Researchers at the University of Pittsburgh studied deaths between 1979 and 1998 among people who reside within five miles of the Pennsylvania plant. Their findings are reported on the Web site of the journal Environmental Health Perspectives.
"The good news is the TMI accident does not appear to have caused an over increase in cancer deaths among residents of that area over the 20-year follow-up period," principal investigator Evelyn Talbott told CBS Radio News. "Twenty years is the latency period for most cancers."
The researchers did note that overall deaths among the residents near the plant were higher than would have been expected, but most of the increase was the result of heart disease, not cancer.
The researchers looked at 32,135 people who lived near the plant at the time of the accident in 1979 and who were interviewed by the Pennsylvania Department of Health at the time.
The new findings are similar to those reported earlier in an analysis of the same population covering 13 years, except that an apparent increase in breast cancer at that time was no longer evident in the 20-year study.
After adjusting for smoking, educational level and other factors, the researchers say there was no significant difference in the number of deaths in the plant area population compared with the expected number of deaths in the general population.
The researchers studied causes of death that included heart disease and cancers, in particular cancers known to be sensitive to radioactivity such as bronchial, throat and lung, breast, lymph system, blood-forming organs and the central nervous system.
The only elevated risk of cancer, they said, was a slight increase in the risk of lymphatic and blood cancers among men, which the researchers said was related to radiation exposure from the accident, and an increased risk of death from lymphatic and blood cancers in women, which they said was related to everyday background radiation exposure.
"While these findings overall convey good news for TMI residents, the slight increased risk of death from lymphatic and hematopoietic (blood) cancers may warrant further investigation," the team said in a statement.