Environmental Health Hazards and Human Health

HIV/AIDS Identified in 1981 According to WHO in 2007 about 33 million people worldwide (1.1 million in the US) were infected with HIV. 2/3 of the infected were located in sub-Saharan Africa. Countries like Botswana are expected to lose half of their adult populations within a decade.

Risks and Hazards Risk – probability of suffering harm from a hazard Risk Assessment – scientific process of using statistical methods to estimate how much harm a hazard can cause Risk Management – deciding whether or how to reduce a particular risk

5 major Types of Hazards Biological Hazards – more than 1400 pathogens that can effect humans. Chemical Hazards – from harmful chemicals in air, water, soil, and food. Physical Hazards – such as fire, earthquakes, volcanic, eruptions, floods, and storms. Cultural Hazards – such as unsafe working conditions, unsafe highways, criminal assault, and poverty Lifestyle choices – smoking, eating too much, drinking too much alcohol, and having unsafe sex. And of course...

Biological Hazards Nontransmissible Disease – caused by something other than a living organism and does not spread from person to person. Can you think of any examples of nontransmissible disease? Infectious Disease – caused when a pathogen such as bacterium, virus, or parasite invades the body. Can you think of any examples of transmissible disease? Transmissible disease – infectious disease that can be transmitted from one person to another.

In 1900 infectious disease was the leading cause of death in the world. Since 1950 the incidences of infectious disease and death rates has decreased drastically. DALY ( disability-adjusted life years) measure of disease burden in population.

Deaths/Year World Health Organization estimates 12.5 million deaths/year from the seven deadliest diseases.

The growing problem Many disease-carrying bacteria have developed genetic immunity to widely used antibiotics. Many disease-transmitting species of insects such as mosquitos have become immune to widely used pesticides

TUBERCULOSIS TB (tuberculosis) is a highly infectious bacterial disease, strikes approximately 9.2 million people/year and kills 1.7 million-about 84% of them in developing countries. Each TB-infected person typically infects other people. Prevalent where large numbers of poor people crowd. There are few TB screenings and control programs, 95% of new cases occur in developing countries, travel has increased person to person contact, it has developed genetic resistance A new deadly and apparently incurable of TB, known as multidrug- resistant TB has been increasing in Africa, China, India, and Russia. When diagnosed, patients must be quarantined

MRSA methicillin-resistant staphylococcus aureus Has become resistant to most common antibiotics The infection appears as a spider bite, but leads to a vicious pneumonia, flesh eating wounds, and a quick death if it enters the blood stream Picked up mainly in hospitals, but is found on playgrounds, in gyms, in meeting rooms, and Can spread through skin contact, tattoo needles, contact with poorly laundered clothing, and shared items such as towels.

MRSA Tuberculosis Other Problematic Biological Hazards Hepatitis B virus – affects liver West Nile Virus (SARS) – Severe Acute Respiratory Syndrome FLU – avian, swine, etc.

Malaria Caused by 4 species of protozoan parasites in the Genus Plasmodium Distributed by any of the 60 species of Anopheles mosquitos Pesticides such as DDT help with Malaria treatment and prevention Anopheles are showing signs of genetic resistance Malaria over history has probably killed more people than all the wars ever fought.

Global Distribution of Malaria

Life Cycle of Malaria

Solutions to Infectious Disease Increase research on tropical diseases and vaccines Reduce Poverty Decrease malnutrition Improve drinking water quality Reduce unnecessary use of antibiotics Educate people to take all of an antibiotic prescription Reduce antibiotic use to promote livestock growth Require careful hand washing by all medical personnel Immunize children against major viral diseases Provide oral rehydration for diarrhea victims Conduct global campaign to reduce HIV/AIDS

Chemical Hazards Toxic chemical – can cause temporary or permanent harm or death to humans and animals. In 2004, EPA listed arsenic, lead, mercury, vinyl chloride, and polychlorinated biphenyls as the five most toxic substances in terms of threats to humans and environmental health

Three Major Types of potentially toxic agents Carcinogens- chemicals, types of radiation, or certain viruses that cause or promote cancer Examples: arsenic, benzene, chloroform, formaldehyde, gamma radiation, nickel, PCB’s, radon, certain chemicals in tobacco smoke, UV radiation, X-rays, and vinyl chloride. Mutagens- chemicals, types of radiation that cause mutations, or changes, in the DNA molecules Examples: Nitrous acid (HNO 2 ) from the digestion of nitrite (NO 2 - ) which is a preservative in food. Teratogens – chemicals that cause harm or birth defects to a fetus or embryo. Examples: Ethyl Alcohol, angel dust, benzene, cadmium, formaldehyde, lead, mercury, mescaline, and PCB’s

PCB’s polychlorinated biphenyls More than 200 chlorine-containing compounds that are very stable and nonflammable. They exist as oily liquids or solids and can enter air as vapor. Between they were widely used as lubricants, hydraulic fluids, and electrical insulators in transformers and capacitors. Also became prevalent in paints, fire retardants in fabrics, preservatives, adhesives, and pesticides. After 1977 research showed that PCB’s can cause cancer and learning disabilities in children. PCB’s breakdown very slowly in the environment and are fat soluble meaning they can biologically magnify in food chains and webs.

Effects on Nervous, Immune and Endocrine Systems Chemicals such as arsenic, methylmercury, and dioxins can weaken the immune system Neurotoxins such as PCB’s, methylmercury, arsenic, lead and certain pesticides can harm the nervous system Example: Farm workers exposed to the weed killer paraquat had 2 to 3 times the normal risk of suffering from Parkinson’s disease. HAAs (hormonally active agents) such as aluminum, atrazine and several other herbicides, DDT, mercury, PCB’s, phtalates, and bisphenol A Note: Estrogen mimics and hormone blockers are sometimes called gender benders because of their possible effects on sexual development. Other HAAs can act as thyroid disrupters which cause growth, weight, brain, and behavioral disorders

Phthalates and Bisphenol A These are both prevalent in a variety of products including baby products, cosmetics, food storage containers, microwave dishes and more. These two HAA’s have shown severe birth defects, liver cancer, kidney and liver damage, premature breast development, drops in male sperm count, early puberty, immune suppression, and abnormal sexual development

Evaluate and Deal with chemical Hazards Toxicology – study of harmful effects of chemicals Toxicity – measure of how harmful a substance is Dose – amount of a harmful chemical that a person has ingested, inhaled, or absorbed through the skin MCS – multiple chemical sensitivity Response – damage to health resulting from exposure to a chemical Factors like how well the body’s detoxification systems work(liver, lungs, and kidneys) and solubility affect the level of harm

Children need Protection First, children generally breathe more air, drink more water, and eat more food per unit of body weight than adults. Second, they are exposed to toxins in dust or soil when they put their fingers, toys, or other objects in their mouths. Third, children usually have less well developed immune systems and body detoxification processes than adults have. In 2005 cord blood from 10 randomly selected newborns in the US. 287 chemicals detected, 180 cause cancer, 217 damage the brain and nervous systems, and 208 cause birth defects or abnormal development

Testing and Laboratory animals Most widely used method for determining toxicity is to expose a population of live lab animals to measured doses of a specific substance. These tests take 2-5 years, involve hundreds to thousands of test animals, and cost as much as $2million per substance tested Dose-response curve – graph plotted with determined effects of various doses of the chemical on test organisms. LD50 – (median lethal dose) dosage of a specific chemical that kills 50% of the animals in the test group.

Mercury Pollution Mercury is teratogen and a neurotoxin It is released into the air from rocks, soil, and volcanoes and by vaporization from the ocean. This accounts for 1/3 of mercury in the atmosphere. The other 2/3 come from human sources. Smelting, coal burning, waste incinerators, and chemical manufacturing Mercury is an element and therefore cannot be degraded. It exists as methylmercury (CH 3 Hg + ) in acidic aquatic environments and can be biologically magnified. Exposure can cause brain damage in fetuses and young children and harm the heart, kidneys, and immune system in adults.