Environmental Decisions Based On Risk Analysis

Environmental Decisions Based On Risk Analysis is further divided into risk assessment and risk management. The former involves a study and analysis o

Risk analysis is further divided into risk assessment and risk management. The former involves a study and analysis of the potential effect of certain hazards on human health. Using statistical information, risk assessment is intended to be a tool for making informed decisions. Risk management, on the other hand, is the process of reducing risks that are deemed unacceptable. In our private lives we are continually doing both. Smoking cigarettes is a risk to our health, and it is possible to calculate the potential effect of smoking. Quitting smoking is a method of risk management because the effect is to reduce the risk of dying of certain diseases.

In effect, the risk of dying of something is 100%. The medical profession has yet to save anyone from death. The question, then, becomes when death will occur and what the cause of death will be. There are three ways of calculating analysis risk of death due to some cause. First, risk analysis can be defined as the ratio of the number of deaths in a given population exposed to a pollutant divided by the number of deaths in a population not exposed to the pollutant. That is,

Risk = D₁ /D₀

where :

D₁ = number of deaths in a given population exposed to a specific pollutant, per unit time

D₀ = number of deaths in a similar sized population not exposed to the pollutant, per unit time.

Environmental Decisions Based On Risk Analysis and Management

Some risks we choose to accept while other risks are imposed upon us from outside. We choose, for example, to drink alcohol, drive cars, or fly in airplanes. Each of these activities has a calculated risk because people die every year as a result of alcohol abuse, traffic accidents, and airplane crashes. Most of us subconsciously weigh these risks and decide to take our chances. Typically, people seem to be able to accept such risks if the chances of death are on the order of 0.01, or 1% of deaths are attributed to these causes. Some risks are imposed from without, however, and these we can do little about. For example, it has been shown that the life expectancy of people living in a dirty urban atmosphere is considerably shorter than that of people living identical lives but breathing clean air.

We can do little about this risk (except to move), and it is this type of risk that people resent the most. In fact, studies have shown that the acceptability of an involuntary risk is on the order of 1000 times less than our acceptability of a voluntary risk. Such human behavior can explain why people who smoke cigarettes still get upset about air quality or why people will drive while intoxicated to a public hearing protesting the siting of an airport because they fear the crash of an airplane.

Some federal and state agencies use a modified risk analysis, wherein the benefit is a life saved. For example, if a certain new type of highway guardrail is to be installed, it might be possible that its use would reduce expected highway fatalities by some number. If a value is placed on each life, the total benefit can be calculated as the number of lives saved times the value of a life. Setting such a number is both an engineering as well as a public policy decision, answerable ideally to public opinion.

Environmental risk analysis takes place in discrete steps:

Defining the source and type of pollutant is often more difficult than it might seem. Suppose a hazardous waste treatment facility is to be constructed near a populated area. What types of pollutants should be considered? If the facility is to mix and blend various hazardous wastes in the course of reducing their toxicity, which products of such processes should be evaluated? In other cases the identification of both the pollutant of concern and the source are a simple matter, such as the production of chloroform during the addition of chlorine to drinking water or gasoline from a leaking underground storage tank.
Identifying the pathway may be fairly straightforward as in the case of water chlorination. In other situations, such as the effect of atmospheric lead, the pollutant can enter the body in a number of ways, including through food, skin, and water.
Identifying the receptor can cause difficulty because not all humans are of standard size and health. The USEPA has attempted to simplify such analyses by suggesting that all adult human beings weigh 70 kg, live for 70 years, drink 2 L of water daily, and breathe 20 m3 air each day. These values are used for comparing risks.
Defining the effect is one of the most difficult steps in risk analysis because this presumes a certain response of a human body to various pollutants. It is commonplace to consider two types of effects: cancerous and noncancerous.
Deciding what is acceptable risk is probably the most contentious parameter in these calculations. Is a risk of one in a million acceptable? Who decides whether this level is acceptable? Certainly, if we asked that one person who would be harmed if the risk were acceptable, he or she would most definitely say no.
Calculating the acceptable levels of pollution is the next step in the risk analysis process. This step is a simple arithmetic calculation because the value decisions have already been made.
Finally, it is necessary to design treatment strategies to meet this acceptable level of pollution.

Environmental Decisions Based On Risk Analysis

Some authorities suggest that the dose-response curve for carcinogens is linear, starting at zero effect at zero concentration, and the harmful effect increases linearly as shown by curve C in Figure below. Every finite dose of a carcinogen can then cause a finite increase in the incidence of cancer.
An alternative view is that the body is resistant to small doses of carcinogens and that there is a threshold below which there is no adverse effect (similar to curve A). The USEPA chose the more conservative route and developed what it calls the potency factor for carcinogens. The potency factor is defined as the risk of getting cancer (not necessarily dying from it) produced by a lifetime average daily dose of 1 mg of the pollutant/kg body weight/day. The dose-response relationship is therefore

Lifetime risk = Average daily dose × Potency factor

The units of average daily dose are mg pollutant/kg body weight/day. The units for the potency factor are therefore (mg pollutant/kg body weight/day)−1. The lifetime risk is unitless. The dose is assumed to be a chronic dose over a 70-year lifespan. EPA has calculated the potency factors for many common chemicals and published these in the Integrated Risk Information System (IRIS) database (www.epa.gov/iris). Potency factors are listed for both ingestion and inhalation.

Environmental Risk Management If it is the responsibility of government to protect the lives of its citizens against foreign invasion or criminal assault, then it is equally responsible for protecting the health and lives of its citizens from other potential dangers, such as falling bridges and toxic air pollutants. Government has a limited budget, however, and we expect that this money is distributed so as to achieve the greatest benefits to health and safety. If two chemicals are placing people at risk, then it is rational that funds and effort be expended to eliminate the chemical that results in the greatest risk.

But is this what we really want? Suppose, for example, it is cost-effective to spend more money and resources to make coal mines safer than it is to conduct heroic rescue missions if accidents occur. It might be more risk-effective to put the money we have into safety, eliminate all rescue squads, and simply accept the few accidents that will still inevitably occur. But since there would no longer be rescue teams, the trapped miners would then be left on their own. The net overall effect would be, however, that fewer coal miners’ lives would be lost.

Even though this conclusion would be risk-effective, we would find it unacceptable. Human life is considered sacred. This value does not mean that infinite resources have to be directed at saving lives but rather that one of the sacred rituals of our society is the attempt to save people in acute or critical need, such as crash victims, trapped coal miners, and the like. Thus, purely rational calculations, such as the coal miners example above, might not lead us to conclusions that we find acceptable.

In all such risk analyses the benefits are usually to humans only, and they are short-term benefits. Likewise, the costs determined in the cost-effectiveness analysis are real budgetary costs, money which comes directly out of the pocket of the agency. Costs related to environmental degradation and long-term costs that are very difficult to quantify are not included in these calculations. The fact that long-term and environmental costs cannot be readily considered in these analyses, coupled with the blatant abuse of benefit/cost analysis by governmental agencies, makes it necessary to bring into action other decision-making tools: alternatives assessment and environmental impact analysis.