Giving blood is safe and easy in China; there are even buses parked in shopping areas that serve as mobile blood donation centres. Because most Chinese people do not have Rhesus (Rh) negative blood, donating can help fellow expats who may not be compatible with the larger pool of local blood. One in eight Caucasians has Rh-negative blood, compared with only around 1% of the Chinese population, so there can be a severely limited supply.