In our view, a code of conduct for research done in disaster zones should include a guarantee that people in the area can choose whether or not to participate (see J. C. Gaillard and L. Peek Nature 575, 440–442; 2019). Fair and voluntary participation is a fundamental human right.

Residents in a disaster area fear for their lives in the acute phase, and face health risks in the recovery phase. They naturally seek help and support from their government and from professionals. Under such circumstances, residents might agree to take part in research without giving the matter enough thought. It is therefore important for researchers to make clear to them that studies could have harmful effects as well as benefits.

As an example, after the 2011 accident at the Fukushima Daiichi nuclear-power station, we undertook screening of local children for thyroid cancer, which can be induced by radioactive iodine (A. Ohtsuru et al. JAMA Otolaryngol. Head Neck Surg. 145, 4–11; 2019). Although participants and their parents gave written consent, they were unaware of the risks of overdiagnosis, which include having unnecessary surgery to remove small, slow-growing tumours (see go.nature.com/2vfd9z7). Also, screening conducted during school time could have given the impression that participation was mandatory.

Such ambiguity underlines the importance of a code of conduct that makes participation in disaster-zone research voluntary.