Precautionary Principle

Implement a Precautionary Principle


The Precautionary Principle is a framework for decision-making that anticipates how actions will affect the environment and health of future generations. When it is apparent that an activity is a potential threat to the environment or human health, full scientific certainty is not necessary to initiate precautionary action. Precautionary decision making is based on thorough examination of alternatives, transparency, community participation, and prevention of harm. It is not a ban on products or practices.

Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation.

Rio Declaration, Principle 15; Rio Earth Summit 1992


  • A Precautionary Principle is necessary to reduce continued harm from the effects of careless human activity before effect before the results are irreversible. Some frequently asked questions put together by the Science and Environmental Health Network describes several points as to why
  • Environmental Policies don’t always sufficiently prevent human and environmental harm. The study “Late Lessons from Early Warnings: The Precautionary Principle 1896-2000” describes one-hundred-year history of policies repeatedly failing to protect human health and the environment.


Create a precautionary principle for your city or county as a method for thinking about all policies and decisions that are made. Or, just start with one policy: create a contained and specific policy (see examples below) which incorporates the precautionary principle as a model for the success. Continue to incorporate the idea further.


Examples of a Precautionary Principle in use:

  • The City of San Francisco uses its Precautionary Principle in a Purchasing Policy to better the health of the workers and residents of the city as well as to spur the market for alternative products.
  • Mendocino County applies the Precautionary Principle to enhance the effectiveness of the Stormwater Discharge Plan required by the EPA. They protect residents by further reducing untreated discharges that contribute high levels of pollutants to the local waters.
  • The US Green Building Council adopted the Precautionary Principle as a guiding force.


Learn more information from the following sources:

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