A pesticide product has two main components: the active ingredient(s) and the inert (other) ingredient(s). The active ingredient is the specific compound designed to adversely effect a pest. Pesticide active ingredients are generally not applied in their pure form, but are usually included in formulations with inert ingredients that improve their storage, handling, application, effectiveness, or safety.
While the term "inert" implies that a substance is non-toxic, many inert pesticide ingredients are toxic to some degree. Assessments of the toxicity of pesticide products must therefore consider both active and inert ingredients. Only inert ingredients approved by U.S. EPA are allowed to be used in pesticide products, and they have been classified into several toxicity categories. However, data identifying the specific inert ingredients in all registered pesticide products is not publicly available.
MORE ON ACTIVE INGREDIENTS
EXTOXNET Frequently Asked Questions (FAQs) http://ace.orst.edu/info/extoxnet/faqs/
MORE ON INERT INGREDIENTS
Northwest Coalition for Alternatives to Pesticides, Toxic Secrets: Inert Ingredients in Pesticides 1987-1997