Environmental HealthFocuses on factors that cause diseaseNatural—biological agentsCultural—social and cultural practices and attitudesTechnological—physical and chemical agentsEnvironmental HealthInfectious DiseaseToxicologyDiseaseAbnormal change in structure/functionMorbidity—illnessMortality—deathMorbidity and Mortality Weekly Report published by CDCAcute/chronic illnessCauses of IllnessMorbidity—too vagueDisability-adjusted life years—DALYsIncludes premature deaths and loss of healthy life from illness, disabilityAttempts to define total costsYoung vs. old; death vs. disabilityPerception vs. realityHazard CategoriesCultural: unsafe work places, smoking, diet, drug use, assault, sex practicesPhysical: ionizing radiation, fire, weather, earthquakes, volcanoesChemical: air, water, soil, foodBiological: pathogens, allergens, animalsBiological HazardsCommunicable & noncommunicable disease, contagiousTransmissable & nontransmissableNontransmissable—caused by something not living & doesn’t spread from person to personTransmissable—caused by living organism,spread from person to personInfectious DiseasePathogens--disease causing agents (living organisms, viruses, prions)Vectors—pathways through which a disease spreadsAnimate: alive—insects, wormsInanimate: air, water, foodInfectious DiseaseReservoir: where the pathogen is found all the timeEpidemiology—study of disease in populationsInfectious DiseaseAcute—short incubation, sudden appearance of symptoms—colds, flu, smallpox, polio, Ebola, anthraxChronic—longer (?) incubation, no dramatic onset, long term—chronic fatigue, tb, malariaEmerging DiseasesNew to humans, not around for period of time or resistant to antibiotics, chemical treatmentNo defenses, no immediate treatmentDepending on virulence and transmissibility—real problemsEmerging DiseaseHIV—25 years agoSARS (severe acute respiratory syndrome)Avian flu—accurate reporting lacking, Chinese government, peasants, farmers live with animalsEbolaPathogensPrions—infectious proteinsCause proteins to change their spatial orientationProteins no longer functional—inactive enzymesNeurodegenerative disease—Creutzfeldt-Jakob disease: human variant of mad cow diseasePrionsSpread vertically—from one trophic level to anotherPrions found in nervous systemPassed in cows when infected NS tissue is ground into livestock feedCows are infected, takes time for BSE to develop, slaughtered, eatenPrionsNot destroyed by heat or acidControl by transmissionUSDA—can’t use CNS tissues or downer cattle???--Peripheral NS, what if infected but not manifested, infected imported cattle or meatPeriodic scaresVirusesGenetic information and associated proteinsAttach to membrane-bound receptors, inject genetic material, commandeer cell functionsProduce new viruses, viruses released and cell destroyedVirusesAcute—measles, colds, flu, isolated or world-wide (flu pandemic in 1918), polio, smallpoxChronic--Hepatitis B, C, …--different viruses, different modes of transfer, HIVBacteriaOne-celled, microscopic, forms clones, (some genetic exchange)Acute and chronic diseasesTuberculosis, cholera, plague—bubonic and pneumonicBacteriaTreat with antibioticProblems—antibiotic resistanceOver-prescribedMisusedIntroduced into livestock feed—residues found in meats and milk, gradually phased outProtozoansOne celled organisms (more complex cellular architecture)Malaria—kills more people than AIDSAmoebic dysenteryWormsMulticellularTapewormsLiver flukesIntestinal parasiteEtc.Why Still a Problem?Poor nutritionPoor infrastructureCrowded living conditionsContact with reservoir—EbolaFood production and processingProblem (cont’d)Change in demographicsTravelIncrease in urban centersWork placeToxicologyStudy of toxins (poisons) and their affectsHazardousChemicalPhysical—radiationHazard assessmentHazard AssessmentWhat—not all things are hazardousHow much--doseHow often—frequencyWho—age, health, sex, detoxification systems, genetic makeupFactorsSolubilityPersistenceBioaccumulationBiomagnificationChemical interactionsToxicitySolubilityWater soluble—inorganic compounds (often) move through ecosystem, water supply, water everywhere, incl. bodyExposure route—drinking, bathing, eatingFat (oil)-soluble—penetrate cell membranes, accumulate in tissuesExposure route—food, dermal applicationToxicityPersistence—resistance to chemical breakdownHeatLightStay active for long time—good and badBioaccumulationMolecules absorbed and stored in tissues or organsHigher amounts than normalLow level in environment can build up in living systems to harmful levelsBiomagnificationLevels of toxins are increased or magnified as they pass from one trophic level to nextLower trophic levels—ingest small amountsNext level up—eats moreAt each higher level, more and more of toxin is ingestedBiomagnificationLong-lived, persistent chemicalsFat-solubleBioaccumulatePersistent organic pollutants (POPS)BiomagnificationDDT—raptors (eagles, falcons) and pelicansPCBsPBDE—flame retardantsMDBE—gas additivesStain-resistant chemicals—PFOS, PFOA or C8Pthalates & plasticizersStrontium-90—not a POP, radiationBiomagnificationOnce released, hard to removeStop releaseRemoveLeave in place, encapsulate or allow sediments to cover depositsEncapsulation/sedimentation prevents re-releaseChemical InteractionsIncrease or decrease effectSynergistic—multiplies effectsAntagonistic—reduce effectsToxicology AssessmentTest effects on animalsDetermine lethal doseMedian lethal dose—LD50Amount received in one dose that kills 50% of test animals within 14 daysToxicology AssessmentDoes the dose make the poison?Yes, but differently for different peopleRepair mechanismsTrace levels may or may not be toxicdependsDetermine ToxicityCase reportsEpidemiological studies: experimental group and control groupAnimal testing—controversialDevelop dose-response curveDose-Response CurveControlled experimentTest group: exposed to chemicalControl group: identical to test group, but not exposed to chemicalBoth groups: identical age, health, genetic makeup, same environmental conditionsDose-ResponseHigh dosagesMathematical models extrapolate resultsEstimate LD50 values: 50% mortality2 modelsNonthresholdthresholdLD50VarySingle dose at low valueImpossible to get lethal dose into body5 most toxic:ArsenicLeadMercuryVinyl chloridePolychlorinated biphenylsNonthreshold Dose ResponseAny dose causes harmDamage increases with