Asbestos containing materials (ACM) have been used for decades in research laboratory products including gloves, tong sleeves, Transite board, and other materials. These materials typically contain chrysotile asbestos with concentrations ranging up to 80%. The objective of this research was to evaluate asbestos exposure from gloves, tong sleeves, and Transite board with simulated laboratory use. An environmental chamber was used to simulate laboratory application of the products. Bulk samples of various products were tested before and after use. Personal breathing zone air samples as well as one cumulative air sample were collected during testing and followed the National Institute for Occupational Safety and Health (NIOSH) 7400/7402 methodologies. Phase contrast microscopy (PCM) and transmission electron microscopy (TEM) were used for sample analyses. Analysis of air samples using PCM, showed airborne fiber concentrations as high as 0.058 f/cc during use of tongs fitted with asbestos sleeves. Further analysis using TEM showed that the highest airborne fiber concentration was 0.0036 f/cc. Manipulation of Transite board resulted in 8-hour time-weighted-average (TWA) asbestos levels as high as 0.02 f/cc. Testing of various asbestos containing materials used in research laboratories indicate low potential for asbestos fiber exposures.
Asbestos is a generic term given to the fibrous variety of six naturally occurring minerals that have been used in a variety of commercial products. Its importance in products derives from its strength, heat resistance, flexibility, weavability, its ability to resist chemical and thermal degradation, and high electrical resistance. This fibrous material has been used as a component in thousands of construction, industrial, and household products including roofing and siding shingles, friction products in automobile parts, thermal systems insulation and electrical wiring, personal protective gear, and in certain laboratory equipment components [
Health concerns were associated with asbestos being classified as a known human carcinogen. In addition, during residency in the lungs, a significant immunological response occurs that facilitates clearance [
To date, few studies have documented exposure assessments involving ACM in the research laboratory environment. As well, the few published articles that do exist have primarily focused on gloves and mitts. Laboratories have used and continue to use a variety of ACM, primarily in applications where thermal insulation is required. In order to assess potential exposure risk while using ACM in a laboratory setting, a series of experiments were conducted in a contained environmental chamber to simulate high exposure “worst-case scenarios” that a laboratory technician might encounter while using an asbestos-containing product. This study reports the exposures measured from the use of asbestos containing gloves, tong sleeves, and Transite board.
The experiments were conducted in an enclosed chamber (dimensions = 3 ft × 7 ft). Each item was individually tested with cleaning of the chamber between tests. The sampling filters were placed 18 inches above the worktable as well as the test material to represent the breathing zone of a laboratory technician. Each sample was collected for 30-minutes. There was one cumulative sample that was run in parallel to all of the individual 30-minute tests (4.5 hour total cumulative exposure). Three used gloves, three used tongs (with asbestos-containing sleeves), and three Transite boards were manipulated and tested. During each test, participants manipulated the item for the entire 30 minutes and >50% of the time more “aggressive” handling was applied. In all testing runs, there were visible fibers on the table that broke off from the test item. The Transite board manipulation included drilling between 12 to 18 holes, cutting it with a saw, chiseling it, and smashing it with a hammer. At the end of the Transite board test, there was dust spread over both horizontal and vertical surfaces (sheeting) in the chamber. The manipulations of the ACM during sample collection were severe to provide the greatest opportunity for fiber release. As well, these air samples were collected in an isolated exposure chamber prohibiting the escape of fibers producing a worst-case exposure scenario.
Air sampling was performed in accordance with NIOSH methods 7400/7402 recommendations: mixed cellulose ester membrane filters with 0.8 μm pores inside 25 μm diameter electrically conductive, extended cowl cassettes. Personal breathing zone sample flow rates were in the 15 L/min range for gloves, tong sleeves, and Transite board. All PCM-intended sampling had a corresponding TEM sample obtained. All tested materials had pre-test bulk sampling performed. Laboratory personnel conducting the experiments were trained to handle ACM and used appropriate personal protective equipment during testing.
Asbestos-containing products including gloves, tong sleeves, and Transite board were evaluated during the study. The nine collected bulk samples tested were found to have a variable amount of asbestos (
All sample exposure measurements obtained were intended to represent personal breathing zone samples (also reported as the regulatory adjusted 8-hour TWA;
Bulk Sample Designation | Sample Run Order | Item Type | Chrysotile Asbestos (unless otherwise noted) | Cellulose |
---|---|---|---|---|
3 | 1 | Glove | 40% | 50% |
9 | 2 | Glove | 35% | 55% |
5 | 3 | Glove | 30% | 65% |
6 | 4 | Tong | 45% | 50% |
7A | 5 | Tong | 40% | 55% |
12A | 6 | Tong | 35% | 55% |
11* | 7 | Transite | 10% (5% Amosite) | Cement |
11* | 8 | Transite | 10% (5% Amosite) | Cement |
11* | 9 | Transite | 10% (5% Amosite) | Cement |
*11, These represent the same bulk sample from which the tested boards for runs 8 - 10 were obtained.
Sample # | Sample Type | PCM (f/cc) | TEM (f/cc) | 8-hour TWA (PCM/TEM) |
---|---|---|---|---|
1 | Glove | -- | -- | -- |
2 | Glove | -- | -- | -- |
3 | Glove | -- | -- | -- |
4 | Beaker tong sleeve | 0.056 | <0.006 | --/BDL |
5 | Beaker tong sleeve | -- | <0.006 | --/BDL |
6 | Beaker tong sleeve | 0.058 | 0.160 | 0.0036/0.01 |
7 | Transite | -- | 0.210 | --/0.013 |
8 | Transite | -- | -- | -- |
9 | Transite | -- | 0.320 | --/0.02 |
Composite | -- | -- | -- |
“―”, Samples were not analyzed due to dust overload. BDL, Below the detection limit.
0.058 f/cc. Tong sleeve sample six, however, was overloaded with dust and could not be analyzed. The TEM results for the tongs identified that two out of three samples had an undetectable fiber load (<0.006 f/cc) while one sample had a fiber count of 0.160 f/cc. These results further demonstrate the value of confirming PCM fiber counts with TEM as PCM may grossly overestimate asbestos exposure. The benefit of TEM analysis is that it measures only asbestos fibers, while PCM reports both asbestos and non-asbestos fibers, which is the reason for the potential overestimation of asbestos fibers. For the Transite board samples, all the PCM samples were unable to be analyzed due to being overloaded with dust. Two of the Transite board TEM samples had asbestos concentrations of 0.210 and 0.320 f/cc, respectively. The third Transite board TEM sample was unable to be analyzed due to being overloaded with dust. Extrapolating the 8-hour TWA, assuming the exposures occurred once in an 8-hour work period, are also reported. To obtain the 8-hour TWA concentration, the values from the PCM and TEM columns were divided by 480 (minutes) and then multiplied by 30 (minutes). The glove samples and the cumulative sample were unable to be analyzed, whether by PCM or TEM, due to dust overload.
Limited literature exists on asbestos exposures from working in a research laboratory. However, in a previous exposure assessment, Garcia et al. (2018) [
Limited literature associated with gloves includes Samimi (1981) [
The tong sleeve analyses showed relatively low exposures for two of the PCM samples with the larger concentration of the two being 0.056 f/cc. This concentration, assuming a single episode over 8 hours, yields a TWA of 0.0036 f/cc. If we assume four times as much exposure (4 × 0.0036 f/cc) in an 8-hour period, the concentration is well below the PEL or 0.014 f/cc. Similarly negligible exposures are reported by TEM for the other tong sleeve samples. However, in one tong sample, the TEM exposure was 0.160 f/cc, approximately 63 percent above the current PEL of 0.1 f/cc. Assuming such exposure in an 8-hour period, the TWA would be 0.01 f/cc, one order of magnitude below the current PEL.
The Transite board sampling yielded 4 unreadable (overloaded) samples (3 for PCM and 1 for TEM). Only two of the three TEM samples yielded a quantifiable concentration for these boards. Exposures ranged between 0.210 and 0.320 f/cc, both approximately double and triple the PEL level, respectively. However, if this aggressive board manipulation is performed once in an 8-hour period, the exposure would be well below the PEL in both instances: 0.013 f/cc and 0.02 f/cc. It is unlikely that one would need to break/shape these boards more than once daily, if at all. More likely than not, the typical lab usage of Transite board would occur sporadically as labs often recycle their customized Transite board for different experiments. The composite sample was also overloaded with dust and was not able to be analyzed by either PCM or TEM.
The conditions simulated during this experiment were intentionally more austere than the expected handling conducted during average laboratory work. While it was determined that in the case of the Transite board and one tong sleeve manipulation that it is possible to generate at least excursion levels of airborne fibers, these levels, are not likely to exceed the 8-hour TWA PEL of 0.1 f/cc given intermittent laboratory work activity. However, since asbestos was detected in some of the air samples, it is important to place this exposure in context. The epidemiological data that linked asbestos to asbestosis, lung cancer, and mesothelioma is derived from environments where airborne fibers have been significantly higher than laboratory work (if the findings in these experiments are representative of such exposure). Williams et al. (2009) [
While none of the air samples were able to be analyzed for the manipulation of gloves in this simulation, past literature has provided results that exposure to asbestos is likely to be relatively low. Cherrie et al. (2005) [
OSHA’s first PEL was 12 f/cc in 1971; this value was reduced over the years arriving at the current PEL of 0.1 f/cc (120 times lower than the first PEL; Williams et al. 2007 [
There are asbestos-containing products used in laboratory settings beyond what have been tested in this experiment. However, the findings reported here suggest that laboratory workers are not likely exposed to levels of asbestos that would increase their risk for asbestos-related disease especially taking into account that the bulk of the epidemiological data for asbestosis and cancer comes from very high exposures to asbestos. Further evaluation of ACM products utilized in laboratory settings should be conducted to expand available literature associated with potential asbestos exposure to workers in research laboratories.
This work was funded by the Center for Environmental and Occupational Risk Analysis and Management at the University of South Florida.
The authors declare no conflicts of interest regarding the publication of this paper.
Garcia, E., Newfang, D., Coyle, J., Johnson, G.T. and Harbison, R.D. (2019) Evaluation of Asbestos Exposure Associated with Research Laboratories. Occupational Diseases and Environmental Medicine, 7, 13-20. https://doi.org/10.4236/odem.2019.71002