Tolerance TestingZero 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. Thresholds, including “no effect thresholds” (NETs) The equine blood concentration of a medication below which pharmacologic activity is insignificant. Withdrawal timeThe length of time after the administration of a medication required for the metabolism and elimination of the medication. After this time the medication no longer present or has insufficient concentration to produce a pharmacological effect. Today, the sensitivity of the testing labs utilized by regulators has become so sensitive that horsemen raise concerns about environmental transfers that may have occurred and can now be detected at the picogram level. See also Doping in sport References External links ELISA tests The Testing Integrity Program (TIP) World Rules for Equine Drug Testing and Therapeutic Medication Regulation by Thomas Tobin, Kimberly Brewer, Kent Stirling. Wind Publications, Nicholasville, Kentucky, 2012. Proposed National Policy on Drug Testing and Therapeutic Medication. Stirling K, Bellocq R, and Tobin T: National Horsemen's Benevolent and Protective Association, Inc. -- J Eq Vet Sci 23(1): 4–5, 18–40, 2003. Association of Official Racing Chemists (AORC) Doping in sport Horse racing Drug testing Animal welfare in sports