortality or changes in behavior and reproduction. • LD50- lethal dose that kills 50% of the individuals • Important for assessing the relative toxicity of a chemical • ED50- effective dose that causes 50% of the animals to display the harmful but nonlethal effect • Sublethal Effect

15. Bioaccumulation • When an individual organism accumulates chemicals in their tissues, like fatty tissues, over time. • Examples: Methyl mercury, DDT

16. Biological Magnification • The chemicals that accumulate in the organisms tissues through bioaccumulation are then taken in to other organisms as they eat in the food chain. • At each trophic level the amount of the chemical increases (magnifies). • The top predator will have a higher concentration of the chemical than the primary consumers. Therefore there are more harmful affects to the top predator.

17. DDT • This is a classic example of biological magnification. • It was the first major synthetic pesticide and was widely used. • Small amounts introduced to the ecosystem made their way up the trophic levels, increasing as they moved up. • Birds that were top predators like peregrine falcons, bald eagles, and ospreys were affected. Their eggshells were thinning which affected their reproductive success.

18. Biological Magnification Image from: Biologycorner.com - Creative Commons Attribution-NonCommercial 3.0 Unported License.