Translation:On individual means for respiratory organs protection against dust

Abstract: The article covers efficiency of individual protective means for respiratory organs in high dust content of workplace air, define ways to increase the efficiency.

Key words: individual protective means for respiratory organs, protective efficiency of respirator, high dust content of air

A pneumoconiosis and other respiratory diseases, associated with exposure to industrial dust, are in the second place in the structure of occupational diseases in the RF for many years. It is important to emphasize that in the conditions of the possible impact of harmful factors on workers use personal respiratory protection (RPE), the use of which in such circumstances dictated by a number of sanitary and legislative documents. In reality, the employer is obliged to fulfill their requirements. However, despite the use of respiratory protective equipment at the workplace with a high dust content, the diagnosis of "pneumoconiosis" and "occupational bronchitis" - are not uncommon. What is the reason?

First of all, it should be noted that the protective properties (protection factor) of the filtering respirators depends on the efficiency of dust collecting filtering material (this efficiency depending on particle size, the properties of the filter and the air velocity through the filter), and the degree of insulation space under the mask from environmental dusty atmosphere. It, in turn, depends on the size and number of gaps in the places where the mask is not sufficiently tight to the skin.

Currently, the industry produces a range of high-efficiency filter media with low breathing resistance [13]. Solve the second problem - to provide a snug fit of the respirator facepiece to the surface of the face - was more difficult.

To determine the degree of effectiveness of the respirator in the workplace, it is necessary to compare the concentration of dust in the working area and in the space under the mask. The results of these studies conducted in the last decade, published in numerous scientific papers, the latest of which date from the period 2000 - 2010. [9],[14],[15],[18-20].

For example, in [15] presents the results of measuring the effectiveness of the protection of respirators - respirators class N95 (US standard, the filter material retains at least 95% solids of the "penetrating" size - about 0.3 microns). The measurements were performed at a metallurgical plant, where steel castings were produced (weight from a few hundred to a few thousand pounds). Workers of different specialties (drivers fork and bucket loaders, workers engaged in forming and re-use of the molding of the earth working on a shaker, and others.) During the measurements performed their normal work - raked and cleaned molding ground, up and down the ladders and stepladders, prepared molds and cores, operated fork and shovel loaders, and others. In general, the work was performed moderate severity, but when cleaning the mold of the earth have been long periods of execution of hard work.

Since the particle size of the working zone air was much higher than the "penetrating" (average diameter about 15 microns), when passing through the filter material in the dust concentration was reduced 753 times (maximum), but not 20 times. In this study, experts measured coefficients respirator protection in 49 cases of its application. It turned out that it varies from 753 to 5. This diversity results was due to the different densities of the mask fit to face - that is, there is a gap of varying size. Such gaps between the face and mask inconsistencies arise from the shape and size of the front portion of the respirator face shape and size, poor dressing and "slippage" of the respirator during use. It should be pointed out that we could not find similar publications in Russian literature.

After analyzing the experimental data, the US and EU experts have concluded that to reduce the leakage of unfiltered air through gaps under the mask - will not be enough to ensure good performance only of respirators as individual devices, but they need to be the right choice for certain conditions of work, the correct selection mask (for each worker - individually), and ensure proper donning and timely application of RPE by the workers. That is, to save the health of workers in the US give them not only masks but also perform a complete respiratory protection program (including training, training and periodic inspections), and in RF just give workers respirators. Selecting and issue a respirator - is only part of a respiratory protection program.

After several decades of work on the problem - separating space under the respirator mask from the surrounding contaminated atmosphere - foreign experts have developed a number of activities that enhance the effectiveness of filtering respirators.

To do this, experts in the US have developed standards of 2 types:

- On respirators - as individual device [11,12];

- Of their choic, the issuance and use - in the workplace conditions [8],[10],21].

There are standards of type 1 in the RF [1-6], but they are different from those of the US standards. The difference is that US standards require perform PPE certification tests with the use of specially selected participants, that the shape and size of the person’s faces conform to the shape and size of faces of most people working in different industries. To do this, a survey was conducted (about 4 thousand workers). A standards for the certification of RPE in RF require testers to pick up such that they face (shape and size) match the mask respirator on its shape and size.

With regard to the standards of the second type, there is not in RF. But the first standard of this type, involving instrumental measurement of the insulation properties of the masks (fit test), was passed in the US in 1980 [11].

To reduce gaps arising from mismatching shape and size of the mask shape and size of the face, the following steps [21]:

- The employer does not give the worker a respirator, allows the operator to select the most appropriate respirator from several proposed; - After selecting a mask, a specialist conducts instrumental checking the quantity of unfiltered air, penetrating through the gaps under the mask, and - In case of insufficient degree of isolation from the surrounding respiratory (contaminated) environment that reveals the said tool inspection, the worker is not allowed to perform work in dusty conditions - as long as it will not get picked up another, more suitable mask.

To reduce the gaps that arise due to incorrect donning respirator facepiece, which corresponds exactly to the shape and size of the working person, the following measures:

- Held periodic validation donning masks with instruments - as the initial choice of the respirator;

- Workers are trained for proper donning and the proper use of respirators by using modern equipment and teaching materials; современного оборудования и учебных материалов;

- Developed, tested and widely used "user" check (fit check) to ensure proper donning the respirator. This check should be carried out at each respirator donning. It takes a few seconds, requires no equipment and reveals the most large mistakes made when donning. To conduct this test, the employee closes air inlets in respirator filters by his hands (or exhalation valve hole in the respirator mask), inhales air (or exhales air), and holds his breath for a few seconds. If vacuum (or positive pressure) is maintained, there was no gross errors when donning the mask. Back in 1983, [16] tests showed that of the 195 cases of donning a respirator mask (when an employee to successfully pass this simple test), there was only one case in which the mask respirator was not donned quite right.

It is important to note that in RF there are no regulations that oblige the employer to train workers to pick up and check the degree of isolation (which provides a selected mask), to perform validation of the respirator donning; and design of half-mask respirators (F-62SH and RPG-67) does not allow "user" test (fit test).

To prevent leakage of dust through the gaps that occurs when the mask is "slipping" during operation (when the mask was originally properly selected and donned correctly), uses the following measure: - the range of permissible use of respirators is limited not only by the properties of the filter material, but also the design of the mask. In 1987, [17] researchers Donald Campbell and Steven Lenhart conducted a statistical analysis of measurements of protective properties of respirators in the workplace, and proposed to limit the use of a respirator mask with a certain type so that 95% of all cases of their application (with the right choice? donning and wearing) the degree of protection in the workplace was higher than the dust content (in the PEL). For example, if one use data from the example above [15], one find that for dust concentration 753 PEL sufficient degree of protection will be only in 1 of 49 cases (about 2%). And 5 for dust concentration 5 PEL - in all 49 cases (100%). But "the lower limit" of protection factor in the workplace - do not exist [19]. Currently, such an approach to solving the problem of respiratory protection adopted by a majority of foreign experts. In the US, the scope of using of the filtering respirators with high-efficiency filters is limited as follows:

- Full-facepiece masks - up to 50 PELs

- Half-mask respirators - up to 10 PELs.

It is important to note that in RF there is no normative document, which would clearly and unambiguously define the boundaries of permissible use (in the PEL) respirators with different designs of masks and with different filters. And it is incorrect to use "foreign restrictions" - 10 and 50 PEL. These restrictions do not apply to all respirators, but only to those who were selected individually, followed by the instrumental checking of the insulating properties of the selected masks (that is donned and worn properly). One can not use these restrictions in RF due to the lack of proper masks selection and validation, and lack of education and training of workers. The protective properties of the same respirator (even import good quality) will be much lower for this reason.

These limitations of scope when performing foreign standards on the use of respiratory protective equipment, and this limitations are very different (smaller) from the requirements to the protective properties of the same respirators during their certification tests in the US and the EU. For example, the protective properties of a full-face mask with P3 filters when certification is not less than 1000, and the scope is limited to 40(50) PEL. Therefore, to limit the scope of respirators on the basis of existing in the RF state standards GOST (that is related to their certification only) is wrong.

In cases where the dust concentration exceeds 10 PEL, the employer must provide workers with respirators with facial part – full facepiece mask. If the dust concentration is over 40(50) PEL, workers should use respirators with forced air supply under the mask. This ensures high (up to 1000 PEL) level of protection due to the almost complete elimination of leakage of unfiltered air under the mask through the gaps. When these respirators were tested in the workplace, then harmful substances under the mask usually cannot be found (using existing analytical methods). For example, in [15] the coefficient of protection in the workplace - more than 11,000. Therefore, in the U.S., more than every tenth used a respirator with forced air supply

Respirators with a forced air supply (manufactured in the RF), cannot be certified for compliance with the recently adopted standards [5,6] due to the lower (with respect to the requirements of the standard) air supply. Imported respirators with forced air supply is more expensive then negative pressure respirators (more than 8 times). Consequently, due to the lack of reliable information about the protective properties of conventional (negative pressure) respirators and the lack of a formal regulatory documents, delimiting the scope of the respirator (for example in the USA: up to 1000 PEL and up to 50 PEL), respirators with forced air supply will not find wide application as required to prevent occupational diseases. And upon the issuance of such respirators with tight fitting mask fit test required.

With increased individual sensitivity of a worker, the individual features of his face (preventing to ensure a tight fit of the mask), or at the request of the employee, the employer is obliged to provide the worker respirator that provides a higher degree of protection than is dictated by the concentration of dust (instead of half-mask respirator - full facepiece mask, and instead of a full facepiece mask – respiratorwith forced air supply).

In this regard, it is necessary to harmonize the regulatory acts of the RF in the field of certification and in the use of respirators with similar instruments in developed countries (preferably in the US). This will contribute significantly to the change in the structure and the amount of newly diagnosed occupational respiratory diseases. In addition, it is necessary to stop the production of masks, developed more then half a century ago, replacing them with new ones (which would correspond to modern requirements); to start the production of equipment for testing the insulating properties of masks (fit test), and to provide enterprises educational literature [7], posters, videos and other educational materials for the selection and use of respirators.

The respiratory protection with RPD in the Russian Federation must conform to modern Western level in this area.

References
 * 1) ГОСТ 12.4.189 - 2001 Маски. Общие технические требования.
 * 2) ГОСТ 12.4.190 - 2001 Полумаски и четвертьмаски из изолирующих материалов.
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