Impact of biodegradation test methods on the development and applicability of biodegradation QSARs.

The biodegradability of a substance depends on the structure and physical form of the substance, the time that has been available for acclimation, and the environmental conditions. Importantly, these later factors can be just as important as structure in determining the outcome of a biodegradation test. The development of appropriate QSARs for biodegradation and the ultimate value of the final QSAR depends on understanding these factors. This paper will describe what is known about the effect of test conditions on the results of biodegradation tests. The ability of these tests to reflect real environmental conditions will also be examined. Finally, we will discuss what we believe, in the light of this information, should be the goal of biodegradation QSARs and how these QSARs can be most appropriately used in fate assessments.

Integrated approach for environmental assessment of new and existing substances.

To ensure the environmental safety of new and existing substances, the environmental fate and potential effects resulting from their release into the environment must be assessed. This requires the development of reasonable, consistent, and effective methods to conduct environmental risk assessments and to prioritize testing for these substances. This assessment must integrate fate and effects at the point-of-entry; it should also extend to an assessment of the potential to persist, and the consequences of increases in exposure concentrations, and to bioaccumulate. The conventional environmental risk assessment approach is used to assess the fate and effects of a substance at its point-of-entry into the environment. In this paper, an approach is presented for conducting quantitative environmental risk assessments of new and existing substances that builds on this conventional approach by including quantitative assessment of the potential for, and consequences of, persistence and bioaccumulation. The approach is described for aquatic, sediment, and terrestrial environments. For each environmental compartment, the approach includes (i) classification of the substance, based on environmental partitioning processes, to ensure that the appropriate data are collected and models used; (ii) a fate assessment to understand the ultimate fate of the substance after entry into the environment or "an environmental compartment" and to predict the exposure concentration of the substance at point-of-entry; (iii) a persistence assessment which determines the potential for increase in the exposure concentration as a result of repeated additions of the substance; (iv) effects assessment; (v) environmental risk assessment to examine the potential for adverse impact on ecosystems; and (vi) a bioaccumulation assessment to evaluate the potential for direct and indirect effects on the species of interest due to bioaccumulation. The assessment approach is illustrated using data for a hypothetical consumer product substance that is disposed down-the-drain.

Antibiotic lock technique.

Central venous catheters deliver life-prolonging medications to Group IVC AIDS patients. Unfortunately, the access device frequently provides a foci for debilitating infections. A Group IVC AIDS patient experienced repeated methicillin-resistant Staphylococcus epidermidis colonization and infection of his central venous access device. An antibiotic lock technique was created using a flush solution of vancomycin 1 mg/ml with 100 unit heparin/ml. The patient locked his catheter with 2.0 ml every evening for a period of 5 days. Repeat catheter and peripheral culturing occurred 72 hours after the 5-day period. After using the antibiotic lock technique, the patient maintained his catheter without further infection for an additional 2 months. This new approach may represent improved therapy and prevent the hazards of catheter exchange and systemic antibiotic therapy.