chapter 7 human health and environmental toxicology
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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
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
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
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