Limits to research risks.

Risk-benefit assessment is a routine requirement for research ethics committees that review and oversee biomedical research with human subjects. Nevertheless, it remains unclear how to weigh and balance risks to research participants against the social benefits that flow from generating biomedical knowledge. In this article, we address the question of whether there are any reasonable criteria for defining the limit of permissible risks to individuals who provide informed consent for research participation. We argue against any a priori limit to permissible research risks. However, attention to the uncertainty of potential social benefit that can be derived from any particular study warrants caution in exposing prospective research participants to a substantial likelihood of serious harm.