Short Communications

UDC 614.72:668.74]-07

Experience in Determining 3,4-Benzpyrene in Ambient Air

B. A. Nemenko, Candidate of Medical Sciences, and N. A. Mazina

Kazakh Research Institute of Oncology and Radiology, Alma-Ata

With the extensive study of carcinogenic substances in the environment, the need to determine 3,4-benzpyrene in the ambient air of populated areas is being raised with increasing frequency. This, however, requires expensive and sometimes scarce equipment and can be accomplished only by a specialized laboratory. Evidence of this is the fact that, until now, aspirated samples of atmospheric pollutants have been tested for 3,4-benzpyrene in our country only in certain large cities (Moscow, Leningrad, Kiev, Tashkent, Alma-Ata, and others).

The main difficulties lie in the complexity of the analytical method and in the collection of aspirated samples. Most investigators have used powerful, bulky air blowers, which cannot always be constructed in a small community. In the method we used, samples were collected with a Migunov aspirator, available at any sanitary and epidemiological station. Air was drawn through an FPA-15 fabric filter housed in a metal cartridge designed by the Institute of Occupational Hygiene and Occupational Diseases of the USSR Academy of Medical Sciences. Air was sampled using two cartridges. The aspiration rate was 18 L/min. The sampling duration depended on the level of atmospheric pollution. Air sampling was usually stopped once the filter had blackened.

After aspiration, the filters were extracted with benzene until fluorescence ceased. The resulting extract was evaporated and subjected to chromatographic fractionation. Ordinary column chromatography is of limited effectiveness in this case because the quantities of resinous substances are very small. We therefore used thin-layer chromatography on a fixed layer of aluminum oxide with gypsum (A. A. Akhrem and A. I. Kuznetsova, 1964).

A mixture of aluminum oxide and gypsum (9:1) was diluted with water to a slurry and poured onto glass plates, which were then placed in a drying oven. The dried plate was divided vertically into two zones. The layer of sorbent between the zones was scraped away with a scalpel. The concentrated extract solution was first applied with a pipette. A mixture of chloroform and n-heptane (1:3) was used as the solvent. Several drops of a 3,4-benzpyrene solution were applied to the other zone at the same level as the extract. The plate was then placed in a chamber containing a mixture of chloroform and n-heptane (1:3). The chamber and plate were illuminated with ultraviolet light through a UFS-3 filter. On the plate, the extract separated into individual components. The 3,4-benzpyrene fraction was readily visible, appearing opposite the line of pure 3,4-benzpyrene. After separation, the aluminum oxide layer containing the 3,4-benzpyrene fraction was scraped off and extracted with benzene. Qualitative and quantitative analyses were then performed with a DFS-12 diffraction spectrometer at liquid-nitrogen temperature. 1,12-Benzperylene was used as the internal standard.

The method described considerably reduces analysis time. Whereas fractionation by column chromatography took several days, thin-layer chromatography takes no more than an hour. In addition, the method for collecting aspirated samples has been greatly simplified. The study was conducted in November 1967. We divided the entire city into designated areas. Air pollution samples were collected in Alma-Ata along four parallel streets—Tashkent Alley, Pasteur and Komsomolskaya Streets, and Abay Avenue. This enabled the study to cover the entire city uniformly. A total of 15 atmospheric pollution samples were collected.

Analysis showed that 100 m³ of ambient air in Alma-Ata contained between 0.022 and 0.413 µg of 3,4-benzpyrene. The greatest atmospheric pollution was observed in the area of Tashkent Alley, the city thoroughfare with the heaviest motor traffic. Somewhat lower, though still considerable, pollution was recorded along Abay Avenue. Finally, the atmosphere was substantially less polluted in the areas of Pasteur and Komsomolskaya Streets. It is noteworthy that these data are fully consistent with the results we obtained in our initial study of atmospheric pollution in Alma-Ata in 1964 and 1966.

It should be noted that when the samples were collected, the heating season had not yet begun, and the contribution of motor vehicles to air pollution was therefore clearly discernible. Experience from previous studies suggests that, at the height of the heating season, atmospheric pollution from motor vehicles will not have such clearly defined boundaries, owing to a substantial increase in the citywide background level of air pollution.

Thus, the method we used makes it possible to assess atmospheric pollution in populated areas with reasonable reliability. It is also simple and considerably reduces the time required for the investigation.

Received February 19, 1968.