Background The disasters at Seveso, Three Mile Island, Bhopal, Chernobyl, the World Trade Centre (WTC) and Fukushima had historic health and economic sequelae for large populations of workers, responders and community members.

Methods Comparative data from these events were collected to derive indications for future preparedness. Information from the primary sources and a literature review addressed:

1. exposure assessment;

2. exposed populations;

3. health surveillance;

4. follow-up and research outputs;

5. observed physical and mental health effects;

6. treatment and benefits; and

7. outreach activities.

Results Exposure assessment was conducted in Seveso, Chernobyl and Fukushima, although none benefited from a timely or systematic strategy, yielding immediate and sequential measurements after the disaster. Identification of exposed subjects was overall underestimated. Health surveillance, treatment and follow-up research were implemented in Seveso, Chernobyl, Fukushima, and at the WTC, mostly focusing on the workers and responders, and to a lesser extent on residents. Exposure-related physical and mental health consequences were identified, indicating the need for a long-term health care of the affected populations. Fukushima has generated the largest scientific output so far, followed by the WTCHP and Chernobyl. Benefits programs and active outreach figured prominently in only the WTC Health Program. The analysis of these programs yielded the following lessons:

• Know who was there;

• Have public health input to the disaster response;

• Collect health and needs data rapidly;

• Take care of the affected;

• Emergency preparedness;

• Data driven, needs assessment, advocacy.

Conclusion Given the long-lasting health consequences of natural and man-made disasters, health surveillance and treatment programs are critical for management of health conditions, and emergency preparedness plans are needed to prevent or minimise the impact of future threats.