Chapter 4 Human Health and Environmental Hazards

In 2005, 52% of Canadian households used pesticides regularly on their lawns or gardens In 2005, 52% of Canadian households used pesticides regularly on their lawns or gardens Greater threat to children: why? Greater threat to children: why? Problems from pesticides? Problems from pesticides? How are children How are children exposed? exposed? Effects on intellectual Effects on intellectual development development Pesticides & Children

A Perspective On Risks Human health has Human health hasimproved Longer life span Longer life span Risk Risk Probability of harm Probability of harm occurring in certain circumstances Part of daily life Part of daily life Must understand nature and size of risk Must understand nature and size of risk

Probabilities Of Risk Probability of 1  risk certain to occur Probability of 1  risk certain to occur Probability of 0  risk certain not to occur Probability of 0  risk certain not to occur

Risk Assessment Quantifying risks of an action Quantifying risks of an action Four steps Four steps 1)Hazard identification 2)Dose-response assessment 3)Exposure assessment 4)Risk characterization Evaluate results Evaluate results

Risk Assessment

Choose Your Risk No choice for some risks No choice for some risks What risks do we worry most about? What risks do we worry most about? Why do we choose Why do we choose risky behaviour? risky behaviour?

Environmental Health Hazards We are exposed to many chemicals We are exposed to many chemicals Toxicology Toxicology Study of toxicants Study of toxicants Mechanisms of toxicity Mechanisms of toxicity Prevent toxic effects Prevent toxic effects Acute toxicity Acute toxicity Chronic toxicity Chronic toxicity

Environmental Health Hazards Noninfectious disease Noninfectious disease Not transmitted from one person to another Not transmitted from one person to another Result of chronic toxicity Result of chronic toxicity Infectious disease Infectious disease Transmissible between people Transmissible between people Contaminated food and water Contaminated food and water

Polluted Water Water is tested for presence of sewage Water is tested for presence of sewage Pathogen: agent that causes disease Pathogen: agent that causes disease Fecal coliform test Fecal coliform test E. coli E. coli Filter water Filter water Let bacteria grow Let bacteria grow Count bacterial colonies Count bacterial colonies

Water And Disease

Environmental Change & Disease Epidemiologists Epidemiologists Links between human health and environmental change Links between human health and environmental change Deforestation, dams, agriculture Deforestation, dams, agriculture How do these cause How do these cause more disease? Social factors Social factors Travel Travel

Avian Influenza Pandemic Pandemic Transferred from birds to humans Transferred from birds to humans High fatality rate High fatality rate

Avian Influenza Major concern Major concern Evolution of a strain easily transferred Evolution of a strain easily transferred to humans to humans  Could kill millions of people in a single year Endemic in domestic wild birds in Endemic in domestic wild birds in Asia, Africa, and Northern Africa Asia, Africa, and Northern Africa

Toxicants In The Environment DDT DDT Insecticide Insecticide Persistent: stored in fatty tissues Persistent: stored in fatty tissues Bioaccumulation: builds up in an organism Bioaccumulation: builds up in an organism Biological magnification: increases as it passes up the food chain Biological magnification: increases as it passes up the food chain

Toxicant Mobility Who got the biggest dose of DDT? Who got the biggest dose of DDT? Banned in Canada in 1970 and in 1972 in U.S. Banned in Canada in 1970 and in 1972 in U.S.

Biomagnification

English-Wabigoon River System River system located in northwestern Ontario River system located in northwestern Ontario Contaminated by wastewater from pulp and paper company Contaminated by wastewater from pulp and paper company 9000 kilograms of mercury dumped into river between 1962 and kilograms of mercury dumped into river between 1962 and 1970 Known as one of the most mercury- contaminated freshwater system in the world Known as one of the most mercury- contaminated freshwater system in the world

English-Wabigoon River System 1970, Ontario government ordered a stop to mercury dumping 1970, Ontario government ordered a stop to mercury dumping Consider the long term damage Consider the long term damage What impacts did this contamination have for nearby Aboriginal communities? What impacts did this contamination have for nearby Aboriginal communities?

Toxicant Mobility Chemicals move throughout environment Chemicals move throughout environment

Toxicant Mobility Pollution intensity can no longer be determined by contamination levels near industrial sites Pollution intensity can no longer be determined by contamination levels near industrial sites Remote areas of the globe are feeling the effects of harmful chemicals Remote areas of the globe are feeling the effects of harmful chemicals Long range transport of harmful chemicals may have an impact on the entire arctic ecosystem Long range transport of harmful chemicals may have an impact on the entire arctic ecosystem

Persistent Organic Pollutants 12 very toxic chemicals 12 very toxic chemicals Persistent, bioaccumulate, Persistent, bioaccumulate, mobile mobile

Persistent Organic Pollutants Stockholm Convention Stockholm Convention Countries must eliminate production and use of POPs Countries must eliminate production and use of POPs Exception to Exception to this? this?

Determining Health Effects Of Pollutants Dose: amount that enters the body Dose: amount that enters the body Response: type & amount of damage Response: type & amount of damage Lethal dose Lethal dose Sub-lethal dose Sub-lethal dose

Determining Toxicity Lethal dose-50 percent Lethal dose-50 percent LD 50 LD 50 Dose that is lethal to 50% of the population Dose that is lethal to 50% of the population Determined for all new synthetic chemicals Determined for all new synthetic chemicals Animal testing Animal testing

Lethal dose-50 percent

Determining Toxicity Effective dose-50 percent Effective dose-50 percent ED 50 ED 50 Dose that causes 50% of population to exhibit specific response Dose that causes 50% of population to exhibit specific response Animal testing Animal testing

Dose-Response Curve Shows effect of different doses Shows effect of different doses Start with high doses Start with high doses Work way down to threshold level Work way down to threshold level Maximum dose with no measurable effect Maximum dose with no measurable effect Below is considered safe Below is considered safe For some toxicants, there is no safe dose For some toxicants, there is no safe dose

Dose-Response Curve

Cancer-Causing Substances Carcinogens Carcinogens Expose animals to large doses Expose animals to large doses Realistic? Ethical? Realistic? Ethical? Assumes one can work backward Assumes one can work backward Process filled with Process filled with uncertainty uncertainty Epidemiological evidence Epidemiological evidence New methods being New methods being developed developed

Chemical Mixtures Most studies on single chemicals: why? Most studies on single chemicals: why? Three types of chemical interactions Three types of chemical interactions Additive: add effects of chemicals Additive: add effects of chemicals Synergistic: greater combined effect than expected Synergistic: greater combined effect than expected Antagonistic: smaller combined effect than expected Antagonistic: smaller combined effect than expected Usually assume additive Usually assume additive

Children & Chemicals Children more susceptible: why? Children more susceptible: why? Air pollution Air pollution Lungs still developing Lungs still developing Higher metabolism  more oxygen needed Higher metabolism  more oxygen needed

Precautionary Principle “ An ounce of prevention is worth a pound of cure” “ An ounce of prevention is worth a pound of cure” New technology/chemicals not introduced until: New technology/chemicals not introduced until: Risks are small Risks are small Benefits outweigh risks Benefits outweigh risks New evidence helps New evidence helps

Precautionary Principle Puts burden of proof on developers Puts burden of proof on developers Controversy Controversy Decreases role of science? Decreases role of science? Europe banned North American beef Europe banned North American beef Protect Protect consumer? consumer? Protect Protect European European farmers? farmers?

Eco Canada Career Focus Consider a career as a ecotoxicologist Consider a career as a ecotoxicologist Study the causes and effects of environmental toxins that affect living organisms Study the causes and effects of environmental toxins that affect living organisms

Case Study: Endocrine Disrupters PCBs, dioxins, mercury, etc. PCBs, dioxins, mercury, etc. Interfere with body’s hormones Interfere with body’s hormones Alter reproductive development Alter reproductive development Lake Apopka, Florida Lake Apopka, Florida 1980 chemical spill 1980 chemical spill Alligator eggs have Alligator eggs have high mortality rate high mortality rate

Case Study: Endocrine Disrupters & Humans Increasing rates of: Increasing rates of: Reproductive disorders Reproductive disorders Infertility Infertility Some Cancers Some Cancers Environment Canada has made EDS research a top priority Environment Canada has made EDS research a top priority Lack of human studies Lack of human studies