With it very likely the world will still be battling the novel coronavirus next summer, one expert is concerned about how protective masks might exacerbate the impact of extreme heat expected during the Tokyo Olympics.
Before the pandemic's arrival, the heat and humidity of Tokyo's summers represented the biggest health concerns for organizers. But the need for protective masks during the games means previous plans to keep staff and spectators cool may be inadequate.
"Protective masks cover the mouth, and that makes it harder for the body to expel heat, raising the risk of heatstroke," said Masuji Hattori, a Hyogo College of Medicine professor who specializes in the condition.
Cost-cutting by Tokyo's metropolitan government has left Sea Forest Waterway, the Tokyo Bay rowing and canoeing venue, with only half of its seats covered by a roof.
Last summer, it was bathed in brilliant sunshine at a test event, forcing spectators to employ parasols to provide a modicum of shade.
Test events at different venues allowed organizers to trial the effectiveness of various methods to combat the effects of the heat on spectators, staff, and competitors.
For example, tent lounges and mist showers were installed at the Oi Hockey Stadium while Japanese folding fans and cold, wet towels were distributed. Staff walked around carrying small water tanks and sprayed down spectators with mist.
But this year's cancelation of further test events has put a stop to this kind of experimentation and prevented efforts to see how masks might change the equation.
The safety problem against both heat and infection is vexing schools around Japan as students return to classrooms. The official view has been to prioritize heat countermeasures over the possibility of reducing the risk of coronavirus infection.
"Wearing a mask is effective in curbing the spread (of the virus), but I would like (schools) to prioritize their responses to heat exhaustion," education minister Koichi Hagiuda said at an August press conference.
But what happens when it is not students at one school but spectators, staff and athletes gathering from around the world and cramming into tight spaces for the Olympics?
After various test events, organizers provided more water fountains and shade tents at venues. They also decided to allow spectators to enter venues with bottled nonalcoholic drinks of up to 750 milliliters per person -- something previously prohibited for security and brand protection reasons.
The organizers have prepared a mobile app that provides temperatures at different venues.
Japan's Environment Ministry urges sporting activities to be stopped when the wet-bulb globe temperature, a metric that combines measures of temperature, humidity, wind and solar radiation, is 31 degrees or above.
There were 13 such days above the mark last year in late July to early August -- overlapping with the Olympics time frame. However, this year, a late end to the rainy season saw the number dip to six, although that is no predictor of conditions once the Tokyo 2020 Olympics start on July 23, 2021.
Olympic organizers are stressing the need to prioritize infection prevention after the pandemic forced an unprecedented one-year postponement of the Tokyo Olympics. Can they adequately do that and beat the heat, or will they eventually have to do like schools and recommend masks be removed in extreme circumstances?
Japanese manufacturers have seized the moment by developing cooler masks, but these are new products with no track record, and plans have to be made now to deal with next summer's twin health threats.
"Effective measures need to be implemented, such as setting up of tents that can house more people than currently planned and possibly combined with cooling fans," Hattori said.
"The current plan is not enough."