Retrospective cohort mortality study of workers at an aircraft maintenance facility. I. Epidemiological results.

A retrospective cohort study of 14,457 workers at an aircraft maintenance facility was undertaken to evaluate mortality associated with exposures in their workplace. The purpose was to determine whether working with solvents, particularly trichloroethylene, posed any excess risk of mortality. The study group consisted of all civilian employees who worked for at least one year at Hill Air Force Base, Utah, between 1 January 1952 and 31 December 1956. Work histories were obtained from records at the National Personnel Records Centre, St. Louis, Missouri, and the cohort was followed up for ascertainment of vital state until 31 December 1982. Observed deaths among white people were compared with the expected number of deaths, based on the Utah white population, and adjusted for age, sex, and calendar period. Significant deficits occurred for mortality from all causes (SMR 92, 95% confidence interval (95% CI) 90-95), all malignant neoplasms (SMR 90, 95% CI 83-97), ischaemic heart disease (SMR 93, 95% CI 88-98), non-malignant respiratory disease (SMR 87, 95% CI 76-98), and accidents (SMR 61, 95% CI 52-70). Mortality was raised for multiple myeloma (MM) in white women (SMR 236, 95% CI 87-514), non-Hodgkin's lymphoma (NHL) in white women (SMR 212, 95% CI 102-390), and cancer of the biliary passages and liver in white men dying after 1980 (SMR 358, 95% CI 116-836). Detailed analysis of the 6929 employees occupationally exposed to trichloroethylene, the most widely used solvent at the base during the 1950s and 1960s, did not show any significant or persuasive association between several measures of exposure to trichloroethylene and any excess of cancer. Women employed in departments in which fabric cleaning and parachute repair operations were performed had more deaths than expected from MM and NHL. The inconsistent mortality patterns by sex, multiple and overlapping exposures, and small numbers made it difficult to ascribe these excesses to any particular substance. Hypothesis generating results are presented by a variety of exposures for causes of death not showing excesses in the overall cohort.

Effect of pregnancy and nursing on the growth of metastases from N-nitroso-N-methylurea-induced mammary carcinomas.

Pregnancy increased the survival times of inbred BUF/N rats bearing occult metastasis of a mammary carcinoma at the time of conception. Nursing following delivery nullified the effect of pregnancy. The similarity of the controlled experimental data with the limited clinical observations is noted. An experimental model of rat mammary carcinoma has been described that possesses a highly metastasizing capacity and can be utilized to study the behavior of clinically silent metastasis.

N-nitrosomethylurea as mammary gland carcinogen in rats.

N-nitrosomethylurea (NMU) given intravenously to rats at age 50 days induced mammary carcinomas in 89% of BUF/N, 73% of Sprague-Dawley, and 89% of F344 females. Latent periods were, respectively, 77, 86, and 94 days. Mortality was negligible. Biologic properties of NMU-induced tumors were tested in the BUF/N inbred strain. Before treatment, it reduced the number of tumors per rat but not the incidence; and after the tumor was established, castration arrested tumor growth or caused a temporary regression of the tumor. Metastases to bone marrow and spleen were constant, but they were rare to the liver and lungs. After the primary tumor was removed, metastases continued to grow but at a slower rate than the growth of the primary tumor. Almost all tumors were transplantable intraperitoneally and/or subcutaneously in the inguinal area of intact as well as ovariectomized and adrenalectomized rats. Transplanted tumors were able to metastasize as were primary tumors. Doubling times of NMU-induced primary and transplanted carcinomas were similar to 7 days. Cachexia ensued at the 5th week from the onset of the first tumor. When the tumor was larger than 15 g, hypercalcemia was usually observed. The treatment described appears to be the simplest method for inducing in rats a most nearly complete model for human mammary carcinomas.

The allografted parathyroid gland: evaluation of function in the immunosuppressed host.

Parathyroid autografts were performed in 19 random bred mongrels and parathyroid allografts were exchanged between seven random bred mongrels. Three pairs of siblings from a beagle colony were immunosuppressed and parathyroid allografts exchanged between them. The parathyroid autografts were successful, while parathyroid allografts failed on all occasions in the non-immunosuppressed host. In immunosuppressed animals, however, the allografts were successful in five of six dogs. The success of parathyroid transplantation was determined by the following observations: 1) The experimental animal, having grafted parathyroid tissue as the only source of hormone, maintained a normal or near normal serum calcium concentration. 2) Following removal of the parathyroid graft, there was an immediate fall in the serum calcium concentration associated with tetany and/or death. 3) Histological study of the grafted gland revealed normal architecture, and 4) Radioimmunoassay of extracted grafts revealed moderate to large quantities of parathyroid hormone.