Department of Agricultural and Resource Economics ARE 298/School of Public Policy PP 290University of California at Berkeley David ZilbermanFall, 2001ENVIRONMENTAL AND HEALTH RISKS OF PESTICIDESTopicsHealth Risks and Environmental Effects of Pesticide UseExamplesWhat Are PesticidesTheir BenefitsWhat’s WrongPesticide-Use StrategiesPesticides in Developing CountriesPesticides Regulations and PoliciesMajor Issues of Debate-Should They Be Banned-International Harmonization of PesticidesHealth Risks and Environmental Effects of Pesticide UseHealth risk is defined as the probability that an individual selectedrandomly from a population contracts adverse health effects (mortality ormorbidity) from a substance. We can distinguish between an individual riskand a group health risk. Risk assessment is a technique to assess health riskand to form policies.The health risk-generating process contains several stages. In the case ofpesticides, we consider three stages:(1) Contamination and movement(2) Exposure(3) Dose/response2Contamination is the result of pesticide application. The chemicals arespread through the air and water and become absorbed by the product.Exposure may result from many activities:• Exposure may be from eating, breathing, and touching.• For food safety, the exposure is to the consumer.• For worker safety, the exposure is to the applicator, mixer, andfactory worker.• For ground water, exposure is to whoever drinks and bathes in thewater• For environmental risk, exposure is to the species that are exposed tothe risk.The dose-response relationship translates exposure to probability ofcontracting certain diseases. We should distinguish between acute andchronic risks.• Acute risks are immediate risks of poisoning.• Chronic risks are risks that may depend on accumulated exposureand which may take time to manifest themselves, for example,cancer.Risk Assessment ModelsThe processes that determine contamination, exposure, and thedose/response relationship are often characterized by heterogeneity,uncertainty, and random phenomena (weather). Thus, contamination,exposure, and the dose/response relationship often exhibit the characteristicsof random variables. Random variables are variables, which can take onseveral values, depending on the outcome of some random process, ordepending on the outcome of some process which is so complicated that3outcomes appear random. When modeling random variables, we often workwith models that contain probabilities. For example, risk assessment modelsestimate health risks associated with pesticide application by making use ofestimated probabilities.A risk-assessment model:Let r = represent individual health riskr f B f B f B X= 3 3 2 2 1 1( ) ( ) ( , )where• X = pollution on site (i.e., the level of pesticide use)• B1 = damage control activity at the site (i.e., protective clothing; re-entry rules)• B2 = averting behavior of individuals (i.e., washing fruits andvegetables)• B3 = the medical control of pollution dosage.The health risk of an average individual is the product of three functions:(1) f1(B1, X) is the contamination function. The function relatescontamination of an environmental medium to activities of aneconomic agent (i.e., relates pesticide residues on apples topesticides applied by the grower). (2) f2(B2) is the human exposure coefficient, which depends on anindividual’s actions to control exposure (i.e., relates ingestedpesticide residues to the level of rinsing and degree of foodprocessing an individual engages in). (3) f3(B3) is the dose-response function which relates health risks to thelevel of exposure of a given substance (i.e., relates the proclivity ofcontracting cancer to the ingestion of particular levels of a certainpesticide), based on available medical treatment methods, B3.4• Dose-response functions are estimated in epidemiological andtoxicological studies of human biologyf2(B2) f1(B1, X) = the overall exposure level of an individual to a toxicmaterial which is the amount of pesticides left on an appletimes the amount consumed.Estimating these functions involves much uncertainty:(1) Scientific knowledge of dose-response relationships of pesticides isincomplete. Pesticides are consumed in small doses over longperiods of time. Dose-response relationships are estimated inanimal studies, and there is uncertainty to what extent they apply tohumans. (2) The contamination function depends partly on assimilation ofpollution by natural systems, which can differ regionally (i.e.,winds distribute residues).(3) The exposure coefficient depends on the education of populations(i.e., are consumers aware of pesticide residue-averting techniques,such as washing?).Policy Goal: To maximize economic welfare (consumer and producersurplus from pesticides use)subject toProbability of (estimated risks exceeds R) > !In other words, the objective is to maximize economic welfare subjectto the constraint that the probability of health risk remains below a certainthreshold level, R, an acceptable percent of the time, !.• R = target level of risk• !. = safety level (measures the degree of social risk aversion)! might represent the degree of confidence we have in our riskestimate.5Because of the uncertainty about the risk-generation process, thedecision-maker may limit the risk level while constraining the probability oferror of the risk estimate.For any target level of risk and any degree of significance, the modelcan be solved for the optimal levels of:• Pesticide use• Damage control activities• Averting behavior by consumers• Preventative medical treatmentsGeneral Implications:• The optimal solution involves some combination of pollutioncontrol, exposure avoidance, and medical treatment.• The cost of reaching the target risk level increases with the safetylevel !.• The shadow price of meeting the risk target depends on the degree ofsignificance we have to assure that the target is being met.- The higher the !, or the greater the uncertainty we have in ourestimate of risk, the higher the shadow value of meeting theconstraint.ExamplesSay there is no uncertainty regarding the health effects of pesticideuse; that is, toxicologists know with certainty a point estimate of the dose-response function.Let:X = level of pesticides used on a fieldA = level of alternate pest control activitiesP = value of farm output (i.e., the price of a basket of produce)6Y = level of farm outputW =
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