{"text":[[{"start":10,"text":"Footballers and fans heading to the World Cup in the US face a dangerous combination of heat and humidity, with growing research highlighting the health effects of high “wet-bulb globe temperatures”."}],[{"start":22.65,"text":"The heat-stress metric, which also takes into account sun and wind exposure, is considered dangerous above 28C — roughly equivalent to an air temperature of 38C in dry heat."}],[{"start":35,"text":"According to FT analysis, many of the host cities for the matches — including Miami, Dallas, Houston and Atlanta — are regularly experiencing WBGT above the threshold that medical experts say can harm human health."}],[{"start":49.95,"text":"Houston recorded WBGT above 30C on nearly three-quarters of June and July days in the past decade. Dallas exceeded that level on about half of those days, while Miami and Atlanta did so on roughly a quarter."}],[{"start":null,"text":""}],[{"start":63.1,"text":"At last year’s Fifa Club World Cup in the US, thunderstorms caused six match delays while players raised concerns about extreme heat. Argentine midfielder Enzo Fernández said he was dizzy and had to lie down in the “incredible” heat during one of Chelsea’s games in New Jersey."}],[{"start":79.8,"text":"At this year’s World Cup, which kicks off on June 11, there is now a one-in-four chance the WBGT will hit a dangerous 30C during at least one of the games, World Weather Attribution, a group of scientists, has calculated."}],[{"start":94.3,"text":"About 26 games, or one quarter, were expected to be played at a WBGT of 26C or above, with nine of those taking place in stadiums without air conditioning, WWA said."}],[{"start":108.64999999999999,"text":"The stadiums in Miami, Philadelphia, Kansas City, Boston and New Jersey are among those with the highest heat risk during the tournament, according to research by scientists in the UK and Canada."}],[{"start":120.99999999999999,"text":"Three stadiums — in Houston, Dallas and Atlanta — have air conditioning while two others have roofs, reducing heat risks during matches. "}],[{"start":130.04999999999998,"text":"The high-risk stadium in Miami lacks both. The WWA scientists said many games in the city were “near certain” to be played at a WBGT of 26C. "}],[{"start":140.85,"text":"The final at MetLife Stadium in New Jersey had a one-in-eight chance of being played at a level of 26C, the scientists said."}],[{"start":null,"text":""}],[{"start":149.45,"text":"In response to rising concerns, football’s governing body Fifa has adjusted the tournament’s schedule to avoid peak heat, including later kick-off times in cities such as Miami. It has also introduced mandatory hydration breaks."}],[{"start":164.14999999999998,"text":"But it has drawn criticism this week after banning fans from bringing water bottles to matches, reversing an earlier decision. "}],[{"start":171.89999999999998,"text":"All host cities offer outdoor fan zones, leaving spectators exposed not only inside venues but also during crowded journeys to and from stadiums."}],[{"start":181.59999999999997,"text":"“When WBGT exceeds 26C, player performance can suffer. Above 28C, the risk of serious heat illness becomes more concerning — not only for players, but also for the hundreds of thousands of fans in stadiums and outdoor fan festivals,” said Chris Mullington, a consultant at Imperial College Healthcare NHS Trust."}],[{"start":203.29999999999995,"text":"Fifa said it was “committed to protecting the health and safety of all players, referees, fans, volunteers and staff”."}],[{"start":null,"text":""}],[{"start":211.34999999999997,"text":"Scientists and sports officials are increasingly looking beyond air temperature to measure the strain heat places on the body."}],[{"start":218.59999999999997,"text":"This is because warm, humid air makes it harder for the body to shed heat through sweat, increasing the strain of any physical activity. Each 1C of global warming means the air can hold 7 per cent more moisture. Exposure to a wet-bulb temperature of about 35C for six hours has long been considered the upper limit of what humans can survive. "}],[{"start":240.39999999999998,"text":"The measure, developed in the 18th century, is named for the temperature a thermometer would read if its bulb were wrapped in a wet cloth and air blown over it. The 20th-century measure of wet-bulb globe temperature seeks to add the impact of solar radiation and was developed in the 1950s to reduce heat-related illness and death among US Army and Marine Corps trainees."}],[{"start":263.5,"text":"Mike Tipton, professor of human and applied physiology at the UK’s Portsmouth university, said fans might fare worse than footballers at the World Cup, especially those with underlying health conditions or travelling from cooler countries. “People are not only going to be physiologically stressed, they’re going to be psycho-physiologically stressed,” he said."}],[{"start":null,"text":""}],[{"start":283.55,"text":"Lab measurements showed that all the sweat produced during the first test evaporated. But in the second test, at 80 per cent humidity, sweat levels were 40 per cent higher — and only a third evaporated. With reduced evaporation, the human body struggles to cool itself. "}],[{"start":301.55,"text":"“Body temperatures will be higher,” said Tipton, who oversaw the experiment. "}],[{"start":306.8,"text":"“The demand on the cardiovascular system is greater, and it may well be that you continue to heat up until you suffer with a heat illness.”"}],[{"start":null,"text":""}],[{"start":314.45,"text":"Other laboratory studies have reached similar conclusions. Harvard University scientist Robert Meade, who has studied wet bulb temperatures, said humans could be “extremely thermally flexible” and become conditioned to warmer temperatures. “However, how far acclimatisation can push the upper limits of heat tolerance is not well understood.”"}],[{"start":334.55,"text":"Last year, scientists in China found that young men exposed to a wet-bulb temperature of 29C for eight hours experienced significant rises in core body temperature and heart rate, alongside hypotension and elevated inflammatory markers, while separate research found the risk of heat stress rose sharply when the WBGT exceeded 27C."}],[{"start":359.5,"text":"Such conditions do not require extreme air temperatures. A wet-bulb temperature of 27C, for example, can occur at an air temperature of 32C and 65 per cent relative humidity. At the same 32C air temperature but with humidity reduced to 35 per cent, the wet-bulb temperature falls to about 21C."}],[{"start":384.25,"text":"Colin Raymond, a research scientist at the University of California, Los Angeles, has mapped wet-bulb temperatures worldwide, showing that over 30 years instances exceeding 32C have more than tripled as climate change has intensified, with the past three years the hottest on record."}],[{"start":402.15,"text":"Many of the most extreme readings have occurred around the Gulf, India and Pakistan, but locations from Italy to parts of the US are also beginning to experience dangerously high wet-bulb temperatures."}],[{"start":null,"text":""}],[{"start":414,"text":"Mass gatherings, such as sporting events, pilgrimages and festivals, had often become deadly epicentres of heat stress, Raymond said, through the combination of dense crowds, heat-exposed venues and limited access to shade or hydration."}],[{"start":428.05,"text":"“In a warming world, having large climate-controlled spaces at the ready in the event of a serious high wet-bulb episode will become ever more critical with each passing World Cup,” he said."}],[{"start":438.65000000000003,"text":"Additional work by Dan Clark and Henry Esterson"}],[{"start":null,"text":""}],[{"start":null,"text":"

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