2019 年 1 巻 2 号 p. 39-45
Objectives: The aim of this study was to clarify the current status of respiratory protection and associated problems among workers engaged in dust-generating work, including the type of respiratory protective equipment (RPE) used, methods for wearing RPE, and awareness of respiratory protection. Methods: We surveyed 212 male workers involved in dust-generating work from 10 plants on the current status and problems associated with respiratory protection. The survey inquired about work environment, type of RPE used, methods for wearing RPE, and knowledge of respiratory protection. Questions about methods for wearing RPE inquired about the position of the headband and placement of something like fabric between the face-piece cushion and face when wearing RPE. Analyses were performed using simple tabulation of each question item. Results: A total of 53.3% of RPE used by participants were replaceable filter dust masks and 19.3% were disposable dust masks. Of the workers who regularly used replaceable filter RPE, 50.0% wore the headband around the helmet. Meanwhile, 27.4% placed a knit cover between the face-piece cushion and their faces, and 11.0% used a towel instead of a knit cover. A total of 69.5% of workers who placed fabric between the face-piece cushion and their face perceived that “there was no problem with respiratory protection”. Conclusion: We found that workers engaged in dust-generating work used a variety of methods for wearing RPE. Workers should be provided with appropriate education on respiratory protection and instruction on appropriate methods for wearing RPE in the workplace.
Appropriate measures should be taken to improve the work environment, practices, and conditions of workplaces in which workers may be exposed to hazardous dust substances. If this is not possible, workers should wear appropriate respiratory protective equipment (RPE), which is used to prevent a variety of occupational respiratory diseases caused by exposure to hazardous dust substances in the workplace. In Japan, RPE use is mandatory as specified in the Ordinance on Industrial Safety and Health1).
Studies have reported the occurrence of occupational respiratory diseases resulting from inappropriate use and management of respiratory protection. Cases of acute and chronic respiratory diseases have been attributed to inadequate or lack of RPE use2,3,4). Inappropriate use and management of RPE may result in not only acute intoxication but also respiratory diseases, such as pneumoconiosis and lung cancer, that develop over many years. Pneumoconiosis, in particular, is one of the most important respiratory diseases, and preventive measures have been implemented in accordance with several laws in Japan5,6,7). While the number of individuals being diagnosed with pneumoconiosis and its complications is decreasing, approximately 200 new cases per year of pneumoconiosis have been diagnosed recently8). Therefore, the improvement of dust exposure prevention measures is necessary. In 2018, the Ministry of Health, Labour and Welfare (MHLW) published the 9th Comprehensive Measures to Prevent Hazards Due to Dust, which made thorough and proper use of RPE one of the priority measures in dust exposure prevention in the workplace9).
The Ordinance on Industrial Safety and Health indicates that workers should be educated on the handling of personal protective equipment (PPE) in the event that they may be exposed to harmful substances4). The notification on the selection and use of dust masks by the MHLW details the appropriate and inappropriate methods for wearing dust masks and the use of fit checkers10). Inappropriate wearing of RPE may result in reduced respiratory protection because of the reduced contact between the RPE and the face. While workplace patrol by industrial health staff and health officers has identified occasional cases of improper wearing of RPE, few reports have surveyed the current status of respiratory protection in workplaces.
Here, we surveyed the types of RPE used by workers engaged in dust-generating work, the methods for wearing RPE, and awareness regarding respiratory protection. The aim of this study was to examine the present status of respiratory protection and the associated problems for workers engaged in dust-generating work and to determine the necessary measures related to RPE to prevent respiratory diseases due to dust.
This was a cross-sectional study on respiratory protection using a questionnaire conducted in 10 plants of nine participating manufacturing companies in Japan. In addition, an on-site investigation was conducted sequentially after the questionnaire to improve the reliability of the questionnaire data. Using the categories provided by the Japan standard industrial classification11), the participating companies were categorized into the following industries: manufacture of iron and steel (n=2); manufacture of petroleum and coal products (n=1); manufacture of chemical and allied products (n=1); manufacture of ceramic, stone, and clay products (n=1); and manufacture of fabricated metal products (n=4). Regarding the number of workers, one factory had more than 1,000 workers, four had between 50 to 500, and five had less than 50. The study period ranged from July until December 2018.
Participants and proceduresWe distributed the original questionnaire regarding respiratory protection to 284 male workers at the participating companies who used RPE daily. We obtained informed consent for participation in the study from 212 participants (response rate, 74.6%), and data from all these participants were included in the analysis. We subsequently conducted an on-site investigation based on the responses.
QuestionnaireThe questionnaire included questions about participants’ basic work-related duties, the types of RPE used, the method for wearing RPE, and participants’ awareness regarding respiratory protection (Supplementary Figure 1). The questionnaire was developed by gathering opinions from eight occupational physicians.
Questionnaire items on basic work-related characteristicsParticipants were asked about their company and division name, nature of dust-generating work according to the Japan standard occupational classification12), the period of engagement in dust-generating work, and the number of working days per week and working hours per day spent in dust-generating workplaces at the time of this study. In addition, participants were asked whether or not they had received training on methods for wearing RPE and assessment of the RPE leakage rate.
Questionnaire items on the type and method for wearing RPEParticipants were asked about the type, manufacturer, and model numbers of RPE that they used regularly (referred to as regular-use RPE). The options provided for the type of RPE were: disposable dust mask, replaceable filter dust mask, gas mask with dust-preventing function (replaceable filter mask), gas mask (replaceable filter mask) without dust-preventing function, powered air-purifying respirator (PAPR), supplied-air respirator, and other.
For workplaces in which both dust and harmful gas are generated, the notification by the MHLW10,13) suggests first choosing a gas mask with dust protection, although it also suggests selecting a gas mask as an alternative option. Therefore, we included a “gas mask without dust-preventing function” as an option. Questions on the methods for wearing RPE enquired about the position of the headband and placement of something like fabric between the face-piece cushion and face when wearing the RPE. The position of the headband included four options that were depicted in the images: on the area from the parietal region to the occipital region (parietal-occipital region) (most appropriate method), on the area from the occipital region to the posterior neck (occipital-posterior neck region), on the helmet, and other positions. Participants who selected the last option were requested to indicate the position of the headband on the image on the answer sheet. The options for the placement of something between the face-piece cushion and face when wearing RPE were: none (most appropriate method), knit covers (Supplementary Figure 2), towels, and other.
Awareness of respiratory protectionParticipants were asked several questions about their awareness of respiratory protection, including whether or not they were following workplace guidelines regarding methods for wearing RPE, and what they thought about their own method of wearing RPE in terms of respiratory protection. The response options were: it is correct, it is incorrect, and no idea. Participants who chose the second response were requested to provide a reason.
On-site investigationAn on-site investigation was conducted to obtain detailed information on wearing RPE that was difficult to investigate using the questionnaire. Of the 10 plants, 8 agreed to the on-site investigation. This survey was started on July 2018 and was conducted sequentially after the questionnaire was completed in each plant. The investigators spent approximately half a day per factory observing the environment in which the participants actually worked when wearing RPE and checking the use of RPE. We also interviewed some participants to confirm the actual use of RPE.
AnalysisSimple tabulation was performed for each question item. Some types of RPE, such as full-face masks and disposable masks, did not allow for variations in how they could be worn because their structures were fixed. Therefore, relevant question items were analyzed only among participants who regularly used replaceable filter half-masks (replaceable filter dust masks, gas masks, and gas mask with dust-preventing function). For assessment of the awareness of respiratory protection, only participants who regularly used replaceable filter masks were analyzed for the same reason. Participants were cross-tabulated for their awareness of RPE protection and the method by which they wore the RPE.
Ethics approvalThis study was approved by the Ethics Committee of Medical Research, University of Occupational and Environmental Health, Japan. We explained the benefits and disadvantages of participating in this study to the participants to ensure that they made an informed decision.
Of the 212 participants, 70 (33.0%) worked in the manufacture of iron and steel, 55 (25.9%) in the manufacture of metal products, and 40 (18.9%) in the manufacture of chemical and allied products. Regarding the type of occupation, 79 participants (37.3%) were manufacturing facility control and monitoring workers (metal products), 55 (25.9%) were product manufacturing and processing workers (metal products), and 41 (19.3%) were manufacturing facility control and monitoring workers (except metal products).
Participants had spent an average of 14.3 years conducting dust-generating work, and 55.7% of participants had conducted such work for more than 10 years. Participants spent an average of 4.9 days per week performing dust-generating work in the current week, and 81.1% of participants worked more than 5 days per week (Table 1). They spent an average of 5.0 hours per day conducting dust-generating work.
| Items | ||
|---|---|---|
| Type of Industry | n | (%) |
| Manufacture of iron and steel | 70 | (33.0%) |
| Manufacture of fabricated metal products | 55 | (25.9%) |
| Manufacture of chemical and allied products | 40 | (18.9%) |
| Manufacture of petroleum and coal products | 38 | (17.9%) |
| Manufacture of ceramic, stone, and clay products | 9 | (4.2%) |
| Type of occupation | ||
| Manufacturing facility control and monitoring workers (metal products) | 79 | (37.3%) |
| Product manufacturing and processing workers (metal products) | 55 | (25.9%) |
| Manufacturing facility control and monitoring workers (except metal products) | 41 | (19.3%) |
| Product manufacturing and processing workers (except metal products) | 37 | (17.5%) |
| Years of dust generating work | ||
| Less than 1 | 7 | (3.3%) |
| 1–4 | 41 | (19.3%) |
| 5–9 | 44 | (20.8%) |
| 10–19 | 59 | (27.8%) |
| Over 20 | 59 | (27.8%) |
| No response | 2 | (0.9%) |
| Days of dust generating work per week | ||
| Less than 3 | 13 | (6.1%) |
| 3–4 | 24 | (11.3%) |
| 5 | 172 | (81.1%) |
| No response | 3 | (1.4%) |
Concerning education, 158 participants (74.5%) had been previously educated about respiratory protection, and 56 participants (26.4%) had previously tested the leakage rates of RPE in the workplace.
Type and method for wearing RPE by the participantsAs regular-use masks, 113 participants (53.3%) used replaceable filter dust masks, 41 (19.3%) used disposable dust masks, 30 (14.2%) used replaceable filter gas masks, and 21 (9.9%) used replaceable filter gas masks with dust protection. None of the participants used PAPR as a regular-use mask (Table 2). In the on-site investigation, we confirmed that both replaceable filter gas masks without dust protection and replaceable filter gas masks with dust protection were used in workplaces in which dust and large amounts of harmful organic gas were generated. Additionally, we noted that a few participants used PAPR when handling large amounts of heavy metal dust.
| Type of respiratory protective equipment | n | (%) |
|---|---|---|
| Replaceable filter dust mask | 113 | (53.3%) |
| Disposable dust mask | 41 | (19.3%) |
| Replaceable filter gas mask | 30 | (14.2%) |
| Replaceable filter gas mask with dust protection | 21 | (9.9%) |
| Powered air purifying respirator (PAPR) | 0 | (0.0%) |
| Supplied-air respirator | 0 | (0.0%) |
| Other respiratory protective equipment | 0 | (0.0%) |
| No response | 7 | (3.3%) |
To examine methods for wearing RPE, we analyzed the position of the RPE headband. Given that the most appropriate position of the headband depends on the type of RPE being used, we only analyzed participants who regularly used replaceable filter half-masks (n=164). Seventy participants (42.7%) wore the headband on the parietal-occipital region, 82 (50.0%) wore it on the helmet, 8 (4.9%) wore it on the occipital-posterior neck region, and 1 (0.6%) wore it on a cloth wrapped around the head. In the on-site investigation, we observed some participants who wore the RPE on their welding hood.
We also examined whether participants placed something like fabric between the face-piece cushion and face. Given that some types of RPE may not allow placement of a piece of fabric between the face-piece cushion and face, we only evaluated participants (n=164) who regularly used replaceable filter masks. One hundred participants (61.0%) responded that they did not place anything between the face-piece cushion and face, while 64 (39.0%) responded that they did. As for the type of fabric, 45 (27.4%) used a knit cover, 20 (11.0%) used towels, and 1 (0.6%) used a non-woven mask (a replaceable mask layered over a non-woven mask) (Table 3). All participants who used towels were working in the manufacture of iron and steel. During the on-site investigation, we identified the reasons for wearing knit covers and towels. Some participants who used knit covers reported doing so to prevent the development of a rash due to the use of a replaceable filter RPE. However, many stated that they used the knit cover to relieve the discomfort associated with wearing the mask. Reasons for the use of towels included protecting the face from heat radiation and hot materials, with many participants using flame-retardant towels.
| n | (%) | |
|---|---|---|
| Position of the headband | ||
| On the parietal-occipital region (most appropriate methoda) | 70 | (42.7%) |
| On the helmet | 82 | (50.0%) |
| On the occipital-posterior neck region | 8 | (4.9%) |
| On the cloth wrapped around the head | 1 | (0.6%) |
| No response | 3 | (1.8%) |
| The fabric placed between face-piece cushion and face | ||
| None (most appropriate methoda) | 100 | (61.0%) |
| Knit cover | 45 | (27.4%) |
| Towel | 18 | (11.0%) |
| Nonwoven mask | 1 | (0.6%) |
Of the 212 participants, 172 (81.1%) responded that they followed workplace protocols regarding methods for wearing RPE, 36 (17.0%) responded that they used their own methods for wearing RPE, 3 (1.4%) did not provide a response, and 1 (0.5%) provided an invalid response because it was an incorrect response method. Of the 212 participants, 156 (73.6%) believed that their method for wearing RPE was correct (in terms of respiratory protection), 18 (8.5%) indicated that their method was incorrect, 33 (15.6%) replied “I don’t know,” and 5 (2.6%) did not provide a response.
A total of 164 participants who regularly used replaceable filter masks were also analyzed. Of these, 114 participants (69.5%) believed that their method of wearing RPE was correct, 17 (10.4%) indicated that their method was incorrect, 29 (17.7%) replied “I don’t know”, and 4 (2.4%) did not provide a response. Of the 114 participants who thought their method for wearing RPE was correct, 29 (25.4%) wore the headband on the parietal-occipital region and did not place anything between the face-piece cushion and face, which is indicated by the MHLW and PPE manufacturers in Japan as the appropriate method. In contrast, 56 participants (49.1%) wore the headband on the helmet and 27 (23.7%) used a knit cover. Of the 17 participants who believed that their method for wearing RPE was incorrect, 2 (11.8%) actually wore it correctly, 10 (58.8%) wore the headband on the helmet, and 7 (41.2%) placed a towel between the face-piece cushion and their face (Table 4). The following were the reasons why the participants were using the incorrect method while wearing RPE despite recognizing that their method is incorrect: “to relieve discomfort” in 9 (52.9%), “to relieve shortness of breath” in 3 (17.6%), and “difficulty detaching the RPE” in 1 (5.9%) participant.
| Position of the headband of RPE | Fabric placed between the face-piece cushion and face | How do you think about your own method of wearing RPE in terms of respiratory protection? | |||||
|---|---|---|---|---|---|---|---|
| It is correct. (n=114) | It is incorrect. (n=17) | I don’t know. (n=29) | |||||
| n | (%) | n | (%) | n | (%) | ||
| On the parietal-occipital region (most appropriate methoda) | None (most appropriate methoda) | 29 | (25.4%) | 2 | (11.8%) | 6 | (20.7%) |
| Knit cover | 15 | (13.2%) | 3 | (17.6%) | 7 | (24.1%) | |
| Towel | 6 | (5.3%) | 2 | (11.8%) | 0 | (0.0%) | |
| On the occipital-posterior neck region | None (most appropriate methoda) | 2 | (1.8%) | 0 | (0.0%) | 2 | (6.9%) |
| Knit cover | 3 | (2.6%) | 0 | (0.0%) | 0 | (0.0%) | |
| On the helmet | None (most appropriate methoda) | 43 | (37.7%) | 2 | (11.8%) | 7 | (24.1%) |
| Knit cover | 9 | (7.9%) | 3 | (17.6%) | 4 | (13.8%) | |
| Towel | 4 | (3.5%) | 5 | (29.4%) | 1 | (3.4%) | |
| Other | 0 | (0.0%) | 0 | (0.0%) | 1 | (3.4%) | |
| On the cloth wrapped around head | None (most appropriate methoda) | 0 | (0.0%) | 0 | (0.0%) | 1 | (3.4%) |
| No response | None | 3 | (2.6%) | 0 | (0.0%) | 0 | (0.0%) |
In this study, more than half of the participants had engaged in dust-generating work for more than 10 years. The average number of days spent conducting dust-generating work was 4.9 per week. This suggests that most participants were frequently exposed to dust. Approximately 75% of participants had previously been educated about respiratory protection, and approximately 25% had tested the leakage rate of RPE. Pneumoconiosis and its complications are known to be caused by very long-term exposure to dust14). To help prevent pneumoconiosis, it is necessary to improve current measures, including providing regular education on respiratory protection and protective equipment.
The most frequently used RPE was the replaceable filter dust mask, followed by the disposable dust mask. No participants regularly used the PAPR, and some workplaces used PAPR only during specific operations, such as when handling large amounts of heavy metal dust. Japanese laws and regulations state that PAPR must be worn during certain work, including tunnel construction, asbestos removal, and handling of indium compound15,16,17). In this study, no participants were engaged in these types of work, so they had no legal obligation to use PAPR. Given that PAPR is generally more effective than other dust masks for preventing respiratory impairment, it is desirable for workers to wear PAPR not only when conducting work that mandates its use but also when conducting other dust-generating work in which workers are frequently exposed to high dust concentrations10). However, PAPR is associated with a higher cost than other dust masks, which may be one reason why it is not more commonly used. We propose that appropriate PAPR use is important for respiratory protection in the future.
We surveyed participants using replaceable filter RPE about their preferred wearing method, including the position of the headband and placement of something like fabric between the face-piece cushion and face. We found that 50% of participants wore the headband on the helmet, which is a higher rate than that of those wearing it on the parietal-occipital region. One reason for a large number of participants wearing the headband on the helmet may be a difficulty with removal. Recently, most replaceable half-masks have now been made such that they are easy to temporarily remove when the headband is worn under a helmet. However, due to differences in methods for removal among replaceable half-masks, it is important for workers to choose a suitable type of RPE and to be provided with appropriate instruction on the correct method for use at worksites.
A total of 39% of participants indicated that they placed something between the face-piece cushion and face. A knit cover was the most commonly used, followed by towels. Face-pieces with knit covers are permitted only when there is a high risk of dermopathy and when the cover conforms to RPE fitting requirements. We found that knit covers were used to reduce discomfort, such as pressure on the face. Towels were also used for this reason, and as protection from radiant heat from furnaces. To ensure that workers receive appropriate respiratory and heat protection, it is necessary to identify measures to protect the body from heat while maintaining adequate respiratory protection, rather than prohibiting the use of towels completely.
Of the participants who reported that they were using the correct method for wearing RPE, approximately 25% were, in fact, wearing the RPE using the appropriate method indicated by the MHLW and PPE manufacturers. Additionally, 75% of all participants received education regarding respiratory protection and 80% were wearing RPE according to their workplace protocol. In this study, we investigated the implementation of education, but did not examine the contents of the education or its comprehension among recipients. Therefore, the education provided may not have been sufficient for participants to fully understand the appropriate methods for wearing RPE. The Occupational Safety and Health Administration in the United States indicates that a fit test must be conducted before workers use RPE in the workplace, and that a retest must be performed at least every 12 months to ensure that the RPE fit is still appropriate18). The Health and Safety Executive in the United Kingdom also provides criteria for fit testing for RPE use19). In Japan, while the Occupational Safety and Health Regulations indicate that employers must educate workers and new employees or when there are changes to employees’ work duties, it does not require fit testing of RPE, including measurement of the leakage rate. There may, in reality, be little opportunity for workers to confirm the fitting of their method of wearing RPE. It may be important and effective to conduct quantitative mask fit tests that include leakage rate measurements using a mask fitting tester20), or qualitative mask fit tests, including evaluation using saccharin aerosol21) at worksites, as doing so will raise workers’ awareness of the proper methods for wearing RPE and respiratory protection. In addition, in accordance with the guidelines for “selection, use, etc. of dust masks” issued by the MHLW Labor Standards Bureau of Japan10), employers should appoint a person to manage the use of RPE in the workplace. This person is responsible for selecting appropriate RPE and for providing instructions about the most appropriate method for wearing the RPE according to the work environment and relevant guidelines9).
When proper use is difficult due to personal factors, such as health conditions, several measures can be taken. For example, the worker can be relocated to a non-dust-generating worksite or to worksites where the personal dust exposure level is sufficiently low when the worker is wearing a disposable mask or an RPE-attached knit cover, or wearing a face-shield type PAPR. In any case, employers should consult an occupational physician or respiratory protection specialist regarding methods for improving the work environment, work condition and practice, and health management.
Limitations and future directionThis study has several limitations. First, all workplaces that participated in the questionnaire were classified into appropriate manufacturing industries according to the Japan standard industrial classification12); therefore, there could have been sampling bias. In addition to the manufacturing industry, other industries, such as mining, quarrying, gravel picking, and construction, also use RPE. Given that there are likely differences in the use and methods for wearing RPE among industries, it may not be possible to generalize the results to all industries or workplaces. Second, because the self-administered questionnaire is slightly complication, it is possible that participants did not completely understand the meaning of the questions. Third, while this study revealed that RPE was worn in a variety of ways in the field, it was not clear to what extent these methods impaired protection. We plan to measure and evaluate the leakage rate for the various methods for wearing RPE identified in this study.
Workers who engaged in dust-generating work used a variety of methods for wearing RPE, some of which may be reducing the effectiveness of the RPE. Our results suggest that work-related environmental factors and insufficient education regarding methods for wearing RPE may be leading to insufficient respiratory protection. Therefore, appropriate education, including background on respiratory protection and appropriate methods for wearing RPE, and fit tests should be conducted in the workplace to improve respiratory protection for workers.
We thank Soft Wave Pro Co., Ltd. for helping with data aggregation work and DMC Corp. for proofreading the manuscript. We would like to thank all participating companies, participants, and staff members.
This study was funded by a Health Labour Sciences Research Grant.
The authors have no conflicts of interest to be disclosed regarding this study.
This article contains supplementary material (Appendix), which is available in the online version (doi: 10.1539/eohp.2019-0005-FS).
