The USDA National List of allowed and prohibited substances is premised on (i) the inherent safety of most natural materials that results from a long history of exposure and adaptation, and (ii) the need to assess synthetic chemicals that may cause harm to health and ecology. Thus, the National List allows natural materials to be used in organic production unless found to be harmful, and prohibits synthetic materials unless recommended by the National Organic Standards Board (NOSB) and codified as safe.

Three criteria must be met for a material to be allowed on the National List:

  1. no adverse effects to humans or the environment,

  2. need for the material (essentiality) in an organic system, and

  3. compatibility with organic practices.

Federal organic law outlines a number of impacts that must be considered in this evaluation. Because continuous improvement is a principle in the organic law, the National List is under a five-year sunset and review cycle to evaluate new information about environmental and health impacts, which may require a change in a listing. A petition process allows the NOSB to evaluate proposed additions or adjustments to the National List.

Tying the List of Products Compatible with Organic Landscape Management to the National List allows communities like South Portland to take advantage of the evaluation, and regular re-evaluation, performed by the NOSB’s public process. The list of organic landscape management products also incorporates EPA’s list of active ingredients that do not need to be registered as pesticides. This is a short list of materials, most of which are non-synthetic and are allowed in organic production.