Biocide

EPA's list sorts pesticide ingredients the way its framing sentence says: "Pesticide active ingredients are described by the types of pests they control or how they work." The biocide entry is three words long, "Biocides kill microorganisms." Algicides and fungicides have entries of their own on the same list.

Each word is its own entry, named for what it kills. The trade's spelling of the algae word, and what it covers, is on algaecide; the mold and mildew side of the vocabulary is on mildewcide.

EPA uses a second frame for products. Its antimicrobial pesticides page describes a group of products "used to destroy or suppress the growth of harmful microorganisms such as bacteria, viruses, or fungi on inanimate objects and surfaces," and it places products that control algae and odor-causing bacteria, microorganisms "of economic and aesthetic significance," in a group "not considered to be human health related."

The list's words describe what an ingredient does; a registration belongs to a specific product. One household bleach maker's 2019 safety data sheet shows one: the product identification page for Clorox Disinfecting Bleach2 prints "EPA Pesticide registration number 5813-111," and EPA says "More than 4000 antimicrobial products are currently registered with EPA and sold in the marketplace."

That number belongs to that one retail product. Whether any solution used to clean a roof is a registered product is a question for that product's label and for EPA, and this entry does not treat a bleach's registration as a statement about any roof.

ARMA's shingle bulletin describes a result in its own verb rather than EPA's: "Discoloration may be lightened by applying a solution of liquid household bleach (sodium hypochlorite) and water." Whether a soft wash kills the growth or clears it is answered on whether soft washing kills the algae or just removes it, and the published roof ingredients are on what is in a soft wash solution.