Bacterial Contamination of the Air in the Workshops of the Krasny Tekstilshchik Spinning and Weaving Mill

Research associates E. P. Ponomareva, G. A. Fishman, and A. E. Pasternak

From the Moscow Regional Scientific Research Institute of Sanitation and Hygiene

Studies of airborne dust in the sorting and scutching and carding workshops of several cotton-spinning mills in the USSR have for the most part been conducted without taking into account the accompanying substantial bacterial contamination of the workplace air. This prompted us to investigate the bacterial contamination of the air in the workshops of the large Krasny Tekstilshchik spinning and weaving mill.

A number of foreign publications have addressed bacterial contamination of different grades of cotton and cotton dust. Prindle (1934), studying the microorganisms present in freshly harvested cotton and cotton that had been stored for a long time, found that the bacterial flora changes during storage, with spore-forming bacteria and molds of the genera Aspergillus and Penicillium becoming predominant. Caminita, Neal, and Schneiter (1942, 1947) studied acute respiratory illnesses among workers processing contaminated low-grade cotton in which large quantities of Aerobacter cloacae were found. The authors attributed the heavy contamination of the cotton with this microorganism to specific climatic conditions during harvesting and to contamination with soil bacteria during storage.

Furness and Maitland (1952) reported data on bacterial contamination of dust from different grades of cotton. Gram-positive cocci and bacilli and spores predominated among the microorganisms found; mycological examination revealed molds, chiefly Aspergillus (especially A. niger). Drummond and Mary Hamlin (1952) studied bacterial contamination of the air in cotton mills and found the greatest numbers of microbes in the carding and “preparatory to carding” workshops (apparently the sorting and scutching workshops), and far fewer in the spinning workshops and at subsequent stages of processing.

Airborne bacterial contamination was greatest during the processing of low grades of American cotton.

In the domestic literature, we found no data on bacterial contamination of cotton and of the air in textile mill workplaces apart from the studies of A. I. Pakhomychev, who found large numbers of bacteria in the air of the Znamya Oktyabrya cotton-waste mill he surveyed (from 345,000 to 835,000 bacteria per \(1\ \text{m}^3\) of air).

The sorting and scutching workshop of the Krasny Tekstilshchik mill has three single-process units that provide continuous sorting and scutching without intermediate storage. After the bales are unpacked, the cotton is loaded onto the lattice of one of the five feeder-blenders comprising a unit. From each feeder-blender, the cotton passes onto a common conveyor (the blending lattice), which feeds it to the head blender. From there the cotton is conveyed pneumatically to other machines—the horizontal and vertical openers, cleaning drum, and others—and then enters the scutching machine. These machines are well enclosed. Dust is released at two points: when cotton is loaded onto the feeder-blender lattice and when the so-called lap emerges from the scutching machine.

A particular grade of cotton is loaded into each feeder-blender according to the desired composition of the cotton blend. The second sorting and scutching unit processed blend No. 12, which had a high proportion of low-grade cotton. It contained 46.5% low-grade cotton (grades 5 and 6), 34.4% waste, and the remainder was return material. Blend No. 15 consisted of 46% low-grade cotton, 44.4% high-grade cotton, and the remainder return material and waste. Combed blend No. 6 and blends 5a and 5b contained only high grades of cotton. These blends were processed on the third unit.

In the carding workshops, the cylinders of the carding machines are cleaned with a cleaning roller, a process that releases considerable dust. The cylinders of the carding machines were cleaned every hour when low-grade blends were being processed.

In the sorting department, considerable dust is released when cotton is loaded onto the feeder-blender lattice. Airborne dust concentrations depend on the composition of the blend being processed. Thus, when a blend consisting of high-grade cotton was processed, the airborne dust concentration at the loading point on the feeder-blender lattice ranged from 11 to \(17\ \text{mg/m}^3\) of air; when a blend with a high proportion of low-grade cotton was processed, it ranged from 27 to \(29.8\ \text{mg/m}^3\).

In carding rooms, cleaning dust from the cylinders of carding machines considerably increases airborne dust concentrations—by a factor of 2–3 when processing blends of high-grade cotton and by a factor of about 4 when processing blends with a high proportion of low-grade cotton. Belt drives increase airborne dust concentrations when the same blend is processed. By creating substantial air currents above the carding machines, transmission belt drives increase airborne dust concentrations because dust remains suspended longer and settles less readily. Thus, at a carding machine fitted with an individual motor, the airborne dust concentration before the cylinders were cleaned was 3.1–3.3 mg/m³ when blend 5б was being processed; at carding machines with belt drives, the concentration under the same conditions was 6.2 mg/m³. A. I. Pakhomychev’s monograph Dust Control in Textile Plants presents evidence that dust concentrations in cotton-mill workshops are substantially affected by the grade and origin of the raw material, the conditions under which it is harvested and stored, and the moisture content of the raw material and intermediate product in the mill. It also notes the importance of workshop humidity, air currents created by ventilation equipment of various systems and designs, the dust-removal efficiency of different ventilation systems, the use of other measures, and so on. All these factors, of course, also affect the degree of bacterial contamination of workplace air.

To characterize the air from a sanitary and hygienic standpoint using bacteriological indicators, the total number of bacteria per unit volume of air was determined, and the composition of the airborne microflora was established with respect to pigment-producing bacteria, spore-forming bacteria, and molds. Determining the pathogenicity of the microflora was not an objective of this study.

Alongside sampling by Krotov’s aspiration method, which reflects the overall pattern of bacterial air contamination, an investigation was also carried out by the sedimentation method.

After several trials, the following exposure times were selected: 1 minute for the aspiration method, at a filtration rate of 20 L/min, and 5 minutes for the settling method. Plates containing Endo medium were exposed for 1 minute.

Samples were inoculated onto meat-peptone agar to count the total number of bacteria, including pigment-producing and spore-forming bacteria; onto wort agar at pH 5.4 to detect molds; and onto plates containing Endo medium to isolate Aerobacter cloacae.

After 24 hours of incubation at 37°C and 24 hours at room temperature, all colonies that had grown on the agar plates were counted with a magnifying glass, and the counts were converted to numbers per cubic meter of air; data obtained by the settling method were converted to numbers per square meter of surface. Pigment-producing bacteria were identified by the appearance of colonies on the surface of the medium in the same plate used for the total count, but pigmented colonies were counted after an additional 24 hours of incubation at room temperature. Spore-forming bacteria were identified on the same plates and at the same times as pigment-producing bacteria, by colony appearance and microscopy. Plates containing wort agar were incubated at 30°C for 72 hours, after which molds were counted. After 24 hours of incubation at 37°C, colonies from the Endo medium plates were subcultured onto agar slants for subsequent study.

The data in Tables 1–3 show that bacterial contamination of the air differs among the workshops of the spinning and weaving mill.

Many factors, including temperature and humidity, can affect the degree of bacterial contamination of the air. We did not address these factors, however, because our objective was to determine how the number of airborne bacteria depends on dust generation, the production process, and air currents.

The greatest bacterial contamination was observed in the sorting and scutching and carding rooms.

At the feeder-mixers of the second and third units in the sorting and scutching room, bacterial air contamination was considerable for all blends. By the aspiration method, the minimum count was 25,400 bacteria per 1 m³ of air and the maximum was 54,800 per 1 m³, at the machines of the second unit processing blend No. 12. The settling method yielded a minimum of 16,600 and a maximum of 43,200 bacteria per 1 m² of surface.

Analysis of the air in the carding rooms revealed a substantial increase in bacterial contamination while dust was being cleaned from the carding-machine cylinders. Different levels of bacterial air contamination were observed during processing of the same blend depending on whether the machines were fitted with individual motors or with belt drives from transmissions. Thus, in the carding room of the new mill, where the machines were fitted with individual electric motors, the number of microorganisms determined by the settling method during processing of blend 5б was 8,200 per 1 m² of surface, 15% of which were spore-forming. In the carding room of the carding mill, equipped with belt-drive transmissions, bacterial contamination during processing of the same blend reached 20,800 microorganisms per 1 m² by the settling method, 50% of which were spore-forming. The highest number of colonies was recorded during processing of blend No. 12 in the room with belt-drive transmissions: 68,000 per 1 m³ by the aspiration method. At the drawing—

…at the roving machines, bacterial contamination of the air ranged from 15,500 to 17,500 bacteria per \(1\ \mathrm{m}^3\), of which 6–20% were spore-forming bacteria.

As expected, the spinning and weaving workshops were the cleanest by bacteriological measures. In the spinning workshops, the number of bacteria ranged from 9,500 to 16,100 per \(1\ \mathrm{m}^2\) of surface by the sedimentation method, with spore-forming bacteria accounting for 3–40%, and from 7,000 to 18,000 per \(1\ \mathrm{m}^3\) of air by the aspiration method, with spore-forming bacteria accounting for 2–37%. In the weaving preparation workshop, airborne bacterial counts ranged from 8,000 to 13,000 microorganisms per \(1\ \mathrm{m}^2\) by the sedimentation method and from 5,700 to 12,300 microorganisms per \(1\ \mathrm{m}^3\) by the aspiration method. Spore-forming bacteria accounted for 3–18%. The lowest airborne counts were found in the weaving workshop: 8,100 bacteria per \(1\ \mathrm{m}^2\) by the sedimentation method and 4,300–6,700 colonies per \(1\ \mathrm{m}^3\) by the aspiration method.

Turning to the composition of the airborne microflora in the workshops studied, it should be noted that the percentage of pigment-producing bacteria was high in the workshops with the lowest bacterial contamination of the air. A high total count—68,000 per \(1\ \mathrm{m}^3\)—was associated with a high percentage of spore-forming bacteria.

No Aerobacter was isolated from any of the 19 samples collected by the sedimentation method on plates of Endo medium in the sorting-and-scutching and carding workshops.

At the feeder-mixers of the second and third units in the sorting-and-scutching section, 254 and 457 mold fungi per \(1\ \mathrm{m}^2\) of surface were found, respectively. In the carding workshop, mold fungi were investigated only by the aspiration method; 30–60 mold fungi per \(1\ \mathrm{m}^3\) of air were found near the carding machines. In the weaving preparation workshop, near the warping machines, only 8 mold colonies per \(1\ \mathrm{m}^3\) were found in one sample, and none in another.

Conclusions

1. The highest levels of airborne dust and bacterial contamination are found in the sorting-and-scutching and carding workshops.

2. Bacterial contamination of workshop air depends on the grade of cotton processed and the nature of the production process. Under the same processes, it is higher when low grades are processed—that is, mixtures with a high content of low-grade cotton (grades 5–6) and cotton waste.

3. Dusting out the drums of carding machines approximately doubles the bacterial contamination of the air in carding workshops.

Air currents produced by the transmission belts increase airborne dust and bacterial contamination in carding workshops.

1. In the spinning, weaving preparation, and weaving workshops, airborne bacterial contamination is considerably lower than in the sorting-and-scutching and carding workshops.

2. Mold fungi were found in small quantities in all workshops.

3. The substantial bacterial contamination of the air in the sorting-and-scutching and carding workshops of the cotton-spinning mill, associated with the high dust levels in these workshops, particularly when low-grade cotton is processed, calls for further dust-control measures: complete enclosure of dust-producing equipment; installation of effective dust-extraction ventilation at the feed points of sorting-and-scutching units; installation of local exhaust ventilation to control dust when carding-machine drums are dusted out; provision of individual electric motors for carding machines; and other measures.

References

Pakhomychev A. I. Dust Control in Textile Enterprises. Moscow–Leningrad, 1940. — Rechmensky S. S. On the Problem of Airborne Infections. Moscow, 1951. — Sobolev V. G. In: Collected Works of the Sanitary Inspection in Ukraine, vol. 2, Kharkov, 1924. — Tribukh S. L. Gig. i san., 1952, no. 2, pp. 20–26. — Shafir A. I. The Microbiological Method of Hygienic Air Examination. Leningrad, 1945. — Drum­mond D., Hamlin M. Brit. J. Indust. Med. 1952, vol. 9, pp. 309–313. — Caminita B. H. A Review of the Literature Relating to Affections of the Respiratory Tract in Individuals Exposed to Cottons Dust. Washington, 1947. — Furness G. and Maitland H. B. Brit. J. Indust. Med. 1952, vol. 9, pp. 138–145.

Received December 6, 1955.