Chapter 7 Human Health and Environmental Toxicology

Overview of Chapter 7 o Risk Assessment o Human Health Health issues in developed countries Health issues in developed countries Health issues in developing countries Health issues in developing countries o Environmental Pollution and Disease Environmental Contaminants Environmental Contaminants Endocrine Disrupters Endocrine Disrupters o Determining Health Effects of Pollutants o Ecotoxicology

Risk Assessment o Risk- probability that a particular adverse effect will result from some exposure or condition o We assess risk daily with four steps 1. Hazard identification 2. Dose response assessment 3. Exposure assessment 4. Risk characterization

Risk Assessment

Ecological Risk Assessment o Difficult to assess because effects occur at wide range of scales Individual plants and animals Individual plants and animals Ecological communities over wide regions Ecological communities over wide regions o Human-induced environmental stressors also range greatly Good to bad Good to bad Acceptable to unacceptable Acceptable to unacceptable o There is a need to quantify risks to the environment

Bioaccumulation o The buildup of a persistent toxic substance in an organism’s body, often in fatty tissues Synthetic chemicals do not metabolize well Synthetic chemicals do not metabolize well They remain in the body for extended periods of time They remain in the body for extended periods of time

Operation Cat Drop

Biomagnification o The increased concentration of toxic chemicals in the tissues of organisms that are at higher levels in food webs o Diagram is example of biomagnification of DDT

Persistence o A characteristic of certain chemicals that are extremely stable and may take many years to be broken down into simpler forms by natural processes Synthetic chemicals (those not found in nature) Synthetic chemicals (those not found in nature) Ex: DDT Ex: DDT o Natural decomposers (bacteria) have not evolved a way to break it down

Human Health o Two indicators of human health Life expectancy- how long people are expected to live Life expectancy- how long people are expected to live Infant mortality- how many children die before age of 1 year Infant mortality- how many children die before age of 1 year o Vary greatly between countries Developed countries Developed countries Developing countries Developing countries

How do you protect yourself?

Health Issues in Highly Developed Countries o By many measures- health is good in these countries Great sanitation Great sanitation Few childhood diseases Few childhood diseases o Average life expectancy in HDC =79 years Men = 76 years Men = 76 years Women = 81 years Women = 81 years o Leading causes of death in US Cardiovascular disease Cardiovascular disease Cancer Cancer Chronic Obstructive Pulmonary Disease (of the lungs) Chronic Obstructive Pulmonary Disease (of the lungs)

Health Issue in Highly Developed Countries o Premature deaths caused by lifestyle Poor diet Poor diet Lack of exercise Lack of exercise Smoking Smoking o Obesity is big problem Body Mass Index (BMI) Body Mass Index (BMI) (Weight X 740)/ (height (in)) 2 (Weight X 740)/ (height (in)) 2 < 18.5 is underweight < 18.5 is underweight is healthy weight is healthy weight is overweight is overweight > 30 is obese > 30 is obese

Health Issues in Developing Countries o Biggest problems Malnutrition, unsafe water, poor sanitation Malnutrition, unsafe water, poor sanitation o Life Expectancy Overall is 65 years Overall is 65 years Very poorest developing countries = 45 years Very poorest developing countries = 45 years Most of these countries have high AIDS epidemics Most of these countries have high AIDS epidemics o Childhood mortality is high (18% of deaths) Diarrheal diseases Diarrheal diseases Malnutrition Malnutrition Malaria Malaria AIDS/HIV AIDS/HIV

Emerging and Reemerging Diseases o Emerging Disease - not previously observed in humans Usually jumps from animal host Usually jumps from animal host Ex: AIDS, lime disease, West Nile Virus Ex: AIDS, lime disease, West Nile Virus o Reemerging Disease- existed in the past and are recently increasing in incidence Ex: tuberculosis, yellow fever, malaria Ex: tuberculosis, yellow fever, malaria

Reasons for Emergence/Reemergence o Evolution of disease so it can move to human host o Evolution of antibiotic resistance in disease o Urbanization and overcrowding o Increased pop. of elderly- susceptible to disease o Pollution and environmental degradation o Growth in international travel and commerce o Poverty and social inequality

Environmental Pollution and Disease o Often difficult to link pollutants to their effects on people Persistence Persistence Bioaccumulation Bioaccumulation Biomagnification Biomagnification

Endocrine Disrupters o A chemical that mimics or interferes with the actions of the endocrine system in humans and wildlife i.e. It effects the ability of the hormones in the organisms to function properly i.e. It effects the ability of the hormones in the organisms to function properly o Examples include: PCBs, Dioxins PCBs, Dioxins Heavy metals – lead and mercury Heavy metals – lead and mercury DDT DDT o Animals exposed to these chemicals have altered reproductive development and are often sterile

Endocrine Disrupters o Case Study: 1980 chemical spill into Lake Apopka, FL Male alligators began to exhibit low testosterone levels and high estrogen levels Male alligators began to exhibit low testosterone levels and high estrogen levels

Endocrine Disrupters and Humans o Infertility and hormonally related cancers are increasing Breast cancer and testicular cancer Breast cancer and testicular cancer o Phthalates have been implicated as potential endocrine disrupters Common ingredient in: cosmetics, fragrances, nail polish, medication, toys, food packaging Common ingredient in: cosmetics, fragrances, nail polish, medication, toys, food packaging o Cannot make a link between endocrine disrupters and human illness Too few studies have been performed Too few studies have been performed

Determining Health Effects of Pollutants o Toxicology is the study of the effect of toxicants on the human body Toxicant- chemical with adverse human health effects Toxicant- chemical with adverse human health effects o Acute toxicity Adverse effects occur within a short period after exposure to toxin Adverse effects occur within a short period after exposure to toxin o Chronic toxicity Adverse effects occur some time after exposure, or after prolonged exposure to toxin Adverse effects occur some time after exposure, or after prolonged exposure to toxin Symptoms often mimic other diseases- hard to assess source Symptoms often mimic other diseases- hard to assess source

Toxicity o Toxicity measured by dose and response Dose: amount that enters the body of an exposed organism Dose: amount that enters the body of an exposed organism Response: the amount of damage caused by a specific dose Response: the amount of damage caused by a specific dose o LD 50 Lethal dose to 50% of the test organisms Lethal dose to 50% of the test organisms Smaller the LD 50, the more lethal the chemical Smaller the LD 50, the more lethal the chemical Determined for all new synthetic chemicals Determined for all new synthetic chemicals

Toxicity o ED 50 Effective dose to 50% of the test organisms Effective dose to 50% of the test organisms ED 50 causes 50% of the population to exhibit whatever effect is under study ED 50 causes 50% of the population to exhibit whatever effect is under study o Dose-Response Curve Illustrates the effect of different doses on a population Illustrates the effect of different doses on a population Threshold Level Threshold Level Maximum dose with no measurable effects Maximum dose with no measurable effects

ED 50

Children and Chemical Exposure o Children more susceptible to chemicals Weigh less than adults Weigh less than adults Bodies are still developing Bodies are still developing Play on floors and lawns Play on floors and lawns Exposed to cleaning products and pesticides Exposed to cleaning products and pesticides Put things into their mouths Put things into their mouths o Diagram Children in foothills not exposed to pesticides Children in foothills not exposed to pesticides Children in valley were exposed Children in valley were exposed

Identifying Cancer Causing Substances o Toxicologist Dose rats with varying levels of chemicals to see if they develop cancer Dose rats with varying levels of chemicals to see if they develop cancer Difficult to extrapolate results to humans Difficult to extrapolate results to humans o Epidemiologists Look at historical exposure of groups of humans Look at historical exposure of groups of humans See if exposed group have increased cancer rate See if exposed group have increased cancer rate

Chemical Mixtures o Most studies look at one chemical, but humans tend to be exposed to chemical mixtures Ex: automobile exhaust Ex: automobile exhaust o Chemical Mixtures interact by Additivity Additivity Synergy Synergy Antagonism Antagonism o These studies are expensive and take a while to complete

Chemical Testing

Ecotoxicology o Dilution Paradigm is not valid “Dilution is the solution to pollution” “Dilution is the solution to pollution” o Boomerang Paradigm is accepted “What you throw away can come back and hurt you” “What you throw away can come back and hurt you” o Ecotoxicology The study of contaminants in the biosphere and their harmful effects on ecosystems The study of contaminants in the biosphere and their harmful effects on ecosystems Helps policy makers determine costs and benefits of industrial and technological “advances” Helps policy makers determine costs and benefits of industrial and technological “advances” And how they often adversely effect ecosystems And how they often adversely effect ecosystems

Case Study: The Ocean o Land based nutrient and pollution runoff into ocean is affecting microorganisms o Ex: Red Tide Red pigmented poisonous algal blooms Red pigmented poisonous algal blooms Toxins kill off fish and make humans sick Toxins kill off fish and make humans sick

Case Study on Ecological Risk Assessment Results in decrease in fish, algal blooms Results in decrease in fish, algal blooms o Ecol. Risk Assessment Used to help government and locals set priorities to manage and protect ecosystem Used to help government and locals set priorities to manage and protect ecosystem o Snake River Ecosystem in Southern Idaho River provides hydroelectric power and water for irrigation River provides hydroelectric power and water for irrigation Human use causes reduced flow, elevated water temperature and nutrient enrichment Human use causes reduced flow, elevated water temperature and nutrient enrichment