Firefighters rushed to the scene of the attack as smoke billowed into the sky.

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While the Colorado researcher didn't know if the study participants were smokers or non-smokers, the CDC's editorial points out that the new study adds to research from eight other studies, which also saw a drop in heart attack related hospitalizations after smoke-free laws are enforced.

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It happened not far from Blackwater's safe houses, and some of the employees had gone to the roof to get a better look at the huge plume of smoke rising from the site of the attack.

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Sitting now on lawns, amid well-tended flowerbeds and chattering picnickers, it is hard to imagine the British Army swarming onto this plain to attack the French, the smoke of gunfire forming a thick haze among the trees, the slashing of bayonets, and the screaming of the wounded.

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They do know that certain things can trigger an attack, like air pollution, cigarette smoke, mold, pets, dustmites and cockroaches.

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Aside from sadness and anger, the smoke engendered an enduring sense of duty to prevent the next big attack.

CENTERFORSECURITYPOLICY: Remarks to the Council on Foreign Relations