In worker group of 10 years senonity . The positive rate of Hb reducing(20.4%) was significantly higher than the worker of 1 year senonity (5.3%). W.

• 10年工龄组工人血红蛋白降低的阳性率（20．4%25）显著高于1年工龄组（5．3%25），差异有显著意义；