1. Risk and Toxicology Chapter 19
The Ebola virus causes a form of hemorrhagic fever, and was first recognized in Africa in The virus is transmitted through direct person-to-person contact and is one of the most virulent viruses known, with a mortality rate usually over 90%. TEM.

2. Dosage amount over a period of time Number of times of exposure
TOXICITY AND HEALTH
A toxin is any substance that is inhaled, ingested, or absorbed at sufficient dosages that it damages a living organism, and the toxicity of a toxin is the degree to which it is biologically harmful. Almost any substance that is inhaled, ingested or absorbed by a living organism can be harmful when it is present in large enough quantities—even water. In order for a substance to be harmful, all of the following must be considered:
Dosage amount over a period of time
Number of times of exposure
Size and/or age of the organism that is exposed
Ability of the body to detoxify that substance
Organism's sensitivity to that substance (due, for example, to genetic predisposition, or previous exposure)
Synergistic effect
more than one substance combines to cause a toxic effect that's greater than any one component

3. Five major factors can affect the harm caused by a substance.
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.
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.
Bioaccumulation is a third factor. Molecules are absorbed and stored in the body at higher than normal levels.
Biomagnification is where toxins accumulate at greater levels as they are moved up from one trophic level to the next higher one.
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

4. Bioaccumulation within species
Biomagnification within the food chain

5. What is Toxicity? How is it Measured?
Substances are usually tested for toxicity using a dose-response analysis. In a dose-response analysis, an organism is exposed to a toxin at different concentrations, and the dosage that causes the death of the organism is recorded.
The information from a set of organisms is graphed and the resulting curve referred to as a dose-response curve. The dosage of toxin it takes to kill 50 percent of the test animals is termed LD50, and this value can be determined from the graph.
A high LD50 indicates that a substance has a low toxicity, while and a low one indicates high toxicity. A poison is any substance that has an LD50 of 50 mg or less per kg of body weight.
Dose-Response Curve

6. Types of dose-response curves
The dosage at which a negative effect occurs is referred to as the threshold dose. Two more terms you should know for the test are acute effect and chronic effect. An acute effect is an effect caused by a short exposure to a high level of toxin; a snake bite, for example, causes an acute effect. A chronic effect is that which results from long-term exposure to low levels of toxin; an example of this would be long-term exposure to lead paint in a house.
What have we been exposed to?
Industrial Chemicals
Impact of Pesticides - Development
Everyday chemicals – Smoking, asbestos, indoor air pollution “Sick-Building Syndrome”
Examples from the Big Screen:
Civil Action & Erin Brockovich

7. The impact of pesticides on cognitive development

8. There are three major types of potentially toxic agents.
Mutagens are chemicals or ionizing radiation that cause or increase the frequency of random mutations in the DNA molecules. It is generally accepted that there is no safe threshold for exposure to harmful mutagens.
Teratogens are chemicals that cause harm or birth defects to a fetus or embryo. Alcohol and thalidomide are examples of teratogens.
Carcinogens are chemicals or ionizing radiation that cause or promote cancer.
Major Pollution Events (Disasters):
Bhopal
Times Beach (dioxin)
Love Canal
Exxon Valdez (Alaska) , BP Gulf Oil Spill
Chernobyl, Japan's Nuclear Reactor Disaster after 2011 Quake
More Recent:
Amazon Crude (Chevron) – 60 seconds – Politics of Pollution
China’s cost of growth

9. Table 9-1 Toxicity Ratings and Average Lethal Doses for Humans
Supertoxic
Extremely toxic
Very toxic
Toxic
Moderately toxic
Slightly toxic
Essentially nontoxic
LD50 (milligrams per
kg of body weight)*
Less than 0.01
Less than 5
5–50
50–500
500–5,000
5,000–15,000
15,000 or greater
Average Lethal Dose†
Less than 1 drop
Less than 7 drops
7 drops to 1 teaspoon
1 teaspoon to 1 ounce
1 ounce to 1 pint
1 pint to 1 quart
More than 1 quart
Examples
Nerve gases, botulism toxin, mushroom toxins, dioxin (TCDD)
Potassium cyanide, heroin, atropine, parathion, nicotine
Mercury salts, morphine, codeine
Lead salts, DDT, sodium hydroxide, sodium fluoride, sulfuric acid, caffeine, carbon tetrachloride
Methyl (wood) alcohol, ether, phenobarbital, amphetamines (speed), kerosene, aspirin
Ethyl alcohol, Lysol, soaps
Water, glycerin, table sugar
*Dosage that kills 50% of individuals exposed
†Amounts of substances in liquid form at room temperature that are lethal when given to a 70.4-kg (155-pound) human

10. Pathogens
An infection is the result of a pathogen invading our body, and disease occurs when the infection causes a change in the state of health. For example, HIV, the virus that causes the disease AIDS, infects the body and typically has a long residence time before it causes a change in the state of health; in the form of the disease called AIDS.
There are five main categories of pathogens.
• Viruses (and other subcellular infectious particles, such as prions)
• Bacteria - Anthrax
• Fungi
• Protozoa – Malaria -Lifecycle
• Parasitic worms – Examples
Top Ten Killer Germs
Pathogens are bacteria, virus, or other microorganisms that can cause disease. Pathogens can attack directly or via a carrier organism (called a vector). One example of a pathogen that relies on a vector is the bacteria that causes Rocky Mountain spotted fever; it is within the bodies of ticks, and when ticks bite humans, the bacteria is injected and causes the disease.
Hot Zones

11. Anopheles mosquito (vector) in aquatic breeding area
eggs
adult
larva
pupa
1. Female
mosquito bites
infected human,
ingesting blood
that contains
Plasmodium
gametocytes
4. Parasite invades
blood cells, causing
malaria and making
infected person
a new reservoir
2. Plasmodium
develops in
mosquito
3. Mosquito injects Plasmodium
sporozoites into human host

12. Bioterrorism & antibiotic resistant disease

13. The degree of likelihood that a person will become ill after exposure to a toxin or pathogen is called risk. Many environmental, medical, and public health decisions are based on potential risk.
Calculating risk is referred to as risk assessment, and risk management uses strategies to reduce the amount of risk. The public health department is an organization that makes use of risk assessment and management; for example, they decide who can receive the flu shot each year.
If the risk of getting the flu is high for a particular year, most of the population is encouraged to have the shot; however, if the risk seems small or the predicted flu stains are mild, only older people and the immunocompromised are advised to have the flu shot.