BEIJING, July 10 (Reuters) - Up to half of the water used in water coolers across China's capital could be "fake", or not as pure as its manufacturers claim, state media said on Tuesday of the latest in a series of health scares.

The bogus water was either tap water or purified water of miscellaneous small brands poured into empty barrels sealed with quality standard marks, the Daily said, quoting Liu Xiaoyun, the Beijing sales manager of a bottled water brand.

Liu said the counterfeits began to appear in Beijing in 2002, five years after barrelled, as opposed to bottled, water emerged as an industry.

"Overall, a barrel of fake water costs bogus producers only 2.5 yuan ($0.33) to 3 yuan, whereas the real ones cost them 6 yuan each," the China Daily said. "In either case, a barrel of water is sold at well over 10 yuan in the market."

The lack of supervision had given "leverage" to counterfeit makers in each chain of the production process, from corporate distributors to unauthorised workshops and water delivery stations, the newspaper said.

Three years ago, a nationwide inspection on barrelled water found a 22 percent substandard rate. In the most serious case, 80 percent of barrelled water in the southern province of Jiangxi was reportedly not the real thing.

China's health safety failings have drawn world attention since mislabelled chemical exports were found in cough syrup in Panama and pet food in the United States. There have been a series of recalls and bans on items ranging from toys and drugs to seafood and toothpaste.