Cambridge Hospital Smokestack's Soot Blankets Cars, Streets and Buildings

In the same week when U.S. Energy Secretary Hazel O'Leary named Boston a national "clean city," some Cambridge residents might have strongly disagreed.

A spray of soot from Cambridge Hospital's smokestack blanketed nearby cars, streets and buildings Thursday morning at around 1 a.m.

"The soot sprayed predominantly on Line Street and extended to Beacon Street and Concord Square," according to a letter sent to area residents by hospital Chief Executive officer John G. O'Brien.

According to preliminary Environmental Protection Agency test results and O'Brien's letter, the soot was not a health hazard. The letter cautioned residents to prevent children and pets from eating soot stained snow.

The soot release was caused by a loose linkage on the boiler's air damper, O'Brien's letter said.

Test results from the EPA and Clean harbors, an environmental consulting firm hired to supervise a clean-up, will not be fully available until March 21.

But both the hospital and the E.P.A. believe that the levels are harmless, said Tom C. Condon, an environmental scientist at the E.P.A

"We conducted some preliminary tests and some were also conducted by Clean Harbors," he said. "Results indicated that there is no reason for concern.... Everything was below detection levels."

"E.P.A called its regional office to confirm that this was not a threatening issue," said Steven P. Shea, risk manager for Cambridge Hospital. "The test results are [expected to be] supporting information for our resolution."