to be harmful

• 有害物质

  harmful substances

• 有害无益

  more harm than good

• 不但无益，而且有害

  not only useless but also harmful

• 极为有害的影响

  extremely pernicious influence

• 这是一种有害的理论和观点。

  This is a destructive theory and view.

• 吸烟对健康有害。

  Smoking is bad for one's health.

• 黄色小说对人的心理极为有害。

  Pornographic novels are very detrimental to people's mental state.