What is “Reporting Limit” on a Laboratory Report?

If a laboratory didn’t detect a chemical in your sample, it doesn’t mean that it is not there. It only means that the concentration of the chemical agent is below that of the instrument’s sensitivity. This brings us to the definition of reporting limits:  The smallest concentration (or amount) of analyte, that can be reported by a laboratory is called the reporting limit.  It must be said that different agencies use slightly different definitions of reporting limits:

• EPA uses the term MDL (method detection limit) which is about 3 times the standard deviation of the results around the analyte’s true concentration. For example, an environmental laboratory tests air for formaldehyde. For QC purposes, clean air was spiked at the level of 10 ppm of formaldehyde, and 7 independent QC samples were collected.  Samples were analyzed and results came as 12; 8; 5; 10; 13; 7; and 8 ppm. The standard deviation was found to be 2.8 ppm, and therefore the MDL≈10 ppm.  The physical meaning of the MDL is the lowest concentration that can be detected (not measured) using this particular procedure when is performed by a particular chemist on a particular instrument. When the laboratory reports results that are just above the MDL, the client needs to understand that the results are reported with an error of about ±50%
• NIOSH uses LOD (limit of detection) which is similar to MDL but in application to analyte load on a filter or tube. For example, Tetrahydrocannabinol (THC)  was collected on a PTFE filter and was analyzed and reported as “Less Than LOD” with LOD=0.5 µg/filter.
• NIOSH also uses LOQ (limit of quantification) which is 3*LOD. The practical meaning of LOQ is that LOQ is the lowest concentration that can be measured with an accuracy of about ±30%
• AIHA LAP uses the term RL (reporting limit) which is LOD times a safety factor selected by the laboratory. RL is selected high enough to ensure that day-to-day variation in laboratory instrument sensitivity does not exceed the RL. For example, asbestos in linoleum can be analyzed with a LOD of 0.4%, while in Joint Compound we can detect it at a concentration down to 0.1%. To simplify the reporting and  to stay in compliance with Ontario Asbestos Regulation, we selected a Reporting Limit of 0.5%

Generally speaking:

LOD<RL≤LOQ

LCS Laboratory Inc. is accredited by AIHA LAP for Indoor Air Quality and Asbestos testing. We offer the best sensitivity for all our tests. If you have any questions, do not hesitate to call us to discuss your project.