Abstract No:
1652
Abstract Type:
Student Poster
Authors:
B Openshaw1, J Johnston2
Institutions:
1Brigham Young University, Highland, UT, 2Brigham Young University, Provo, UT
Presenter:
Brinley Openshaw
Brigham Young University
Faculty Advisor:
James Johnston
Brigham Young University
Description:
Exploring the underresearched connection between the brick industry and silica exposures.
Situation/Problem:
Our study sought to quantify exposures to crystalline silica by job category among brick kiln workers in Bhaktapur, Nepal.
Methods:
Our cross-sectional, observational study took place over three sampling periods in February and March between 2023 and 2025. In total, we sampled the breathing zones of workers (N = 249) at four brick kilns in Bhaktapur, Nepal using NIOSH method 7500 for respirable crystalline silica (SiO2). Participants were drawn from common job categories, including excavator operator, top loader, red and green brick carriers, machine molders, hand molders, fire masters, coal carriers, and administrators.
Samples were collected on cassettes housing matched-weight 5.0 µm, 37mm PVC membrane filters (SKC inc., Eighty Four, PA) connected to an aluminum cyclone pre-separator (4.0 µm cut-point) and an SKC AirLite Pump (SKC inc., Eighty Four, PA). Pumps were calibrated to ± 1.0% of 2.5 L/min using DryCal mid-flow calibrators (Mesa Labs, Lakewood, CO) and a calibration blank. The calibration blanks were replaced with a matched-weight filter cassette, and the sampler was affixed to the worker within their breathing zone. After sampling, pumps were post-calibrated using the same calibrator used for pre-calibration.
Samples were delivered to ALS Labs in Salt Lake City, Utah. Silica mass (cristobalite, tridymite, and quartz) was determined by XRD following NIOSH method 7500 respirable silica.
Exposure concentrations were calculated as mass silica (µg)/volume of air (m^3). The natural log (ln) of concentrations was used for silica due to the data being right skewed. Analysis of variance was used to compare differences between job categories, followed by post-hoc Tukey test to determine pairwise comparisons. Results were back transformed to concentration values using e^(logged value). A total of 36 participants were excluded from the final analysis due to either grit pot inversion or because of pump flow rate drift > 5.0% from pre- to post-calibration.
Limitations: Participants were drawn from four kilns, representing about 3.0% of the total kilns in the Kathmandu Valley, and may not represent the whole valley. Kilns were not selected randomly, which may have introduced selection bias into our study. The cross-sectional design was limited to sampling workers for one shift, which may not be indicative of exposure overall.
Results / Conclusions:
No samples were positive for cristobalite or tridymite. The mean exposure concentration across job categories for respirable quartz was 34.0 µg/m^3. Significant differences were found for respirable quartz exposures between job categories (p < 0.01). Job categories with significantly higher exposure concentrations included Green/Red Brick Carrier/Loader/Stacker 51.2 µg/m^3 (95% CI: 40.79 – 64.2); Red Brick carrier/loader/stacker 66.2 µg/m^3 (95% CI: 43.65 – 100.3); and Top Loader 90.4 µg/m^3 (95% CI: 51.47 – 158.8). Nepal recently proposed a permissible exposure limit for respirable silica of 50 µg/m^3. Assuming the concentrations found in our study are consistent throughout the work shift, workers involved in red and green/red brick handling and those responsible for placing/removing the insulating layer of soil in the kiln are at risk for silica-related health problems. Intervention measures should target those brick workers within the categories of highest risk.
Core Competencies:
Exposure Assessment
Secondary Core Competencies:
Work Environments, Occupations, and Industrial Processes
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
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.
ANOVA, R version 4.5.2. ;Emmeans package, R version 2.0.0
How will this help advance the science of IH/OH?
Though exposures to and health effects from respirable silica have known implications and have been examined within many industries, this relationship remains understudied within the brick industry. This lack of information is exacerbated in developing countries and rural areas, likely due to a lack of exposure quantification and access to screening. Within Nepal, 200,000 people work within the brick industry across 1,200 kilns. Many workers come from marginalized groups, lacking education about and protection from the health risks related to their profession. They often report a high burden of disease and negative respiratory symptoms.
This study seeks to contribute to a newer body of research regarding the rural brick industry. Building upon a previous study, we quadrupled the sample size to provide valuable information about the job categories within the brick industry with the greatest risk of silica-related disease. Our research seeks to inform interventions that prioritize these high-risk groups to maximize their effectiveness.
Have you presented this information before?
No
I have read and agree to these guidelines.
Yes