推《JournaoftheNation－alCancerInstitute》1993年第85卷第18期报道，在美国国立癌症研究所（NCI）资助下正在进行一系列的地学预防实验，采用了不同的化学制剂，包括维甲酸、钙、纤维、三苯氧肢及其他．有一些是前瞻性实验研究．如在中国河南林县被证实有降低癌症死亡的β- The “Journa of the Nation-al Cancer Institute,” vol. 85, No. 18, 1993, reported that under the auspices of the National Cancer Institute (NCI), a series of geologic prevention experiments were being conducted using different chemical agents including retinoic acid, calcium, and fiber. , Triphenyl oxygen limbs and other. Some are prospective experimental studies. For example, in Linxian, Henan, China, it has been confirmed that β-cancer can reduce cancer deaths.