Impact of lifting the mandatory evacuation order after the Fukushima Daiichi Nuclear Power Plant accident on the emergency medical system: a retrospective observational study at Minamisoma City with machine learning analysis

Abstract

ObjectivesThis study aimed to identify factors that delayed emergency medical services (EMS) in evacuation order zones after the 2011 Great East Japan Earthquake and Fukushima Daiichi Nuclear Power Plant accident and to investigate how the lifting of the evacuation affected these factors over time.DesignThis research was a retrospective observational study. The primary outcome measure was onsite EMS time. A gradient boosting model and a decision tree were used to find the boundary values for factors that reduce EMS.SettingThe target area was Minamisoma City, Fukushima, Japan that was partly designated as an evacuation order zone after the 2011 Fukushima disaster, which was lifted due to decreased radiation.ParticipantsThis study included patients transferred by EMS from 1 January 2013 through 31 October 2018. Patients who were not transported and those transported for community events, interhospital patient transfer and natural disasters were excluded.Outcome measuresThis study evaluated the total EMS time using on-site time which is the time from arrival at the scene to departure to the destination, and other independent factors.ResultsThe total number of transports was 12 043. The decision tree revealed that the major factors that prolonged onsite time were time of day and latitude, except for differences by year. While latitude was a major factor in extending on-site time until 2016, the effect of latitude decreased and that of time of day became more significant since 2017. The boundary was located at N37.695° latitude.ConclusionsThe onsite time delay in EMS in evacuation order zones is largely due to regional factors from north to south and the time of day. However, the north-south regional factor decreased with the lifting of evacuation orders.

Primary care clinic visits in formerly evacuated areas due to radiation disaster following the Great East Japan Earthquake: A retrospective descriptive study

“…Notably, after the Chornobyl accident in 1986, evacuation orders were not lifted; thus, a small number of residents who could not adapt to their new location and were attached to their familiar surroundings returned home, who called “self-settlers.” [ 12 , 13 ] Unlike the Chernobyl accident, in the Great East Japan Earthquake (GEJE) and subsequent radiation disaster in 2011, air doses in Minamisoma were low and residents were able to return early. [ 14 – 17 ] Although there are some reports of emergency medical systems in evacuation areas after the disaster, [ 18 – 20 ] there are no reports of usual medical visits before and after the lifting of the evacuation order. The reopening of medical facilities is a top priority for residents when making decisions about returning to their homes.…”