Current problems in safety evaluation of plastics (introductory lecture)

The design and development of comparative quantitative procedures for evaluating the safety and biocompatibility of plastics to be used in medical and para-medical fields, are important considerations. The increasing number of applications for plastic devices requires inquiry into the value of present evaluation procedures and into the possibilities of improving them. Tests designed to establish the safety of a plastic as a simple transfusion apparatus may be completely unsuitable for testing the potential toxicity of large amounts of plastic tubing used in extracorporeal circulation. Tests for detecting the presence of toxic substances that could migrate from a plastic container into a drug solution provide only a limited evaluation of the toxic potential of plastics to be used in prolonged direct contact with blood and other tissues and may not be acceptable for final determination of the safety of a plastic implant. This could only be accomplished with long-term animal implant studies in vivo in conjunction with limited human experimentation. Biocompatibility as a concept is still fairly recent and definitive biocompatibility tests remain to be developed. The importance of a producer's declaration of the components of any given plastic and of submitting plastic equipment to experiments pertaining to the practical use of the material, is stressed. The urgent need for both short- and long-term toxicological investigations of the components of plastic medical devices in individuals with normal as well as in individuals with abnormal elimination capacity, is emphasized.