Professionalism/The Precautionary Principle

Precaution is a systemic change that transforms the way we approach environmental regulation and decision making. This change is rooted in a paradigm shift away from risk/benefit and cost/benefit decision-making that asks, "what level of harm is acceptable?" to a precautionary approach which asks, "how can we prevent harm?" - Center for Health, Environment, and Justice

Professionals often face complex decisions that carry unknown risks. Traditional risk analysis, which comes from the world of engineering, uses formulas based on costs and probabilities to determine the optimal action. While it has had its successes, this type of analysis is limited by the knowledge of the analysts. Because it attempts to quantify risk, the analysis requires the analyst either estimate or ignore any unmeasurable variables. Risk analysis can quantify the acceptable safe bearing weight of a suspension bridge, but is unable to accurately determine if a new drug for pregnant woman should be allowed to enter the market.

In cases where human safety could be compromised, professionals have the social responsibility to act ethically and minimize risk. The "Precautionary Principle" is an approach to risk management that treats public safety as paramount. The principle is best applied to policies of unknown risk when quantitative risk analysis may require unreasonable estimation, such as the value of human life - see Valuing of Human Life in Risk Analysis. The Precautionary Principle states that in the absence of scientific consensus, the burden to prove that the action or policy will not harm the public lies with those that support it. The Precautionary Principle has evolved into two general forms that depend on the level of risk avoidance desired: the strong form and the weak form.

Origin and HistoryEdit

The concepts underpinning the Precautionary Principle are widely known. Aphorisms such as "look before you leap" and "better safe than sorry" reflect the general idea of the principle.[1] The concept of precautionary judgment is also not unique to public policy. The precepts of the principle can be seen in modern bioethics, where "primum non nocere" or "first, do no harm" is a key tenet. Blackstone's Ratio in criminal justice also demonstrates a precautionary approach of harm reduction.

The first interpretation of the current principle originated in Europe in the early 1970's.[2] The term itself is believed to be a translation of the German vorsorgeprinzip.[3] The official application of the precautionary principle in public policy was introduced by the United Nations in 1992 to describe their approach to environmental policy. During the 1992 conference, the UN drafted the most notable instance of the precautionary principle used as a decision making framework: the Rio Declaration. The Rio Declaration is a document of the UNCED currently used as the standard for promoting sustainable development. The 15th principle of the 27 principle document explicitly calls for the precautionary principle to be widely applied by countries for decisions involving the environment.[4]

The principle was originally developed as a framework for issues concerning sustainable development but soon spread into other fields. Currently, the precautionary principle has been adopted in some form by four major nations: The United States, European Union, United Kingdom, and Australia.[5] Each party has their own interpretation of what the precautionary principle entails, but there is an effort to internationally standardize and promote the principle called the Precautionary Principle Project. The project attempts to outline the benefits of the precautionary principle and develop guidelines of use. [6]


The reception of the principle has been mixed. Advocates state that the principle is the only manner in which social harm at all levels can be prevented. They assert that the high degree of generality in the principle allows application to all environmental protection and health safety issues. A stricter, more formulaic approach would remove the flexibility of the principle and allow potentially harmful policies to go unchallenged.[7]

However, many criticize the Precautionary Principle for its vagueness. The lack of clarity of both the definition of potential harm and proof have been called "unscientific" and "anti-progress." A quote by Sir Austin Bradford Hill is often cited in the argument against the Precautionary Principle. "All scientific work is incomplete - whether it be observational or experimental. All scientific work is liable to be upset or modified by advancing knowledge. That does not confer upon us a freedom to ignore the knowledge we already have or postpone the action that it appears to demand at a given time."[8] The argument is that the Precautionary Principle, in trying to be a catch-all, precludes any real progress.

Key Elements of The Precautionary Principle[9]Edit

  1. Taking anticipatory action to prevent harm in the face of scientific uncertainty.
  2. Exploring alternatives, including the alternative of "no action."
  3. Considering the full cost of environmental and health impacts over time.
  4. Increasing public participation in decision making.
  5. Shifting the responsibility for providing evidence to the proponents of an activity.

Risk PerceptionEdit

Before accounting for unknowns and uncertainty through risk assessment, it is important to understand common pitfalls of risk perception. For actual risks that are relatively low, like nuclear meltdowns, extreme vaccine reactions, plane crashes, and shark attacks, people perceive the risk to be significantly higher than it really is. In contrast, higher-risk activities like driving, exhibit a lower perceived risk. The basic theory behind this psychological phenomenon is that an increase in risk from 0% to 1% will be perceived as a much larger increase than from 98% to 99%. This may be generalized to infer that risk perception is based on relative proportions rather than absolute magnitudes. Also, the availability bias, where more readily recallable events drive reasoning, will come into play here in perceptions of risk, as is commonly in the case of plane crashes.

To quantitatively account for unknowns and uncertainties, a sensitivity analysis may be utilized to allow for a range of values per variable in modeling outcomes. Sensitivity analyses can estimate unknowns and account for varying levels of risk aversion. This way, risks are clearly documented and an accurate application of the Precautionary Principle may follow.

Example CasesEdit

The following three cases exhibit some form of the Precautionary Principle. All three were in a position to apply it, and only after they made their decisions were they able to determine whether or not their decision was correct.

Rodney RochaEdit

Rodney Rocha was an aerospace engineer at NASA who headed the Debris Assessment Team following the foam impact to the wing of the Columbia shuttle. He recommended mobilizing additional resources to assess the damage caused by the debris for there was insufficient evidence to determine the safety of re-entry. This lack of proof of danger or safety is an example of a case where the Precautionary Principle may be applied. Rocha wanted to get proof but ultimately chose not to send a crucial email; the re-entry took place, disregarding the Precautionary Principle, and Columbia crew died. By the Precautionary Principle, NASA should have chosen to prove the lack of danger rather than assume safety in the absence of evidence. A decision tree illustrating this situation is given below.

Frances Oldham KelseyEdit

Frances Oldham Kelsey spearheaded the FDA's stand against thalidomide, a popular drug for aiding sleep and nausea alleviation during pregnancy. A decision tree summarizing Kelsey's options regarding thalidomide is shown below. She postponed the approval of thalidomide based on the lack of proof of danger or safety. The drug's benefits had been shown, but the time period was too narrow for Kelsey. She waited instead, and waiting produced the proof she needed. It was later found out that thalidomide was the cause for a mass outbreak of phocomelia, especially in European countries where thalidomide had been previously approved for general consumption. This case exemplifies the application of the Precautionary Principle in the face of unknowns. Additional time allowed for the collection of more data to confirm safety information.

Milgram Experiment Defiant SubjectEdit

A defiant subject of the well-known Milgram experiment is another example of the application of the Precautionary Principle. The subject confessed to a lack of knowledge of electricity and was unsure of the learner’s condition. Instead of continuing on the with experiment in face of unknowns regarding safety, the defiant subject chose to stop participating and to end the trial. He was then informed of the safety information regarding the experiment after the trial was terminated. A decision tree summarizing the defiant subject's options during the experiment is provided below.

Strong vs. Weak ApplicationEdit

In modern applications, there are two general forms of the Precautionary Principle, called the strong and weak forms. The strong form states that unknown risk should be treated as infinite, such that preventative action must be taken if the risk exists - this is the form given by the United Nations General Assembly[10]. The weak form, from the same assembly, states that lack of full scientific consensus regarding an action need not prevent the action if the opposite decision would result in harm.

These forms have distinctly different use cases: The strong form is generally used in environmental policy and for other large-scale policies where negative consequences can be long-lasting and difficult to predict. The weak form is used much more commonly as a tool for designing safety protocol and evaluating risk at a qualitative level. It is best to think of the Precautionary Principle as containing a sliding scale of acceptable unknown risk - when zero unknown risk is desired, the strong form is used. When some unknown risk is acceptable due to technological or other limitations, the weak form is acceptable. In this way, the Precautionary Principle has a response to its critics - the weak form of the Precautionary Principle is significantly less restrictive on progress.

For The ProfessionalEdit

The professional, seeking to apply the Precautionary Principle to their policies, should first consider the scale of the impact of their policy. Policies that would operate on large physical and time scales - such as the policy of burying chemical waste - should be governed by the strong form of the Precautionary Principle. In these scenarios, it is up to the professionals involved to investigate all possible outcomes of their policies and operate only under complete certainty. Policies that operate on smaller scales, such as a required height on guard rails, will be able to apply the weaker form.

It is important to note that the use of the word policy throughout this chapter might be misleading - while the Precautionary Principle has its origins in policy-making, it has applications in all fields where major decisions are made that affect the general public. Professionals, backed by the trust of their clients and the general public, had a responsibility to carefully consider when the Precautionary Principle is needed to prevent or minimize risk in the face of uncertainty.

Part of the difficulty of implementing the Precautionary Principle as a professional is the time-dependence component - when making decisions guided by the Precautionary Principle, it is often very difficult to evaluate the quality of the decision in retrospect. Professionals who apply the Precautionary Principle, such as Frances Oldham Kelsey, must acknowledge that their decision may not be validated in a known amount of time.


  2. Adams, Mags D. "The precautionary principle and the rhetoric behind it." Journal of Risk Research 5.4 (2002): 301-316.
  3. Sonja Boehmer Christiansen. The Precautionary Principle in Germany: Enabling Government. Chapter 2 in Interpreting the Precautionary Principle, eds Tim O'Riordan and James Cameron Earthscan Publications Ltd, 1994
  4. Declaration, Rio. "Rio declaration on environment and development." (1992).
  5. Cameron, Linda. Environmental Risk Management in New Zealand: is There Scope to Apply a More Generic Framework?. New Zealand Treasury, 2006.
  6. Ackerman, Frank, and Rachel Massey. "Precautionary Principle Project." (2002).
  7. Cooney, Rosie and Barney Dickson (2005) "Precautionary principle, precautionary practice: Lessons and insights.” Chapter 18 in R Cooney and B Dickson eds Biodiversity and the precautionary principle: Risk, uncertainty and practice in conservation and sustainable use. (London: Earthscan).
  9. Gilbert, S. G. (2005). Precautionary Principle. Northwest Public Health.