Environmental Health
Objectives
•Define health and disease and describe how global disease burden is changing
•Identify some major infectious organisms and hazardous agents that cause environmental diseases
•Identify examples of emergent human and ecological diseases
Objectives
•Distinguish between toxic and hazardous chemicals and between chronic and acute exposures and responses
•Compare factors that affect toxin movement and persistence in the environment as well as routes of entry and effects on our bodies
•Evaluate the major environmental risks we face and how risk assessment and risk acceptability are determined
Health
•WHO (World Health Organization) defines health as “a state of complete physical, mental, and social well-being”
–Is anyone really healthy?
Disease
•Disease - a deleterious change in the body’s condition in response to an environmental factor
–Disease can lead to both morbidity (illness) and mortality (death)
Environmental health
•Focuses on external factors that cause disease, including natural, social and cultural factors
–Diet and nutrition
–Infectious agents
–Toxic chemicals
–Physical factors
–Psychological stress
DALYs
•In the past, health organizations used death as a measure of world health
•Now use disability-adjusted life years (DALYs) to measure health
–Recognizes that illness or disabilities lead to loss of a healthy life
Global disease burden
•Communicable diseases are responsible for nearly half of all DALY’s lost each year
–About 90% of all DALY losses occur in developing world
•Malnutrition exacerbates many diseases
Communicable diseases
•Communicable diseases are responsible for one-third of all disease-related mortality
–Majority in countries with poor nutrition, sanitation, and vaccination programs
•Pathogens are disease-causing organisms
Pathogens
•Influenza epidemic of 1918
•50-100 million died in less than 12 months
•Recently recreated this virus and it is similar to bird flu today
Pathogens
•One-third of human population suffers from worms and flukes
Pathogens
•Giardia is the largest single cause of diarrhea in the US
–Daycare centers and nursery schools
Pathogens
•Malaria is one of the most prevalent remaining infectious diseases
–Spread by mosquitos in tropical areas
•Global warming
–1 million die each year
–Simple treatment solutions
•Insecticide-treated bed nets
•Chloroquine pills
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 the speed and frequency of modern travel
SARS (Severe Acute Respiratory Syndrome)
•First appeared in China
•Quickly spread to 31 countries
•8,500 cases, 800 deaths
•Linked to consumption of wild game species
West Nile Virus
•Spread by mosquitos
•Causes encephalitis or brain inflammation
•First found in US in 1999
•4,000 infected, 285 died in 2002
•High amount of bird deaths
•Horses affected
HIV/AIDS
•Virtually unknown until 15 years ago
•Fifth greatest cause of contagious disease
•60 million currently affected
•3 million die each year
•40% of all adults in Botswana are HIV positive
Recent outbreaks of infectious diseases
Ecological diseases
•Domestic animals and wildlife also experience sudden and widespread epidemics
•Many times these epidemics are exacerbated by human activities
Distemper
•Distemper virus killed ½ the seals in western Europe
•Toxic pollutants and hormone disrupters may have made seals more vulnerable to infection
•May be reappearing
–In 2002, more dead seals seen in Denmark
Chronic Wasting Disease (CWD)
•Affects deer and elk
•Caused by protein called a prion
•Degenerate neurological disease
•Related to Mad Cow Disease
•Concern that it may jump to humans
Sudden Oak Death Syndrome (SODS)
•Caused by fungus-like organism called a water mold
•Possibly imported with Asian rhododendrons
•Close relative to pathogen that caused Ireland’s potato blight
•Douglas fir and redwoods affected
Black-band disease
•Algae kills coral
•Pathogenic bacteria from human feces may trigger the algal attack
Antibiotic and pesticide resistance
•Protozoan parasite that causes malaria is now resistant to most antibiotics
•Mosquitoes that transmit it have developed resistance to many insecticides
Why are these organisms resistant?
•Short life spans
–Speeds up natural selection and evolution
•Human tendency to overuse pesticides and antibiotics
–Overuse of antibiotics is an evolutionary force that leads to natural selection of resistant types
Antibiotic use leads to resistance
•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
Diet
•Strong correlation between cardiovascular disease and the amount of salt and fat in an individual’s diet
–Highly-processed foods, fat, and smoke-cured, high-nitrate meats appear to be associated with cancer
Diet
•Sixty-percent of all U.S. adults are now considered overweight
–Estimated 1 billion worldwide
•Second leading cause of death in the US
•U.S. Centers for Disease Control (CDC) warn one in three U.S. children are at risk of becoming diabetic