致癌 (zhì ái) is a separable verb (离合词) composed of 致 (to cause) and 癌 (cancer). It means 'to cause cancer'. Since it has a verb-object structure, you can insert aspect markers (了, 过), measure words, or other elements between the two syllables, e.g. 致过癌 (caused cancer before), 致几种癌 (causes several types of cancer). The particle 了 can also appear sentence-finally: 致癌了 (has become carcinogenic). The concept is often used in medical, environmental, and lifestyle contexts.