Hazards and human health

• Infectious disease is caused by a pathogen entering the body and multiplying in cells and tissues, examples include bacteria, viruses, and parasites
• Bacteria are single-cell organisms that multiply rapidly on their own, with most being harmless
• Viruses invade a cell, replicate themselves throughout the body, and can cause diseases like flu and AIDS
• Parasites live in or outside organisms and feed on them, causing diseases like malaria
• Transmissible diseases can be transmitted from one person to another, while non-transmissible diseases do not spread between individuals
• An epidemic occurs when there is a large-scale outbreak in an area or country, while a pandemic is a worldwide spread of a disease
• Infectious diseases are favored by warmer climates due to climate change, providing better breeding grounds for them
• Antibiotics kill bacteria but are becoming less effective as bacteria develop genetic immunity to them
• Superbugs: are bacteria that resist all available antibiotics, posing a significant challenge in treatment
• Risk is the probability of suffering harm from a hazard that can cause injury, disease, death, economic loss, or damage
• Risk assessment uses statistical methods to estimate how much harm a particular hazard has on human health or the environment
• Risk management involves deciding whether and how to reduce a risk to a certain level, and at what cost
• ED50= effective dose for 50% of a test population
• TD50=toxic dose for 50% of a test population
• Threshold Level of Toxicity=minimum dose required to produce a toxic effect
• LD50= Lethal dose for 50% of a test population (important step for determining toxicity)
• Animal to Human Factor for infectious diseases:

  1. push of suburban development
  2. hunting wild game
  3. international trade of wild species
  4. industrialized meat production
• Safe drinking water prevents infectious diseases
• Toxic chemical: element or compound that can cause temporary or permanent harm or death to humans (arsenic lead, mercury, vinyl chloride, PCB's)
• The 3 Major Types of Chemical Hazards:

  1. Carcinogens: chemicals, some types of radiation and certain viruses that can cause/promote cancer
  2. Mutagens: chemicals or forms of radiation that cause or increase the frequency of mutations in the DNA
  3. Teratogens: chemicals that cause or harm birth defects in a fetus or embryo
• PCBs: liver cancer and other cancers, underweight, low IQ babies, neurological damage, growth problems.

  (found almost everywhere)
• Long term exposure can: disrupt immune and nervous system
• Immune system: specialized cells and tissues that protect the body by forming antibodies
• Antibodies: specialized proteins
• Nervous system damage caused by neurotoxins: behavioral changes, learning disabilities, ADD, paralysis, death
• Biological magnification: it continues to exist in the environment, the spread of the toxin becomes cyclical
• Endocrine system:

  • glands release hormones
  • hormones have shape
  • shape attaches to receptor
  • transmits chemical message
• HAAs or endocrine disruptors: Synthetic chemicals have similar shapes, attach to the natural hormone, and disrupt endocrine system
• Toxicology: Study of the harmful effects of chemicals on humans how other organisms
• Toxicity: Measure of the ability of a substance to cause injury, illness, or death to a living organism
• Critical Question: At what level of exposure to a particular toxic chemical will the chemical cause harm?
• Dose: that amount of a harmful chemical a person has injected, absorbed, etc. at any one time
• Genetic makeup: determines that persons sensitivity to a chemical, can be multiple chemical sensitivity
• Fetuses, infants, children: experience more harmful effects
• Oil and fat soluble toxins slip through the cell membrane
• Persistence: how easily the chemical breaks down, the harder they are to break down, the more harmful they are.
• Acute effect: immediate, rapid, harmful reaction
• Chronic effect: permanent, long-lasting consequence
• Dose Response Curve: The higher the dose, the greater the response
• Non threshold dose-response curve: any dosage of toxin causes harm