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The United States Environmental Protection Agency (EPA) recently updated guidelines for antimicrobial efficacy testing.

Formerly, EPA required the main tests for disinfection to be performed on several batches of product, with at least one batch aged for a minimum of 60 days. The new guidelines do not change the number of batches required, but the batches must now be tested at the Lower Certified Limit (LCL) as stated in the Confidential Statement of Formula. Aging products for 60 days prior to testing is no longer required.

The new guidance applies to microorganisms that are required to be tested to supporting a specific efficacy class, such as disinfectant, tuberculocide, virucide, sporicide, or food contact sanitizer. Testing at LCL is not required for additional organisms, with the exception of Carbapenem-Resistant Enterobacteriaceae (CRE).

The rationale behind this shift is to guarantee antimicrobial efficacy at any active ingredient concentration within the specified manufacturing range, for the entire period of time from purchasing to product expiration.

Many antimicrobial pesticide registrants appreciate the change, since the absence of an aged batch requirement removes 60 days from product development timelines. However, if a product is near the borderline of efficacy, setting active ingredient levels to be just at or below the LCL takes a considerable amount of chemistry expertise. Some manufacturers now find product preparation to be a challenging aspect of efficacy studies.

EPA appreciates the difficulties of setting product to exactly the LCL, so the recently published guidance document includes a minor tolerance for values above LCL.

Acceptable active ingredient concentration ranges for testing are presented below:

Nominal Concentration

Maximum Testing Range

≤ 1.0%

≤ 2.0% above LCL

Above 1.0% but ≤ 20.0%

≤ 1.0% above LCL

Above 20.0% but ≤ 100.0%

≤ 0.6% above LCL

For information about the EPA’s new Lower Certified Limit efficacy testing criteria for your product, please request a quote or contact Microchem today.

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