Environmental Problems, Their Causes, and Sustainability 1

The dose makes the poison.PARACELSUS, 1540This chapter addresses the following questions:■■■■■What types of hazards do people face?What is toxicology, and how do scientists measuretoxicity?What chemical hazards do people face, and howcan they be measured?What types of disease (biological hazards) threatenpeople in developing countries and developedcountries?How can risks be estimated, managed, andreduced?19-1 RISK, PROBABILITY,AND HAZARDSWhat Is Risk? The Chances We TakeRisk is a measure of the likelihood that you willsuffer harm from a hazard.Risk is the possibility of suffering harm from a hazardthat can cause injury, disease, death, economic loss, orenvironmental damage. Risk assessment is the scientificprocess of estimating how much harm a particularhazard can cause to human health. Risk managementinvolves deciding whether or how to reduce a particularrisk to a certain level and at what cost.Risk is usually expressed in terms of probability: amathematical statement about how likely one is tosuffer harm from a hazard. Scientists often state probabilityin terms such as “The lifetime probability ofdeveloping lung cancer from smoking a pack of cigarettesa day is 1 in 250.” This means that 1 of every250 people who smoke a pack of cigarettes a day willdevelop lung cancer over a typical lifetime (usuallyconsidered 70 years).It is important to distinguish between possibilityand probability. When we say that it is possible that asmoker can get lung cancer we are saying that thisevent could happen. Probability gives us an estimate ofthe likelihood of such an event. Figure 19-2 summarizeshow risks are assessed and managed.What Are the Major Types of Hazards?They Are All Around Us, But How RiskyAre They?We can suffer harm from cultural hazards,chemical hazards, physical hazards, and biologicalhazards, but determining the risks involved isdifficult.We can suffer harm from four major types of hazards:Risk AssessmentHazard identificationWhat is the hazard?Probability of riskHow likely is theevent?Consequences of riskWhat is the likelydamage?Risk ManagementComparative risk analysisHow does it comparewith other risks?Risk reductionHow much shouldit be reduced?Risk reduction strategyHow will the riskbe reduced?Financial commitmentHow much moneyshould be spent?Figure 19-2 Risk assessment and risk management.■ Cultural hazards such as unsafe working conditions,smoking, poor diet, drugs, drinking, driving, criminalassault, unsafe sex, and poverty■ Physical hazards such as ionizing radiation, fire,tornado (Figure 6-3, p. 103), hurricane (Figure 6-4,p. 104), flood (Figure 15-24, p. 327), volcanic eruption(Figure 16-8, p. 338), and earthquake (Figure 16-6,p. 337)■ Chemical hazards from harmful chemicals in the air,water, soil, and food■ Biological hazards from pathogens (bacteria, viruses,and parasites), pollen and other allergens, and animalssuch as bees and poisonous snakes19-2 TOXICOLOGY: ASSESSINGCHEMICAL HAZARDSWhat Determines Whether a ChemicalIs Harmful? How Much, How Often,and GenesThe harm caused by exposure to a chemicaldepends on the amount of exposure (dose),frequency of exposure, who is exposed, how wellthe body’s detoxification systems work, and one’sgenetic makeup.Toxicity measures how harmful a substance is in causinginjury, illness, or death to a living organism. Thisdepends on several factors. One is dose, the amount ofa substance a person has ingested, inhaled, or absorbedthrough the skin. Other factors are frequency ofexposure, who is exposed (adult or child, for example),and how well the body’s detoxification systems (suchas the liver, lungs, and kidneys) work.410 CHAPTER 19 Risk, Toxicology, and Human Health