Chapter33-ToxicologyINTRODUCTIONEllenK.SilbergeldToxicologyisthestudyofpoisons,or,morecomprehensively,theidentificationandquantificationofadverseoutcomesassociatedwithexposurestophysicalagents,chemicalsubstancesandotherconditions.Assuch,toxicologydrawsuponmostofthebasicbiologicalsciences,medicaldisciplines,epidemiologyandsomeareasofchemistryandphysicsforinformation,researchdesignsandmethods.Toxicologyrangesfrombasicresearchinvestigationsonthemechanismofactionoftoxicagentsthroughthedevelopmentandinterpretationofstandardtestscharacterizingthetoxicpropertiesofagents.Toxicologyprovidesimportantinformationforbothmedicineandepidemiologyinunderstandingaetiologyandinprovidinginformationastotheplausibilityofobservedassociationsbetweenexposures,includingoccupations,anddisease.Toxicologycanbedividedintostandarddisciplines,suchasclinical,forensic,investigativeandregulatorytoxicology;toxicologycanbeconsideredbytargetorgansystemorprocess,suchasimmunotoxicologyorgenetictoxicology;toxicologycanbepresentedinfunctionalterms,suchasresearch,testingandriskassessment.ItisachallengetoproposeacomprehensivepresentationoftoxicologyinthisEncyclopaedia.Thischapterdoesnotpresentacompendiumofinformationontoxicologyoradverseeffectsofspecificagents.Thislatterinformationisbetterobtainedfromdatabasesthatarecontinuallyupdated,asdescribedinthelastsectionofthischapter.Moreover,thechapterdoesnotattempttosettoxicologywithinspecificsubdisciplines,suchasforensictoxicology.Itisthepremiseofthechapterthattheinformationprovidedisrelevanttoalltypesoftoxicologicalendeavoursandtotheuseoftoxicologyinvariousmedicalspecialitiesandfields.Inthischapter,topicsarebasedprimarilyuponapracticalorientationandintegrationwiththeintentandpurposeoftheEncyclopaediaasawhole.Topicsarealsoselectedforeaseofcross-referencewithintheEncyclopaedia.Inmodernsociety,toxicologyhasbecomeanimportantelementinenvironmentalandoccupationalhealth.Thisisbecausemanyorganizations,governmentalandnon-governmental,utilizeinformationfromtoxicologytoevaluateandregulatehazardsintheworkplaceandnonoccupationalenvironment.Aspartofpreventionstrategies,toxicologyisinvaluable,sinceitisthesourceofinformationonpotentialhazardsintheabsenceofwidespreadhumanexposures.Toxicologicalmethodsarealsowidelyusedbyindustryinproductdevelopment,toprovideinformationusefulinthedesignofspecificmoleculesorproductformulations.Thechapterbeginswithfivearticlesongeneralprinciplesoftoxicology,whichareimportanttotheconsiderationofmosttopicsinthefield.Thefirstgeneralprinciplesrelatetounderstandingrelationshipsbetweenexternalexposureandinternaldose.Inmodernterminology,“exposure”referstotheconcentrationsoramountofasubstancepresentedtoindividualsorpopulations—amountsfoundinspecificvolumesofairorwater,orinmassesofsoil.“Dose”referstotheconcentrationoramountofasubstanceinsideanexposedpersonororganism.Inoccupationalhealth,standardsandguidelinesareoftensetintermsofexposure,orallowablelimitsonconcentrationsinspecificsituations,suchasinairintheworkplace.Theseexposurelimitsarepredicateduponassumptionsorinformationontherelationshipsbetweenexposureanddose;however,ofteninformationoninternaldoseisunavailable.Thus,inmanystudiesofoccupationalhealth,associationscanbedrawnonlybetweenexposureandresponseoreffect.Inafewinstances,standardshavebeensetbasedondose(e.g.,permissiblelevelsofleadinbloodormercuryinuri...
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