The researchers conducted two large, countrywide studies on the health effects of smoking. The first study took place in the 1990s and involved about 250,000 men. The second study was launched only recently and is continuing. This study involves about 500,000 adults, both men and women.________________________研究人员针对吸烟的健康影响进行了两项大规模的全国研究.第一次研究是在20世纪90年代,涉及250000名男子.第二次研究最近才展且在进行中,涉及约500000名成年男女性.__________________________
