Paying people to give blood can bring 'enormous' health risks, the Red Cross warned yesterday amid the launch of a nationwide campaign to encourage more people to donate the most valuable of resources. To mark yesterday's World Blood Donor Day, promotions were held in the centres of several main cities, encouraging passers-by to sign up as donors. Statistics show 15 per cent of the blood given last year was paid for, while 24 per cent came from employees of state-owned enterprises, who were obliged to donate. The Ministry of Health says that in 1998 as much as 78 per cent of blood was paid for. 'China has made incredible improvements in the past few years when you look at the figures,' said John Sparrow, a regional representative of the Red Cross and Red Crescent Societies. 'The target is to achieve 100 per cent voluntary donors. It's hard to predict how long it will take to achieve that goal,' he said. The nation's blood supply would be at risk as long as people were paid, Mr Sparrow said. In recent years the authorities have been trying to curb profit-oriented donor centres, which have been blamed for contaminating blood supplies and promoting the spread of HIV/Aids and other viruses such as hepatitis B and C. Experts said a scarcity of volunteers and a chronically low blood supply had created the market for paid donations, a practice that attracted people carrying infections. Mainland authorities closed down three blood centres for mismanagement this year. Mr Sparrow applauded the crackdown and said they should be continued across the country.