In Vitro Toxicity Testing for Pesticides and Disinfectants

In a series of guidance documents and conference presentations, the U.S. Environmental Protection Agency (EPA) has rolled out recommendations for using in vitro, non-animal toxicology testing as replacement for in vivo animal tests for pesticide and disinfectant products.  In the past, the so-called “six pack” tests – using rabbits – were required for toxicity evaluation for these products, which included acute oral toxicity, acute inhalation toxicity, acute dermal toxicity, primary eye irritation, primary skin irritation, and skin sensitization. These in vivo tests are not only time consuming and expensive to run, but also draw criticism of animal welfare and the inability of the tests to robustly represent the reaction of the human body to chemical exposure.

With the development of in vitro, ex vivo and in silica toxicity evaluation methodologies, it has become apparent that these alternative methods can provide data as predictive and accurate, if not more, as in vivo testing. They also offer a clear advantage of less cost, faster turnaround, better reproducibility, and easiness to generate multiple data points. Most of these methods have been extensively validated by international standardization bodies such as the Organization for Economic Cooperation and Development (OECD), and are recognized globally.

The first animal assay within the “six-pack” that was eliminated is acute dermal toxicity. Through an extensive data research, it has been concluded by the EPA that this assay does not provide any more value for tox categorization than the data from the other assays. Thus, per EPA, this assay can be waived for all formulated products.

Secondly, data for primary eye irritation evaluation can now be wholly generated using a group of in vitro assays, namely, the Bovine Corneal Opacity and Permeability (BCOP) assay (OECD 437), EpiOcular™ (EO) (OECD 492), and, if necessary, the Cytosensor Microphysiometer (CM). These assays can entirely replace the animal primary eye irritation test.

With the development of in vitro skin irritation and skin sensitization assay, such as the EpiDerm™ Skin Irritation Test (SIT) (OECD 439), EpiDerm™ Skin Corrosion Test (SCT) (OECD 431), Corrositex & Skin Corrosion (OECD 435), Direct Peptide Reactivity Assay (DPRA) (OECD 442C), KeratinoSens™ assay (OECD 442D) and Human Cell Line Activation Test (h-CLAT) (OECD 442E), it’s widely expected that EPA will soon accept alternative toxicity testing methods as a full replacement for the animal primary skin irritation and skin sensitization.

The pesticide and disinfectant industry are also embracing the new technology with enthusiasm.  Many manufacturers have begun to test their products via in vitro methods. Obtaining experience and identifying any possible difference between the in vivo and in vitro data, early in the game, is pivotal for a speedy and smooth product development and registration. This key differentiation can potentially save manufacturers enormous time and resources.



US EPA: Use of an Alternative Testing Framework for Classification of Eye Irritation Potential of EPA Pesticide Products (2 March, 2015)

US EPA: Process for Evaluating & Implementing Alternative Approaches to Traditional In Vivo Acute Toxicity Studies for FIFRA Regulatory Use (4 February, 2016)

US EPA: Strategic Vision for Adopting 21st Century Science Methodologies

US EPA: Guidance for Waiving Acute Dermal Toxicity Tests for Pesticide Formulations and Supporting Retrospective Analysis (9 November, 2016)

US EPA: Guidance for Waiving for Bridging of Mammalian Acute Toxicity Tests for Pesticides and Pesticide Products (Acute Oral, Acute Dermal, Acute Inhalation, Primary Eye, Primary Dermal, and Dermal Sensitization) (1 March, 2012)