The researchers at the University of Pittsburgh and the University of Illinois at Chicago said they identified 723 workers diagnosed with tumors between 1976 and 2004 at the United Technologies Corp. subsidiary. The tumors were malignant, benign or unspecified and included 277 cases of brain cancer.
The researchers also reviewed 11 chemical or physical agents on the basis of known or suspected carcinogenic potential that could affect the central nervous system or other organs.
The $12 million study, commissioned by Pratt & Whitney, was overseen by the state Department of Public Health.
Comparisons among Pratt & Whitney plants showed a slightly higher incidence of tumors and cancer among workers at the North Haven plant, the researchers said. But further evaluation found no association with estimated workplace exposures.
Pratt & Whitney spokesman Ray Hernandez said: "We are pleased that employees have answers to their questions and there is no correlation between cancer and the workplace."
The principal University of Pittsburgh researcher, Gary Marsh, said employees can be reassured that working at Pratt & Whitney before 2002, the start of the study period, "does not increase your risk of developing brain cancer and does not increase your risk of dying."
"The news is good," he said.
The slightly elevated cancer rates at the North Haven plant may reflect external occupational factors that researchers did not measure or other factors unique to North Haven or the baseline plant used in the internal comparisons, Marsh said.
The researchers analyzed the records of nearly 250,000 workers over a 53-year period, making it one of the largest and most comprehensive such studies in an occupational setting, Marsh said. It also is the first large-scale study of workers in the jet engine manufacturing industry.
The results echo what was released in the first stage of the three-stage study in 2008. The researchers said then they did not find statistically significant excesses in deaths from malignant brain tumors among North Haven workers.
Workers and their families, joined by the International Association of Machinists, pushed for the study after widows and union officials said they were concerned with what appeared to be numerous and similar deaths at Pratt & Whitney plants.
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