Risk assessors and regulatory agencies use the term "Precautionary Principle" for when a product is prohibited for sale and use in the public sector because a credible risk is associated with its use, but not necessarily supported by conclusive scientific evidence of the presumed adverse effects (toxicity).
In general, the Precautionary Principle is a political term and moral principle that states that a product (or action) should not be used (or performed) if it can reasonably predicted that it will lead to unacceptable consequences. Unacceptable consequences are severe and irreversible harm to humans or the environment.
The Precautionary Principle is most often applied in the context of evaluating risk to humans and the environment due to human actions. This means halting use and sales of a product for which there is a reasonable, logical risk of adverse effects on the environment or health and safety of the public, until further study has either disproved the theoretical risk, or until changes to the product and/or use have been made that alleviate the risk.
The Precautionary Principle has been applied to solve bioethical dilemmas such as the xenotransplantation debate. Organ transplants from animals are currently not permitted in the USA, because the consequences of infection by animal viruses, and other possible health risks, have not been fully investigated.
In contrast, nanotechnology, despite known potential environmental and human health risks, has not been subjected to such stringent controls, as of yet.
