[The assessment of the noise factor and the state of the auditory analyzer in workers in metal rolling production]. / Otsenka na shumoviia faktor i sustoianieto na slukhoviia analizator pri rabotnitsi ot prokatnoto proizvodstvo.

At main workplaces in F. "Stomana" (Pernik City) sorting and sheetrolling works, measurements and evaluation of the noise factor were carried out, and hearing sensitivity of workers was investigated in 229 subjects of mean age 36.1 +/- 9.8 years and mean occupational experience 9.7 +/- 7.4 years. Findings at workplaces indicated presence of noise of excessive equivalent levels and pulsing nature varying in degrees. Hearing thresholds for 4 and 6 kHz and average speaking frequency were elevated, and the proportion of subjects with hearing threshold above 30 dB for all frequencies tested was larger among the job groups of roller workers, furnace men, cutters, crane workers, markers, packers, quality control surveyors, and dispatchers as compared to subjects working at lower noise levels or exposed for shorter times to intense noise, notably, operators, fitters, welders, electrotechnicians. Regression analysis revealed the dynamics of change in hearing sensitivity to be more closely related to age than to duration of occupational experience.

[The assessment of the occupational risk to workers in electric steel production]. / Otsenka na professionalniia risk na rabotnitsite ot elektrostomanodobiva.

These studies, centering on occupational environmental factors, biologic monitoring, and toxicodynamic investigations, involved a total of 105 workers distributed into eight job groups, who were 45 years, of age on the average and had from 5 to 10 years of special occupational experience at "Electrosteel" Works. Evidence was obtained for presence of unfavorable microclimate conditions, elevated equivalent levels of noise, excess of general and local vibrations, exposure to manganese aerosols, carbon monoxide, and nitrogen oxides; some of the subjects and deviations in hepatic status and connective tissue. Job groups found to be at risk were those of steel founders, crane workers, and pourers.

Noise evaluation and estimation of some specific and non-specific health indicators in telephone operators.

Noise loading has a considerable effect on the working conditions of telephone operators. This study comprises noise field and laboratory measurements and field investigation of workers at three departments of the Telephone and Telegraph Communication Services in Sofia. Noise measurements revealed a background noise in the range of 57.4-70.6 dB A in the International Department, 70.6-71.7 dB A in the Intercity Department and 68.7-70.1 dB A in the Information Department and highest intensities of 63.5, 62.1 and 58.2 dB for frequencies of 0.5, 1 and 2 kHz. The registered noise (Leq) from the inner telephone receiver-microphone (type Star-set) was in the range of 78.4-86.6 dB A. Peaks of 90-96 dB A were registered during different working operations ("dialing", "speaking", "fax", "occupied") with duration less than 5s and stochastic appearance during the 15 min measuring periods. A total of 260 female telephone operators (mean age 36.7 +/- 8.22 years and mean length of employment 12.7 +/- 7.12 years) with similar job activities at the three departments were investigated. No marked decreased hearing sensitivity for 0.5, 1, 2, 4, 6 and 8 kHz was observed. A high percentage of the examinees gave positive answers in different questionnaires regarding subjective symptoms (psychological, neurovegetative, neurological), mental health, depression and anxiety. An elevated urine excretion of catecholamines (11-OCS, adrenalin and noradrenalin) was found during the morning and afternoon working shifts. The intensity of the noise and its annoying effect were subjectively estimated as "high" and "very high" by most of the examined telephone operators. In a large percentage of operators in the Intercity Department, the changes of the audiometric, psychological and biochemical examinations were more pronounced. The obtained results indicate that redesign of the work place should be undertaken in order to prevent health effects on the telephone operators.

[The potentials for errors in the hygienic assessment of the general vibrations in tractors]. / Vuzmozhnosti za greshki pri khigiennata otsenka na obshtite vibratsii pri traktori.

The data for the parameters of the general vibrations in tractors are comparatively scanty and contradictory. In the present work are analyzed the most frequently met omissions and errors in the measurement and evaluation of the general vibrations, as well as the factors, which can effect the intensity of the general vibrations; constructive and technological peculiarities, technical state, rate of machine amortization, construction, damping qualities, and regulation of the seat, motion velocity, relief, type of the performed agricultural activity. The necessity for taking under consideration these factors in measuring the general vibrations and the hygiene interpretation of the data, as well as precise report on the daily, weekly and general exposure, in view of defining the total vibration loading, is underlined.

[New sorbents for industrial gas marks with a visual reading of their depletion]. / Novi sorbenti za promishleni protivogazi s vizualno otchitane na iztoshtavaneto im.

The current status of problems, referrable to the use of industrial gas masks, is reviewed, with special reference to the type of sorbent to be used, the pathways of gas mask modernization in respect of the sorbents used, and the modern trends in adsorption cartridge manufacturing; decrease of weight, alleviated construction, adjustment to serve definite toxico-chemical agent, use of ion-exchange resins and hemosorbents. Aspects are discussed for producing sorbents, permitting visual registration of filter mass exhaustion, i.e. sorbents wtih alternating color in the process of sorption, with the purpose of increasing gas mask security and efficiency. The physico-chemical parameters of reference hemosorbent samples with alternating color in the process of sorption were compared with those of widely used sorbents - active carbon (specially processed and crude) and ion-exchange resins: relative dynamics, aktivity protection time, weight, mass activity, etc. Inferences are drawn from which one may see, that these new hemosorbents are highly perspektive, and their industrial acceptance is justifiable.