Risk and Risk and Toxicology Toxicology Chapter 19 Chapter 19 The Ebola virus causes a The Ebola virus causes a form of hemorrhagic fever, form of hemorrhagic fever, and was first recognized in and was first recognized in Africa in 1976. The virus Africa in 1976. The virus is transmitted through is transmitted through direct person-to-person direct person-to-person contact and is one of the contact and is one of the most virulent viruses most virulent viruses known, with a mortality known, with a mortality rate usually over 90%. TEM. rate usually over 90%. TEM.
Transcript
Risk and ToxicologyRisk and Toxicology
Chapter 19Chapter 19
The Ebola virus causes a form of The Ebola virus causes a form of hemorrhagic fever, and was first hemorrhagic fever, and was first recognized in Africa in 1976. The recognized in Africa in 1976. The virus is transmitted through direct virus is transmitted through direct person-to-person contact and is one person-to-person contact and is one of the most virulent viruses known, of the most virulent viruses known, with a mortality rate usually over with a mortality rate usually over 90%. TEM.90%. TEM.
TOXICITY AND HEALTHTOXICITY AND HEALTH
A toxin is any substance that is inhaled, ingested, or absorbed at sufficient A toxin is any substance that is inhaled, ingested, or absorbed at sufficient dosages that it damages a living organism, and the dosages that it damages a living organism, and the toxicity toxicity of a toxin is of a toxin is the degree to which it is biologically harmful. Almost any substance that 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 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 is present in large enough quantities—even water. In order for a substance to be harmful, all of the following must be considered:to be harmful, all of the following must be considered:
Dosage amount over a period of timeDosage amount over a period of time
Number of times of exposureNumber of times of exposure
Size and/or age of the organism that is exposedSize and/or age of the organism that is exposed
Ability of the body to detoxify that substanceAbility of the body to detoxify that substance
Organism's sensitivity to that substance (due, for example, to genetic Organism's sensitivity to that substance (due, for example, to genetic predisposition, or previous exposure)predisposition, or previous exposure)
Synergistic effect Synergistic effect
more than one substance combines to cause a toxic effect that's greater than any one more than one substance combines to cause a toxic effect that's greater than any one componentcomponent
Five major factors can affect the harm caused by a Five major factors can affect the harm caused by a substance.substance.
a.a. SolubilitySolubility. Water-soluble toxins can move throughout the environment. . Water-soluble toxins can move throughout the environment. Oil- or fat-soluble toxins (generally organic compounds) can penetrate Oil- or fat-soluble toxins (generally organic compounds) can penetrate the membranes surrounding an organism’s cells and accumulate in the membranes surrounding an organism’s cells and accumulate in the body.the body.
b.b. PersistencePersistence of a substance is also important. Some substances resist of a substance is also important. Some substances resist breakdown and remain in the environment a long time and can have breakdown and remain in the environment a long time and can have long-lasting harmful effects.long-lasting harmful effects.
c.c. BioaccumulationBioaccumulation is a third factor. Molecules are absorbed and stored is a third factor. Molecules are absorbed and stored in the body at higher than normal levels.in the body at higher than normal levels.
d.d. BiomagnificationBiomagnification is where toxins accumulate at greater levels as they is where toxins accumulate at greater levels as they are moved up from one trophic level to the next higher one.are moved up from one trophic level to the next higher one.
e.e. Chemical interactionsChemical interactions can decrease or multiply the harmful effects of a can decrease or multiply the harmful effects of a toxin. An antagonistic interaction reduces the harmful effect, while a toxin. An antagonistic interaction reduces the harmful effect, while a synergistic interaction multiplies the harmful effectssynergistic interaction multiplies the harmful effects
Bioaccumulation within speciesBioaccumulation within species
Biomagnification within the food chainBiomagnification within the food chain
Substances are usually tested for Substances are usually tested for toxicity using a toxicity using a dose-response dose-response analysisanalysis. In a dose-response . In a dose-response analysis, an organism is exposed to analysis, an organism is exposed to a toxin at different concentrations, a toxin at different concentrations, and the dosage that causes the and the dosage that causes the death of the organism is recorded. death of the organism is recorded.
The information from a set of organisms The information from a set of organisms is graphed and the resulting curve is graphed and the resulting curve referred to as a referred to as a dose-response dose-response curvecurve. The dosage of toxin it takes to . The dosage of toxin it takes to kill 50 percent of the test animals is kill 50 percent of the test animals is termed termed LD50LD50, and this value can be , and this value can be determined from the graph. determined from the graph.
A high LD50 indicates that a substance A high LD50 indicates that a substance has a low toxicity, while and a low has a low toxicity, while and a low one indicates high toxicity. A one indicates high toxicity. A poisonpoison is any substance that has an LD50 is any substance that has an LD50 of 50 mg or less per kg of body of 50 mg or less per kg of body weight. weight.
Dose-Response Curve
What is Toxicity? How is it Measured?What is Toxicity? How is it Measured?
Types of dose-response curvesTypes of dose-response curvesThe dosage at which a negative effect occurs is referred to as the The dosage at which a negative effect occurs is referred to as the threshold threshold dosedose. Two more terms you should know for the test are . Two more terms you should know for the test are acute effectacute effect and and chronic effectchronic effect. An acute effect is an effect caused by a short exposure to a . 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 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 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.example of this would be long-term exposure to lead paint in a house.
What have we been exposed to?What have we been exposed to?
There are There are threethree major types of potentially toxic agents. major types of potentially toxic agents.
a.a. MutagensMutagens are chemicals or ionizing radiation that cause or increase the are chemicals or ionizing radiation that cause or increase the frequency of random mutations in the DNA molecules. It is generally frequency of random mutations in the DNA molecules. It is generally accepted that there is no safe threshold for exposure to harmful mutagens.accepted that there is no safe threshold for exposure to harmful mutagens.
b.b. TeratogensTeratogens are chemicals that cause harm or birth defects to a fetus or are chemicals that cause harm or birth defects to a fetus or embryo. Alcohol and thalidomide are examples of teratogens.embryo. Alcohol and thalidomide are examples of teratogens.
c.c. CarcinogensCarcinogens are chemicals or ionizing radiation that cause or promote are chemicals or ionizing radiation that cause or promote cancer. cancer.
Major Pollution Events (Disasters):Major Pollution Events (Disasters):
Bhopal
Times Beach (dioxin)
Love Canal
Exxon Valdez (Alaska) , BP Gulf Oil Spill(Alaska) , BP Gulf Oil Spill
Chernobyl, Japan's Nuclear Reactor Disaster after 2011 Quake, Japan's Nuclear Reactor Disaster after 2011 Quake
More Recent:More Recent:
Amazon Crude (Chevron) –– 60 seconds –– Politics of Pollution
China’s cost of growthChina’s cost of growth
Table 9-1 Toxicity Ratings and Average Lethal Doses for Humans
Toxicity Rating
Supertoxic
Extremely toxic
Very toxic
Toxic
Moderately toxic
Slightly toxic
Essentially nontoxic
LD50 (milligrams perkg 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
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
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
*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
PathogensPathogensAn infection is the result of a pathogen invading our body, and An infection is the result of a pathogen invading our body, and diseasedisease occurs when occurs when the infection causes a change in the state of health. For example, HIV, the virus that 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 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 before it causes a change in the state of health; in the form of the disease called AIDS.AIDS.
There are five main categories of pathogens.There are five main categories of pathogens.• • Viruses (and other subcellular infectious particles, such as prions)Viruses (and other subcellular infectious particles, such as prions)• • Bacteria - Bacteria - Anthrax• • FungiFungi• • Protozoa – Protozoa – Malaria -Lifecycle• • Parasitic worms – Parasitic worms – Examples
Top Ten Killer GermsTop Ten Killer Germs
PathogensPathogens are bacteria, virus, or other microorganisms that can cause disease. are bacteria, virus, or other microorganisms that can cause disease. Pathogens can attack directly or via a carrier organism (called a Pathogens can attack directly or via a carrier organism (called a vectorvector). One ). One example of a pathogen that relies on a vector is the bacteria that causes Rocky 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, Mountain spotted fever; it is within the bodies of ticks, and when ticks bite humans, the bacteria is injected and causes the disease.the bacteria is injected and causes the disease.
The degree of likelihood that a person will The degree of likelihood that a person will become ill after exposure to a toxin or become ill after exposure to a toxin or pathogen is called pathogen is called riskrisk.. Many Many environmental, medical, and public environmental, medical, and public health decisions are based on health decisions are based on potential risk. potential risk.
Calculating risk is referred to as Calculating risk is referred to as riskrisk assessmentassessment, and , and risk managementrisk management uses strategies to reduce the amount uses strategies to reduce the amount of risk. The public health department of risk. The public health department is an organization that makes use of is an organization that makes use of risk assessment and management; for risk assessment and management; for example, they decide who can receive example, they decide who can receive the flu shot each year.the flu shot each year.
If the risk of getting the flu is high for a If the risk of getting the flu is high for a particular year, most of the population particular year, most of the population is encouraged to have the shot; is encouraged to have the shot; however, if the risk seems small or the however, if the risk seems small or the predicted flu stains are mild, only older predicted flu stains are mild, only older people and the immunocompromised people and the immunocompromised are advised to have the flu shot.are advised to have the flu shot.
