"Low Level
Radiation Health Effects: Compiling  the Data"

Revision 1
March 19, 1998
by Radiation, Science, and Health, Inc.,
Edited by J. Muckerheide

1.2.2
Ocupational

1.2.2.1
Nuclear Shipyard & Power Plant Workers

"...the Nuclear Shipyard Workers Study (NSWS 1991)... groups were selected from a database of almost 700,000 shipyard workers, including about 108,000 nuclear workers. The three study groups consisted of 28,542 nuclear workers with a working lifetime dose-equivalent (DE) equal to or greater than 5 mSv (0.5 rem), referred to here as NW >5; 10,462 nuclear workers with a working lifetime DE <5 mSv, referred to here as NW <5; and 33,352 non-nuclear workers, referred to as NNW..."

"Both nuclear worker groups had a lower death rate from leukemia and lymphatic and hematopoietic cancers than the non-nuclear group. All three groups had lower LHC death rates than the general population. Table I summarizes the data.

"The most significant and surprising finding of the NSWS research was that the nuclear workers with the greatest radiation exposure, a cumulative lifetime occupational dose-equivalent of 5 mSv or more, had a standardized mortality rate (SMR) of deaths from all causes of only 0.76 that for their age and sex in the general population, while the non-nuclear workers had an SMR of 1.0. The standard deviation of the SMR was ~0.015; i.e., the mortality rate for the nuclear workers was ~16 standard deviations below that of the non-nuclear worker group!

"The occupational exposure to the nuclear shipyard workers was comparable to the cumulated effective dose-equivalent they received from natural radiation. Their total radiation, occupational plus natural, is comparable to natural radiation exposures in some parts of the world.

"This study is probably the best scientific evidence, of many scientific data sources, to show that low levels of ionizing radiation exposure are without health hazard. The results clearly contradict the conclusions of BEIR that even small amounts of radiation have risk (in BEIR V and earlier reports), which have been largely based on the data from the Japanese atomic bomb survivors, who largely received their radiation exposures in very brief, high dose rate conditions and who are also now demonstrating that effective radiation health effects thresholds exist in the range of 20 to 200 rem."