Environmental Health and Toxicology Chapter 22

Outline: Environmental Health Hazards Distribution and Fate of Toxins Infectious Organisms Emergent Diseases Antibiotics and Pesticide Resistance Toxic Chemicals Distribution and Fate of Toxins Minimizing Toxic Effects Measuring Toxicity Risk Assessment Public Policy

ENVIRONMENTAL HEALTH HAZARDS Health - A state of complete physical, mental, and social well-being. Disease - A deleterious change in the body’s condition in response to an environmental factor. Diet and nutrition, infectious agents, toxic chemicals, physical factors, and psychological stress all play roles in morbidity (illness) and mortality (death).

Infectious Organisms For most of human history, the greatest health threats have been pathogenic organisms. Infectious diseases are still responsible for about 33% of all disease-related deaths. Majority of deaths in poorer countries with poor nutrition, sanitation, and vaccination programs.

Morbidity and Quality of Life Death rates do not tell everything about burden of disease. Total economic and social consequences of diseases are difficult to obtain. Disability-Adjusted Life Year (DALY) combines premature deaths and loss of healthy life resulting from illness or disability.

Disability-Adjusted Life Year WHO reports communicable diseases are responsible for nearly half of all 1.2 billion DALY’s lost each year. About 90% of all DALY losses occur in developing world where one-tenth of all health care dollars are spent. Malnutrition exacerbates many diseases.

Emergent Diseases An emergent disease is one never known before, or has been absent for at least 20 years. An important factor in the spread of many diseases is speed and frequency of modern travel. Foot and Mouth Disease Ebola

Emerging Ecological Diseases Domestic animals and wildlife also experience sudden and widespread epidemics. Distemper (Seals) Chronic Wasting Disease (Deer and Elk) Transmissible Spongiform Encephalopathies Black Band Disease (Coral)

In the News…. http://www.npr.org/templates/story/story.php?storyId=4586823&sourceCode=RSS

Infectious Disease Outbreaks

Antibiotic and Pesticide Resistance Protozoan parasite that causes malaria is now resistant to most antibiotics, while the mosquitoes that transmit it have developed resistance to many insecticides. Short life spans. Speeds up natural selection and evolution. Human tendency to overuse pesticides and antibiotics.

Antibiotic and Pesticide Resistance

Antibiotic Use At least half of the 100 million antibiotic doses prescribed in the US every year are unnecessary or are the wrong drug. Many people do not finish full-course. More than half of all antibiotics manufactured in the US are routinely fed to farm animals to stimulate weight gain.

Vivian Vermillion Vivian picked up a strain of antibiotic resistant E. coli at the Vet Hospital This strain is resistant to six antibiotics!!!

Antibacterial Mustard Introduced by French’s ROCHESTER, NY—In response to increasing American demand for tangier, more hygienic meals, condiment giant French's has introduced a new antibacterial mustard.

Toxic Chemicals Dangerous chemicals are divided into two broad categories: Hazardous - Dangerous Flammable, explosive, irritant, sensitizer, acid, caustic. Toxic - Poisonous Can be general or very specific. Often harmful even in dilute concentrations.

Toxic Chemicals 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. Other allergens act indirectly by binding to other materials so they become antigenic.

Toxic Chemicals Sick Building Syndrome Headaches, allergies, and chronic fatigue caused by poorly ventilated indoor air contaminated by molds, carbon monoxide, nitrogen oxides, and other toxic chemicals. Worker absenteeism and reduced productivity. EPA estimates $60 billion annual loss.

Toxic Chemicals Neurotoxins - Special class of metabolic poisons that specifically attack nerve cells. Different types act in different ways. Heavy Metals kill nerve cells. Anesthetics and Chlorinated Hydrocarbons disrupt nerve cell membranes. Organophosphates and Carbamates inhibit signal transmission between nerve cells.

Toxic Chemicals Mutagens - Agents that damage or alter genetic material. Radiation Teratogens - Specifically cause abnormalities during embryonic growth and development. Alcohol - Fetal Alcohol Syndrome Carcinogens - Substances that cause cancer. Cigarette smoke

US Age-Adjusted Cancer Death Rates

Endocrine Hormone Disrupters Chemicals that disrupt normal endocrine hormone functions. Hormones are chemicals released in blood by glands to regulate development and function of tissues and organs elsewhere in the body. Environmental Estrogens and Androgens

Diet Strong correlation between cardiovascular disease and the amount of salt and animal fat in an individual’s diet. Highly-processed foods, fat, and smoke-cured, high nitrate meats appear to be associated with cancer. Nearly 2/3 of all Americans are considered overweight.

DISTRIBUTION AND FATE OF TOXINS Solubility - Chemicals are divided into two major groups: Dissolve more readily in water. Dissolve more readily in oil. Water-soluble compounds move rapidly through the environment, and have ready access to most human cells. Oil-soluble molecules generally need a carrier to move through the environment.

Bioaccumulation and Biomagnification Cells have special mechanisms for Bioaccumulation - Selective absorption and storage. Dilute toxins in the environment can build to dangerous levels inside cells and tissues. Biomagnification - Toxic burden of a large number of organisms at a lower trophic level is accumulated and concentrated by a predator at a higher trophic level.

Sensitivity and Developmental Stage Many factors help determine reaction of an individual to a given dose. Age Sex Body Weight Nutritional / Immunological Status Repair Mechanisms

Persistence Some chemical compounds are very unstable and degrade rapidly under most conditions, thus their concentrations decline quickly after release. Others are more persistent. Stability can cause problems as toxic effects may be stored for long period of time and spread to unintended victims. (DDT)

Bioaccumulation

Chemical Interactions Antagonistic Reaction - One material interferes with the effects, or stimulates the breakdown, of other chemicals. Aluminum and phosphate ions form solid Additive Reaction - Effects of each chemical are added to one another. Xenoestrogens + estrogens Synergistic Reaction - One substance multiplies the effect of the other. Nitrate ion and phosphate ion

MECHANISMS FOR MINIMIZING TOXIC EFFECTS Every material can be poisonous under certain conditions. Most chemicals have a safe threshold under which their effects are insignificant. Metabolic Degradation In mammals, the liver is the primary site of detoxification of both natural and introduced poisons.

Excretion Effects of waste products and environmental toxins reduced by eliminating via excretion. Breathing Kidneys Urine

MEASURING TOXICITY 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 (dies).

LD50

Population Sensitivity Variations

Acute vs. Chronic Effects Acute Effects - Caused by a single exposure and result in an immediate health problem. Chronic Effects - Long-lasting. Can be result of single large dose or repeated smaller doses. Very difficult to assess specific health effects due to other factors.

RISK ASSESSMENT Factors influencing risk perception: Rating risks based on agendas. Most people have trouble with statistics. Personal experiences can be misleading. We have an exaggerated view of our abilities to control our fate. News media sensationalizes rare events. Irrational fears lead to overestimation of certain dangers. Fear of the unknown.

Accepting Risks Most people will tolerate a higher probability of occurrence of an event if the harm caused by that event is low. Harm of greater severity is acceptable only at low levels of frequency. EPA generally assumes 1 in 1 million is acceptable risk for environmental hazards.

ESTABLISHING PUBLIC POLICY Biggest problem in making regulatory decisions is that we are usually exposed to many sources of harm, often unwillingly. May not be reasonable to demand protection from every potentially harmful contaminant in our environment, no matter how small the risk.

ESTABLISHING PUBLIC POLICY In setting standards for environmental toxins, need to consider: Combined effects of different exposures. Individual sensitivities within population. Effects of chronic and acute exposures.

Food for Thought

From the Star - Tribune

Summary: Environmental Health Hazards Distribution and Fate of Toxins Infectious Organisms Emergent Diseases Antibiotics and Pesticide Resistance Toxic Chemicals Distribution and Fate of Toxins Minimizing Toxic Effects Measuring Toxicity Risk Assessment Public Policy