Nature of Environmental Health HazardsTitik RespatiUNISBA

OBJECTIVE:To describe the difference between hazard & riskTo explain the logic of the various methods of classifying environmental hazardsTo describe a scheme for identifying the level of hazard & toxicityTo explain why knowledge of the toxicology, microbiology, or physical properties of an environmental hazard is essential to determining the most appropriate approach to its risk assessmentTo identify different experimental investigative methodsTo explain the biological significance of bio-transformation processTo list the basic characteristics of chemical, physical, biological, mechanical, & psychosocial hazards

Required Reading Yassi A, Kjellstrm T, de Kok T, Guidotti TL. Basic Environmental Health. Chapter 2: Nature of Environmental Health Hazards. New York: Oxford University Press, 2001

Menuurt sbeauh penilitean di Cmabrigde Uinervtisy, tiadk meajndi malsaah bgaiamnaa uratun hruuf-hruuf di daalm seubah ktaa. Ynag pailng pnetnig adlaah leatk hruuf peratma Dan terkahir itu beanr. Sisnaya daapt breatnakan smaa seakli Dan kmau maish dpaat meaambcnya dgaen bnaer.

DefinitionHazarda factor or exposure that may adversely affect health (Last, 1995)

a source of danger a qualitative term expressing the potential of an environmental agent to harm the health of certain individuals if the exposure level is high enough &/or if other conditions apply

Definition (contd)Riskthe probability that an event will occur, e.g. that an individual will become ill or die within a stated period of time or before a given age; the probability of a (generally) unfavorable outcome (Last, 1995)

the quantitative probability that a health effect will occur after an individual has been exposed to a specified amount of a hazard

Types of EH Hazards Biological hazardse.g. bacteria, viruses, parasites Chemical hazardse.g. toxic metals, air pollutants, solvents, pesticides Physical hazardse.g. radiation, temperature, noise Mechanical hazardse.g. motor vehicle, sports, home, agriculture, & workplace injury hazards Psychosocial hazardse.g. stress, lifestyle disruption, workplace discrimination, effects of social change, marginalization, unemployment

Classified according to: nature natural vs anthropogenic traditional vs modern route of exposure settingTypes of EH Hazards (contd)

Traditional HazardsDisease vectorsInfectious agentsInadequate housing & shelterPoor-quality drinking water & sanitationIndoor air pollution from cookingDietary deficienciesHazards of child birthWildlife & domestic animalsInjury hazards in agricultureModern HazardsTobacco smokingTransport hazardsPollution from sewage & industryOutdoor air pollution from industry & motorcarsOveruse or misuse of chemicalsIndustrial machineryUnbalanced diet

Biological, chemical & physical hazards by routes of exposure

BiologicalChemicalPhysicalAIR Agent/sourceMicroorganismsFumes, dust, particlesRadiation, heat, noise Vectorial factorsCoughing, exhalationsContaminated airClimate, unguarded exposures RoutesInhalation, contactInhalation, contactInhalation, direct penetrationWATER Agent/sourceMicroorganisms, decayed organic materialDischarges, teaching, dumpingRadiation, heat in power station cooling water Vectorial factorsInsects, rodents, snails, animal excreta, food chainContaminated food & waterAccidents, contaminated food & water RoutesBites, ingestion, contactIngestion, contactIngestion, contact

BIOLOGICAL HAZARDSInclude all of the forms of life (as well as the nonliving products they produce)plants, insects, rodents, other animals, fungi, bacterial, viruses, protozoa, a wide variety of toxins & allergens; & prion

Routes of exposure:AirWaterFoodDirect penetrationBiting

Person exposed the agent distributed via blood, lymph, or other body fluids to the parts of the body most favorable for it to grow

Prions (proteinaceous infectious particles)Infectious agents (not organisms) made of protein (yet to be fully characterized)Multiply by converting normal protein molecules into dangerous ones by changing their shapesResponsible for the various forms of spongiform encephalopathy, e.g.: -bovine spongiform encephalopathy (BSE) or mad-cow disease) - Creutzfeldt-Jakob disease (CJD) - kuru (transmitted by ritual handling of bodies & brains of the dead)Symptoms of the human prion diseases: dementia, loss of coordination

Virusesa piece of nucleic acid (either DNA or RNA), which makes its progeny by orchestrating the production of virus particles by a cellviruses that lack a lipoprotein envelope (e.g. hepatitis A, gastroenteritis viruses) can grow in the human gut & be spread by food & waterviruses with a lipoprotein envelope have limited survival outside a host & so are spread in aerosols or inoculations of body fluids from person to person (e.g. measles)reproduces only inside a host cellviral diseases do not respond to antibiotics, but some respond to specific antivirals

Bacteriamost have sufficient energy supply to reproduce outside a cellhave genetic material but no nucleusdivide by splitting in halfexist singly or in short chains of two or moreclassified by shape, oxygen requirement & ability to take up a special stain

Fungisimple plant plant organisms that lack the chlorophyll needed to use carbon dioxide & sunlight to build sugars & structural moleculesclassified into yeast (single-celled) or moulds, which grow as branching filaments called hyphaeyeast reproduce by budding, moulds by branching & longitudinal growth of hyphae, as well as by producing sexual spores

Protozoathe simplest class of animal & consisting of a single nucleated celleach cells has organelles that carry on such functions as locomotion, nutrition, excretion, respiratione.g. : plasmodium, cryptosporidium, giardia

Arthropodsthe large phylum of animal life that includes insects, spiders, mites & ticks (as well as crabs & lobsters)some of these creatures bite, sting, cause allergic reactions, and may serve as vectors for viruses & other infectious agents

PathwayDiseaseInadequate sanitation, the dumping of untreated sewage into surface water, poor hygienic practices water polluted by human excretacholera, typhoid fever, dysentry, other diarrheal diseases, hepatitis A, schistosomiasisOvercrowding, poorly ventilated housing airborne transmissiontuberculosis, measles, influenza, pneumonia, pertussis, cerebrospinal meningitisUnhygienic animal husbandry zoonoses transmissionplague & hydatids diseasesStagnant waters, unsanitary housing, refuse dumping vector-borne transmissionmalaria, trachoma, schistosomiasis, filariasis, yellow fever, plague, typhus, trypanosomiasis

Growth of biological agents are slowed down or stopped by:defense mechanisms of the bodydrugs

CHEMICAL HAZARDSInorganic Substanceshalogens (e.g. fluorine, chlorine, bromine, iodine)alkaline compounds (e.g. NH3, Ca(OH)2, KOH, NaOHozone (O3)NOx and SOxmetals (e.g. cadmium, chromium, copper, lead, manganese, mercury, nickel, arsenic)

Organic Compoundsaliphatic hydrocarbons (e.g. methane, ethane, propane, butane, pentane, hexane, heptane, octane)alicyclic hydrocarbons (e.g. cyclohexane, methylcyclohexane, turpentine)aromatic hydrocarbons (e.g. benzene, toluene, styrene, naphthalene)halogenated hydrocarbons (e.g. chloromethane, dichloromethane, chloroform, carbon tetrachloride, trichloroethyene, polyviyl chloride)alcohols (e.g. methanol, ethanol, propanol)

Route of exposuresSource:natural eventsman-made: industrial, agricultural, commercial, domestic, manufacturing wastesExposure:inhalation- breastfeedingoral ingestion- placental transferabsorption via the skin- inoculation & direct penetrationabsorption via the eyes

Air, water,dirt, etcFood, water,drugsAirSkinRespiratorytractGI-tractBloodOtherorgansLiverKidneySweatHairUrineFaecesbileexfoliationinhalationexhalationingestionexternal contaminationExposureMediaMajor uptakepathwaysTransport &distributionMajorexcretorypathways

BiotransformationHydrophobic or lipophilic hydrophilic

Phase I : - the molecule is altered by the introduction of electrostatically charged (polar) groups- result of oxidation, reduction, or hydrolysisPhase II: substances are combined w/ hydrophilic endogenous compounds

Bioactivation of BenzeneBenzene(the original chemical)Benzene epoxide(a dangerously toxicproduct)Phenol(an intermediate thatthe body can handle)Phenylglucuronide(hydrophilic; easilyexcreted)Phase IPhase II

xenobioticsbiliary excretionextracellular mobilizationplasma circulationrenal excretionsecretionphase II(bioinactivation) conjugationphase I(bioactivation or inactivation)oxidation, reduction, hydrolysisaccumulation in body fatlipophilicpolarhydrophilichighly lipophilicmetabolically stablepolarhydrophilic

Toxicityany harmful effect of a chemical or a drug on a target organSystemic toxicityLiver toxicityKidney toxicitySkin toxicityNeurotoxicityImmunotoxicity

Multistage process of carcinogenesis:InitiationPromotionProgression Gene mutation:the result of single or multiple base pair changes (substitutions, deletions, insertions)in the DNA. Normally, the cell defense mechanisms can repair DNA damages, recreatingthe original structures. Repair can be faulty, leading to heritable changes Chromosomal alterationsvia damage by genotoxic agents, leading to structural aberrations (breaks, deletions, translocations), &via loss or gain of one or more chromosomes & sometimes changes in the number of chromosomes Gene rearrangements: characterized by altered gene expression (gene amplification, loss of activity). The underlying causesmight be translocations or inversions of large parts of chromosomes

Toxicity TestingAcute toxicity studiesto predict human effects of short-term, high-level exposures; can provide a measure of the toxic potential of different compoundsED50 : dose that would cause the effect in half of the test populationLD50 : dose that would kill half of the test populationLC50 : concentration of gas or vapor that kills half the test populationLD50 & LC50 : crude indices of toxicitySub-chronic testsanimals exposed repeatedly to a given chemical over a relatively long period (28 days or longer), normally 10% of the lifetime of the selected animalsChronic toxicity testingperformed by exposing animals to the chemical being tested for the whole of the animals lifetimeReproductive studieson parents & offspring

Toxicity Testing (contd)Genotoxic short-term testsshort-term tests for gene mutation & chromosome alterations both in vitro & in vivoHuman studiesclinical or epidemiological studiesStructure-activity relationships

Right-to-know legislation hazard identification & control

PHYSICAL HAZARDSForms of potentially harmful energy in the environment that can result in either immediate or gradually acquired damage when transferred in sufficient quantities to exposed individualse.g.: sound waves, radiation, light energy, thermal energy, electrical energy

NoiseNoise: an unwanted soundSound intensity: measured in decibels (dB)Risk of incurring hearing loss begins w/ prolonged exposure to sound of + 75 dB(A)Rule of thumb:if a loud voice is not understandable at a distance of 1 m b/c of excessive background noise, the background noise level is above 85 dB & likely to be dangerous

Hearing conservation programRegular monitoring of the workplaceBaseline & annual audiograms (for all exposed workers)In-service & pre-service (worker) educationSystematic record keepingWorker notificationProvision of hearing protection

Other physical hazards:vibration, radiation, light, lasers, pressure, temperaturesWhat are potential health effects of such hazards?

Mechanical Hazardsthose posed by the transfer of mechanical or kinetic energy (the energy of motion) Injury, trauma, accidents

Vulnerable groups: children, the elderly, & disadvantaged groups

The Haddon Matrix

FactorsPhasesHumanVehicleEnvironmentPre-injuryInjuryPost-injury

Psychosocial HazardsPotential sources of work-related psychosocial stress:factors intrinsic to the jobthe role of the worker in the organizationcareer developmentinterpersonal relationships at workorganizational structure & climate

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