Collection Occupational hygiene, Issue 27, 1991 year

To the methodology for regulating the content of welding aerosols in the air of the working area

L.N. Gorban

doi

Kiev Research Institute of Occupational Hygiene and Occupational Diseases

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Air pollution in the working area during electric welding and thermal cutting of metals by harmful substances released in the composition of welding aerosols (SA) is one of the important hygienic problems. The role of SA as the main etiological factor in the development of pneumoconiosis, chronic diffuse bronchitis, intoxication with manganese, copper, zinc, chromium and other metals, as well as the so-called welding gases (CO, 03, HP, N02) in welders is well known [3, 6, 13 ]. the impact of CA on workers promotes the growth of nonspecific respiratory diseases, diseases of the cardiovascular and nervous systems among them. CA containing St + 6 and N1 + have carcinogenic properties [14, 16, 17].

One of the main hygienic measures in the primary prevention of diseases in welders is the establishment of safe levels of exposure to CA on the body. However, the solution of this issue is fraught with significant methodological difficulties. They are due to the fact that CAs are multicomponent gas-aerosol (dust-gas) mixtures of harmful substances and are often very complicated even for sanitary-chemical analysis. Depending on the composition of the electrode materials used, shielding gases, welded, deposited or cut metals, modes of welding, surfacing and cutting in the solid component CA (TCCA), metal oxides and their complex complex compounds may be present in different percentages.

The accumulated domestic and foreign experience in studying the biological action of CA of various compositions and the available theoretical developments of the problem of the combined effect of gas-aerosol mixtures on the body allowed us to formulate the following basic requirements for the hygienic regulation of the content of CA in the air of the working area.

  1. CAs subject to hygienic regulation should be grouped into large classes according to the principle of compliance with the criteria of gas-aerosol (vapor-gas-aerosol) mixtures of relatively constant composition. For such CA, based on the assessment of the combined action of the most typical and frequently occurring combinations of chemical compounds, “group” MPCs should be established, expressed in terms of the MPC values ​​of the leading or main toxic components.
  2. The established MPCs should apply to quantitative ratios of TCCA and GSSA gases that are real for practice, since their concentrations in the breathing zone of welders are, as a rule, proportional to the rate of formation in an arc or other heat source (plasma, gas flame, etc.).
  3. A prerequisite for establishing MPC. for SA, there should be long-term (within 4 months) experiments on animals with the determination of the threshold concentration of their harmful effects - 21mcb.

In contrast to the generally accepted approaches to assessing the combined effect of harmful substances, the requirements set forth do not provide for a mandatory preliminary study and, moreover, for the regulation of each component of the gas-aerosol mixture taken separately. In fact, there is no particular need for this, since the biological effect of individual SA ingredients, in particular metals and gases, has been studied in isolation from their intake into the body. Moreover, it is hardly possible to question the fact that the danger of simultaneous exposure to several chemical substances included in gas-aerosol mixtures of relatively constant composition, from a hygienic point of view, it is generally preferable to assess it in combination, and not separately [5, 9]. One of the methodological features of the proposed approach is the need for a certain standardization of the concentration and time parameters of the effect of SA on animals. As a mandatory "working" concentration of CA for their toxicological and hygienic assessment and regulation, it is proposed to use the TCCA concentration equal to 10 mg / m3. On the one hand, this is dictated by the fact that this concentration is the maximum possible value of the maximum one-time MPC for any dust and aerosols, regardless of their nature and predominant type of action on the body. On the other hand, obtaining such information is especially important for a comparative assessment of the biological activity of CA of various composition, even in cases where the justification of the hygienic regulations is not required.

The outlined approaches have been widely tested when setting up experimental studies to substantiate the maximum permissible concentration of CA formed during welding of low- and high-alloy steels and containing various amounts of manganese and fluorides, manganese and iron, manganese, chromium and nickel [8, 14]. Their important result was the establishment of the predominantly additive nature of the effect of the toxic ingredients TCCA and GSSA. This can be explained by the fact that inhalation of several harmful substances simultaneously, even at concentrations equal to or lower than their MPC, leads to an increase (in total) of the load on the natural mechanisms of self-purification of the lungs - the target organ for any aerosols and gases.

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