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In a case-control study, the authors investigated the association of parental occupational exposure to low-level external whole-body penetrating ionizing radiation and risk of congenital malformations in their offspring. Cases and controls were ascertained from births in two counties in southeastern Washington State, where the Hanford Site has been a major employer. A unique feature of this study was the linking of quantitative individual measurement of external whole-body penetrating ionizing radiation exposure of employees at the Hanford Site, using personal dosimeters, and the disease outcome, congenital malformations. The study population included 672 malformation cases and 977 matched controls from births occurring from 1957 through 1980. Twelve specific malformation types were analyzed for evidence of association with employment of the parents at Hanford and with occupational exposure to ionizing radiation. Two defects, congenital dislocation of the hip and tracheoesophageal fistula, showed statistically significant associations with employment of the parents at Hanford, but not with parental radiation exposure. Neural tube defects showed a significant association with parental preconception exposure, on the basis of a small number of cases. Eleven other defects, including Down syndrome, for which an association with radiation was considered most likely, showed no evidence of such an association. When all malformations were analyzed as a group, there was no evidence of an association with employment of the parents at Hanford, but the relation of parental exposure to radiation before conception was in the positive direction (one-tailed p value between 0.05 and 0.10). Given the number of statistical tests conducted, some or all of the observed positive correlations are likely to represent false positive findings. In view of strong contradictory evidence, based on no demonstrated effects in genetic studies of atomic bomb survivors in Hiroshima and Nagasaki, it is unlikely that these correlations result from a cause and effect association with parental radiation exposure.

The authors examined the prevalence of congenital malformations among births in Benton and Franklin counties, in southeastern Washington State, from 1968 through 1980. The Hanford Site is in this area and serves as a major employer. In addition, various agriculturally and chemically related activities are in the area. Hospital and vital records were used to identify 454 malformation cases among 23,319 births; this yielded a malformation rate of 19.6 per 1,000 births, a rate similar to those reported in other studies. The rates of specific malformations ascertained during the first year of life were compared with combined rates from the states of Washington, Oregon, and Idaho from the Birth Defects Monitoring Program. Among defects that would be expected to be comparably ascertained, a statistically significant elevated rate of neural tube defects was observed (1.72 per 1,000 births vs. 0.99 per 1,000). Rates of cleft lip were significantly lower in Benton and Franklin counties than in the Birth Defects Monitoring Program (0.59 per 1,000 vs. 1.17 per 1,000). For congenital heart defects, pyloric stenosis, and Down syndrome, which are often not diagnosed in the newborn period, Birth Defects Monitoring Program data did not offer appropriate comparisons. The rates of these defects did not appear to be elevated in relation to rates found in other relevant populations. When rates of neural tube defects were compared with those in populations other than the Birth Defects Monitoring Program, the Benton and Franklin county rates were still considered to be elevated. The increased bicounty rate cannot be explained by employment of the parents at Hanford or by the impact of plant emissions on the local population.

Epidemiologic studies of workers exposed occupationally to protracted low doses of radiation provide a direct assessment of health effects resulting from such exposure and thus supplement information provided by studies of populations exposed at high doses of radiation and high dose rates. Analyses based on combined data from several studies can be expected to provide a more thorough assessment of low dose occupational studies and more precise risk estimates than can be obtained from any single study. Statistical methods for conducting such combined analyses are discussed, and different approaches, such as basing analyses on various levels of aggregation of exposure data, are compared and evaluated. Emphasis is given to methods for obtaining risk estimates and confidence limits that can be appropriately compared with estimates that form the basis for current radiation protection standards; these estimates have been obtained through extrapolation from high dose data. Methods are illustrated using combined data on workers at three US Department of Energy facilities: the Hanford Site, Richland, Washington; the Oak Ridge National Laboratory, Oak Ridge, Tennessee; and the Rocky Flats Nuclear Weapons Plant, Denver, Colorado.

The use of biofilms for the degradation of recalcitrant environmental contaminants or for the production of secondary metabolites necessitates understanding and controlling gene expression. In this work, dual labeling with green fluorescent protein (GFP) variants was used to investigate inducible gene expression in a biofilm. Colocalization of GFP emissions was used to determine regions of attached cells and to correlate structure and activity within the biofilm. The labeling strategy reported here is unique in that the two GFP signals were distinguished by differential excitation rather than differential emission.