Risk assessment - Brief Introduction

Paracelsus statement "All substances are poisons, there is none that is not poison. The right dose differentiates a poison from a remedy" describes the central theme that underlies the processes of risk estimation and risk management. Any chemical given in excess can cause harm, while in moderation it can be of benefit. However, at a given dose one personel may be cured, an additional one will see no effect, and a third one may die because of hypersensitivity to the substance. A variety of other effects may be seen in the middle of the extremes of death and no response.

Determining what constitutes a "safe" level of exposure becomes a difficult task when we reconsider the wide array of chemicals in existence as well as the variability of personel response to them. Two informations for determining standard exposure levels: 1) the toxic effects related with exposure to the substance, 2) the level of risk the social or the user is willing to accept.

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All human activities are related with some degree of risk. It is defined as the probability (chance) that an adverse consequent will occur under a exact set of circumstances. In the final analysis an personel will undertake a particular action based upon his/her perception of the risk complicated weighed against the apparent benefits that will be derived.

Regulatory agencies such as Epa, Fda and Osha are complicated in determining risk related with chemical exposure. Epa, straight through a variety of environmental laws, regulates exposure to toxic substances that may be released into the environment. Fda is involved with toxic substances added to foods and cosmetics. Osha evaluates and regulates toxic substances in the workplace. One of the original functions of these agencies is to create guidelines and safe levels of exposure for toxic substances.

It must be noted that in reality, there is always some risk because of the differences in susceptibility and sensitivity of individuals to a particular toxic substance. Therefore, it is not possible for regulatory agencies to create absolute, safe levels guaranteeing that no personel will ever create an adverse effect. However, agencies can decide the circumstances and concentrations where the risk of an adverse response is very low, thus defining the level of exposure that may be carefully safe.

There are two phases in the establishment of standard exposure levels; risk estimation and risk management. Facts derived from these activities is used to decide the risk complicated in exposure to toxic substances and how to best manage risk.

There are qualitative and quantitative definition for risk. These approaches are critical to fully comprehend and comprehend how risk are being established for security purpose.

Qualitatively, risk at minimum degree must involve the possibility of an adverse outcome and uncertainty over the occurence, timing or magnitude of that adverse outcome. Thus, risk is a combination of uncertainty and damage that may result. Hazard is the source of the risk, there must be a safeguards value to compensate possible hazardous consequent to human health.

Risk = uncertainty + damage

Risk = hazard/safeguards

Risk as defined quantitatively may be formulated as follows:

Triplet: R , i=1,2,3...N

S represents scenario (what can happen?)

P represents probability (how likely is it that it will happen?)

X represents consequences (what are the consequences if it does happen?)

Reference:
Kent, C. 1998. Basics of Toxicology. John Wiley & Sons, Inc. New York
Class material: Environmental Toxicology and Risk Assessment

Risk assessment - Brief Introduction

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