Chapter 7Chapter 7Human Health and Human Health and Environmental Environmental ToxicologyToxicology

Overview of Chapter 7Overview of Chapter 7

Human HealthHuman Health In developed countriesIn developed countries In developing countriesIn developing countries

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

Determining Health Effects of Determining Health Effects of PollutantsPollutants

EcotoxicologyEcotoxicology Risk AssessmentRisk Assessment

Human HealthHuman Health

Two indicators of human healthTwo indicators of human health Life expectancy - how long people are Life expectancy - how long people are

expected to liveexpected to live Infant mortality - how many children die Infant mortality - how many children die

before the age of 1 yearbefore the age of 1 year Vary greatly betweenVary greatly between

countriescountries Developed countriesDeveloped countries Developing countriesDeveloping countries

Health in Highly Developed Health in Highly Developed CountriesCountries

Health is generally good in these Health is generally good in these countriescountries

Average life expectancyAverage life expectancy Men = 76.4 years (2014)Men = 76.4 years (2014) Women = 82 years (2014)Women = 82 years (2014)

Leading causes of death in USLeading causes of death in US Cardiovascular disease, Cancer, Lung Cardiovascular disease, Cancer, Lung

DiseaseDisease Premature deaths caused by lifestylePremature deaths caused by lifestyle

Poor diet, Lack of exercise, Smoking, ObesityPoor diet, Lack of exercise, Smoking, Obesity

Health in Developing Health in Developing CountriesCountries Biggest problemsBiggest problems

Malnutrition, unsafe water, poor sanitationMalnutrition, unsafe water, poor sanitation Life ExpectancyLife Expectancy

Overall is 65 yearsOverall is 65 years Very poorest developing countries = 45 Very poorest developing countries = 45

yearsyears Due to AIDS epidemics, nutrition, wars, etc.Due to AIDS epidemics, nutrition, wars, etc.

Childhood mortality is highChildhood mortality is high Diarrheal diseasesDiarrheal diseases MalnutritionMalnutrition MalariaMalaria AIDS/HIVAIDS/HIV

Emerging and Reemerging Emerging and Reemerging DiseasesDiseases Emerging Disease - notEmerging Disease - not

previously observed inpreviously observed inhumanshumans Usually jumps fromUsually jumps from

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

West Nile VirusWest Nile Virus Reemerging Disease - existed in the Reemerging Disease - existed in the

past and are recently increasing in past and are recently increasing in incidenceincidence Ex: tuberculosis, yellow fever, malariaEx: tuberculosis, yellow fever, malaria

Reasons for Reasons for Emergence/ReemergenceEmergence/Reemergence Evolution of disease so it transitions to Evolution of disease so it transitions to

human hosthuman host Evolution of antibiotic resistance in diseaseEvolution of antibiotic resistance in disease Urbanization and overcrowdingUrbanization and overcrowding Increased pop. of elderly - susceptible to Increased pop. of elderly - susceptible to

diseasedisease Pollution and environmental degradationPollution and environmental degradation Growth in international travel and commerceGrowth in international travel and commerce Poverty and social inequalityPoverty and social inequality

Environmental Pollution and Environmental Pollution and Disease Disease Pathways of Pathways of

PollutionPollution Often difficult Often difficult

to link to link pollutants to pollutants to their effects on their effects on peoplepeople PersistencePersistence BioaccumulatioBioaccumulatio

n & n & magnificationmagnification

PersistencePersistence

A characteristic of certain chemicals A characteristic of certain chemicals that are extremely stable and may that are extremely stable and may take many years to be broken down take many years to be broken down into simpler forms by natural into simpler forms by natural processes processes Synthetic chemicals (those not found in Synthetic chemicals (those not found in

nature)nature) Ex: DDTEx: DDT

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

BioaccumulationBioaccumulation

The buildup of a persistent toxic The buildup of a persistent toxic substance in an organismsubstance in an organism’’s body, s body, often in fatty tissues often in fatty tissues Synthetic chemicals do not metabolize Synthetic chemicals do not metabolize

wellwell They remain in the body for extended They remain in the body for extended

periods of timeperiods of time

BiomagnificationBiomagnification

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

Diagram (right) is Diagram (right) is example of example of biomagnification biomagnification of DDTof DDT

Endocrine DisruptersEndocrine Disrupters

A chemical that mimics or interferes with the A chemical that mimics or interferes with the actions of the endocrine system (sustained actions of the endocrine system (sustained bodily communication – growth, puberty, bodily communication – growth, puberty, menopause, etc.) in humans and wildlife menopause, etc.) in humans and wildlife

Examples include:Examples include: PCBs, DioxinsPCBs, Dioxins Heavy metals - lead and mercuryHeavy metals - lead and mercury DDTDDT

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 Disrupters

Case Study: 1980 chemical spill into Case Study: 1980 chemical spill into Lake Apopka, FLLake Apopka, FL Male alligators began to exhibit low Male alligators began to exhibit low

testosterone levels and high estrogen testosterone levels and high estrogen levelslevels

Endocrine Disrupters and Endocrine Disrupters and HumansHumans Infertility and hormonally related Infertility and hormonally related

cancers are increasingcancers are increasing Breast cancer and testicular cancerBreast cancer and testicular cancer

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

Determining Health Effects Determining Health Effects of Pollutantsof Pollutants

Toxicology is the study of the effect Toxicology is the study of the effect of toxicants on the human bodyof toxicants on the human body Toxicant - chemical with adverse human Toxicant - chemical with adverse human

health effectshealth effects Toxicity measured by dose and Toxicity measured by dose and

responseresponse Dose: amount that enters that body of Dose: amount that enters that body of

an exposed organisman exposed organism Response: the amount of damage Response: the amount of damage

caused by a specific dosecaused by a specific dose

ToxicologyToxicology

Acute toxicityAcute toxicity Adverse effects occur within a short Adverse effects occur within a short

period after exposure to toxinperiod after exposure to toxin Chronic toxicityChronic toxicity

Adverse effects occur some time after Adverse effects occur some time after exposure, or after prolonged exposure exposure, or after prolonged exposure to toxinto toxin

ToxicityToxicity

LD50LD50 Lethal dose to Lethal dose to

50% of the test 50% of the test organismsorganisms

Smaller the Smaller the LD50, the more LD50, the more lethal the lethal the chemicalchemical

Determined for Determined for all new all new synthetic synthetic chemicalschemicals

ToxicityToxicity

ED50ED50 Effective dose to 50% of the test organismsEffective dose to 50% of the test organisms ED50 causes 50% of the population to ED50 causes 50% of the population to

exhibit whatever effect is under studyexhibit whatever effect is under study Dose-Response CurveDose-Response Curve

Illustrates the effect of different doses on a Illustrates the effect of different doses on a populationpopulation

Threshold LevelThreshold Level Maximum dose with no measurable effectsMaximum dose with no measurable effects

Toxicity: ED50Toxicity: ED50

Children and Chemical Children and Chemical ExposureExposure Children are more susceptible to Children are more susceptible to

chemicalschemicals Weigh less than adultsWeigh less than adults Bodies are still developingBodies are still developing Play on floors and lawnsPlay on floors and lawns Put things into theirPut things into their

mouthsmouths Diagram (right)Diagram (right)

Children in foothills notChildren in foothills notexposed to pesticidesexposed to pesticides

Children in valley wereChildren in valley wereexposedexposed

Identifying Cancer Causing Identifying Cancer Causing SubstancesSubstances

ToxicologistToxicologist Dose rats with varying levels of Dose rats with varying levels of

chemicals to see if they develop cancerchemicals to see if they develop cancer Difficult to extrapolate results to Difficult to extrapolate results to

humanshumans EpidemiologistsEpidemiologists

Look at historical exposure of groups of Look at historical exposure of groups of humanshumans

See if exposed group have increased See if exposed group have increased cancer ratecancer rate

Chemical MixturesChemical Mixtures

Most studies look at one chemical, Most studies look at one chemical, but humans tend to be exposed to but humans tend to be exposed to chemical mixtureschemical mixtures Ex: automobile exhaustEx: automobile exhaust

Chemical Mixtures interact byChemical Mixtures interact by AdditivityAdditivity SynergySynergy AntagonismAntagonism

These studies are expensive and These studies are expensive and take a while to completetake a while to complete

EcotoxicologyEcotoxicology

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

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

hurt youhurt you”” EcotoxicologyEcotoxicology

The study of contaminants in the The study of contaminants in the biosphere and their harmful effects on biosphere and their harmful effects on ecosystemsecosystems

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

Case Study: The OceanCase Study: The Ocean

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

Ex: Red TideEx: Red Tide Red pigmented Red pigmented

poisonous algal bloomspoisonous algal blooms Toxins kill off fish and Toxins kill off fish and

make humans sickmake humans sick

Risk AssessmentRisk Assessment

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

We assess risk daily with four stepsWe assess risk daily with four steps Hazard identificationHazard identification Dose response assessmentDose response assessment Exposure assessmentExposure assessment Risk characterizationRisk characterization

Risk AssessmentRisk Assessment

Risk AssessmentRisk Assessment

Ecological Risk AssessmentEcological Risk Assessment

Difficult to assess because effect Difficult to assess because effect occur at wide range of scalesoccur at wide range of scales Individual plants and animalsIndividual plants and animals Ecological communities over wide regionsEcological communities over wide regions

Human-induced environmental Human-induced environmental stressors also range greatlystressors also range greatly

There is a need to quantify risks to There is a need to quantify risks to the environmentthe environment