Risk, Toxicology, & Human Health Miller Chapter 11

Risk What is Risk? Definition: the possibility of suffering harm from a hazard that can cause injury, disease, economic loss, or environmental damageDefinition: the possibility of suffering harm from a hazard that can cause injury, disease, economic loss, or environmental damage RISK = EXPOSURE x HARMRISK = EXPOSURE x HARM Expressed in terms of probabilityExpressed in terms of probability

Risk Assessment Involves:Involves: –Identifying real/potential hazard –Determining the probability of its occurrence –Assessing how much damage it could cause

Risk Management Making decisions about:Making decisions about: –How serious it is in comparison to other risks? –How much the risk should be reduced? –How can reduction be accomplished? –How much money to allocate to reduction of risk? More difficult & controversial than risk assessment b/c of lack of info & economic, health, & political implicationsMore difficult & controversial than risk assessment b/c of lack of info & economic, health, & political implications

Trade Offs What are trade offs?What are trade offs? –Sometimes to lessen one risk you have increase another type of risk. –Ex #1: Spraying for mosquitoes –Ex #2: Chlorinating water

Types of Hazards Cultural  unsafe working conditions, smoking, poor diet, drugs/alcohol, driving, unsafe sex, povertyCultural  unsafe working conditions, smoking, poor diet, drugs/alcohol, driving, unsafe sex, poverty Chemical  from soil, air, water, & foodChemical  from soil, air, water, & food Physical  ionizing radiation, fire, flooding, natural disastersPhysical  ionizing radiation, fire, flooding, natural disasters Biological  pathogens, pollen, allergens, harmful insects and animalsBiological  pathogens, pollen, allergens, harmful insects and animals

FACT: Annually, 40% of the world’s deaths are caused by environmental factors (Malnutrition, cooking fires, smoking, skin cancer, etc.)

Toxicology Toxicity  how harmful a substance isToxicity  how harmful a substance is Depends on:Depends on: –Dose  amount inhaled, ingested, exposed to –How often the exposure occurs –Age of the individual –How well the body’s detox systems work –Genetic makeup of individual

“All substances are poison; there is none which is not a poison. The right dose differentiates a poison from a remedy.” »Philippus Paracelsus (1540’s)

A substance’s harm is affected by: Solubility  water soluble (water supply) or oil/fat soluble (tissues)Solubility  water soluble (water supply) or oil/fat soluble (tissues) Persistence  resistance to breakdownPersistence  resistance to breakdown Bioaccumulation  storage in tissues at higher levels than expectedBioaccumulation  storage in tissues at higher levels than expected Biomagnification  magnification of toxins as they pass through food chainsBiomagnification  magnification of toxins as they pass through food chains Chemical interactions  decreases or magnifies effects of a toxinChemical interactions  decreases or magnifies effects of a toxin

Biomagnification

Biomagnification

Any Chemical Can Be Toxic Which is more poisonous: caffeine or trichloroethylene (dry cleaning fluid)?Which is more poisonous: caffeine or trichloroethylene (dry cleaning fluid)? Caffeine – 50 times normal daily dose can be fatalCaffeine – 50 times normal daily dose can be fatal Vitamins A and D can also kill you in high enough doses.Vitamins A and D can also kill you in high enough doses.

What is a Poison? Definition: a chemical with an LD 50 of 50 mg or less per kg of body weight.Definition: a chemical with an LD 50 of 50 mg or less per kg of body weight. What is LD 50 ? (this should be review!)What is LD 50 ? (this should be review!) –Median lethal dose: the amount of a chemical received in one dose that kills exactly 50% of the animals in a test population within a 14-day period

Typical Dose-Response Curve

Remember: some individuals will die at lower doses and some will be able to take very high doses with little or no harm.

ToxicityCategory LD50 (mg/kg) Probable Lethal doses for 70 kg adult Examples Super Toxic <0.01 <1 drop Botulin, Nerve gas, Aflatoxin Extremely Toxic <5 < 7 drops Cyanide, Vitamin D, Nicotine Very Toxic drops – 1 oz Codeine, DDT, Caffeine Moderately Toxic oz – 1 pint Aspirin, Salt, Speed Slightly Toxic pint – 1 qt Ethanol, Lysol Practically Nontoxic >15000 > 1 qt Sugar, Water

Chemical Hazards Toxic Chemicals  substances that are fatal to more than 50% of LD 50 at given concentrationsToxic Chemicals  substances that are fatal to more than 50% of LD 50 at given concentrations Examples: benzene (found in gasoline), arsenic, hydrogen cyanideExamples: benzene (found in gasoline), arsenic, hydrogen cyanide

Hazardous ChemicalsHazardous Chemicals –Flammable/ explosive –Irritating/ damaging to skin or lungs –Interfere/ prevent O2 uptake or distribution –Induces allergic reactions Examples: oven cleaner, CO, H2SExamples: oven cleaner, CO, H2S

Mutagens Cause mutations in DNACause mutations in DNA If occurs in egg or sperm cells, can cause:If occurs in egg or sperm cells, can cause: –Bipolar disorder –Cystic fibrosis –Down Syndrome –Hemophilia Most mutations are harmless since there are repair mechanisms in DNAMost mutations are harmless since there are repair mechanisms in DNA Examples: ionizing radiation, nitrous acidExamples: ionizing radiation, nitrous acid

Teratogens Chemicals, radiation, or virusesChemicals, radiation, or viruses Cause birth defects while embryo is still growing & developingCause birth defects while embryo is still growing & developing Examples: PCBs, thalidomide, steroid hormones, arsenic, lead, mercuryExamples: PCBs, thalidomide, steroid hormones, arsenic, lead, mercury

Carcinogens Chemicals, radiation, or viruses that cause the growth of a malignant tumorChemicals, radiation, or viruses that cause the growth of a malignant tumor Spread by metastasis  cells break off tumor & spread to other parts of body via body fluidsSpread by metastasis  cells break off tumor & spread to other parts of body via body fluids Late onset of symptomsLate onset of symptoms Sources: Cigarette smoke (30-40%), diet (20-30%), occupational exposure (5-15%), environmental pollutants (1-10%)Sources: Cigarette smoke (30-40%), diet (20-30%), occupational exposure (5-15%), environmental pollutants (1-10%)

Neurotoxins Attack nerve cells (neurons)Attack nerve cells (neurons) Examples: chlorinated hydrocarbons (DDT, dioxins), organophosphate pesticides, formaldehyde, industrial solvents (toluene, xylene)Examples: chlorinated hydrocarbons (DDT, dioxins), organophosphate pesticides, formaldehyde, industrial solvents (toluene, xylene)

Disease in Developed & Developing Countries Nontransmissible Diseases:Nontransmissible Diseases: –Not caused by living organisms –Examples: Cardiovascular disordersCardiovascular disorders Most cancersMost cancers DiabetesDiabetes AsthmaAsthma MalnutritionMalnutrition Incidence expected to increaseIncidence expected to increase

Transmissible Diseases Cause by a living organism & can be spreadCause by a living organism & can be spread Ex: bacteria, protozoa, viruses, parasitesEx: bacteria, protozoa, viruses, parasites Pathogens  infectious agents spread by air, water, body fluids, food, & by human or insect vectorsPathogens  infectious agents spread by air, water, body fluids, food, & by human or insect vectors

Acute vs. Chronic Acute effectsAcute effects –caused by exposure to a single dose Chronic effects –develop slowly due to long term exposure