Gaseous formaldehyde and hydrogen chloride induction of nasal cancer in the rat.

The carcinogenic response to the combined and separate exposures to formaldehyde (HCHO) and hydrochloric acid (HCl) was investigated in male inbred SD rats. The rats were exposed to gaseous HCHO, 14 ppm, and HCl, 10 ppm, in two experiments. In one experiment the gases were premixed at high concentrations before being diluted in the exposure chamber air to maximize the formation of the carcinogen bis(chloromethyl)ether (BCME). In the second experiment exposure was repeated to HCl and HCHO premixed at high concentrations, and not premixed (to minimize BCME formation), as well as to HCHO alone and HCl alone. The second experiment is being reported on at an interim stage. HCHO alone induced squamous carcinomas of the nasal cavity as did the combined exposures to HCHO and HCl. No carcinogenic response was observed with HCl alone. HCHO accounted for most, if not all, of the carcinogenic activity of the mixture of HCHO-HCl.

Inhalation carcinogenicity of epichlorohydrin in noninbred Sprague-Dawley rats.

Inhalation exposure experiments with the direct-acting alkylating agent epichlorohydrin (ECH) were done on noninbred male Sprague-Dawley rats. Single 6-hour exposure to ECH and follow-up for 14 days showed the median lethal concentration to be about 360 ppm. Further inhalation experiments were done with 6-hour exposure 5 days/week. A short-term 30-exposure regimen with 100 ppm ECH produced malignant squamous cell carcinomas of the nasal cavity in 15 of 140 rats and respiratory tract papillomas in 3 rats. Among 100 rats, lifetime exposure to 30 ppm yielded 1 malignant squamous carcinoma of the nasal cavity plus 1 nasal papilloma. No nasal or respiratory tract tumors were produced by lifetime exposure of 100 rats to 10 ppm. As controls, 100 air-treated and 50 untreated rats were used. A dose-rate effect was observed for ECH inasmuch as 30-day exposure to 100 ppm (3,000 ppm-days) produced 15 cancers in comparison to the 1 cancer from the lifetime exposure to 30 ppm (8,700 ppm-days) and no cancers from lifetime exposure to 10 ppm (2,500 ppm-days).

In vitro transformation of BHK21 cells grown in the presence of calcium chromate.

Concentrations of 0.25 and 0.5 mug/ml calcium chromate (CaCrO4-2H2O)dissolved in Dulbecco's medium were found to alter the growth behavior of BHK21 cells in culture. Treated cells grew as shortened fibroblasts and in random orientation. The changes detected during the first two weeks of culture in the presence of the metal became more pronounced as the number of growth passages increased. In addition to the alterations noted above, chromate-treated cells grew into large clusters in Methocel (an alternative technique to the agar suspension system), while untreated cells underwent, at most, only one or two divisions in Methocel. These alterations in growth properties were irreversible and persisted after removal of the treated cells from chromate-containing medium, suggesting that a heritable change had occurred as opposed to a transient, chromate-dependent alteration of cell growth. This experimental observation suggests that chromate salts and perhaps salts of other metals can transform BHK21 cells in vitro or can select for spontaneously transformed cells.

The carcinogenicity of beryllium.

Beryllium, some of its alloys, and a variety of its compounds have induced malignant tumors of the lung and osteogenic sarcoma in experimental animals. Three animal species, monkeys, rabbits, and rats, have been shown to be susceptible. Beryllium induces morphological transformation in mammalian cells and enhances viral transformation of mammalian cells. It has been shown to decrease fidelity of DNA synthesis. It has been recognized that exposure to compounds of this metal will, in some individuals, result in a chronic granulomatous disease of the lung. A series of overlapping recent human epidemiological studies have been suggestive of an increase in the incidence of lung cancer in populations occupationally exposed to beryllium. Such studies, together with animal and in vitro studies, argue for the strong presumption of a carcinogenic hazard to man in occupational beryllium exposures.

Experimental approaches for exposure to sized glass fibers.

A number of studies have shown that glass fibers induce both malignant mesothelioma and fibrosis in rats and that these reactions may be primarily a function of the physical properties of the fiber. However, these studies were carried out with fibers having broad size distributions and used methods of administration which bear little resemblance to the way man is exposed. To better characterize the health effects of glass fibers, techniques have been developed to expose rats to glass fibers of defined sizes by intratracheal instillation of aqueous suspensions and by "nose only" inhalation exposure, and to determine the deposition, translocation, and ultimate fate of these fibers in the rat. The fibers have known size distributions with geometric mean diameters of 1.5 micrometers (sigma g = 1.1) and lengths of either 5 micrometers (sigma g = 1.49) or 60 micrometers (sigma g = 3.76). The fibers have been activated with neutron irradiation. Of the several resulting radionuclides, 65Zn appeared to be the most suitable for long-term clearance studies by use of in vivo whole body radioassay techniques. A fluidized bed aerosol generator has been developed to expose rats by "nose only" inhalation to approximately 500 fibers/cm3. The generator and exposure system permits reuse of fibers which pass through the exposure chamber and produces no significant alteration of the fiber size distribution. Rats were exposed by intratracheal instillations to 20 mg of the longer fibers and to equal numbers (2 mg) and equal mass (20 mg) of the shorter fibers. Through approximately 19 weeks little difference was observed in the whole rat clearance rate of long versus short fibers in the initial exposure group. Histopathology, however, showed differences at this time with the short fibers apparently successfully phagocytized by alveolar macrophages and cleared to the lymph nodes, while the long fibers were not.

Contribution of environmental fibers to respiratory cancer.

This article reviews studies of the carcinogenicity of mineral fibers, notably asbestos, and presents seven major recommendations for further research. Mineral fibers represent the greatest cause--after cigarette smoke--of respiratory cancer due to air pollutants. Past asbestos exposure may currently account for 2000 mesothelioma deaths per year and 4000 to 6000 lung cancer deaths per year. All major commercial types of asbestos (crocidolite, amosite, and chrysotile) can cause each of the major asbestos-related respiratory diseases. Lung cancers in asbestos-exposed individuals probably do not have a different distribution of histological types from that of non-asbestos-related lung cancers. Nonoccupational exposures are likely to be associated with malignant disease outcomes qualitatively similar to those associated with occupational exposures. Further investigations of fibers are needed to characterize the relationships among physicochemical properties, patterns of migration and clearance, dose, and adverse health effects. Transmission electron microscopy has been found to be the preferred method of analysis of environmental fibers. Relations among time factors (e.g., age at first exposure), dose, and risk for adverse health effects require analyses of existing and new epidemiologic studies of exposed cohorts. Concomitant exposure, behavioral factors, and host factors affecting susceptibility to asbestos should be identified.

Inhalation carcinogenicity of alpha halo ethers. I. The acute inhalation toxicity of chloromethyl methyl ether and bis(chloromethyl)ether.

A range of acute studies were performed with chloromethyl methyl either (CMME) and bis(chloromethyl)ether (BCME), including 14-day LC50's following single seven-hour inhalation exposures. The LC50's for CMME were 55 ppm for rats and 65 ppm for hamsters. The LC50's for BCME were 7 ppm for both species. All animals showed characteristic changes of acute irritation of the respiratory tract manifested by congestion, edema, and hemorrhage. Severe shortening of life span was seen in 30-day exposures of rats to CMME and in all studies with BCME. Incidences of mucosal changes, including atypia, were generally increased in a dose-related manner in both species. The carcinogenicity of BCME in these range finding experiments was demonstrated by a skin cancer in a rat after three exposures and a nasal tumor in a hamster after one exposure to 1 ppm BCME.

Inhalation carcinogenicity of alpha halo ethers. II. Chronic inhalation studies with chloromethyl methyl ether.

Rats and hamsters were exposed to 1 ppm of chloromethyl methyl ether six hours per day, five days per week, throughout their lifetime. Mortality and weight gain of the exposed animals paralleled that of the control animals. Malignant tumors of the respiratory tract were found in two rats. These were a squamous cell carcinoma of the lung with blood vessel invasion and an esthesloneuroepithelioma originating in the olfactory epithelium and invading the forebrain. One hamster was found to have an adenocarcinoma of the lung and another, a squamous papilloma of the trachea. A single exposed rat had a pituitary tumor of primitive cell type that may well have been coincidental.

Inhalation carcinogenicity of alpha halo ethers. III. Lifetime and limited period inhalation studies with bis(chloromethyl)ether at 0.1 ppm.

Rats and hamsters were exposed to 0.1 ppm bis(chloromethyl)ether (BCME) six hours per day, five days per week throughout their lifetime. Additional groups of rats were given 10, 20, 40, 60, 80, and 100 exposures to 0.1 ppm BCME and then held until death. Forty cancers originating in the respiratory tract were found in the 200 rats involved in these studies. These included 14 cancers of the lung and 26 cancers of the nasal cavity. They occurred in dose-related fashion. A single undifferentiated carcinoma of the lung was seen in a hamster.

The influence of varying lengths of glass and asbestos fibres on tissue response in guinea pigs.

Intratracheal injection of samples of naturally occurring and man-made mineral fibres into guinea pigs showed that while long fibre samples produced marked fibrosis, short fibre specimens produced only a macrophage reaction. In most cases the long fibre samples were administered in smaller doses than the short. The samples tested were crocidolite asbestos, a synthetic fluoramphibole and two specimens of glass fibre with different mean diameters. With all the minerals tested some short fibres, but not long fibres, were transported to the hilar lymph nodes. In some instances the numbers of short fibres found in these nodes appeared to be much higher than would be expected from the percentage of short fibres in the original sample, and it is suggested that this may be due to the breakdown of long fibres within the lung.

Relationship of radioactive radon daughters and cigarette smoking in the genesis of lung cancer in uranium miners.

This article documents the study of 383 cases of lung cancer in uranium miners and presents for the first time the relationship of radioactive radon gas and cigarette smoking. There is evidence that alpha radiation from radon gas at exposure levels above 465 working level months (WLM) is a strong contributor to the development of lung cancer. Cigarette smoking plays the most significant role in causing lung tumor; this is also noticed in nonminers who smoke cigarettes. A synergistic or additive effect of these two carcinogens is strongly suggested. The data indicate that small cell tumors develop in younger nonsmoking miners exposed to radon levels above 465 WLM. Lung cancers develop in smoking miners at lower levels of radon exposure than in nonsmoking miners. Based on an average mining experience of 15 years, there is substantial evidence that the present maximum allowable limit of 0.3 working levels (WL), or 4 working level months (WLM) per year, is safe, representing a margin of safety of approximately 10:1. Furthermore, a comparison of these data with the radon levels in some homes, averaging in the neighborhood of 0.025 WL, would indicate that health risks at these levels are negligible. It is suggested that 20 picocuries/liter, which equals 0.10 WL, be the maximum allowable level in homes.

Analysis of fatal pulmonary hantaviral infection in New York by reverse transcriptase in situ polymerase chain reaction.

The purpose of this study was to analyze the histological distribution of polymerase chain reaction (PCR)-amplified hantaviral cDNA in three cases of fatal hantaviral infection that occurred 2 years ago in Long Island, NY. The three otherwise healthy patients had a rapid death characterized by fever and pulmonary failure and were identified from the autopsy files at University Hospital, Stony Brook. Six autopsy controls with either no pulmonary disease (three) or fatal pneumonitis of known etiology (three) were also studied. PCR-amplified hantaviral cDNA was detected in the lung tissue of the three cases and none of the six controls using the reverse transcriptase in situ PCR technique. In the positive cases, viral RNA was detected in approximately 20% of pneumocytes and alveolar endothelial cells as determined with a consensus and Four Corners-specific primer pair. Infected endothelial cells were identified in a wide variety of other sites, but at rates much lower than in the lungs. The selective localization of the viral RNA in many pneumocytes and pulmonary endothelial cells using a highly sensitive PCR-based test demonstrates a correlation between direct viral infection in the lung and the disease process.

Histologic findings in the tracheobronchial tree of uranium miners and non-miners with lung cancer.

The remaining tissue of the tracheobronchial tree from 210 men who died from lung cancer was studied to compare the histologic alterations leading to further sites of primary cancer. These men were uranium miners matched with nonminers for age and smoking habits. In the examination of a total of 28,928 cross-sections carcinoma in situ was found in 96% of the miners and in 92% of the nonminers. The number of slides from miners showing degree 2 or 3 atypia in areas of carcinoma in situ was about double the number found from the nonminers. Although the difference was not statistically significant, 32% of the miners had at least one section showing early primary invasive carcinoma compared with 22% of the nonminers. The data indicate that the synergistic effect of the exposure to uranium dust along with cigarette smoking increases the risk of lung cancer and that in addition to a main tumor mass, other sites of tissue alterations leading to tumor development are frequently already present in the lung.