Chapter 7Chapter 7Human Health and Environmental Human Health and Environmental Toxicology Toxicology

Overview of Chapter 7Overview of Chapter 7

o Human HealthHuman Health• Health issues in developed countriesHealth issues in developed countries• Health issues in developing countriesHealth issues in developing countries

o Environmental Pollution and DiseaseEnvironmental Pollution and Disease• Environmental ContaminantsEnvironmental Contaminants• Endocrine DisruptersEndocrine Disrupters

o Determining Health Effects of PollutantsDetermining Health Effects of Pollutantso EcotoxicologyEcotoxicologyo Risk AssessmentRisk Assessment

Human HealthHuman Healtho Two indicators of human health in a given Two indicators of human health in a given

country are:country are:• Life expectancy- how long people are expected Life expectancy- how long people are expected

to liveto live• Infant mortality- how many children die before Infant mortality- how many children die before

age of 1 yearage of 1 year

o Vary greatly Vary greatly between countriesbetween countries• Developed countriesDeveloped countries• Developing countriesDeveloping countries

Health Issues in Health Issues in Highly Developed CountriesHighly Developed Countries

o By many measures- health is good in these By many measures- health is good in these countriescountries• Great sanitationGreat sanitation• Few childhood diseasesFew childhood diseases

o Average life expectancyAverage life expectancy• Men = 75 yearsMen = 75 years• Women = 80 yearsWomen = 80 years

o Leading causes of death in US:Leading causes of death in US:• Cardiovascular diseaseCardiovascular disease• CancerCancer• Chronic Obstructive Pulmonary Disease (of the Chronic Obstructive Pulmonary Disease (of the

lungs)lungs)

Health Issue inHealth Issue inHighly Developed CountriesHighly Developed Countries

o Premature deaths caused by individual Premature deaths caused by individual lifestyle decisionslifestyle decisions• Poor dietPoor diet• Lack of exerciseLack of exercise• SmokingSmoking

o Obesity is big problemObesity is big problem• Body Mass Index (BMI)Body Mass Index (BMI)

• (Weight X 740)/ (height (in))(Weight X 740)/ (height (in))22

• If your BMI is less than 18.5, you are underweightIf your BMI is less than 18.5, you are underweight• If your BMI is 18.5-24.9, you are at a healthy weightIf your BMI is 18.5-24.9, you are at a healthy weight• If your BMI is 25-29, you are overweightIf your BMI is 25-29, you are overweight• A BMI of greater than 30 is obeseA BMI of greater than 30 is obese

Health Issues in Developing Health Issues in Developing CountriesCountries

o Biggest problemsBiggest problems• Malnutrition, unsafe water, poor sanitationMalnutrition, unsafe water, poor sanitation

o Life ExpectancyLife Expectancy• Overall is 65 yearsOverall is 65 years• Very poorest developing countries = 45 yearsVery poorest developing countries = 45 years

• Most of these countries have high AIDS epidemicsMost of these countries have high AIDS epidemics

o Childhood mortality is high (18% of deaths)Childhood mortality is high (18% of deaths)• Diarrheal diseasesDiarrheal diseases• MalnutritionMalnutrition• MalariaMalaria• AIDS/HIVAIDS/HIV

Emerging and Reemerging DiseasesEmerging and Reemerging Diseaseso Emerging Disease - not Emerging Disease - not

previously observed in previously observed in humanshumans• Usually jumps from Usually jumps from

animal hostanimal host• Ex: AIDS, lyme disease, Ex: AIDS, lyme disease,

West Nile Virus, SWINE West Nile Virus, SWINE FLU!!!!!FLU!!!!!

o Reemerging Disease- existed in the past and are recently Reemerging Disease- existed in the past and are recently increasing in incidenceincreasing in incidence• Ex: tuberculosis, yellow fever, malariaEx: tuberculosis, yellow fever, malaria

Reasons for Reasons for Emergence/ReemergenceEmergence/Reemergence

o Evolution of disease so it can move to Evolution of disease so it can move to human hosthuman host

o Evolution of antibiotic resistance in diseaseEvolution of antibiotic resistance in diseaseo Urbanization and overcrowdingUrbanization and overcrowdingo Increased pop. of elderly- susceptible to Increased pop. of elderly- susceptible to

diseasediseaseo Pollution and environmental degradationPollution and environmental degradationo Growth in international travel and Growth in international travel and

commercecommerceo Poverty and social inequalityPoverty and social inequality

Environmental Pollution and Environmental Pollution and DiseaseDisease

o Often difficult to Often difficult to link pollutants to link pollutants to their effects on their effects on peoplepeople

o Three ways to Three ways to analyze toxic analyze toxic effects of effects of pollutants:pollutants:

1.1. PersistencePersistence

2.2. BioaccumulationBioaccumulation

3.3. BiomagnificationBiomagnification

1. Persistence1. Persistenceo A characteristic of certain chemicals that are A characteristic of certain chemicals that are

extremely stable and may take many years extremely stable and may take many years to be broken down into simpler forms by to be broken down into simpler forms by natural processes natural processes • Synthetic chemicals (those not found in nature)Synthetic chemicals (those not found in nature)• Ex: DDTEx: DDT

o Natural decomposers (bacteria) have not Natural decomposers (bacteria) have not evolved a way to break it downevolved a way to break it down

BioaccumulationBioaccumulationo The buildup of a persistent toxic substance The buildup of a persistent toxic substance

in an organism’s body, often in fatty tissues in an organism’s body, often in fatty tissues • Synthetic chemical do not metabolize wellSynthetic chemical do not metabolize well• They remain in the body for extended periods of They remain in the body for extended periods of

timetime

BiomagnificationBiomagnification

o The increased The increased concentration of concentration of toxic chemicals toxic chemicals in the tissues of in the tissues of organisms that organisms that are at higher are at higher levels in food levels in food webs webs

o Diagram is Diagram is example of example of biomagnification biomagnification of DDTof DDT

Endocrine DisruptersEndocrine Disrupters

o A chemical that mimics or interferes with the A chemical that mimics or interferes with the actions of the endocrine system in humans actions of the endocrine system in humans and wildlife and wildlife • i.e. It effects the ability of the hormones in the i.e. It effects the ability of the hormones in the

organisms to function properlyorganisms to function properly

o Examples include:Examples include:• PCBs, DioxinsPCBs, Dioxins• Heavy metals – lead and mercuryHeavy metals – lead and mercury• DDTDDT

o Animals exposed to these chemicals have Animals exposed to these chemicals have altered reproductive development and are altered reproductive development and are often sterileoften sterile

Endocrine DisruptersEndocrine Disrupterso Case Study: 1980 chemical spill into Lake Case Study: 1980 chemical spill into Lake

Apopka, FLApopka, FL• Male alligators began to exhibit low testosterone Male alligators began to exhibit low testosterone

levels and high estrogen levelslevels and high estrogen levels

Endocrine Disrupters and HumansEndocrine Disrupters and Humans

o Infertility and hormonally related Infertility and hormonally related cancers are increasingcancers are increasing• Breast cancer and testicular cancerBreast cancer and testicular cancer

o Phthalates have been implicated as Phthalates have been implicated as potential endocrine disrupterspotential endocrine disrupters• Common ingredient in: cosmetics, Common ingredient in: cosmetics,

fragrances, nail polish, medication, toys, fragrances, nail polish, medication, toys, food packagingfood packaging

o Cannot make a link between endocrine Cannot make a link between endocrine disrupters and human illnessdisrupters and human illness• Too few studies have been performedToo few studies have been performed

Determining Health Effects of Determining Health Effects of PollutantsPollutants

o Toxicology is the study of the effect of Toxicology is the study of the effect of toxicants on the human bodytoxicants on the human body• Toxicant- chemical with adverse human Toxicant- chemical with adverse human

health effectshealth effectso Acute toxicityAcute toxicity

• Adverse effects occur within a short period Adverse effects occur within a short period after exposure to toxinafter exposure to toxin

o Chronic toxicityChronic toxicity• Adverse effects occur some time after Adverse effects occur some time after

exposure, or after prolonged exposure to exposure, or after prolonged exposure to toxintoxin

• Symptoms often mimic other diseases- hard Symptoms often mimic other diseases- hard to assess sourceto assess source

ToxicityToxicityo Toxicity measured by dose and responseToxicity measured by dose and response

• Dose: amount that enters the body of an Dose: amount that enters the body of an exposed organismexposed organism

• Response: the amount of damage caused by a Response: the amount of damage caused by a specific dosespecific dose

o Dose – Response CurveDose – Response Curve• Typically the dose is plotted against the Typically the dose is plotted against the

percentage of the population of test organisms percentage of the population of test organisms showing the response…on logarithmic graph showing the response…on logarithmic graph paperpaper

ToxicityToxicityo Dose-Response CurveDose-Response Curve

• Illustrates the effect of different doses on a populationIllustrates the effect of different doses on a population• Threshold LevelThreshold Level

• Maximum dose with no measurable effectsMaximum dose with no measurable effects

Threshold Level

Toxicity: Dose-Response CurvesToxicity: Dose-Response Curveso EDED50 50 = Effective Dose= Effective Dose

• The dose that causes 50% of the population to The dose that causes 50% of the population to exhibit whatever effect is under study (effective exhibit whatever effect is under study (effective dose)dose)

o LDLD50 50 = Lethal Dose= Lethal Dose• The dose that is lethal to 50% of the test The dose that is lethal to 50% of the test

organismsorganisms• Smaller the LDSmaller the LD5050, the , the more lethalmore lethal the chemical the chemical• Determined for all new synthetic chemicalsDetermined for all new synthetic chemicals

EDED5050

EDED5050

o This dose-response This dose-response curve demonstrates curve demonstrates two assumptions of two assumptions of classical toxicology.classical toxicology.• The biological The biological

response increases as response increases as the dose is increasedthe dose is increased

• There is a “safe” dose There is a “safe” dose below which there is below which there is no response (the no response (the threshold level)threshold level)

Results of Toxicology TestingResults of Toxicology Testingo Dose response Dose response

curves for 2 curves for 2 hypothetical hypothetical toxicants, A and Btoxicants, A and B

o Toxicant A has a Toxicant A has a lower Effective lower Effective Dose than toxicant Dose than toxicant BB

o Toxicant B, Toxicant B, however, is MORE however, is MORE toxic at lower toxic at lower doses!doses!

Results of Toxicology TestingResults of Toxicology Testingo Hormesis = occurs Hormesis = occurs

when a toxin is when a toxin is healthy at low healthy at low doses (necessary) doses (necessary) but harmful at high but harmful at high doses (cadmium, doses (cadmium, vitamin D, etc)vitamin D, etc)

o Aka the “hormetic Aka the “hormetic effect”!effect”!

Children and Chemical ExposureChildren and Chemical Exposureo Children more Children more

susceptible to chemicalssusceptible to chemicals• Weigh less than adultsWeigh less than adults• Bodies are still developingBodies are still developing• Play on floors and lawnsPlay on floors and lawns

• Exposed to cleaning Exposed to cleaning products and pesticidesproducts and pesticides

• Put things into their Put things into their mouthsmouths

o DiagramDiagram• Children in foothills not Children in foothills not

exposed to pesticidesexposed to pesticides• Children in valley were Children in valley were

exposedexposed

Identifying Cancer Causing Substances Identifying Cancer Causing Substances (Carcinogens)(Carcinogens)

o ToxicologistsToxicologists• Dose rats with varying levels of chemicals to Dose rats with varying levels of chemicals to

see if they develop cancersee if they develop cancer• Difficult to extrapolate results to humansDifficult to extrapolate results to humans

• Both mammals, but very different body size, Both mammals, but very different body size, metabolic rates, diet, etc. Humans may respond the metabolic rates, diet, etc. Humans may respond the same as rats, or very differently for a given toxin!same as rats, or very differently for a given toxin!

• Doses given to animals are usually much larger than Doses given to animals are usually much larger than the typical doses humans are exposed to!the typical doses humans are exposed to!

• Lab animals only live about 2 years…humans 75-80!Lab animals only live about 2 years…humans 75-80!• Human exposure is much more sporadic…and Human exposure is much more sporadic…and

involves multiple chemicals and exposure pathwaysinvolves multiple chemicals and exposure pathways

Toxicology vs. Epidemiology…Toxicology vs. Epidemiology…o EpidemiologistsEpidemiologists

• Look at historical exposure of groups of humansLook at historical exposure of groups of humans• See if exposed group have increased cancer rateSee if exposed group have increased cancer rate• Make generalizations about risk based upon Make generalizations about risk based upon

likelihood of exposure and effects.likelihood of exposure and effects.

o A very uncertain science!A very uncertain science!

Chemical MixturesChemical Mixtureso Most studies look at one chemical, but humans Most studies look at one chemical, but humans

tend to be exposed to chemical mixturestend to be exposed to chemical mixtures• Ex: automobile exhaustEx: automobile exhaust

o Chemical Mixtures interact byChemical Mixtures interact by• Additivity = exactly what one would expect, the combined Additivity = exactly what one would expect, the combined

effect of two toxins is the sum of the two toxins effect of two toxins is the sum of the two toxins • Synergy = when the effect of two toxins has a greater Synergy = when the effect of two toxins has a greater

combined effect than the sum of the two individual toxinscombined effect than the sum of the two individual toxins• Antagonism = when the combined effect of two toxins is Antagonism = when the combined effect of two toxins is

less than the sum of the two individual toxinsless than the sum of the two individual toxins

o Toxicity studies are expensive and take a while to Toxicity studies are expensive and take a while to completecomplete

Chemical TestingChemical Testing

EcotoxicologyEcotoxicology

o Dilution Paradigm is not validDilution Paradigm is not valid• ““Dilution is the solution to pollution”Dilution is the solution to pollution”

o Boomerang Paradigm is acceptedBoomerang Paradigm is accepted• ““What you throw away can come back and What you throw away can come back and

hurt you”hurt you”o EcotoxicologyEcotoxicology

• The study of contaminants in the biosphere The study of contaminants in the biosphere and their harmful effects on ecosystemsand their harmful effects on ecosystems

• Helps policy makers determine costs and Helps policy makers determine costs and benefits of industrial and technological benefits of industrial and technological “advances”“advances”

• And how they often adversely effect ecosystemsAnd how they often adversely effect ecosystems

Case Study: The OceanCase Study: The Ocean

o Land based nutrient and Land based nutrient and pollution runoff into pollution runoff into ocean is affecting ocean is affecting microorganismsmicroorganisms

o Ex: Red TideEx: Red Tide• Red pigmented poisonous Red pigmented poisonous

algal bloomsalgal blooms• Toxins kill off fish and Toxins kill off fish and

make humans sickmake humans sick

Red Tides…. (Diatoms)Red Tides…. (Diatoms)

o Algal bloom = a sudden Algal bloom = a sudden increase in the diatom increase in the diatom population in shallow population in shallow coastal waterscoastal waters• ““Brown tides” on Long Island Brown tides” on Long Island

were a sudden diatom bloom were a sudden diatom bloom that occurred in the 1980’s…that occurred in the 1980’s…and devastated the scallop and devastated the scallop industry….no known cause industry….no known cause for this!for this!

o Harmful Algal Blooms (Harmful Algal Blooms (HAB’sHAB’s) are now monitored ) are now monitored by NOAAby NOAA

Harmful Algal Blooms Bulletin…Harmful Algal Blooms Bulletin…o See a HAB bulletin fromSee a HAB bulletin from

January 2008 for NE Fl January 2008 for NE Floridaorida

Gulf of Mexico

“The Dead Zone”…

Can you tell the difference?

The Dead Zone• The dead zone is a large area of the Gulf of

Mexico, where the Mississippi River drains and deposits sediment into the delta

• Hypoxia = an oxygen-free condition; this is why the area is “dead”– this occurs in the Gulf of Mexico due to excess

nutrient loading from the Mississippi River watershed

D.O. contours show the extent…

Hypoxia:• Every summer, this environmental phenomenon

occurs off the coast of Louisiana, covering over 7,000 square miles of the Gulf of Mexico at times.

• The Gulf of Mexico "Dead Zone", or hypoxic zone, is an expanse of oxygen-depleted waters that cannot sustain most marine life.

• This hypoxic zone is caused by excessive amounts of nitrogen pollution delivered to the Gulf by the Mississippi River, and the subsequent eutrophication process (dead algae eaten by bacteria)

•  

The Dead Zone….• The Dead Zone has become a serious threat to

commercial fishing, shrimping and recreation industries.

• The livelihoods of many thousands of people and their communities are at risk, as is the large marine ecosystem on which they depend.

• The vast size of the Dead Zone and the severity of its impact are largely a consequence of human activity — such as river course and landscape alterations, industry, municipal waste treatment and agriculture — throughout the Mississippi River Basin.

The Dead Zone….• Human activity has resulted in enormous

increases in the amount of dissolved inorganic nitrogen delivered to the Gulf by the Mississippi River.

• Current estimates suggest that three times as much nitrogen is being carried into the Gulf today compared with levels 30 years ago or at any previous time on record.

Life in the Dead Zone • During the summer months of low oxygen, while fish

and other mobile animals can escape the developing Dead Zone, bottom dwellers that are attached to the ocean floor are doomed as the normal bottom ecosystem collapses.

• Significantly, when the autumn mixing brings oxygen levels back to normal, the bottom communities do not have the chance to revive. Instead, the area tends to be re-colonized by only a few short-lived species (such as polychaete worms) that can establish themselves in the aftermath of the Dead Zone.

Life in the Dead Zone• Larger, longer-lived species (such as

gastropods, bivalves, starfish, brittle stars and sea anemones) vanished from this part of the Gulf 30-40 years ago.

• These new bottom communities fall far short of the normal ecosystems in diversity, abundance or biomass.

• Ken Teague of the U.S. Environmental Protection Agency says “In the Dead Zone, the original bottom communities were lost a long time ago.”

Risk AssessmentRisk Assessment

o Risk- probability that a particular adverse effect Risk- probability that a particular adverse effect will result from some exposure or conditionwill result from some exposure or condition

o Risk Assessment = the use of statistical methods Risk Assessment = the use of statistical methods to quantify the risks of a particular action so they to quantify the risks of a particular action so they can be compared or contrasted with other riskscan be compared or contrasted with other risks

o We assess risk daily with four stepsWe assess risk daily with four steps1.1. Hazard identificationHazard identification

2.2. Dose response assessmentDose response assessment

3.3. Exposure assessmentExposure assessment

4.4. Risk characterizationRisk characterization

Risk AssessmentRisk Assessment

Risk AssessmentRisk Assessment

Using Risk AssessmentUsing Risk Assessmento Risk assessment is used in several ways for Risk assessment is used in several ways for

environmental regulationenvironmental regulation• Government may establish a “maximum risk” Government may establish a “maximum risk”

(one in one million chance, for example) (one in one million chance, for example) standard for a toxin, or a “Maximum standard for a toxin, or a “Maximum Contaminant Level” (actual dosage) that people Contaminant Level” (actual dosage) that people should not be exposed toshould not be exposed to

• MCL is what is “feasible” considering cost and MCL is what is “feasible” considering cost and available technologyavailable technology

• MCLG is the dosage “goal” that the EPA is MCLG is the dosage “goal” that the EPA is striving for to protect health betterstriving for to protect health better

• Example: TCE (Tri-chloro-ethylene) has an MCL of Example: TCE (Tri-chloro-ethylene) has an MCL of 0.005 mg/L and a MCLG of 0.000 mg/L0.005 mg/L and a MCLG of 0.000 mg/L

• NOTE: mg/L is the same as ppmNOTE: mg/L is the same as ppm

Ecological Risk AssessmentEcological Risk Assessment

o Difficult to assess because effects occur Difficult to assess because effects occur at wide range of scalesat wide range of scales• Individual plants and animalsIndividual plants and animals• Ecological communities over wide regionsEcological communities over wide regions

o Human-induced environmental Human-induced environmental stressors also range greatlystressors also range greatly• Good to badGood to bad• Acceptable to unacceptableAcceptable to unacceptable

o There is a need to quantify risks to the There is a need to quantify risks to the environmentenvironment

Case Study on Ecological Risk Case Study on Ecological Risk AssessmentAssessment

• Results in decrease Results in decrease in fish, algal in fish, algal bloomsblooms

o Ecol. Risk Ecol. Risk AssessmentAssessment• Used to help Used to help

government and government and locals set priorities locals set priorities to manage and to manage and protect ecosystem protect ecosystem

o Snake River Ecosystem in Southern IdahoSnake River Ecosystem in Southern Idaho• River provides hydroelectric power and water River provides hydroelectric power and water

for irrigationfor irrigation• Human use causes reduced flow, elevated Human use causes reduced flow, elevated

water temperature and nutrient enrichmentwater temperature and nutrient enrichment

Addressing Environmental ProblemsAddressing Environmental Problems

o Case in Point: Lake WashingtonCase in Point: Lake Washington

•Scientific assessment (U. of Washington)

•Public education and involvement

•Political action (Washington Pollution Control Commission)

Addressing Environmental ProblemsAddressing Environmental Problems

o Case in Point: Lake WashingtonCase in Point: Lake Washington

Evaluation

Addressing Environmental ProblemsAddressing Environmental Problems

o Case in Point: Lake WashingtonCase in Point: Lake Washington

Evaluation

Precautionary Principle!Precautionary Principle!o ““An ounce of prevention is worth a pound of An ounce of prevention is worth a pound of

cure”…cure”…o When a new technology or chemical product When a new technology or chemical product

is suspected of threatening health or the is suspected of threatening health or the environment, precautionary measures environment, precautionary measures should be taken, even if there is uncertainty should be taken, even if there is uncertainty about the scope of danger.about the scope of danger.

o Puts the burden of proof on the developers Puts the burden of proof on the developers of the new technology or substanceof the new technology or substance

o Critics of this principle often cite the Critics of this principle often cite the extensive cost of “proving” safety of a extensive cost of “proving” safety of a substance/technology, and a negative substance/technology, and a negative economic impact.economic impact.