Mortality rates for leukaemia and brain tumour of highly exposed train drivers ( 21 ? t average annual exposure ) were compared with medium and low exposed occupational groups ( i . e . station masters with an average exposure of 1 ? t ) 高暴露的火车驾驶(年暴露平均为21微特司拉)的白血病及脑瘤死亡率与中、低暴露的族群进行比较(如年平均暴露为1微特司拉的站长) 。
