The National Registry for Radiation Workers (NRRW) is the largest epidemiological study of UK radiation workers. Following the first analysis published in 1992, a second analysis has been conducted using an enlarged cohort of 124,743 workers, updated dosimetry and personal data for some workers, and a longer follow-up. Overall levels of mortality were found to be less than those expected from national rates; the standardised mortality ratio for all causes was 82, increasing to 89 after adjusting for social class. This 'healthy worker effect' was particularly strong for lung cancer and for some smoking-related non-malignant diseases. Analysis of potential radiation effects involved testing for any trend in mortality risk with external dose, after adjusting for likely confounding factors. For leukaemia, excluding chronic lymphatic leukaemia (CLL), the central estimate of excess relative risk (ERR) per Sv was similar to that estimated for the Japanese atomic bomb survivors at low doses (without the incorporation of a dose-rate correction factor); the corresponding 90% confidence limits for this trend were tighter than in the first analysis, ranging from just under four times the risk estimated at low doses from the Japanese atomic bomb survivors to about zero. For the grouping of all malignancies other than leukaemia, the central estimate of the trend in risk with dose was closer to zero than in the first analysis; also, the 90% confidence limits were tighter than before and included zero. Since results for lung cancer and non-malignant smoking-related diseases suggested the possibility of confounding by smoking, an examination was made, as in the first analysis, of all malignancies other than leukaemia and lung cancer. In this instance the central estimate of the ERR per Sv was similar to that from the A-bomb data (without the incorporation of a dose-rate correction factor), with a 90% confidence interval ranging from about four times the A-bomb value to less than zero. For multiple myeloma there was an indication of an increasing trend in risk with external dose (p = 0.06), although the evidence for this trend disappeared after omitting workers monitored for exposure to internal emitters. The second NRRW analysis provides stronger inferences than the first on occupational radiation exposure and cancer mortality; the 90% confidence intervals for the risk per unit dose are tighter than before, and now exclude values which are greater than four times those seen among the Japanese A-bomb survivors, although they are also generally consistent with an observation of no raised risk. Furthermore, there is evidence, of borderline statistical significance, of an increasing risk for leukaemia excluding CLL, and, as with solid cancers, the data are consistent with the A-bomb findings.

We conducted a study of the relationship between the dissolution rates of organic compounds that are sparingly soluble in water and the biodegradation of these compounds by mixed cultures of bacteria. The rates of dissolution of naphthalene and 4-chlorobiphenyl were directly related to their surface areas. The bacteria caused a decline in the concentration of the soluble substrate. The rate of bacterial growth fell abruptly when 4-chlorobiphenyl or naphthalene was no longer detectable in solution. The population continued to increase in media with different surface areas of insoluble 4-chlorobiphenyl, but the final counts were higher in media in which the surface areas of the substrate were larger. The rates of dissolution of palmitic acid, octadecane, di(2-ethylhexyl) phthalate, and 1-naphthyl N-methylcarbamate were determined in the absence of microorganisms. A mixed culture of microorganisms mineralized palmitic acid, di(2-ethylhexyl) phthalate, and Sevin (1-naphthyl N-methylcarbamate) at a logarithmic rate, but octadecane mineralization was linear. The rates of mineralization at the end of the active phase of the biodegradation were lower than the rate of dissolution of

Using data from the National Longitudinal Study of the High School Class of 1972, we examine the effect of the legal status of coresidential unions on the likelihood of dissolution. We find that legal unions are much more stable than nonlegal unions. In addition, current legal status is more important for predicting stability of union than is legal status at the initiation of the union. We also find that the effect of current legal status remains constant over various durations of unions and that legalizing a nonlegal union has little effect beyond that expected on the basis of a occupying a particular legal status.

No abstract

The microbial ecology and potential for biodegradation of benzene, toluene, ethylbenzene, and o- and m-xylene (BTEX) in core materials contaminated with unleaded gasoline were investigated. The site studied was unique because a portion of the contaminated area was biostimulated in a demonstration of the use of hydrogen peroxide as an oxygen source in in situ biorestoration. Two years after termination of the field demonstration, core samples were collected from uncontaminated, contaminated, and biostimulated areas at the site and analyzed for inorganic nutrients, microbial numbers, mineralization potential of glucose, benzene, and toluene using liquid scintillation counting, and biotransformation of BTEX using gas chromatography. The results indicated that the subsurface microflora at the site was active and capable of degrading a variety of compounds. Microbial numbers and contaminant biodegradation potential in samples from the biostimulated area were greater than in uncontaminated and contaminated zones. Toluene, ethylbenzene, and m-xylene were removed in all core materials, whereas o-xylene was recalcitrant. Mineralization experiments indicated that toluene was mineralized to a greater extent than benzene. These data indicated that the biodegradation potential of the subsurface material from the biostimulated zone, which still contained residual hydrocarbon, remained enhanced for at least 2 yr after the in situ biorestoration process had been terminated.