Biological- those risks associated with diseases. Disease- any impaired function of the body w/ a characteristic set of symptoms.

Transcription

1 1 2 Environmental Hazards and Human Health Chapter 14 3 Major Categories of Risks to Human Health Physical- includes environmental factors like natural disasters, exposure to radiation, or excessive sun. Biological- those risks associated with diseases. Disease- any impaired function of the body w/ a characteristic set of symptoms. Chemical- associated w/ exposure to chemical natural or synthetic. 3 Disease Biological risks cause the most deaths. Infectious diseases are transmissible & caused by pathogens Pathogens- can be a bacterium, virus, or other microorganism that cause disease Cause of most infectious diseases: Viruses, bacteria, fungi, protists, and parasitic worms called helminths. Some diseases are not caused by pathogens; heart disease All diseases fall into 2 categories acute & chronic Chronic diseases slowly impair the functioning of a person s body. Acute diseases rapidly impair the functioning of a person s body. 4 Death & Disease Only six types of illnesses account for 94% of all deaths caused by infectious disease. Top 3 caused by: Respiratory infections HIV/AIDS 1

2 HIV/AIDS The variety of viruses that cause diarrhea Next 3 illnesses: Malaria Tuberculosis Childhood disease like measles and tetanus 5 6 Risk Factors For low income countries: poverty, unsafe drinking water, poor sanitation, & malnutrition For example, poor nutrition can weaken the body s ability to recover from an illness. Do you remember the causes of these factors? For high income countries: tobacco, less active lifestyles, poor nutrition, overeating, combination leads to high blood pressure and obesity. 7 8 Disease Distribution Environmental scientists are generally interested in disease that have environmental causes; especially pathogens. Variety of pathways for transmission- from other humans, other animals, the food we eat, air we breathe, and the water we drink. An epidemic is when a pathogen causes a rapid increase in disease. A pandemic is when an epidemic occurs over a large geographic region such as a continent. Growing Resistance to Antibiotics High bacterial reproductive rate Genetic resistance 2

3 Genetic resistance Global travel Use of pesticides Overuse of antibiotics Historical Diseases Plague is caused by an infection from a bacterium (Yersinia pestis) that is carried by fleas. Malaria is caused by an infection from any one of several species of protists in the genus Plasmodium. The vector for it is a mosquito. The plasmodium spends another stage of its life inside a human. Causes recurrent flu-like symptoms Traditional approach was to use insecticides 350 to 500 M people contract it and nearly 1 M die, mostly kids Hardest hit regions: sub-saharan Africa, Asia, Middle East, Central and South America. Animation: Life Cycle of Plasmodium Distribution of Malaria Historical Diseases Tuberculosis is a highly contagious disease caused by a bacterium. 1/3 of world population thought infected. It is spread when a person coughs and expels the bacteria into the air. It can persist in the air for several hours. Can be treated by taking antibiotics for a year In developing countries the medicine is not readily available and may not be taken properly. 3

4 and may not be taken properly. Symptoms Weakness Night sweats Coughing up blood Emergent Infectious Diseases Emergent infectious diseases are those diseases that had not been previously described or have not been common for the past 20 years. Many of these new diseases have come from pathogens that normally infect animal hosts, but unexpectedly jump to a human host. HIV Ebola Mad cow disease Bird flu West Nile virus Ecological Medicine Zoonotic diseases- transmitted from animals to humans. Avian flu, West Nile, Lyme disease, HIV Ecological (conservation) medicine- is a new field that deals with the study of how zoonotic diseases spread and how they can be prevented. Human actions encourage spread of disease Clear-cutting and fragmentation Harvesting animals Global trade and travel Trade in wild species 16 HIV/AIDS In the 70s rare types of pneumonia & cancer began appearing in people w/ weak immune systems. It was spread through sexual contact and the sharing of needles by drug users. 4

5 It was spread through sexual contact and the sharing of needles by drug users. In 2006, researchers found a genetically similar virus in a wild population of chimpanzees in Cameroon. More than 30 M people infected with HIV. 25 M people have died from AIDS related illnesses. New antiviral drugs are able to keep populations of the virus low inside the human body. Expensive and not widely available Animation: HIV Replication Core Case Study: HIV/AIDS Acquired immune deficiency syndrome (AIDS) Human immunodeficiency virus (HIV) Mode of transmittance Exponential increase of infection worldwide No vaccine for HIV No cure for AIDS Kaposi s Sarcoma Impact of AIDS on the Age Structure of Botswana, Africa Ebola Hemorrhagic Fever Discovered in the Congo near the Ebola River. Caused by the Ebola virus, it has infected several hundred humans. Natural source remains unknown Though it has not reached epidemic proportions, it is of concern b/c it kills a large percentage of those infected. Death occurs within 2 weeks, and there are no drugs available to fight the virus. Symptoms: fever, vomiting, and sometimes internal and external bleeding 22 Transmissible Spongiform Encephalopathies 5

6 Spongiform refers to the appearance of the brain under microscope. Slow working illness caused by a prion. A prion is a protein that acts like a pathogen and is very difficult to destroy. (no nucleic acid) Symptoms: coordination problems, dementia, personality changes, mental impairment, deteriorates into coma. Family of diseases mostly found in animals Mad Cow- bovine spongiform encephalopathy Creutzfeldt-Jakob disease (CJD)- in humans (rare) Can be contracted by exposure to contaminated brain matter or spinal fluid containing these prions Animation: Positron-Emission Tomography H5N1 & West Nile Virus H5N1 the avian flu jumped to people and humans had no defenses for it nor did domesticated bird species. As a result, government destroyed large numbers of infected birds. West Nile lives in hundreds of species of birds and is transmitted among birds by mosquitoes. First human case in 1937 in Uganda. Causes inflammation of the brain leading to illness and sometimes death. Lead to increased control of mosquito populations. Video: Bird Flu Preventing or Reducing Diseases Ecological Medicine Zoonotic diseases- spread to humans by the eating of bush meat 6

7 Ecological (conservation) medicine Human actions encourage spread of disease Clear-cutting and fragmentation Harvesting animals Global trade and travel Trade in wild species 28 Toxicology Toxicology is the study of chemical risks to humans. Neurotoxins are chemicals that disrupt the nervous systems of animals. Many insecticides include neurotoxins. Lead and mercury are neurotoxins that can damage the kidneys and central nervous system. Carcinogens are chemicals that cause cancer through cell damage leading to uncontrolled growth. Mutagens cause damage to the genetic material of a cell. (not all are carcinogens) Asbestos, radon, formaldehyde, chemicals in tobacco Teratogens interfere with the normal development of embryos or fetuses. Ex. Thalidomide for morning sickness. Alcohol is the most common modern teratogen 29 Toxicology (2) Allergens are chemicals that cause allergic reactions. Are not pathogens, but are capable of causing an abnormally high immune response. Can cause breathing difficulties and even death Common allergens: peanuts, milk, penicillin, & some drugs Endocrine disruptors are chemicals that interfere with the normal functioning of hormones in an animal s body. These are also called hormonally active agents. Ex. Hormones from birth control pills found in waterways affecting fish and amphibians. Disruptors causes the failure 7

8 Ex. Hormones from birth control pills found in waterways affecting fish and amphibians. Disruptors causes the failure of estrogen to be converted into testosterone in males as it normally would. Some pesticides are made w/ this purpose in mind. Phthalates- used to soften pvc plastics. 30 Risk assessment To assess the risk a chemical poses to any organism, we need to determine the concentrations that cause harm. To learn this scientists use: Dose response studies Prospective studies Retrospective studies Dose Response Dose-response studies expose animals or plants to different concentrations of a chemical and then observe a variety of possible responses including mortality or changes in behavior or reproduction. Dose is the amount of chemical that is absorbed or consumed by an organism. Dose-response studies most commonly measure mortality as a response. The dose at which an effect can be detected is called the threshold. LD50 is the lethal dose that kills 50% of the individuals ED50 is the effective dose for observing sublethal effects Divide that value by 10 for safe concentration amount for rats, by 10 again for sensitivity differences, by 10 again for human safety Testing Standards The Toxic Substances Control Act of 1976 gives the EPA the authority to regulate many chemicals. Although this excludes food, cosmetics, and pesticides Pesticides are regulated under a separate law, the Federal Insecticide, Fungicide, and Rodenticide Act of

9 Pesticides are regulated under a separate law, the Federal Insecticide, Fungicide, and Rodenticide Act of Under this act, a manufacturer must demonstrate that a pesticide will not generally cause unreasonable adverse effects on the environment. Scientists test only a few species: A bird, mammal, fish, and invertebrate Chronic Studies Chronic studies are conducted for longer periods of time. Often from the time an organism is very young to when it is old enough to reproduce. The goal of chronic studies is to examine the long-term effects of chemicals, including their effects on survival and their impacts on reproduction. Epidemiology seeks to understand the causes of illness and disease in human and wildlife populations. Retrospective studies monitor people who have been exposed to a chemical at sometime in the past. Compare to a group that has not been exposed. Prospective studies seek to determine if the lifestyle and habits have any association with future health problems. Chemicals in the Environment Routes of exposure are the ways in which an individual might come into contact with a chemical. Usually there are just a few routes. For example, bisphenol A is a chemical used in the manufacturing of hard plastic items such as toys and food containers. So sometimes scientists need to determine the solubility of a chemical. Also determine the potential of it to biomagnify-- accumulate in the tissues of animals and then throughout the food web. Persistence refers to how long the chemical remains in the environment. Determining Chemical Safety (2) 9

10 Water and fat soluble toxins Persistence Bioaccumulation Biomagnification Chemical interactions Risk and Hazards Risk analysis involves: Risk assessment Risk acceptance Risk management Comparative Risk Analysis Risk Assessment Risk analysis helps us assess, accept, and manage risk. Risk assessment seeks to identify a potential hazard and determine the magnitude of the potential harm. Two types: qualitative and quantitative Qualitative assessments are based on our perceptions not on actual data. Ex: icy road conditions Perceived risk vs. actual risk Quantitative Risk= prob of exposure x prob of harm Uses tremendous amounts of data The risk assessment on PCBs showed that the risk from eating contaminated fish is higher than the risk from drinking contaminated water. Hence, signs were posted on the Hudson River not to eat the fish. Risk Acceptance & Management Risk acceptance involves determining the level of risk that can be tolerated. 10

11 Risk acceptance involves determining the level of risk that can be tolerated. Often the precise amount of acceptable risk is open to heated disagreement According to the EPA a 1 in 1 million risk is acceptable for most environmental hazards. Risk management seeks to balance possible harm against other considerations. It is a regulatory activity that is typically carried out by local, national, or international government agencies. 40 Arsenic Regulation Despite the fact that scientists knew that 50 µg/l of arsenic could cause cancer in people, from 1942 to 1999 the federal government set the acceptable level of arsenic in drinking water at 50 µg/l. In 1999, the EPA lowered it to 10, which matched the standard set by the European Union. Placed a burden on mining companies that produced arsenic as a by-product. Placed a burden on Western municipalities to remove arsenic from water even though it occurred naturally Risk Assessment and Risk Management How Can We Avoid these Dangers? Concept 14-5 We can reduce the major risks we face by becoming informed, thinking critically about risks, and making careful choices Annual Deaths in the United States from Tobacco Use and Other Causes in 2004 Number of Deaths Per Year in the World 47 11

12 Comparison of Risks in the United States Video: Polio Scare Video: Food Allergy Increase Video: AIDS Conference in Brazil Video: Beach Pollution Video: World AIDS Day Video: Clean Air Act Video: MTBE Pollution Video: U.S. Earth Summit 12