Chapter Outline – Chapter 8 – Environmental Health and Toxicology
I. Risk, Probability, and Hazards
Risks and hazards—some avoidable, some not—compromise everyday life. A.
A risk is a measure of your likelihood of suffering harm from a hazard. 1.
Such a hazard may cause injury, disease, economic loss, or environmental damage. 2. Risk assessment is projected as a probability: a mathematical statement about how likely it is that harm will result from a hazard. It gives the estimate of an event’s actually happening. 3. Risk management involves deciding whether or how to reduce a particular risk to a certain level and at what cost. B.
There are four major types of hazards.
One major hazard is a cultural hazard, such an unsafe working conditions, smoking, poor diet, drugs, unsafe sex, poverty, criminal assault, etc. 2.
Chemical hazards are harmful chemicals in the air, water, soil, and food. 3.
Physical hazards include radioactivity, fire, earthquake, floods, etc. 4. Biological hazards come from pathogens, pollen, other allergens, and animals such as bees and poisonous snakes.
II. Toxicology: Assessing Chemical Hazards
A. Harm from chemical exposure depends on the amount of exposure (dose), frequency of exposure, which chemical is exposed, the body’s detoxification system, and one’s genetic makeup. 1. Toxicity measures how harmful a substance is in causing injury, illness, or death to a living organism. Several factors to consider are: a. dose, the amount of a substance a person is exposed to, b. frequency of exposure,
c. age and size of the individual exposed,
d. the health of the body’s detoxification system, and e. the genetic makeup of the individual, which is also important for determining sensitivity to a toxin. 2. Five major factors can affect the harm caused by a substance. a. Solubility. Water-soluble toxins can move throughout the environment. Oil- or fat-soluble toxins (generally organic compounds) can penetrate the membranes surrounding an organism’s cells and accumulate in the body. b. Persistence of a substance is also important. Some substances resist breakdown and remain in the environment a long time and can have long-lasting harmful effects. c. Bioaccumulation is a third factor. Molecules are absorbed and stored in the body at higher than normal levels. d. Biomagnification is where toxins accumulate at greater levels as they are moved up from one trophic level to the next higher one. e. Chemical interactions can decrease or multiply the harmful effects of a toxin. An antagonistic interaction reduces the harmful effect, while a synergistic interaction multiplies the harmful effects. 3. The effects of a chemical can be chronic or acute. An acute effect is immediate; a chronic effect is a long-lasting consequence from exposure to a harmful substance. The type and amount of health damage from exposure to a chemical is called the response. B. In toxicology, any synthetic/natural chemical can be harmful if a large enough quantity is ingested. Therefore, it is critical to determine the amount of exposure that produces a harmful response. 1. The critical question is: How much exposure to a particular toxic chemical causes a harmful response? It is different for each individual. 2. The body has three major mechanisms for reducing the harmful effects of some chemicals. a. It can break down, dilute, or excrete small amounts of most toxins to keep them from reaching harmful levels. b. Certain enzymes can sometimes repair damage to DNA and protein molecules. c. Cells in certain parts of the body (skin, gastrointestinal tract, lungs, and blood vessels) can reproduce fast enough to replace damaged cells. C. Trace levels of toxic chemicals in human bodies or in the environment may be benign or harmful; it depends on the...
Please join StudyMode to read the full document