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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: Scope of Results to be Plotted on Semi-log Graph

Question 1

Section 1.7.2.3 of the TNI standard (V1M7, both the 2009 and 2016 standards) states that “Toxicity data shall be plotted on semi-logarithmic graph paper, relating time, mortality, and effluent concentration to verify computational results.”

Is this requirement specific to the CUSUM reference toxicant charts or, since the language in the TNI standard vague and confusing, is this applicable for all toxicity data, and not just reference toxicant tests. Is there any additional information you could give me that would shed some light to this section?

Section 1.7.2.3.b of the TNI standard (V1M7, both the 2009 and 2016 standards) does state that “Toxicity data shall be plotted on semi-logarithmic graph paper, relating time, mortality, and effluent concentration to verify computational results.”  This language is not clear and any further interpretation of it would require expanding the language of the standard beyond what is considered an interpretation.  Some available information is helpful, however, when combined with the standard’s requirement that EPA methods must be followed where applicable.

The EPA freshwater chronic manual [EPA-821-R-02-013] says about plotting of control charts is below:

“4.16.2 DOCUMENTING ONGOING LABORATORY PERFORMANCE. The chart should plot logarithm of concentration on the vertical axis against the date of the test or test number on the horizontal axis.”

For non-reference toxicity testing, the EPA freshwater chronic manual [EPA-821-R-02-013] provides the following guidance:

“9.4.2. PLOTTING THE DATA. 9.4.2.1 The data should be plotted, both as a preliminary step to help detect problems and unsuspected trends or patterns in the response, and as an aid in interpretation of the results.” 

Data transformations (i.e., log transformation) are mentioned in the following section:

9.4.3. DATA TRANSFORMATIONS, 9.4.3.1 Transformations of the data (e.g., arc sine square root and logs), are used where necessary to meet assumptions of the proposed analyses, such as the requirement for normally distributed data.”

There does not appear to be additional language regarding plotting the effluent toxicity test data (i.e., non-reference toxicant data) on a semilog basis in either the acute or chronic manuals although it repeatedly mentions (and shows in figures throughout the document) plotting those data.  Therefore, our best practice recommendation is that reference toxicant data should be plotted on a semi-logarithmic basis but there is discretion in plotting effluent toxicity data on a semi-logarithmic basis.


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 V1M7

V1M7 Section 1.7.2.3