Abstract No:
1428
Abstract Type:
Professional Poster
Authors:
C Boles1
Institutions:
1Insight Exposure & Risk Sciences Group, Spring Hope, NC
Presenter:
Corey Boles, PhD
Insight Exposure & Risk Sciences Group
Description:
Inhalation dosimetry is used to model how airborne contaminants interact with, deposit in, and become absorbed systematically through the respiratory system, providing a link between external exposure and internal dose. Inhalation dosimetry models are commonly used for the derivation of occupational exposure limits (OELs) but also have applications of relevance to OEHS practitioners, such as informing exposure assessment strategies. This poster presents a case study where the application of inhalation dosimetry can be used to characterize mixed-phase (vapor and aerosol) exposures to a workplace disinfectant. For certain chemicals, traditional sampling and analytical methods capture only the vapor phase, while OELs are based on combined vapor and aerosol exposures. Using a common inhalation dosimetry tool, the multiple-path particle dosimetry (MPPD) model, regional lung deposition of aerosol particles was simulated and combined with measured vapor data to estimate total internal dose. Results demonstrate that exposures may be judged acceptable when considering vapor exposures alone, but exceed the OEL once aerosol exposure is incorporated. This case study demonstrates how inhalation dosimetry provides a more comprehensive and biologically relevant basis for risk characterization, enabling OEHS professionals to refine sampling strategies, assess control needs, and communicate risk more effectively.
Situation / Problem:
In some cases, conventional exposure assessments may underestimate dose when the sampling and analytical method does not correspond to the toxicological basis of the OEL. In this case study, vapor-only exposure assessment provided an exposure concentration that was below the OEL; however, because the OEL was derived from combined vapor and aerosol exposures, the inhaled and deposited doses were underestimated. A more comprehensive exposure assessment approach is required to account for mixed-phase exposures and provide a biologically relevant comparison to the OEL.
Methods:
The assessment combined measured vapor-phase exposure concentrations with modeled aerosol deposition to evaluate dose relative to the OEL. Vapor concentrations were collected using standard adsorbent tube sampling and expressed in mg/m³. Inhaled dose was calculated by multiplying the vapor-phase concentration by the default worker inhalation volume for an 8-hour shift. For the aerosol fraction, particle size distribution parameters (MMAD = 2.8 µm, GSD = 2.1) and measured aerosol concentrations were input into MPPD.
The model was run using human airway morphometry and breathing parameters representative of light workload conditions to estimate the regional deposition fractions within the respiratory tract. Deposited dose was then calculated by multiplying the aerosol exposure concentration by the modeled deposition fraction and daily inhalation volume. Finally, inhaled vapor dose and deposited aerosol dose were combined to estimate the total inhaled and deposited dose for comparison with the OEL-equivalent dose.
Results / Conclusions:
The vapor-phase exposure concentration corresponded to an inhaled dose of 7.8 mg across an 8-hour shift, which was below the OEL-equivalent dose of 10 mg. However, inhalation dosimetry modeling indicated that aerosol deposition contributed an additional deposited dose of approximately 2.5 mg, resulting in a combined inhaled and deposited dose of 10.3 mg. This total dose exceeded the OEL-equivalent dose, yielding a hazard quotient of 1.03. These findings demonstrate that while vapor-only sampling may suggest compliance with OELs, inclusion of the aerosol fraction of exposure may reveal that exposures reach or exceed exposure benchmarks. The case study illustrates how integrating inhalation dosimetry into exposure assessment provides a more biologically relevant estimate of deposited dose following exposure, reduces uncertainty in risk characterization, and supports more informed risk management decisions regarding monitoring strategies and control implementation.
Core Competencies:
Exposure Assessment
Secondary Core Competencies:
Risk Assessment
Risk Management
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.
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)
Exposure Assessment Strategies Committee
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?
No
How will this help advance the science of IH/OH?
This poster illustrates how OEHS professionals can integrate inhalation dosimetry into routine exposure and risk assessments, improving the comprehensiveness of exposure characterization, refining exposure limits, and ensuring that control strategies are aligned with biologically relevant dose metrics.
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