Hazard Assessment of Toxic Substances: Environmental Fate Testing of Organic Chemicals and Ecological Effects Testing

In order to evaluate the potential hazards associated with the commercial use of chemical substances, an assessment of their ultimate environmental fate must be made. Fate, in this sense, can be defined as the transport and disposition of a chemical after it is released into the environment from a point source (manufacturing plant) or a disposal site (landfill, waste treatment plant, etc.). Determination of chemical fate could have considerable impact on predicting the potential adverse environmental effects of chemical pollutants, since it would help identify: (a) the areas over which pollutants would be distributed; (b) the types of reactions they would be subjected to during transport and after deposition; (c) the chemical form(s) and concentration(s) in which they would be deposited; (d) the sensitive biological targets that would be brought under their influence; and (e) the sequence of biological tests and conditions relative to the site of impact, concentration, period of exposure, and specificity of biological impact. Therefore, tests designed to allow assessments to be made of the environmental fate of chemical contaminants must address the generic areas of chemical mobility and persistence, and toxicological and ecological significance of the exposure to the organism, population, and community. Several studies have reviewed and evaluated test methods for determining the environmental fate of chemical contaminants. While these reports cover current test methods, few attempts have been made to design test protocols or to prioritize tests for individual chemicals. Unfortunately, available documents on environmental fate testing indicate that the design of experimental procedures is often made on an ad hoc basis and is extremely variable. In contrast to the documentation of toxicity testing, literature concerned with environmental fate testing does not provide any degree of standardization, and the cost of such testing is virtually unknown. This lack of standardization is perhaps a result of the almost infinite ways that chemicals may be released into and reside in the environment. However, the hazard involved in using unstandardized. tests is that, despite the expenditure of a great deal of money and effort, little insight is provided regarding the mobility of a chemical through the environment and its subsequent fate as a result of degradation and alteration processes. This is particularly true if the test is not well designed. Furthermore, the interpretation of unstandardized tests frequently varies and this, in turn, makes it difficult to compare one chemical with another. The following discussion is intended to furnish systematic guidelines for the testing of chemical-environmental fate. It is an attempt to provide a basis for constructing logical test protocols which are both cost effective and productive in that they would expedite reasonable adjudications concerning the safety of commercially useful chemicals. It must be emphasized that the development of any methodology is dependent upon the state of the art at the time it is devised. Therefore, the approach described here must be considered an interim solution to the problem of assessing the environmental fate of chemical pollutants and must be amenable to revision as new information and technologies are made available.