Analysis of NIOSH Health Hazard Evaluation (HHE) Data on the Use of Asbestos-Containing Products (1973-1994)

1283 

Professional Poster 

M Vahora¹

¹Benchmark Risk Group, Chicago, IL

Moin Vahora, MPH  
Benchmark Risk Group

The NIOSH Health Hazard Evaluation (HHE) Program is a valuable resource that assesses the potential exposures experienced by workers during on-site surveys of U.S. workplaces. This analysis: 1) compiles, characterizes, and contextualizes personal air sampling data on asbestos fiber concentrations evaluated under the HHE program, and 2) evaluates trends in the data. We searched for HHE reports published through August 12, 2025, that collected personal breathing zone (PBZ) measurements for asbestos during end-use applications of asbestos-containing materials (ACMs). Qualitative and quantitative data were extracted to characterize exposure scenarios across various occupational settings. PBZ samples were then grouped based on sample duration (e.g., full shift, task, or short-term). Data were stratified by ACM type, job title, and job task, and stratified in relation to corresponding OSHA PELs. Descriptive statistics were calculated for the entire dataset and each data group, and trends were identified. The final dataset included 46 reports (N=256 samples). Of these, ~40% (N=102) were below the limit of detection (LOD). This analysis revealed that full-shift fiber concentrations across various industries have been below OSHA's 8-hour PELs, and airborne fiber concentrations have generally decreased over time. These results can assist OEHS professionals in assessing exposure to fiber concentrations from asbestos-containing products.

Asbestos refers to a group of fibrous mineral silicates that includes serpentine (chrysotile) and amphiboles (amosite, crocidolite, tremolite, actinolite, and anthophyllite) (ATSDR 2001). Asbestos fibers are naturally resistant to heat, fire, and chemical and biological degradation, and were used in thousands of products, including insulation, building materials, friction products, coatings, gaskets, and textiles (ATSDR 2001; IARC 2012). U.S. consumption of asbestos rapidly declined in the 1970s, and its current domestic use is less than 0.1% of peak consumption in the early 1970s (ATSDR 2001; EPA 2024; TSCA 2024).

The NIOSH HHE Program evaluates potential health hazards during on-site surveys of U.S. workplaces, which can be requested by employees, employers, and union representatives. NIOSH publishes its findings and recommendations on ways to reduce or eliminate occupational hazards following each evaluation, which are available to the public on its website. Over 16,000 HHEs have been conducted since the program's inception in 1972, covering a variety of workplace settings and a range of physical, biological, and chemical agents, including asbestos.

HHE reports contain information on asbestos exposure that has not yet been compiled or summarized in the scientific literature. This analysis: 1) compiles, characterizes, and contextualizes personal air sampling data on asbestos fiber concentrations evaluated under the HHE program, and 2) evaluates trends in the data.

HHE reports that evaluated occupational asbestos exposure were systematically identified using the Centers for Disease Control and Prevention's (CDC) HHE search portal (https://www2a.cdc.gov/hhe/search.asp), using the terms "asbestos," "asbestos exposure," and "asbestos-containing material". All reports published through August 12, 2025, were considered. The contents of each HHE report identified by the search query were independently reviewed and screened by two reviewers. The a priori inclusion criteria were limited to HHE reports that specifically documented PBZ exposure measurements involving end-use applications of ACMs. End use of a product was defined as ACMs used as finished products or components. Reports containing both qualitative and quantitative data on personal asbestos exposure were extracted to characterize exposure scenarios across various occupational settings.

Once relevant HHE reports were identified, information (i.e., sample date, analytical method, sample duration, pump flow rate, sample volume, company/facility name, job title, job task, ACM type, and airborne fiber concentrations) was extracted and added to a database. All data were reviewed for accuracy by two authors. Notably, no information on the use of personal protective equipment (PPE) was extracted; therefore, these exposure values represent the potential exposure that may have occurred. PBZ samples were grouped according to sample duration (e.g., full shift, task, or short-term). Samples were classified as full-shift if explicitly described as such in the HHE reports, or if the recorded sampling duration was equal to or greater than 420 minutes (i.e., consistent with a seven-hour work shift). Samples were classified as task-based or short-term if the sampling durations were between 30 and 420 minutes or less than 30 minutes, respectively.

Data were stratified by ACM type, job title, and job task. When sample sizes allowed, the data were further stratified by the time period corresponding to the contemporaneous OSHA PELs for asbestos, specifically: May 1971 to November 1971 (PEL = 12 f/cc), December 1971 to May 1976 (PEL = 5.0 f/cc), June 1976 to June 1986 (PEL = 2.0 f/cc), July 1986 to July 1994 (PEL = 0.2 f/cc), and August 1994 to the present day (PEL = 0.1 f/cc). Relevant ACMs identified in the reports included, but were not limited to, pipe and equipment insulation, cement-based products, electrical insulation, friction materials, refractory materials, and surfacing materials. It should be noted that we reported individual ACM exposure and combined exposure from two ACMs (e.g., insulation and gaskets).

Censored data were substituted with one-half the limit of detection. Descriptive statistics were calculated for the entire dataset and for each data grouping of airborne fiber concentrations, including the geometric mean, geometric standard deviation, median, 95th percentile, minimum, maximum, and sample size.

Our study leveraged exposure data from end-use applications of ACMs. The final dataset included 46 reports (N=256 samples) with 102 samples below and 154 samples above the respective LOD.

The largest group of observations was for insulation (n=96). The remaining product categories included electrical insulation, friction products, roofing materials, insulation and gaskets, insulation and cement siding, cement products, and refractory materials (each n≥10), as well as asbestos gloves and millboard, asbestos-containing plaster, insulation and refractory, an unspecified product, asbestos mill rods, asbestos-containing talc stone, and Fibra-flo filter aid (each n<10). A total of 107 observations were reported in the 1970s, 101 in the 1980s, and 48 in the 1990s; no samples were collected relevant to the use of ACMs in the 2000s and beyond.

The resulting geometric means (GM) and ranges of PBZ fiber concentrations associated with the use of various products are presented below. For insulation, the GM (range) of full-shift, task, and short-term fiber concentrations were 0.031 f/cc (0.004–0.6 f/cc; n=24), 0.018 f/cc (0.002–0.77 f/cc; n=59), and 0.773 f/cc (0.2–2 f/cc; n=12), respectively. Corresponding fiber concentrations for friction products were 0.009 f/cc (0.004–0.01 f/cc; n=11), 0.014 f/cc (0.004–0.15 f/cc; n=15), and 1.061 f/cc (0.75–1.5 f/cc; n=2), respectively. For electrical insulation, the GM (range) was 0.038 f/cc (0.034–0.042 f/cc; n=2), 0.025 f/cc (0.025–0.025 f/cc; n=26), and 0.005 f/cc (0.005–0.005 f/cc; n=2), respectively. Task samples for roofing materials had a GM of 0.096 f/cc (0.02–1.12 f/cc; n=20), while the only short-term sample was 0.16 f/cc. Task samples for insulation and gasket materials had a GM of 0.138 f/cc (0.017-0.61 f/cc; n=17). Full-shift samples for insulation and cement siding materials had a GM of 0.013 f/cc (0.01-0.04 f/cc; n=14). Task samples for cement products had a GM of 0.567 f/cc (0.05–3.54 f/cc; n=12), while the only short-term sample was 10.48 f/cc. For refractory materials, the GM for task samples was 0.403 f/cc (0.07–3.02 f/cc; n=9), while the lone short-term sample was 0.86 f/cc. The GMs for the remaining products ranged from 0.013-0.139 f/cc for full-shift samples and 0.03-0.04 f/cc for task samples, with one short-term sample concentration of 15 f/cc "during the addition of 'Fibra-Flo' at the Deep Well Area" (77-34-471: p. 14).

None of the 66 full-shift samples exceeded contemporaneous OSHA PELs. Job titles in this subgroup included contractors, electricians, firemen, insulators, laborers, maintenance workers, masons, mechanics, NIOSH observers, operators, pipefitters, supervisors, postal workers, and welders. This analysis revealed: personal samples of fiber concentrations for full-shift samples across various industries have been below contemporaneous OSHA 8-hour asbestos PELs since the inception of the HHE program, and airborne fiber concentrations have generally decreased over time.

Exposure Assessment

Chemical Hazards