Silicosis is a debilitating lung disease caused by inhalation of crystalline silica. An estimated 2 million U.S. workers are at risk for silicosis (1); approximately 100,000 of these work as sandblasters. On April 21, 1995, CDC's National Institute for Occupational Safety and Health (NIOSH) received a technical assistance request from the Ohio Department of Health (ODH) to conduct medical screening of Cleveland area workers involved in or around abrasive blasting activities. The request was based on the identification of high exposures to crystalline silica and deficiencies in the respiratory protection program at a worksite where an employee who worked as an abrasive blaster had died with accelerated silicosis in 1992 (2). This report summarizes the results of the survey conducted in response to this request, which identified eight workers with radiographic evidence of pneumoconiosis and indicated that inappropriate selection and use of respirators during abrasive blasting operations were common.

The objectives of the survey were to identify workers with silicosis and to assess the workers' knowledge about proper use of respiratory protection and appropriate industrial hygiene practices for the prevention of exposures to silica. Participants were recruited from the membership rosters of a trade union, through the Cleveland office of the ODH, and through media advertisements. Screening was performed by NIOSH investigators during August 7-11 and August 21-25, 1995, in the metropolitan Cleveland area.

Screening consisted of a work history, a medical questionnaire, and a chest radiograph. Occupational questions focused on the intensity and characteristics of exposures to silica. Evaluation of workers' knowledge and the adequacy of respiratory protection programs was based on the NIOSH Respirator Decision Logic (3) and the Occupational Safety and Health Administration (OSHA) regulations *. Radiographs were sent for independent readings by two NIOSH-certified B readers (physicians trained and certified in the classification of chest radiographs for pneumoconioses) who, without knowledge of the participant's age, occupation, or smoking history, classified the films according to the international classification system for pneumoconiosis (4). A case of silicosis was defined as a chest radiograph with an International Labor Organization (ILO) classification of greater than or equal to 1/0 (4) in a worker with a history of exposure to silica dust. No exposure assessments or worksite visits were performed.

Of 170 participants, 122 (72%) were employed, and 48 (28%) were unemployed (including retired or disabled persons). Most were male (166 {98%}), white (160 {94%}), and non-Hispanic (166 {98%}). The median age was 48 years (range: 24-78 years). The prevalence of current smoking was 37%; 42% were former smokers.

Three fourths of participants described their usual job title as painter (62%) or drywall finisher (13%). Eighty (47%) reported ever having performed blasting; the median number of years these workers had performed blasting duties was 11 (range: 1-45 years). Ninety-six (56%) participants had ever worked as a blaster's helper ** (median tenure: 8 years), and 63 (37%) reported performing both blasting and blaster's helper duties.

Among the 122 employed workers, 47 (39%) had duties directly related to blasting -- 11 (9%) were exclusively blasters, 13 (11%) were helpers, and 23 (19%) performed both activities. Of these 47, a total of 43 (92%) reported that their employers did not require them to use respirators at their current jobs. However, only one employee reported that his employer did not provide respirators, and 43 (92%) workers reported using a respirator while performing their duties. Thirty-one (66%) reported that their current employer had informed them about the health hazards of sand or silica dust, and the same number indicated that their current employer had given them training in the use of a respirator.

Among the 34 workers directly performing blasting (i.e., blasters and those who worked both as blasters and as helpers), 11 (32%) reported using an air-supplied hood with tight-fitting face piece, but only two had been fit-tested for this respirator. A total of 27 (79%) reported using a replaceable-cartridge air-purifying respirator (10 {37%} of these had been fit-tested), and six (18%) reported using a dust mask while operating blasting equipment. In addition, 12 used a dust mask when working around blasters and 17 when cleaning up. *** Eight (24%) of the 34 had interfering facial hair. ****

Silica sand was the most commonly used abrasive (21 {62%} of the 34 workers used this abrasive most often). Other frequently used abrasive materials included steel shot and coal slag.

Of the 113 survey participants who had ever blasted or worked as helpers, eight (7%) had chest radiographs that were classified as being consistent with pneumoconiosis; all eight were classified as major profusion category one or greater (ILO classification greater than or equal to 1/0). All were men; their median age was 63 years (range: 41-71 years). Two (25%) were current smokers, and three (38%) were former smokers. Only one of these eight had known that his chest radiograph showed evidence of pneumoconiosis. All eight had performed blasting *****; half were employed, but only one was currently blasting.

Reported by: A Migliozzi, MSN, K Gromen, Ohio Dept of Health. Clinical Investigations Br, Div of Respiratory Disease Studies, National Institute for Occupational Safety and Health, CDC.

Editorial Note

Editorial Note: Silicosis is a disabling and potentially fatal lung disease that has no cure but is completely preventable by controlling exposures to respirable crystalline silica. Identification of silicosis in a worker is considered a sentinel event and should prompt an investigation of workplace exposures and work practices. NIOSH has published reporting guidelines and a surveillance case definition for silicosis (5), and seven states conduct surveillance for silicosis (6).

The findings in this report highlight continued lack of knowledge about proper selection and use of respirators and other silicosis-prevention practices among workers in occupations with exposures to crystalline silica. The only respirators suitable for use in abrasive blasting operations are type CE abrasive-blast supplied-air respirators; air-purifying and powered-air purifying respirators are not recommended for abrasive blasting operations but may be suitable for auxiliary work (e.g., outside clean-up operations). In this report, only 11 (32%) of the 34 workers directly involved in blasting activities reported using an air-supplied hood with a tight-fitting face-piece respirator, an appropriate respirator for these workplace circumstances, and most of these 11 had not been fit-tested for this respirator. As a result, even workers who had selected the type of respirator recommended for their duties may not have been using their respirators effectively (all respirators must be properly fit-tested when initially assigned to a user). Of particular concern is the reported use of simple dust masks in conjunction with blasting. Finally, approximately one fourth of survey participants who were directly involved in blasting activities had interfering facial hair and would not have had the proper face-to-respirator seal necessary for adequate protection. NIOSH recently updated information about recommendations for selection and use of respirators by workers involved in abrasive blasting (7).

Respiratory protection is considered supplementary to dust source controls at the workplace; NIOSH has recommended that silica sand or other substances containing more than 1% crystalline silica should not be used as blasting abrasives and that less hazardous materials should be substituted. In blasting activities using silica sand as the abrasive material, the concentrations of airborne dust containing respirable silica can vary considerably but are generally well above recommended safe levels. The results of chest radiograph screening and work practice questionnaires among survey participants indicate that a potential health hazard exists in these workers and that they may be at risk for developing silicosis.

The findings in this report are subject to at least three limitations. First, a large portion of the high-risk group was not evaluated (the union surveyed for this report has approximately 1500 members, and an additional 500 to 1000 nonunionized area workers are engaged in abrasive blasting). Second, survey participants may not have been representative of all workers engaged in abrasive blasting in the Cleveland area. Therefore, the observed results may underestimate the extent of the problem in the Cleveland area, and the degree to which these results may reflect conditions in other regions is uncertain. Finally, no worksite assessments or environmental samplings were performed as part of this study. Nevertheless, the survey identified unrecognized cases of pneumoconiosis, and the findings underscore a lack of knowledge about potential exposures to silica dust and good workplace practices among workers engaged in high-risk occupations such as abrasive blasting.

To better inform both employers and workers about the hazards of silica dust exposure and about good work practices for silicosis prevention, OSHA implemented the Special Emphasis Program for Silicosis Prevention within the state of Ohio. Outreach activities began in June 1996, followed by enforcement activities in July. Activities to educate workers exposed to airborne crystalline silica are continuing through the efforts of the OSHA regional office in Cleveland. NIOSH has published an alert requesting assistance in preventing deaths among sandblasters (8).

References

1. National Institute for Occupational Safety and Health. Work-related lung disease surveillance report, 1994. Cincinnati, Ohio: US Department of Health and Human Services, Public Health Service, CDC, 1994; DHHS publication no. (NIOSH)94-120.

2. National Institute for Occupational Safety and Health. Hazard evaluation and technical assistance report: commercial steel treating company, Cleveland, OH. Cincinnati, Ohio: US Department of Health and Human Services, Public Health Service, CDC, 1992; NIOSH report HETA 92-0174.

3. National Institute for Occupational Safety and Health. NIOSH respirator decision logic. Cincinnati, Ohio: US Department of Health and Human Services, Public Health Service, CDC, 1992; DHHS publication no. (NIOSH)87-108.

4. International Labor Organization. Guidelines for the use of ILO international classification of radiographs of pneumoconioses. Geneva, Switzerland: International Labor Organization, 1980.

5. CDC. Silicosis: cluster in sandblasters -- Texas, and occupational surveillance for silicosis. MMWR 1990;39:433-7.

6. Maxfield R, Alo C, Reilly MJ, et al. Surveillance for silicosis, 1993 -- Illinois, Michigan, New Jersey, North Carolina, Ohio, Texas, and Wisconsin. In: CDC surveillance summaries (January) MMWR 1997;46(no. SS-1):13-28.

7. National Institute for Occupational Safety and Health. NIOSH respirator users notice. Cincinnati, Ohio: US Department of Health and Human Services, Public Health Service, CDC, May 23, 1996.

8. National Institute for Occupational Safety and Health. NIOSH alert: preventing silicosis and deaths from sandblasting. Cincinnati, Ohio: US Department of Health and Human Services, Public Health Service, CDC, 1992; DHHS publication no. (NIOSH)92-102.

* 29 CFR 1926.103. 

** Blaster's helpers are apprentices to workers involved in abrasive blasting and are required to keep the blasting pot filled with abrasive and to oversee other activities directly related to the abrasive blasting process (e.g., the functioning of the air compressor). Because of their proximity to blasting operations, they also are at risk for high exposure to silica dust. 

*** Some workers reported using more than one type of respirator or using different types of respirators for different activities. 

**** Facial hair that lies along the sealing area of a respirator and may interfere with the face-to-respirator seal. 

***** Only one of the eight had a history of other occupational exposures in which high exposures to silica could have led to silicosis; this worker had worked in a coal mine for 3 years, in a foundry for 2 years, and in a glass factory for 3 years.

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