The Use of Ultrasound and High-Frequency Currents to Detoxify Carcinogenic Chamber-Process Shale Tar

Candidate of Medical Sciences O. L. Danetskaya

From the Leningrad Sanitary-Hygienic Medical Institute

Alongside low-temperature processes for the treatment of oil shale, the shale-processing industry has recently begun using a chamber process based on high-temperature pyrolysis (\(900\text{–}1000^\circ\)). This process yields high-calorific-value commercial gas (up to \(5000\ \text{kcal/m}^3\)), chamber-process shale tar, and shale coke.

Chamber-process shale tar has broad prospects for use, since highly valuable organic substances can be isolated from it by fractional distillation. At present, shale tars, including chamber-process tar, are widely used in the metalworking, engineering, textile, rubber, plastics, and other industries.

As the work of L. F. Larionov, A. P. Soboleva, and L. M. Shabad has shown, shale tars produced by the low-temperature pyrolysis of oil shale (\(450\text{–}500^\circ\)) are weakly carcinogenic. L. F. Larionov’s work established the high carcinogenicity of chamber-process shale tar taken from an experimental chamber-furnace unit at the Scientific Research Institute for Shale Processing in Leningrad. Our previous studies established the high carcinogenic activity of chamber-process tar taken from the decanter (tar collector) of a new shale-gas plant.¹

Because shale tars are widely used in many industries by large groups of industrial workers, and because of the considerable danger posed by skin contamination among workers who directly operate the tar-collection units (decanters) at shale-gas plants, concern arose—particularly in the latter case—that chamber-process shale tar might cause occupational cancer among workers. This suggested the need for thorough preventive measures, namely, pretreatment of chamber-process tar in a way that would substantially reduce its harmfulness.

It should also be noted that, owing to the high temperature of the chamber-process tar entering the decanter (\(500\text{–}600^\circ\)), its vapors contaminate the air and may cause illness among residents of workers’ settlements.

In our previous experimental studies,² various physical and chemical agents were applied for this purpose. As is known from the extensive oncology literature, the slightest changes in the structure of carcinogenic substances—the introduction of certain elements or radicals into their molecules, and so forth—can completely eliminate their carcinogenic activity. In the case of chamber-process shale tar, this is a difficult task because of the abundance and complex chemical composition of its constituents. No precise chemical analysis of chamber-process tar by individual chemical compounds is yet available.

¹ See the Leningrad Sanitary-Hygienic Medical Institute collection, Problems of Hygiene and Methods of Hygienic Research, 1953.

² Hygiene and Sanitation, 1952, no. 10; 1954, no. 12.

According to A. F. Dobryansky, shale chamber tar contains the following groups of chemical compounds: 1) hydrocarbons: a) aliphatic hydrocarbons, represented mainly by olefins, and b) aromatic hydrocarbons, including polycyclic compounds; 2) organic oxygen compounds (phenols, cresols, xylenols, etc.); 3) organosulfur compounds (thiophene, thiophane, and their derivatives); 4) nitrogen compounds (pyridine, pyrrole, and their derivatives).

Recently, the presence of benzpyrene in chamber tar was established by fluorescence analysis in the oncology laboratory of the Institute of Normal and Pathological Morphology of the Academy of Medical Sciences of the USSR. This aromatic polycyclic hydrocarbon is one of the most potent carcinogens.

In the present study, in order to destroy or bring about certain structural changes in the carcinogenic substances contained in chamber tar, the tar was pretreated with high-frequency currents in the ultrashort-wave range (UKV), which produce deep intramolecular heating during prolonged exposure, and with ultrasound at frequencies of 600,000 and 300,000 hertz/sec. The use of ultrasound was prompted by its chemical action, manifested in the extremely vigorous oxidation reactions it induces (for example, the luminescence of water).

It has been established that when ultrasound passes through a liquid, minute voids, known as cavitations, form within it. The walls of these cavities carry electric charges, so that when they collapse, microscopic electric sparks are produced. In addition, pressures of tens of thousands of atmospheres and temperatures of thousands of degrees develop, as do accelerations of liquid particles millions of times greater than normal gravitational acceleration (\(9.81\ \text{m/sec}^2\)). As a result, large molecules of carcinogenic hydrocarbons may rupture. Under the influence of electric spark discharges, dissolved oxygen is activated and, moreover, some of it is converted into its allotropic form, ozone. In addition, as reported in the specialist literature, ultrasound causes the destruction and fragmentation of large molecules, including those of benzpyrene. This is extremely important, given that carcinogenic hydrocarbons are polycyclic compounds with large molecules. These findings gave grounds to expect that the tar could be effectively decarcinogenized through oxidative destruction of the molecules of carcinogenic compounds.

We now turn to the methods used in the present study.

The experiments were conducted on white mice. A total of 250 intact white mice were divided into 5 series of 50 mice each. Two series served as controls. In the first control series, intact mice that were not subjected to any intervention were observed throughout the experimental period—white control, K (white). The second control consisted of white mice to which untreated shale chamber tar was applied at specified intervals. This second control was designated the black control, K (black). In the remaining three series, chamber tar treated by different methods was used. The chamber tar applied in the third series was treated with high-frequency currents in the ultrashort-wave range for 1 hour 30 minutes, at a frequency of 65.7 million hertz and an electrode separation of 38 mm (the treatment was carried out at the Institute of High-Frequency Currents). This series was designated UKV. For the fourth series, the chamber tar was pretreated with ultrasound at a frequency of 600,000 hertz for 16 hours. The thickness of the tar layer being treated was 15 mm. The treatment was carried out at the All-Union Institute of Plant Protection. The series was designated UZ-600. For the fifth series, the chamber tar was pretreated with ultrasound at a frequency of 300,000 hertz for 10 hours. The thickness of the tar layer being treated was 10 mm (Lesgaft Institute of Natural Sciences, head of the physicochemical laboratory: Prof. A. A. Glagoleva). The series was designated UZ-300.

As noted above, 50 mice aged 2½–3 months were assigned to each series. The experiment was conducted under biological conditions: females and males were therefore kept together in glass vessels and selected so that females constituted 60% and males 40%. The young were kept with the females until the end of lactation and were then transferred to separate vessels. Thus, the females in the experiment were provided with normal biological living conditions.

All mice were weighed monthly. They received a standard diet supplemented with fish oil in winter and green fodder in spring.

Chamber tar was applied to the white mice by placing a small drop in the interscapular region; applications were repeated three times a week (every other day) for six months. Each mouse was observed individually until a cancerous tumor appeared and it was euthanized with ether, or until it died. In parallel with the experiment, the temperature and humidity in the animal facility were monitored so that they could be maintained at a fixed, constant level, which, as experience showed, improved the survival of the mice in the experiment.

Observations showed that after 3–4 applications of tar, the white mice lost hair in the interscapular region (at the application site). The hair loss was not permanent, however, and the coat grew back for a short time, after which the mice again lost their hair.

Fig. 1. Squamous cell carcinoma and horn-like growths in a mouse from series K (black) (10 months in the experiment).

This process was usually repeated several times. Shale chamber tar is thus a very potent depilatory. In the second or third month, small benign papillomatous tumors (1–2 mm) appeared at the tar application site in some mice; these usually grew and subsequently became cancerous tumors (Fig. 1). In addition to its specific action on the skin, chamber tar had a strong systemic toxic effect on the white mice, as reflected in the more rapid death of mice in series K (black), in which untreated tar was applied (Fig. 2). In addition, a few young mice weighing less than 20 g at the start of the experiment suffered extensive hair loss, rapidly became emaciated, and died without even developing papillomas.

The skin cancers sometimes metastasized to the lungs (6 cases), the renal medulla (2 cases), the right axillary lymph node (1 case), and the spleen (1 case). The skin cancers were predominantly squamous cell carcinomas (Fig. 3). The metastases mentioned above were also squamous cell carcinomas. In four animals, cancerous tumors first appeared in the internal organs (lungs, kidney, spleen, or right axillary lymph node) in the absence of a cancerous tumor on the skin, that is, at the application site (Fig. 4). In series UZ-300, obser—

…a case of generalized cancer of the internal organs was observed in the absence of a cancerous tumor on the skin at the application site; cancerous tumors were present in the lungs, spleen, renal medulla, and axillary lymph nodes. In this case, the tumors of the internal organs were squamous cell carcinomas.

In addition to the specific changes in the skin and internal organs described above, nonspecific pathological changes were also observed in a number of cases: in the liver, inflammation, necrosis, an increase in the number of cellular elements, degenerative changes, and amyloidosis; in the spleen, follicular atrophy, necrosis, follicular hyperplasia, and amyloidosis; in the lungs, pneumonia, sometimes with suppuration, atelectasis, and necrosis; in the heart, necrosis; in the kidneys, degenerative changes and abscesses; in the axillary lymph nodes, hyperplasia and necrosis.

Fig. 2. Survival of experimental mice in different experimental series, by month.

Horizontal axis: Months.
Legend: K (white); K (black); UHF; US-600; US-300.

Thus, in addition to its specific action, chamber tar may also exert an adverse effect on experimental animals, causing septicopyemia to develop in some of them. Numerous abscesses in various parts of the body were observed in the experimental white mice, especially in the K (black) control series and in young animals. Mortality was more rapid in the experimental series than in the series of untreated mice, K (white), and in the K (black) control series than in the other series (see Fig. 2). The 59 cancerous tumors that developed in the experiments were mainly squamous cell carcinomas, with varying degrees of keratinization and epithelial tissue differentiation and varying intensities of infiltrative growth. Of the 59 tumors, 3 were sarcomatoid. There were 26 cancerous tumors in the K (black) series, 22 in US-300, 9 in US-600, and 2 in UHF.

The distribution of cancerous tumors by month in the different experimental series is shown in Fig. 5.

As Fig. 5 shows, the largest number of cancerous tumors was observed in the K (black) control series—26 tumors—and the smallest number in the UHF series, in which the chamber tar was pretreated with high-frequency currents in the ultrashort-wave range—2 tumors. As Fig. 5 shows, the first cancerous tumor appeared in the “black” control after 4 months, in the series in which the tar was treated with ultrasound after 6 months, and in the series in which the chamber tar…

…had been pretreated with UHF—only after 8 months. The maximum number of cancerous tumors in the “black” control was observed after 7 months; in the US-600 and US-300 series (ultrasound treatment of the tar), it was observed after 8 months in the first case and after 9 months in the second. In the UHF series (treatment of the tar with ultrashort-wave high-frequency current), there is no meaningful maximum, since only 2 cancerous tumors occurred during the entire experiment, at 8 and 9 months.

Fig. 3. Keratinizing squamous cell carcinoma. Series K (black) (5 months on experiment).

Fig. 4. Squamous cell carcinoma of the internal organs; no cancer on the skin. Series US-300 (10 months on experiment).

Although equal numbers of white mice were used in all experimental series, survival over the months differed among the series. Therefore, to make the results comparable, it was necessary to—

Figure 5 graph labels: Number of cancerous tumors; Months. Series: K, UHF, US-600, US-300.

Fig. 5. Distribution of cancerous tumors by month in the different experimental series.

—adjust the number of cancerous tumors in each series to account for animal survival. For this purpose, the total number of tumors in each series was expressed as a percentage of the number of mice surviving to 5 months. Thus, the carcinogenic activity of chamber…

the tar in each series was expressed as a percentage. This calculation showed that, with the carcinogenic activity of chamber tar at 87% [see series K (black)], the reduction in carcinogenic activity, as shown in Fig. 6, was 95% in the UKV series, 73% in the UZ-600 series, and 18.4% in the UZ-300 series. Thus, the greatest reduction in carcinogenic activity occurred in the UKV series, followed by the UZ-600 series. In the UZ-300 series, the reduction was slight and of no practical significance.

Fig. 6. Reduction in the carcinogenic activity of chamber tar in the different experimental series (percent).

Conclusions

1. In the experiment, cancerous tumors developed earlier in mice when untreated chamber tar was applied to the skin [series K (black)].

2. Cancerous tumors developed later when chamber tar treated by various methods was applied.

3. The greatest reductions in the carcinogenic activity of shale chamber tar treated with various physical agents occurred after irradiation of the tar with ultrashort waves of high-frequency currents (95%) and pretreatment with ultrasound at a frequency of 600,000 cycles per second (73%).

4. With appropriate technical development of the equipment and operating conditions, both methods could be used directly at shale-gas plants.

References

Zhunko, V. I. Combustible Gases from Baltic Shales. Leningrad–Moscow, 1948. — Larionov, L. F. In: Materials on the Toxicology of Shale Products. Leningrad, 1947, pp. 111–118. — Petrov, N. N. Malignant Tumors. Leningrad, 1932–1934, vol. 1. — Problems of Oncology, collected papers. Moscow, 1950. — Shabad, L. M. Essays on Experimental Oncology. Moscow, 1947. — Shanin, A. P. Malignant Neoplasms of the Skin. Leningrad, 1938. — Hueper, W. C. Occupational Tumors and Allied Diseases. Springfield, 1942. — Hieger, I. Brit. J. Industr. Med., 1949, vol. 9, pp. 1–23. — Bergmann, L. Der Ultraschall und seine Anwendung in Wissenschaft und Technik. Stuttgart, 1949.

Received June 7, 1956.

The Use of Ultrasound and High-Frequency Currents for Decancerisation of the Slate Chamber Tar

O. L. Donetskaya, candidate of medical sciences

The aim of this investigation is the prophylaxis of cancer which can be produced by the high temperature slate products both among labourers and population. Cancer tumours developed at much earlier periods when untreated slate chamber tar had been applied on the skin of white mice. The maximum of cancer tumours developed at much

later periods after the application of shale chamber tar subjected to various treatments. The greatest reduction in the carcinogenic activity of the chamber tar was observed after irradiation with ultrashort waves (by 95%); after exposure to ultrasound waves (frequency 600,000 hertz/sec), it was reduced by 73%. Both methods might be used in gas-shale plants.