harmful後不能直接跟名詞

be harmful for後面接名詞,多是人或物,如Eating junk food is harmful for you.

be harmful to 意思是“對......有害”。例如：chemicals that are harmful to the environment 對環境有害的化學品 （摘自《朗文高階英語應試詞典》英漢雙解）,後面接動詞,如It is harmful to eat junk food.

be harmful for+doing 或事物

be harmful to+sb

在某些情況可以通用.

be harmful (to ) (對……)有害

例1：Smoking is harmful to your health. 吸菸有害於你的健康。

例2：Reading in bed is harmful to your eyesight. 躺在床上看書對你的視力有害。

例3：It can help stabilize the situation, and for a long time too, and is harmful to neither side.這樣能向人民交代，局勢可以穩定，並且是長期穩定，也不傷害哪一方。

例4：If we are weak and irresolute, if we are tolerant and indulgent, it will bring harm to the people and alienate us from the masses如果我們優柔寡斷，姑息養奸，則將遺禍人民，脫離群眾。

例5：If we are weak and irresolute, if we are tolerant and indulgent, it will bring harm to the people and alienate us from the masses.如果我們優柔寡斷，姑息養奸，則將遺禍人民，脫離群眾。

例6：When the four weasels felt that they were free from harm they walked toward the chicken coop這四隻黃鼠狼覺得後顧無憂，就朝著雞圈走去。

例7：I told her if she did me any harm I would return tit for tat.我告訴她，如果她傷害我，我會對她以牙還牙。