Abstract No:
1500
Abstract Type:
Professional Poster
Authors:
A McCann1
Institutions:
1Liberty Mutual Insurance, Mission Viejo, CA
Presenter:
Adam McCann
Liberty Mutual Insurance
Description:
When grinding rounded or non-flat concrete surfaces, current commercially available vacuum systems fail to contain silica dust. The rigid shroud on these tool-mounted systems cannot maintain a seal, allowing large amounts of airborne dust to be released directly into the operator's breathing zone. While wet grinding systems, which use a continuous water mist to control dust at the source to effectively mitigate this hazard, their commercial availability for concrete finishing applications is limited. Consequently, manufacturers have not provided adequate engineering controls to suppress or capture silica-containing dust during the detailing of non-flat concrete infrastructure.
Employees faced high silica exposure, reaching levels 38.8 times the ACGIH TLV, primarily due to the limited capture efficiency of HEPA-filtered dust collectors. A key challenge was the failure of conventional local exhaust ventilation for concrete grinding on non-flat surfaces. Commercially available shrouds could not properly conform to these shapes, leading to inadequate suction and high employee dust exposure. To address this issue, wet grinding methods were introduced at a major infrastructure manufacturer. This approach has proven effective in real-world conditions, reducing personal silica exposure to a safe level below the ACGIH TLV. While this is currently the most effective and practical solution, the limited availability of suitable equipment means it may not be viable for every si
Situation / Problem:
Using tool-mounted vacuum systems to grind rounded or non-flat concrete and granite surfaces can lead to dangerous levels of airborne silica dust. Because the grinder's shroud cannot maintain a complete seal on these irregular surfaces, significant amounts of dust are released into the air.
Testing reveals that exposure levels can exceed safety limits by a wide margin:
• 1.28 to 38.8 times higher than the ACGIH Threshold Limit Value (TLV) of 0.025 mg/m3.
• Up to 19.4 times higher than the OSHA Permissible Exposure Limit (PEL) of 0.05 mg/m3.
Methods:
Air samples were collected from each worker's breathing zone to evaluate potential exposure to airborne contaminants. Personal sampling pumps drew air at a measured flow rate through sampling media, specifically PVC membrane filters in BGI 4L cyclones for respirable crystalline silica. The sampling train was calibrated before and after sampling with a primary standard airflow calibrator. Pump flow rate variations were kept within 5% of the initial calibration.
All samples were submitted to the Liberty Mutual Insurance Industrial Hygiene Laboratory. The Liberty Mutual Insurance Industrial Hygiene Laboratory (ID 100045) is accredited by AIHA Laboratory Accreditation Programs, LLC (AIHA LAP, LLC) in the IHLAP accreditation program for specific Fields of Testing. Refer to the AIHA LAP, LLC website for the current Scope of Accreditation. Details of the analysis and sample results are included in the laboratory data pages.
Results / Conclusions:
To assess exposure, personal air samples were collected from workers in the breathing zone during two distinct activities:
• Dry Grinding: Tasks involving dry grinding on rounded or non-flat concrete or granite surfaces with an attached vacuum system (7 samples).
• Wet Grinding: Tasks involving wet grinding on rounded or non-flat concrete or granite surfaces (2 samples).
The implementation of wet grinding methods reduced respirable crystalline silica exposure to concentrations below the ACGIH TLV. Measured results ranged from below Limit of Quantification (LOQ) to <88% of the ACGIH TLV.
Core Competencies:
Engineering Controls and Ventilation
Secondary Core Competencies:
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.
Aerosol and airborne particulate monitoring
Exposure Assessment
Regulatory Compliance
Risk assessment and management
Ventilation
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)
Practitioner: Practitioner is a job title given to persons in various occupational fields who are trained to assist professionals but are not themselves licensed or certified at a professional level by a certification body recognized by the National Accreditation Recognition (NAR) Committee of IOHA. The IH/OH practitioner performs tasks requiring significant knowledge and skill in the IH/OH field, such as conducting worker exposure monitoring and, in some cases, may even function independently of a professional IH/OH but may not be involved in the breadth of IH/OH practice nor have the level of responsibility of a professional IH/OH certified by examination.
The IH/OH practitioner requires a certain level of education that can be obtained from an accredited university or equivalent. Additional training in specific skill sets that provide additional career paths to the IH/OH practitioner can also be obtained. IH/OH practitioners may also serve as team leaders or project managers.
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.
IHSTAT_Bayes
How will this help advance the science of IH/OH?
It provides the practicing field industrial hygienist with a proven control to help minimize potential employee exposure to respirable crystalline silica, a known human carcinogen.
What level would you consider your presentation content geared towards?
Introductory: Introduces an elementary or basic subject area. Participant expected to have zero (0) to two (2) years of experience in industrial hygiene or OEHS, or a technical career path. Prerequisite: general knowledge.
Have you presented this information before?
No
I have read and agree to these guidelines.
Yes