Water is not an effective shield against the sun's more harmful rays.

　　水不能有效阻擋太陽(yáng)中更有害的射線(xiàn)。

　　Many household products are potentially harmful.

　　很多家用產(chǎn)品有潛在的害處。

　　Fruit juices can be harmful to children's teeth.

　　果汁可能損壞兒童的牙齒。

　　The drug is not harmful per se, but is dangerous when taken with alcohol.

　　這種藥本身無(wú)害，但與酒同服就危險了。

　　The drug is to be reclassified after trials showed it to be more harmful than previously thought.

　　試驗顯示這種藥比先前想象的危害更大，要重新歸類(lèi)。