Quality in environmental toxicology measurements.

From the clinical chemist's point of view, environmental toxicology can be defined as the identification or quantitation or both of environmental toxicants, their metabolites, and the biochemical consequences in easily accessible human specimens. Requirements as to specificity, accuracy, precision, and sensitivity will vary depending on the purpose of the analysis (e.g., diagnosis of acute intoxication vs. population baseline study). Laboratories must therefore clearly indicate the scope of their analytic methods. To ensure consistency of results, quality guidelines, such as International Standards Organization (ISO) guide 25, should be adhered to. However, to demonstrate accuracy, external proficiency assessment is required. Interlaboratory comparison programs, by using representative reference material, can document laboratory performance over time. Examples taken from the Quebec Toxicology Centre's program for toxic metals in biologic fluids indicate that laboratory performance has improved in recent years. The quality of results is generally adequate for most applications of environmental toxicology measurements.