Environmental Health
Overview of Environmental Health
One third of death and disease in the least developed nations is a direct result of environmental causes.
Types of Environmental Health Hazards
• Biological: Viruses, bacteria, and other organisms that cause disease
• Social: Lifestyle choices that endanger health
• Chemical: Harmful artificial and natural chemicals in the environment
• Physical: Natural disasters and ongoing natural phenomena, such as UV radiation, that can cause health problems
Epidemiology
The study of disease in human populations—how and where they occur and how they can be controlled
• Often involves studying large groups over long periods
• Can determine associations between health hazards and effects, but can’t prove the hazards actually caused the effects
Toxicology
The study of how poisonous substances affect an organism’s health
• Toxicity is a measure of how harmful a substance is.
• Toxicologists look at toxicity by determining dose-response relationships.
Biological and Social Hazards
Three quarters of infectious disease deaths are caused by five types of diseases: respiratory infections, AIDS, diarrheal diseases, tuberculosis, and malaria.
Tuberculosis-causing
bacteria
Infectious Diseases
Did You Know? In 2002, AIDS killed about 2 million people worldwide—almost equal to the entire population of Arkansas.
• Caused by pathogens
• Spread by human and animal contact and through contaminated food and water
• Cause of almost half of all deaths in developing nations
• Covering your mouth when you cough, washing your hands often, and staying home from school if you’re sick help prevent the spread of infectious disease.
Emerging Diseases
Diseases appearing in the human population for the first time or suddenly beginning to spread rapidly
•Humans have little or no resistance, and no vaccines have been developed.
• Facilitated by increasing human mobility, growing antibiotic resistance, and environmental changes
Swine Flu Could Be a Global Pandemic
Watch the ABC News video Swine Flu Could Be a Global Pandemic. Have students use their own experiences to talk about how the spread of H1N1 virus was controlled in the months after the video was made. Then, discuss the ways that biological hazards are monitored and controlled by national and international agencies.
Social Hazards
• Some social hazards are easier to avoid than others.
• Examples of social hazards include smoking, being exposed to secondhand smoke, living near an old toxic waste site, working with harmful chemicals, and eating fatty foods.
Toxic Substances in the Environment
Chemicals are all around us, and all of them can be harmful to our health in large enough amounts. In other words, “The dose makes the poison.”
Chemical Hazards•Any chemical can be harmful in large enough amounts.
•A pollutant is something released into the environment that has some harmful impact on people and other organisms.
• Chemical hazards are not necessarily pollutants, and pollutants are not necessarily chemical hazards.
Oil Pollution
Types of Chemical Hazards
• Carcinogens: Cancer-causing chemicals
• Chemical mutagens: Chemicals that cause genetic mutations
• Teratogens: Chemicals that harm embryos and fetuses
•Neurotoxins: Chemicals that affect the nervous system
• Endocrine disruptors: Chemicals that interfere with the endocrine system
•Allergens: Chemicals that over-activate the immune system
Dust mite protein is a common
allergen.
Indoor Chemical Hazards
Sources of Outdoor Chemical Hazards
• In the air: Natural sources, such as volcanic eruptions, or human sources, such as pesticides
• In the ground: Pesticide use, improper disposal of electronics, etc.
• In the water: Chemical runoff from land or direct drainage of toxic substances into water A leaking oil line
Bioaccumulation and Biomagnification
Bioaccumulation: The buildup of toxic substances in the bodies of organisms
Biomagnification: The increased concentration of toxic substances with each step in a food chain
• Persistent organic pollutants are biomagnified and stay in the environment for long periods of time and over long distances.
Bioaccumulation
The Rise and Fall—and Rise?—of DDT
•DDT is the least expensive way of killing the mosquitoes that cause malaria.
•DDT harms fish and birds, and can cause liver damage, cancer, and convulsions in humans.
• In the 1970s many countries banned the use of DDT, but some African countries have resumed its use to control malaria.
Talk About It Evidence shows that DDT damages
ecosystems but helps eradicate malaria in areas
where millions of people die of the disease each
year. Should DDT be used in malaria-stricken areas?
Why or why not?