Development of a guide to applying precaution in local public health.

Purpose: The precautionary principle (PP) urges actions to prevent harm even in the face of scientific uncertainty. Members of Toronto Public Health (TPH) sought guidance on applying precaution.

Methods: We searched five bibliographic databases (yield 60 articles from 1996 to 2009 and 8 from 2009 to 2011) and Google (yield 11 gray literature sources) for material relevant to local public health. From these sources, we extracted questions until saturation was reached (n =55). We applied these questions retrospectively to eight case studies where TPH felt precaution was applied. We ranked questions for their importance in applying precaution.

Results: Our final guide included 35 questions in five domains: context, assessment, alternative interventions, implementation, and monitoring and evaluation. Importance rankings varied across cases, but the role of stakeholders in driving precautionary action was consistent. Monitoring and evaluation components could have been strengthened across cases.

Conclusion: The TPH guide can assist municipal environmental health practitioners in applying precaution in a more transparent manner.