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TNI Standards Guidance

Disclaimer: This material represents the opinion of its authors. It is intended solely as guidance and does not include any mandatory requirements except where such requirements are referenced. This guidance does not establish expectations of being implemented universally, exclusively, in whole, or in part.

This guidance does not establish or affect legal rights or obligations and is not finally determinative of the issues it addresses. It does not create any rights enforceable by any party in litigation with TNI, its accreditation bodies, or affiliated institutions. Any decisions made by TNI regarding requirements addressed in this guidance will be made by applying the applicable standards, policies or procedures to the relevant facts.

 

Module: Toxicity


Subject: Reference Toxicant Tests Outside of Control Limits

Question 1

Whenever a reference toxicant test is out of range (greater than +/- 2 std. dev. from the mean), and there is no explanation for the deviation, it must be immediately repeated.  Can you tell me where this is mentioned in the protocol (EPA-821-R-02-013) and/or TNI standard?

The control limits for SRT testing is +/- 2SD. The EPA freshwater acute/chronic method manuals [EPA-821-R-02-012, EPA-821-R-02-013, EPA-821-R-02-014] say in sections 4.15.4 / 4.16.4

“If more than one out of 20 reference toxicant tests fall outside the control limits, the laboratory should investigate sources of variability, take corrective actions to reduce identified sources of variability, and perform an additional reference toxicant test during the same month.” 

The EPA manual goes on to provide guidance if the laboratory can provide documentation for the outlier, that it can be excluded and if two or more consecutive tests do not fall within the control limits, as it is not unreasonable to have a value fall outside the control limits based on chance alone. Ultimately, each lab must follow their own internal procedures on how they deal with these instances and follow any guidance provided by their appropriate AB as well as the WET guidance.



References:

EPA WET Methods as codified at 40 CFR 136.3, Table 1A

Methods for Measuring the Acute Toxicity of Effluents and Receiving Waters to Freshwater and Marine Organisms, Fifth Edition. October 2002.  United States Environmental Protection Agency. Office of Water, Washington, D.C., EPA 821-R-02-012

Short Term Methods For Estimating The Chronic Toxicity of Effluents and Receiving Water to Freshwater Organisms
, Fourth Edition. October 2002. United States Environmental Protection Agency. Office of Water, Washington, D.C., EPA 821-R-02-013

Short-term Methods for Estimating the Chronic Toxicity of Effluents and Receiving Waters to Marine and Estuarine Organisms,
Third Edition.  October 2002. United States Environmental Protection Agency. Office of Water, Washington, D.C., EPA 821-R-02-014

2009 TNI V1M2§5.9.3c The quality control protocols specified by the laboratory’s SOP shall be followed (see §4.2.8.5 of V1M2.)  The laboratory shall ensure that the essential standards outlines in Technical Modules or mandated methods or regulations (whichever are more stringent) are incorporated into their method manuals.  When it is not apparent which is more stringent, the QC in the mandated method or regulations is to be followed.