11.   In the US military campaign against terrorism, air operations, particularly those involving rotorcraft like helicopters, have proven to be a serious hazard.

12.   In water sports, two serious hazards are drowning and spinal injury when someone dives into water that is too shallow.

13.   Los Angeles Unified School District officials routinely covered up serious environmental hazards at campuses throughout the district, jeopardizing students, according to a report released Tuesday.

14.   Safety officials know that distraction is a serious hazard on the road, but have little data so far about what kinds of mental activity are more dangerous.

15.   Supporters of the program said each gun purchased removed a serious hazard.

16.   That single-minded focus can distract people from more serious bacterial hazards.

17.   The rationale is that experience indicated that freezing rain was not a serious hazard.

18.   Today experts believe lead dust, which can be invisible to the naked eye, can be a more serious hazard, because it can be inhaled.

19.   Underage drinking is a serious hazard not just because it can lead to injury or death, but because it increases the likelihood of eventual alcohol dependence or abuse.

20.   Whether the inspector is actually identifying serious hazards is another matter.