Toxicology• Toxicology—measure of how armful a

substance is– Potential harm is dependent on

• Dosage• Bioaccumulation—some molecules are absorbed

& stored in specific organs or tissues at levels higher than normally would be expected

• Biomagnification—levels of some toxins in the environment are magnified as they pass through a food web– DDT, PCBs, & some radioactive isotopes

• Chemical interactions that can decrease or multiply the effects of a toxin

Toxicology

• Antagonistic interaction—reduce the harmful response– Vitamins A & E interact to reduce body’s response

to carcinogens• Synergistic interaction—multiplies harmful

effects– Asbestos increase chances of lung cancer– workers who smoke increase chances of lung

cancer 400x

Toxicology• Poison—chemical that has an LD50 of 50 mg or

less per kg of body weight– LD50—median lethal dose• The amount of chemical that in one dose that kills

exactly 50% of the animals in a test population within a 14 day period

Toxicology

• Toxicity Testing– Dose-response curves—shows the effects of various

dosages of a toxic agent on a group of test organisms• X-axis plot concentration of toxin & y-axis plots response• Usually follows an S-shaped curve

• Epidemiology—study of the patterns of disease or other harmful effects from toxic exposure within defined groups of people to figure out why some people get sick and other do not

Chemical hazards• Toxic chemicals—substances that are fatal to

more than ½ of test animals (LD50) at given concentrations

• Hazardous chemicals—cause harm by being flammable, irritating or damaging to skin or lungs, interfering with oxygen uptake, or inducing allergic reactions

Chemical Hazards

• Mutagens—agents that cause random mutations to DNA molecules– Most mutations are harmless due to repair mechanisms

• Teratogens—chemicals, radiation, or viruses that cause birth defects while the human embryo is growing & developing during pregnancy– PCBs, thalidomide, steroid hormones, arsenic, cadmium, etc.

• Carcinogens—chemicals, radiation, or viruses that cause or promote the growth of malignant tumors in which cells multiply uncontrollably

Chemical Hazards• Effects of Chemicals on Human Body Systems– Immune system—HIV, ionizing radiation, malnutrition, &

synthetic chemicals

– Nervous system—Neurotoxins• Chlorinated hydrocarbons (DDT, PCBs, dioxins)• Organophosphate pesticices• Formaldehyde• Chemicals of arsenic, mercury, lead, & cadmium• Industrial solvents (toluene, xylene)

– Endocrine system—synthetic chemicals called hormonally active agents disrupts effects of hormones

Biological Hazards• Nontransmissible Diseases—not caused by

living things & do not spread from person to person– Cardiovascular diseases, cancers, diabetes, etc

• Transmissible diseases—caused by living things and can be spread from person to person

Biological Hazards

• Pathogens are spread via air, water, food, body fluids, insects

• WHO’s seven deadliest infectious diseases– Acute respiratory infections (pneumonia & flu)—3.7 million/yr– HIV/AIDS—2.6 million/yr– Diarrheal diseases—2.5 million/yr– Tuberculosis—2 million/yr– Malaria—1.5 million/yr– Measles—1 million/yr– Hepatitis B—1 million/yr

Biological Hazards

• Treatments for infectious diseases– Bacterial & protozoan diseases are treated with

antibiotic drugs– Viral disorders are treated with vaccines before

infection

Biological Hazards

• Factors affecting the spread of transmissible diseases– Increased international air travel– Migration to urban areas– Migration to uninhabited rural areas & deforestation of

tropical developing nations– Hunger & malnutrition– Increased rice cultivation (mosquito breeding)– Global warming– High winds or hurricanes– Accidental introduction of insect vectors– Flooding

Biological Hazards• Epidemiological transition—infectious

diseases of childhood become less important and the chronic diseases of adulthood become more important in causing mortality– Infectious & parasitic diseases cause 43% of

deaths in developing nations but only 1% in developed nations