Zero Tolerance Testing
Zero tolerance testing is not testing down to "zero" molecules, which no chemist can accomplish, but rather testing to the limit of detection (LOD) of the best available technology. In other words, "zero tolerance" refers to the racing regulators' philosophy in regulating drug use in race horses—even trace amounts of drugs are not tolerated.  While detecting trace amounts may be an entirely appropriate approach for performance altering substances which have no approved veterinary use, it is not considered appropriate for therapeutic medications which may be present in trace amounts having negligible or no pharmacological activity. Therapeutic medications are approved substances used to maintain the health and welfare of horses.