Chapter 17 Human Health and Environmental Risks Human

Chapter 17 Human Health and Environmental Risks

Human Health Risk Factors § Include physical risks § Exposure to UV radiation § Include chemical risks § Exposure to pesticides § Include biological risks § Pathogens and diseases § Include cultural risks § Smoking, poor diet

Infectious Diseases § Are caused by pathogens § Can be chronic § Act slowly over a long period of time § Heart disease § Can be acute § Act quickly over a short period of time § Ebola

Historical Infectious Diseases § Plague § Caused by bacterium Yersinia pestis § Transmitted by fleas § Malaria § Caused by parasitic protist Plasmodium § Transmitted by mosquitoes § Tuberculosis (consumption) § Caused by bacterium Mycobacterium tuberculosis § Transmitted by human breath § Can be treated with antibiotics or other drugs § Can become resistant to drugs

Emergent Infectious Diseases § Are diseases that are new to medicine § Effective treatments do not exist § Are frequently zoonoses § Diseases that reside in animal populations and can infect humans

HIV/AIDS § Human Immunodeficiency Virus (HIV) § Crossed species from apes to humans § Transmissible in body fluids § Attacks the immune system § Antiviral drugs can reduce viral load § Human Immune Deficiency Syndrome (AIDS) § Significantly weakened immune system § Death results from infection by other pathogens

Ebola and other Hemorrhagic Fevers § Also crossed species from apes to humans § Unlike AIDS it kills its primate hosts § Natural host is unknown § Cause massive bleeding and organ failure § Death rate is 60 -90%

Bovine Spongiform Encephalopathy (Mad Cow Disease) § Called Creutzfeldt-Jakob Disease in humans § Caused by mutated proteins called prions § Not destroyed by cooking § Damages the brain and nervous system § Destroys motor coordination § Can be transmitted from infected meat § Spread in cow population from adding ground-up remains from meat processing

Bird/Swine Flu (H 1 N 1 and H 5 N 1 Viruses) § Crossed species from birds to humans § Similar to virus that caused 1918 worldwide pandemic § Could mutate and become far easier to transmit § Could cause another pandemic

West Nile Virus § Is transmitted by mosquitoes § Aggressive mosquito control has limited the virus in the US § Causes brain inflammation

Toxicology § Is the study of harmful chemicals (toxicants) § Includes § Neurotoxins § Mutagens and carcinogens § Teratogens § Allergens § Endocrine disruptors

Neurotoxins § Harm the nervous system § Include lead, mercury, insecticides, and chemical weapons

Mutagens and Carcinogens § Are chemicals that mutate DNA § Can cause cancer § Include asbestos, radon, benzene, formaldehyde, and polycyclic aromatic compounds (PAHs) from smoke § Can also include radiation

Teratogens § Are chemicals that interfere with normal embryonic development § Include thalidomide, alcohol, and tetrahydrocannabinol (THC)

Allergens § Can cause an extreme reaction from the immune system that can lead to death § Include dust, pollen, nuts, milk, eggs, wheat, soy, penicillin, and codeine

Endocrine Disruptors § Are chemicals that interfere with normal hormonal function § Prevent normal hormonal bonding to cell surfaces and disrupt cell signaling § Can interfere with gender and developmental hormone pathways § Found in plastics and health and beauty products

Epidemiology § Is the study of the causes and duration of disease in animals, especially humans § Looks for levels at which toxicants cause disease § Establishes safe levels of exposure in the environment and in tissues

Dose-Response Studies § Expose organisms to toxicants and observe any changes § Can be measured in concentration of chemical exposed § Can also be measured in the dose an organism ingests § Include the LD 50 and ED 50

Dose-Response Studies § LD 50 § Are studies that measure the lethal dose that kills 50% of the test subjects § ED 50 § Are studies that measure the effective dose that causes nonlethal but harmful effects in 50% of test subjects § Results from these studies can be used to set safe levels and exposures § Invertebrates, fish, birds, mammals

Do the Math p. 475 § Using the LD 50 to determine safe levels for the environment § Can calculate the safe level by dividing LD 50 by 10 (safe level = 10% of LD 50) 2 mg/kg of mass/10 = 0. 2 mg/kg of mass

Do the Math p. 475 § Safe exposures for humans are set by dividing the LD 50 by 1000 (safe level = 0. 1% of LD 50) 2 mg/kg of mass/1000 = 0. 002 mg/kg of mass

Union Carbide Pesticide Factory Leak § Occurred in Bhopal, India in 1984 § Released methyl isocyanate gas § Worst industrial accident ever § 2, 000 people died in first 24 hours § 15, 000 more died in the weeks to follow § As many as 500, 000 injured

Acute and Chronic Studies § Acute studies examine the effects of toxicants over short periods of time § LD 50, ED 50 § Occur over hours to days § Chronic studies examine the effects of toxicants over long periods of time § Often follow test subjects for years

Retrospective and Prospective Studies § Retrospective studies monitor organisms that have been exposed to a toxicant § Prospective studies monitor organisms that may be exposed to a toxicant § Must compare group that is exposed to a non-exposed group § Need to take into account socioeconomic factors, and exposure to multiple toxicants § Synergistic effects can occur from exposure to multiple toxicants

Routes of Exposure for Toxicants § Are the same as those for infectious diseases § Can have multiple toxicants from multiple sources § Can be difficult to distinguish which toxicant is causing which symptoms § Are affected by a toxicant’s solubility § Soluble toxicants have a greater likelihood of becoming part of a food chain § Bioaccumulation and biomagnification

Persistence § Is how long a toxicant remains in the environment § Depends on temperature, humidity, p. H, solubility, radiation, and whether it can be broken down by bacteria § May be different for the same toxicant in water or in soil § Can be measured in halflives § Pesticide DDT has a half-life in soil of 30 years

Risk Assessment § Identifies hazards and determines their potential harm § Can be qualitative § Based on perceptions or personal values § Can be quantitative § Based on data § Risk = proability of being exposed to a hazard X probability of being harmed if exposed § Perceived risk can be different than actual risk

Risk Acceptance § Is the level of risk that can be tolerated § Some individuals can tolerate more risk than others § EPA risk acceptance is usually set at 1 in 1 million § Case Study: PCBs § PCBs in the Hudson River System were high enough to ban fishing § Fish were thought to be the main vector for humans to acquire PCBs § Swimming and drinking water were discouraged but not banned § EPA recommended dredging river bottom to remove PCBs

Rick Management § Strikes a balance between possible harm and other interests § Case Study: Arsenic § EPA allowed levels of 50 μg/L in water for many years even though the safe level was 10 μg/l § It was too expensive for some municipalities to remove that much arsenic § Finally reduced levels to 10 μg/L when new research showed that 5 μg/L was the true safe limit

Principles of Risk § Innocent-until-proven-guilty principle § Substances must be shown to be harmful before they are treated as toxicants § Precautionary principle § All potentially harmful substances are assumed to be toxicants § Case Study: Asbestos § Use would have been regulated far sooner and more lives would have been saved under the precautionary principle

International Standards § Stockholm Convention § Established a list of 12 Persistent Organic Pollutants (POPs) to be banned outright or their use reduced § 127 nations signed an agreement to ban these chemicals, phase out their use, or severely restrict their use § Additional meetings have added new chemicals to the list each year since 2001 Name Use Aldrin Pesticide Chlordane Pesticide Dichlorodiphenyl trichloroethane (DDT) Pesticide Dieldrin Pesticide Endrin Heptachlor Pesticide Hexachlorobenzene Pesticide Mirex Pesticide Toxaphene Pesticide Polychlorinated biphenyls (PCBs) Industrial emissions Polychlorinated dibenzofurans Industrial emissions Dioxins Industrial emissions

International Standards § REACH § Registration, Evaluation, Authorization and restriction of CHemicals § Puts the precautionary principle into action § Requires risk analysis of all chemicals before they are used industry or consumer products § Is the how the European Union regulates toxicants