Abstract No:
1455
Abstract Type:
Professional Poster
Authors:
S Zentner1
Institutions:
1Benchmark Risk Group, Grand Rapids, MI
Presenter:
Sara Zentner, MPH
Benchmark Risk Group
Description:
Benzene is a known human carcinogen that has been associated with acute myeloid leukemia (AML) in workers after prolonged, high exposure. We retrieved all available benzene sampling data collected in the petroleum and gasoline industries from 1984 through 2025 in the Occupational Safety and Health Administration's (OSHA) Chemical Exposure Health Data (CEHD) database. Concentrations were stratified by sample type (i.e. personal air, area air, and bulk material) and analyzed for temporal trends and industry-level trends according to North American Industry Classification System (NAICS) 6-digit industry code. Personal air concentrations were contextualized using the contemporaneous OSHA permissible exposure limit (PEL).
We identified 109 area, 71 bulk, and 937 personal samples that represented 13 distinct NAICS 6-digit industry titles from 1984 to 2024. After adjusting for industry, personal benzene concentrations decreased by 0.11 ppm per year (p<0.05) on average since 1984. Personal 8-hour TWA-adjusted benzene levels measured post-1987 were predominantly non-quantifiable (i.e. <LOQ) and therefore well below the contemporaneous OSHA PEL of 1 ppm. Just 1.8% (n=16) of all 8-hour TWA-adjusted personal samples collected in 1987 and later exceeded the 1987 OSHA PEL. Our results provide important context on historical benzene exposures during petroleum and gasoline operations, offering a conservative, upper-bound estimate of occupational exposure for workers in these industries.
Situation / Problem:
Benzene is a known human carcinogen that has been linked to AML in workers after prolonged, high exposure. In May 1971, OSHA established the first legally enforceable occupational exposure limit for benzene at 10 ppm as an 8-hour TWA. Following reports of leukemia in rubber workers with high occupational exposure to benzene, OSHA finalized a revised limit for occupational benzene exposure in 1987, lowering the PEL from 10 ppm to 1 ppm as an 8-hour TWA. OSHA excluded from the 1987 benzene standard "some segments and operations" where "exposures are consistently below the action level because of the nature of the process". The occupational exposure limit for benzene remains unchanged to date.
The early epidemiological evidence of hematopoietic cancers in rubber workers led to subsequent evaluations of benzene-exposed workers in other industries, including those related to petroleum and gasoline products. Across these studies, no clear patterns of risk were observed for hematopoietic cancers in petroleum and gasoline workers, suggesting that benzene exposures were lower than those levels observed during rubber manufacturing; however, few published studies reported benzene concentrations during petroleum and gasoline operations. To address this data gap, we used OSHA sampling records in the CEHD database to characterize benzene exposure in petroleum and gasoline industries from 1984 to 2025 and contextualize the measured exposures with the contemporaneous OSHA PEL.
Methods:
OSHA monitors exposure to chemical hazards among workers through collecting industrial hygiene samples at workplaces throughout the United States. Since 2010, OSHA has published the results of their workplace monitoring in their CEHD database. Sampling data in the CEHD database spans from 1984 to present and includes personal, bulk, and area samples of various industrial chemicals, including benzene. OSHA sampling typically targets activities with the highest exposure potential, therefore data in the CEHD database reasonably estimates worst-case, upper-bound exposure levels.
We used the OSHA CEHD database to characterize historical upper-bound exposure to benzene among workers in industries related to petroleum and gasoline. We included all personal, area, and bulk benzene (IMIS substance code 320) samples in the CEHD database collected from petroleum- or gasoline-related industries from 1984 (the lower bound of available data) to 2025. Industries related to petroleum or gasoline were selected by examining the NAICS 6-digit national industry descriptions for explicit mention of petroleum, petrochemical, gasoline, or crude oil.
Measurements were stratified according to sample type (i.e. personal air samples, area air samples, and bulk material samples) and analyzed for temporal trends and industry-level trends according to NAICS 6-digit national industry code. We used the Kruskal Wallis test paired with Dunn's post-hoc test and a Bonferroni correction for multiple testing to assess whether there was a statistically significant (p<0.05) difference in personal air concentrations across the 6-digit NAICS industry codes. For contextualization, personal air concentrations were converted to 8-hour TWA equivalent values using the reported sampling duration and then compared to the contemporaneous OSHA PEL. Concentrations above the limit of quantification (LOQ) were summarized using geometric means (GM), geometric standard deviations (GSD), and medians to facilitate contextualization with relevant occupational exposure limits. All statistical tests were conducted at the alpha=0.05 significance level. All analyses were conducted using R (RStudio version 2025.05.1).
Results / Conclusions:
We identified a total of 1,337 personal, area, and bulk benzene samples. Of those samples, we excluded blanks (n=200), and those with missing unit values (n=20), leaving a total of 109 area, 71 bulk, and 937 personal benzene samples collected across 13 distinct NAICS industry titles from 1984 to 2024. More than half of all samples (n=590, 52.8%) were categorized under the NAICS code for Petroleum Refineries. Of the 1,117 total samples, benzene was quantifiable in 470 (42.1%) samples, including 355 (37.9%) personal samples, 56 (51.4%) area samples, and 59 (83.1%) bulk samples.
Across all years, area benzene concentrations ranged from <LOQ to 3,704 ppm (median 0.06 ppm), personal benzene concentrations ranged from <LOQ to 168 ppm (median <LOQ), and bulk concentrations ranged from <LOQ to 39% (median 0.1%). Among the subset of samples with quantifiable levels of benzene (n=470, 42.1%), the geometric mean (GM) concentrations were 0.3 (GSD 7.8) ppm in personal, 1.7 (GSD 13.4) ppm in area, and 0.14 (GSD 3.9) percent in bulk samples. After adjusting for industry, personal benzene concentrations decreased by an average of 0.11 ppm per year (p<0.05) since 1984. After conversion to 8-hour TWA equivalent concentrations, personal benzene levels ranged from <LOQ to 24 ppm (median <LOQ). Personal 8-hour TWA-adjusted benzene levels measured post-1987 were predominantly non-quantifiable (i.e. <LOQ) and therefore below the contemporaneous OSHA PEL of 1 ppm. Just 1.8% (n=16) of all 8-hour TWA-adjusted personal samples collected in 1987 and later exceeded the 1987 OSHA PEL. However, no information was provided regarding the use of personal protective equipment, thus it is unclear if these concentrations represented actual exceedances of the OSHA standard. Furthermore, in each instance in which the measured concentration exceeded the 1987 OSHA PEL, additional samples were collected on the same day that were well below the OSHA PEL.
Our results provide important context on historical exposure to benzene in petroleum and gasoline industries. While epidemiology studies from the 1970s, 1980s, and 1990s showed no consistent evidence of hematopoietic cancers across these industries, suggesting that benzene exposures were generally low, only a limited subset of these studies quantitatively assessed benzene exposure. Our findings contribute to this data gap by characterizing reasonable upper-bound benzene exposure levels during petroleum and gasoline operations using a publicly available database with more than 1,000 samples collected over approximately four decades. Although the CEHD database does not offer information on the specific job titles, use of PPE, or activities of workers or areas from which measurements were collected, they are presumed to represent higher-exposure scenarios within the industry based on the targeted nature in which they were sampled; they therefore provide a conservative estimate of exposure for workers in these sectors.
Core Competencies:
Work Environments, Occupations, and Industrial Processes
Secondary Core Competencies:
Chemical Sampling and Instrumental Analysis
Exposure Assessment
Choose at least one (1), and up to five, (5) keywords from the following list. These selections will optimize your presentation's search results for attendees.
Environmental protection and monitoring
Exposure Assessment
Risk assessment and management
Toxicology
Based on the selected primary competency area of your proposal, select one group below that would be best suited to serve as a subject matter expert for peer review:
(Select one)
Oil and Gas Working Group
Based on the information that will be presented during your proposed session, please indicate the targeted audience practice level: (select one)
Professional: Professional is a job title given to persons who have obtained a baccalaureate or graduate degree in IH/OH, public health, safety, environmental sciences, biology, chemistry, physics, or engineering or who have a degree in another area that meets the standards set forth in the next section, Knowledge and Skill Sets of IH/OH Practice Levels, and has had 4 or more years of practice. One significant way of demonstrating professional competence is to achieve certification by a 3rd party whose certification scheme is recognized by the International Occupational Hygiene Association (IOHA) such as the Board of Global EHS Credentialing (BGC).
Was this session organized by an AIHA Technical Committee, Special Interest Group, Working Group, Advisory Group or other AIHA project Team?
No
Are worker exposure data and/or results of worker exposure data analysis presented?
Yes
If yes, i.e., If worker exposure data and/or results of worker exposure data analysis are to be presented please describe the statistical methods and tools (e.g. IHSTAT, Expostats, IHSTAT_Bayes, IHDA-AIHA, or other statistical tool, please specify) used for analysis of the data.
RStudio Version 2025.05.1
How will this help advance the science of IH/OH?
Our results provide important context on historical exposure to benzene in petroleum and gasoline industries. While epidemiology studies from the 1970s, 1980s, and 1990s showed no consistent evidence of hematopoietic cancers across these industries, suggesting that benzene exposures were generally low, only a limited subset of these studies quantitatively assessed benzene exposure. Our findings contribute to this data gap by characterizing reasonable upper-bound benzene exposure levels during petroleum and gasoline operations using a publicly available database with more than 1,000 samples collected over approximately four decades. Although the CEHD database does not offer information on the specific job titles, use of PPE, or activities of workers or areas from which measurements were collected, they are presumed to represent higher-exposure scenarios within the industry based on the targeted nature in which they were sampled; they therefore provide a conservative estimate of exposure for workers in these sectors.
What level would you consider your presentation content geared towards?
Intermediate: Specific topics within a subject. The participant would have two (2) to ten (10) years experience in industrial hygiene or OEHS and a good understanding of the subject area, but not of the specific topic presented. Prerequisites required: another course, skill, or working knowledge of the general subject.
Have you presented this information before?
No
I have read and agree to these guidelines.
Yes