Hong Kong's turf war: Heat given off by artificial pitches poses health risk to athletes and children, academic warns

Hong Kong is hot on artificial grass, but it may be time to pour cold water on the idea taking root in the city, as the first comprehensive study on heat stress and turf raises serious concerns. The finding that fake grass can be 90 per cent hotter than the air temperature in summer means that athletes and children are particularly vulnerable to "heat stress" and the risk of heat stroke. This is on top of concerns that artificial grass can intensify urban temperatures, contributing to the heated island effect. Data compiled by Professor Jim Chi-yung, chair professor of geography at the University of Hong Kong, shows that the surface temperature of natural grass was more in line with air temperature, making it a much safer option for sports. The first detailed analysis on turf and heat stress in Hong Kong should give the administrators of government-run pitches cause for pause. The Leisure and Cultural Services Department is committed to replacing most natural grass pitches with artificial ones to raise "availability and quality" - and reduce maintenance costs. A consultancy report commissioned by the department in 2009 found the cost of pitch repairs on natural turf to be equivalent to HK$700 per session, or HK$336,000 per pitch per season. It recommended the department increase the number of synthetic pitches to 34 by this year. The department manages 81 soccer pitches - 47 natural and 34 artificial. Three natural pitches have been converted since 2011 and the department plans to convert five more in the next two years to third-generation "Fifa-recognised" artificial turf - synthetic grass fibres with a base of sand and rubber granules. This would mean the ratio of natural to artificial pitches would be roughly half - 42 to 39 - by 2017. According to Jim's data, the surface temperature of artificial turf in 35-degree-Celsius heat can shoot up to a sizzling 70 degrees, while real turf peaks no higher than 38 degrees. On artificial grass, Jim also found that the air temperature 50cm above ground was higher than that at 150cm, meaning young children were at greater risk to this high heat exposure. The research also found that heat stress - the effect of heat in generating pressure or discomfort on the body - to be far greater on artificial grass pitches than natural grass pitches. "A human being will not be feeling just the air temperature but the heat sensation," Jim said. His research shows that the heat stress created from artificial turf in 35-degree heat could go as high as 48 degrees. Under the same conditions and air temperature, the heat stress on a natural grass pitch usually remains in the 30s. Occupational safety and health organisations from many countries have already established heat stress index thresholds for reference by people working or doing outdoor activities in hot weather. Jim spent two summers collecting data at the university's Stanley Ho Sports Centre complex in Sandy Bay over the course of about 10 consecutive days with a heat stress monitoring system comprising infrared radiometers and temperature sensors at different levels from the ground. He is now analysing the data and will publish a paper in the following months. Natural grass pitches serve important ecosystem purposes and help mitigate the urban heat island effect - the increase in temperatures in urban areas compared with suburban areas due to urbanisation. Water evaporation from natural turf produced a cooling effect, Jim said. He criticised the policy of replacing natural turf with artificial grass, noting that the trend in cities such as Singapore and in Japan was to convert more hard ground into grass. "It is very disappointing that while every developed country is working to reduce the urban heat island effect, the government here is doing things to intensify it," he said. The department argued that the "thermal effect" of artificial turf pitches tended to be "rather localised". Artificial pitches would be provided with "run guns" that sprayed water to cool surface temperatures, a spokesman said. Urban planning expert Paul Zimmerman of Designing Hong Kong also argued that with such limited land resources, the only way to get the public to do more sport was to create such pitches and maximise their use. "The benefits of artificial turf far outweigh the issue of temperature," he said. "It's very hard to get new pitches built, and while it would be lovely to have natural grass everywhere in the city, the reality is that artificial pitches can get three times more usage. In such an urban environment, everyone wins." Artificial turf could be used for active recreation while various measures to cool the turf down, such as by planting more trees around pitches to provide shade, could be considered, he said. But an expert in sustainable architecture and urban climatology at Chinese University, Professor Edward Ng Yung-yan, said even if thermal effects were localised and not directly related to the urban heat island of an entire city, there was no running away from the fact that more natural grass helped to cool down a city. "The key scientific reason is water evaporation," he said, pointing out that a process called evapo-transpiration cools both the turf and the air above. "Real grass, not the fake stuff, has a cooling benefit for entire neighbourhoods." Ng said studies had shown that grass cools the surrounding air by about 1 degree and reduces radiation temperature by 20 to 30 degrees. "Real grass is harder to maintain, but it's not impossible," he said. "While other cities are moving from the concept of 'garden in a city' to 'city in a garden', we are reversing the trend entirely." Convenience vs safety in pitch debate The hidden dangers of artificial grass are all too well known to soccer player Caleb Ekwegwo. The Wofoo Tai Po forward has suffered two serious injuries playing on such pitches. "I hate AstroTurf," the Nigerian player said. While playing in a match in Lithuania in 2011, Ekwegwo attempted to change direction on the grass only to hit the dirt knee first. "I had to crawl off the pitch. It was so severe I couldn't walk," he said. The injury put a two-year hiatus on his career. When he returned to play for Tai Po, he suffered another surgery-inducing injury in his other knee on artificial grass - a surface most second division teams play on. "You are more careful about how you fall on artificial turf. When I fall I usually try to land on my palms," he said. "It's much safer landing on natural grass." Ekwegwo said long-term play on artificial grass would make players more prone to injury as the comparatively harder surface puts stress on joints. "You can compare it to horse racing. They would never let horses race on artificial grass as natural grass is much softer and shock-absorbing," he said. "Most professional footballers prefer natural grass." South China fullback Jack Sealy agreed, but acknowledged the problems of managing natural grass, which deteriorated with overuse and bad management. "Finding natural grass pitches is tough," said Sealy, a member of the Hong Kong representative team. "The ones in Happy Valley for example are heavily used from morning to night … The grass is often not in good shape and is hard to maintain." Sealy said third-generation artificial surfaces were "nice when brand new", but after a while the synthetic fibres flattened and the surface hardened. Professor Lobo Louie Hung-tak, of Baptist University's department of physical education, said the safety and performance of artificial grass were still being debated among sports scientists. While the grass and loose soil from natural turf helped absorb the impact of falls and facilitated sliding movements, "artificial turfs, even the newest versions, have not really stood out", he said. Louie said it all came down to the lack of land in Hong Kong. "When it rains they must close the pitches because constant playing on wet grass will destroy the turf," he said. The Leisure and Cultural Services Department argues converting more natural pitches to artificial turf would increase playing time. A third-generation artificial pitch can provide 270 sessions per month - more than four times that of a natural pitch. "It eliminates the need for regular closures for maintenance and can be opened all year round to the public," a spokesman said. "It would also eliminate the need for fuel-powered lawnmowers for trimming, pesticides, herbicides, fertilisers or other chemical materials that would affect the environment." Ernest Kao

Hong Kong's turf war: Heat given off by artificial pitches poses health risk to athletes and children, academic warns

.css-1c6uqr6{color:inherit;font-weight:inherit;font-size:inherit;font-family:inherit;line-height:inherit;overflow-wrap:break-word;}A study warning of the health risks of artificial grass is at odds with official thinking in the city

A study warning of the health risks of artificial grass is at odds with official thinking in the city