人类大多数肿瘤是由天然的和人工合成的化学诱变剂和放射性引起的。环境化学诱变剂引起的遗传损伤可能产生肿瘤、畸形以及其它疾病。哺乳类在胚胎和胎儿期接触遗传毒物(Genotoxic agents)较易引起体细胞中基因的慢性损伤,这种损伤往往是不可逆的、有害的以及能累积的。在多种哺乳类包括灵长类已证明,孕期接触诱变剂能增加肿瘤的发生率。已知至少有30种化学品能经胎盘致癌。胎儿生殖细胞受到的遗传损伤能 Most human tumors are caused by both natural and synthetic chemical mutagens and radioactivity. Genetic damage caused by environmental chemical mutagens can cause tumors, deformities, and other illnesses. Mammals in the embryonic and fetal exposure to genotoxic agents (genotoxic agents) are more likely to cause chronic damage to genes in somatic cells, the damage is often irreversible, harmful and can accumulate. In a variety of mammals, including primates, it has been demonstrated that exposure to mutagens during pregnancy increases the incidence of tumors. At least 30 chemicals are known to cause cancer through the placenta. Fetal germ cells are subject to genetic damage