Education And Debate

Personal paper: Risk language and dialects

BMJ 1997; 315 doi: (Published 11 October 1997) Cite this as: BMJ 1997;315:939
  1. Sir Kenneth C Calman, chief medical officera,
  2. Geoff Royston, head of operational researchb
  1. a Department of Health, London SW1A 2NS
  2. b NHS Executive, Leeds LS2 7UE
  1. Correspondence to: Dr Royston
  • Accepted 20 May 1997


For something which matters so much to us all and is such an important consideration in medicine it is odd that we have no common language for discussing the hazards of life.1 2 An earlier article contained some suggestions for clarifying our language for describing risk.3 This paper extends those ideas setting out several ways in which the magnitude of risks might more easily be presented understood and discussed.

Risk, or the chances that a hazard will give rise to harm,4 is generally couched in terms of numerical odds or probabilities (see table 1) yet research has shown that people find it difficult to digest such measures.5 One difficulty is that the range of risks is so wide—from, say, the greater than 1 in 10 risk that cancer will be our eventual cause of death to the less than 1 in 10 million chance per year of being killed by lightning. We all find it hard to grasp such extremes.

View this table:
Table 1

Some risk probabilities (for Great Britain)

Summary points

Better ways are required for presenting risk magnitudes in a digestible form, and a logarithmic scale provides a basis for a common language for describing a wide range of risks

Various “dialects” of this language—visual, analogue, and verbal scales—could help with grasping different risk magnitudes

Combining the above ideas with the idea of anchoring risk magnitudes to the classification by size of human communities produces a “community risk scale”

Factors other than magnitude are important in considering risk, but an appreciation of magnitude is a crucial first step

The proposed risk scales need to be tested to see if and how they improve people's ability to understand and communicate about risks

A logarithmic scale for risk

Risk is not the only area that presents a wide range of size. Other examples include earthquakes, sound, and …

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