What is Risk?

ritcher scale illus. Risk Assessment is the scientific process of estimating the threat that environmental contaminants pose to human health. Although risk assessment is an imperfect science, it does offer something of a "Richter Scale" for toxic substances, allowing comparison of the health threats different chemicals pose.

Risk means many different things to different people. Consider the difference between scientific, economic and perceived risk.

  1. Scientific risk refers to the health risk posed by a compound and is based on toxicity data gathered in animal and human studies.

  2. Economic risk describes the statistical likelihood of making a positive return on a financial investment.

  3. Perceived risk is based primarily on emotional response to a perceived threat. Perceived risk is greatly affected by such things as whether a hazard is voluntary, familiar, the time lag until an effect is noticed, whether the compound is a natural or man-made source, and whether the person at risk is the one to benefit from the source of the risk.

Although risk assessment can estimate the degree of risk a chemical presents, risk assessment can't tell a person whether or not the risk is acceptable. That can only be determined by balancing the risk with its expected benefits. A risk assessment also can not definitively state whether a potentially harmful effect will actually occur in a specific instance (unless the risk is 100%).

People routinely accept some risks because the benefits are clear. Some examples are driving a car and child immunization.

drinking water contaminants illus. Drinking water contamination presents a more complicated picture. Oven cleaners, furniture polishes, bathroom drain openers, paint and paint thinners, paper and ink, and countless other products contain chemicals that can turn up in drinking water if the products are not properly manufactured, used, and disposed. Every time you dry-clean clothes, put gas in the car, or buy fruits and vegetables undamaged by insects, you make use of products and services that use potentially hazardous substances.

An important question in balancing risks and benefits is whether the people experiencing the risk also experience the benefits. Obviously no one personally chooses to have contaminated drinking water. Nearly everyone, however, willingly uses and benefits from the products that can contaminate drinking water.

In the past, the term "unsafe" water typically implied water containing waterborne disease organisms, some naturally occurring inorganic chemicals, or at most, a few common industrial chemicals. Detecting and correcting these threats has become relatively easy and inexpensive.

Today we are concerned with protecting our water supply from a wide variety of toxic chemicals, of which thousands are in daily use. Many of the health effects of these chemicals are uncertain. They are often colorless, odorless, and tasteless, even at harmful levels. They can often be detected only with sophisticated and expensive tests. Their interaction and combined health effects are as yet unknown.

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