Living with COVID-19: mass gatherings and minimizing risk.

During the COVID-19 pandemic, it has been important to both minimize the risk of infection and restore daily life. As a typical example, mass gathering events, such as sporting events, are gradually becoming more common, thanks to the measures taken to contain COVID-19. Some pilot studies have been launched at governments' initiative to investigate the risk of infection without measures such as face masks and physical distancing at mass gathering events, but the ethics of these studies should be carefully considered. On the other hand, it is still beneficial to implement infection control measures at mass gathering events and, in parallel, to estimate the risk of infection with measures in place, especially under a lack of vaccination progress or the spread of mutant strains possibly resistant to vaccines. To help improve compliance with measures taken by spectators and organizers and to ensure their effectiveness, we have conducted quantitative evaluations of the implementation of such measures by monitoring CO2 concentrations, assessing the proportion of people wearing face masks and analysing human flow at the event. This approach allows us to share our observations with stakeholders and participants, enabling us to protect the culture of mass gathering events, minimize the risk of infection and restore a sense of well-being in daily life.

Role of individual dosimetry for affected residents in postaccident recovery: the Fukushima experience.

The accident at Fukushima Daiichi nuclear power plant on 11 March 2011 released radioactive material into the atmosphere, and contaminated land in Fukushima and several neighbouring prefectures. During rehabilitation, it is important to accurately understand and determine individual external doses to allow individuals to make informed decisions about whether or not to return to the affected areas. Personal dosimeters (D-Shuttle), used together with a global positioning system and geographic information system device, can provide realistic individual external doses and associated individual external doses, ambient doses, and activity patterns of individuals in the affected areas of Fukushima. This study involved more than 250 affected residents. The results help to determine realistic individual external doses, and corresponding time-activity patterns and airborne monitoring ambient dose rates, which can be used to predict future cumulative external doses after residents return to their homes in evacuation areas. In addition, insights gained by the study can help to explain the role of individual external dose measurements for affected residents in postaccident recovery, based mainly upon the experience gained in measuring, assessing, and communicating individual external doses.