Water is not an effective shield against the sun's more harmful rays.
水不能有效阻挡太阳中更有害的射线。
Many household products are potentially harmful.
很多家用产品有潜在的害处。
Fruit juices can be harmful to children's teeth.
果汁可能损坏儿童的'牙齿。
The drug is not harmful per se, but is dangerous when taken with alcohol.
这种药本身无害，但与酒同服就危险了。
The drug is to be reclassified after trials showed it to be more harmful than previously thought.
试验显示这种药比先前想象的危害更大，要重新归类。