Disability-Adjusted Life Year (DALY) combines premature deaths and loss of healthy life resulting from illness or disability. (1.4 billion a year) 90% of DALY occur in developing countries WHO reports 50% due to communicable disease For most of human history, the greatest health threats have been pathogenic organisms, accidents, and violence.

EMERGENT DISEASE – Never known before or has been absent for 20 years or more Spreads Rapidly – modern travel means Example – FOOT & MOUTH DISEASE  Infectious diseases are still responsible for about 24% of all disease-related deaths. Majority of these deaths in poorer countries with poor nutrition, sanitation, and vaccination programs.  AIDS now largest single cause of communicable death in the world.

Risk Assessment & Management Risk = probability of exposure x probability of harm Risk Assessment 1)ID potential hazard 2)Probability of occurrence 3)Determine how much damage (social; env; economic) Controversy over assessments – WHY? Disputes over variables such as - # exposed, level of exposure, and impact due to age/health/sex of organism 1)How Serious? 2)Can it be reduced? 3)How can it be reduced? 4)$$ to clean it up? Risk Management After Assessment

4 Main Types of Hazards smoking (case study), unsafe working conditions, diet, drinking, driving, poverty! Cultural Chemical synthetic chemicals from water & air pollution – human body contains over 500 syn.chemicals not known prior to 1920 ionizing radiation, earthquakes, volcanoes, hurricane, tornadoes pathogens (bacteria, viruses, parasites), pollen and other allergens; animals (bees, snakes) Physical Biological

Biological Hazards Epidemiology – the study of factors affecting the health and illness of a population Dose Response Curve – Non-Transmittable Disease – not caused by living organisms and does not spread from person to person Cardiovascular disease, obesity, diabetes, most cancers, bronchitis – Transmissible Disease – caused by living organisms (bacteria, protozoa, and parasites) and viruses Pathogens (disease causing organisms) spread through water, air, food, insects, & body fluids - VECTORS

TRANSMISSIBLE DISEASE According to the WHO & UNICEF 2 million children in developing countries die each year due to preventable infectious disease. 80% of the infectious disease is spread through waterborne infections (diarrhea, hepatitis, typhoid fever, and cholera) Seven Deadliest Infectious Disease: 1)Tuberculosis (TB) bacterial disease 2)Malaria – protozoa 3)Respiratory Disease – mostly pneumonia (bacteria and viruses) 4)Diarrheal Disease – bacterial & viruses (unclean water) 5)Measles – viral 6)Hepatitis – viral 7)HIV/AIDS – Viral

CHEMICAL Hazards Immune Systems – protects the body against disease Disruptors – viruses, bacteria, parasites, malnutrition, ionizing radiation, synthetic chemicals Nervous System – brain; spinal cord; peripheral nerves Neurotoxins – synthetic chemicals = chlorinated hydrocarbons (DDT, PCBs, dioxins); organophosphates (malathion); formaldehyde; heavy metals (mercury, lead, cadmium) Endocrine – glands and hormones that regulate body functions Disruptors – (HAA’s – hormonally active agents) = can mimic or block natural hormone responses – many synthetic chemicals such as atrazine, DDT, PCB’s Endocrine disruptors have major impacts on reproductive systems

1)Size of the dose over time 2)How often exposure occurs 3)Who is exposed 4)How well the body’s detox system works 5)Genetic make-up of organism Factors affecting Toxicity Toxicity – measure of how harmful a substance is. Dosage – the amount inhaled, absorbed, or ingested

EXAMPLES: DDT (synthetic organic pesticide), PCB’s (oils used in electrical equipment); Mercury (heavy metal) Many chemicals are used because of their long persistence or resistance to breakdown: plastics, CFC’s, Chlorinated Hydrocarbons (DDT) This also means they have a lasting impact on the environment Bioaccumulation – chemicals are stored in specific organs or tissues at levels higher than normal Biomagnification – levels of toxins in the environment are magnified as they pass through food chains

DANGEROUS CHEMICALS Dangerous chemicals are divided into two broad categories:  Hazardous - Dangerous - Flammable, explosive, irritant, acid, caustic.  Toxic -Harmful - Can be general or very specific. Often harmful even in dilute concentrations. Poison – has an LD 50 of 50 mg or LESS

Allergens - Substances that activate the immune system.  Antigens - Allergens that are recognized as foreign by white blood cells and stimulate the production of specific antibodies. Neurotoxins - Special class of metabolic poisons that specifically attack nerve cells. - Heavy Metals kill nerve cells. - Chlorinated Hydrocarbons disrupt nerve cell membranes. (DDT, PCBs, dioxins) - Organophosphates inhibit signal transmission between nerve cells. (malathion) Insecticides

Mutagens - Agents that damage or alter genetic material.  Radiation (x-ray equipment) Teratogens - Specifically cause abnormalities during embryonic growth and development.  Alcohol - Fetal Alcohol Syndrome  PCB’s, steroids, lead & mercury Carcinogens - Substances that cause cancer.  Cigarette smoke, dioxins, radon gas, asbestos

100 million Antibiotic doses prescribed each year in the US – many unnecessary ANTIBIOTICS More than ½ of the antibiotics manufactured in the US are fed to farm animals to stimulate weight gain RESISTANCE Many protozoans and insects are now immune to most antibiotics & pesticides (rapid evolution) Humans overuse and therefore add pressure to adapt and change.

Solubility - One of most important characteristics in determining the movement of a toxin. Chemicals are divided into two major groups: - Those that dissolve more readily in water. - Those that dissolve more readily in oil.  Water soluble compounds move rapidly through the environment, and have ready access to most human cells. RATE OF MOVEMENT & DISTRIBUTION

Animal Testing  Most commonly used and widely accepted toxicity test is to expose a population of laboratory animals to measured doses of specific toxins. - Sensitivity differences pose a problem.  Dose Response Curves  LD50 - Dose at which 50% of the test population is sensitive.

LD 50 = median lethal dose: the amount of a chemical received in one dose that kills exactly 50% of the organisms in a population (typically in a 2 week period of time) Animal Testing Takes 2-5 years – costs between 200,000 – 2 mil Threshold = dosage amount at which no negative effects are seen

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