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Use of the Local Lymph Node Assay and Reduced Dose Protocol for LLNA in Assessing Pesticide Products

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Applicants for pesticide registration may use the existing OPPTS 870.2600 dermal sensitization guideline for both the technical grade active ingredients and end use pesticide products with the radiolabeled (or traditional) Local Lymph Node Assay (LLNA). None of the non-radiolabeled LLNA test methods are included. The “reduced or limit dose” LLNA (rLLNA) radiolabeled assay is also available, which further reduces the number of animals used in laboratory tests by 40% when compared to the multi-dose LLNA.


The objective of this policy is to expand the usefulness the traditional (or radiolabeled) LLNA protocol for assessment of dermal sensitization potential to single component pesticide products (i.e., technical grade active ingredients) and to pesticides with multiple components (i.e., end use products). In most cases, the traditional LLNA continues to be the preferred assay because it incorporates replacement, refining, and reducing animal testing (also referred to as “the 3 R’s” or the three main goals animal testing) while also providing a more quantitative assessment of dermal sensitization in a way that is less subjective than similar guinea pig assays.


A 2001 OPPTS guideline (870.2600) lists the LLNA (which uses the mouse as the test species) as the preferred assay over the two other traditional guinea pigs assays used for dermal sensitization. These other acceptable assays are the Guinea-Pig Maximization Test (GPMT) or Buehler Test (BT). They will be used in situations where the LLNA is not applicable.

  • ICCVAM – April 2009 Review and Recommendations to the Federal Agencies:
    • ICCVAM evaluated 22 pesticide end use products which contained both guinea pig and mouse LLNA data.
    • The 22 end use products represented 9 conventional active ingredients (i.e., one insecticide, six herbicides and two fungicides).
    • On this basis ICCVAM recommends that the traditional LLNA may be used to test most chemicals and products for their potential to cause allergic contact dermatitis.

EPA concurs with the ICCVAM recommendation that the traditional LLNA should be used to test any active ingredient or product. The LLNA should not be used if the properties of the chemical or product interfere with the LLNA in detecting sensitizing substances.


Expansion of LLNA radiolabel assay to test end use pesticide products:

  • Now applicable to the following manufacturing and end use pesticide products:
    • Antimicrobial.
    • Biological & microbial.
    • Conventional.
  • However, registrants cannot test out of a positive sensitizing result by submitting another assay on the same end use product.
  • The scope of the expansion applies only to the published OECD & OPPTS traditional (radiolabeled) LLNA assays and is effective immediately. Expansion will remain in effect until:
    • a revision of OECD 429 test guideline; or
    • a published revision of the OCSPP guidelines.

Adoption of the Reduced LLNA (rLLNA) radiolabeled test method:

  • The reduced LLNA test method can be used in situations where dose-response information is not required. For example, it can be used for a 1 dose level (limit dose).
  • Test substance concentration is the maximum concentration that does not induce excessive local irritation or overt systemic toxicity.
  • The acceptance of this method is consistent with published EPA guidelines for LLNA: 5 animals, individual data (not pooled), historical controls and same mouse strains.

View the Policy

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