Study warns of pollution from ships.

Byline: Robert Nolin

FORT LAUDERDALE, Fla. _ Thousands of merchant ships chug in and out of South Florida's bustling ports each year, bringing boatloads worth of economic benefit to the region.

They also deliver a more dangerous cargo: airborne pollution from giant diesel engines that can sicken coastal residents, or even shorten people's lives.

A study by the National Oceanic and Atmospheric Administration, the most comprehensive yet, found that commercial vessels _ freighters, tankers and cruise ships _ generate enough air pollution to pose "a significant health concern for coastal communities."

The study caught South Florida's public health officials by surprise. But while they acknowledged the …