Poisons, People and the EnvironmentLecture 14: Risk AssessmentWhat is risk?Risk: the possibility of loss or injury.Risk in Environmental Toxicology: the possibility ofan undesirable biological response (toxicity) that results from exposure to a toxicant.Virtual riskPerceived directlyPerceived through scienceThree Kinds of Risk?observed directlythrough scientificobservation;e.g., cancer, cholera, reproductive decreasesdiffering opinionsof cause/effect; e.g.,global-warming, HRT, cell phonespersonal choice; driving, flying, climbing a ladderTaken from Three Framing Devices for Managing Risk by John Adams @UCL.ac.ukRisk can be expressed as aprobability (e.g., P=0.00001 orincidence (e.g., 1 in 100,000of a particular response occurring for a given exposurebased on statistical estimates or other observationsLay people Ranking24631052291819Differences in risk perceptionActivityExperts RankingMotor vehicles 1Smoking 2Alcoholic beverages3Handguns 4Surgery 5Motorcycles 6Xrays 7Pesticides 8Electric power (nonnuclear)9Swimming 10Risk assessment is the process of examiningtoxicological and epidemiological data for a suspected toxicant and if needed estimatingthe allowable exposure.Steps for characterization:toxicant identificationtoxicant evaluationexposure evaluationrisk estimationToxicant Toxicant identification evaluationExposure evaluationRisk estimationExposure evaluationExposure for noncarcinogenic toxicants is expressed as maximum daily dose (MDD) (mg/kg/day)Exposure to carcinogens is stated as lifetime averagedaily dose (LADD) (mg/kg/day/lifetime)Risk is approximated by the equation:R=TxER=riskT = toxicityE = exposureor as a function of the equationR = T x f(E)Risk Management:Examine risk assessment dataDevelop regulatory options addressingpublic healthsocial concernseconomic concernsSafety:The possibility that an undesirable biological response (toxicity) will not result from exposure to a toxicantEstimated as:1/PIf risk is P = 0.00001, safety equals 1 divided by 0.00001 (or 1/0.00001).Thus, for every 100,000 exposures only 1 will result in an adverse response.Safe Human Dose formula:SHD = mg/day=ED0.0xAt/hxT1/2t/hxWtxDt/hSFED0.0 = threshold dose of toxicant (NOEL)At/h = ratio of absorption of toxicant in test organism and humanT1/2t/h = ratio of half-life of toxicant in test organism and humanWt = weight of exposed individualDt/h = ration of toxicant test dosages in animals to exposure dosages in humansSF = safety factor"Yeo.h the J'ob's got great benefits, but mainly•I like the safe work environment.•' .AtJDIT';; LGA'!X::I:> WIT APP1I1VE.5e,,<wt- 'c-' - TKE.