Abstract No:
1715
Abstract Type:
Student Poster
Authors:
T Nguyen1, T Huỳnh1
Institutions:
1University of Minnesota, Minneapolis, MN
Presenter:
Thang Nguyen
University of Minnesota
Faculty Advisor:
Trân Huỳnh, PhD, CIH
University of Minnesota
Description:
This study evaluates the effects of sample size, GSD, exceedance fraction (EF), and the LOQ/OEL ratio on compliance decision accuracy. A dataset containing various scenarios was generated using computer simulations. Bayesian statistical methods assuming a lognormal distribution were then applied to model compliance decision accuracy based on the proportion of correct decisions under different conditions.
Situation/Problem:
Occupational exposure limits (OELs) established by regulatory organizations such as OSHA and the EPA are often revised downward. Many sampling and analytical methods may have not been updated to reliably detect lower LOQs as OELs decrease, resulting in a higher proportion of non-detect measurements. The NIOSH Manual of Analytical Methods recommends that the LOQ be one-tenth or less of the OEL when a single sample is compared to the OEL. Current best practice defines exposure compliance as having at least 70% certainty that fewer than 5% of exposures exceed the OEL. As censoring increases with higher LOQ/OEL ratios, the ability of industrial hygienists to accurately determine compliance is affected.
Methods:
This study evaluated 990 simulated exposure scenarios with varying LOQ/OEL ratios, exceedance fractions (EF), geometric standard deviations (GSD), and sample sizes. EF values included 1%, 2.5%, 4%, 6%, 7.5%, and 10%; GSD values were 2.5, 3.9, and 6.6; and sample sizes were 6, 9, 12, 15, and 30. LOQ/OEL ratios ranged from 0 to 0.8. True compliance was defined as an EF below 5%. Following AIHA guidance, an accurate compliance decision required at least 70% certainty that no more than 5% of exposures exceeded the OEL. For each scenario, 5,000 datasets were generated. The rate of correct compliance decisions was calculated for conditions with no censoring (LOQ/OEL = 0) and increasing levels of censoring (LOQ/OEL = 0.01–0.8). This was repeated 3 times for accuracy. Performance change at each LOQ/OEL level was calculated relative to the reference scenario with no censoring.
Results / Conclusions:
Performance loss was most pronounced for scenarios with EF values of 6% or higher across all GSDs and sample sizes. In these scenarios, performance loss increased substantially when the LOQ/OEL ratio exceeded 0.5, whereas ratios of 0.1 or less resulted in minimal change. For EF 6% or greater and GSDs of 3.9 and 6.6, performance loss ranged from approximately 5% at an LOQ/OEL ratio of 0.2 to nearly 25% at 0.8, with larger decreases observed at smaller sample sizes. For EF values of 4% or less, performance change varied by sample size and GSD and did not consistently decline with increasing LOQ/OEL ratio. Instead, both increases and decreases in the proportion of correct compliance decisions were observed relative to the ideal, uncensored scenario. The largest changes occurred when the LOQ/OEL ratio exceeded 0.5, ranging from about 2% to over 20%. In most scenarios with EF 4% or less, performance change remained below 5% when the LOQ/OEL ratio was 0.1 or less.
These results demonstrate that increasing LOQ/OEL ratios can affect industrial hygienist's ability to accurately make exposure compliance decisions especially when exceedance fractions and GSDs are high and sample sizes are small. When the LOQ/OEL ratio is 0.1 or less, performance change is minimal even with small sample sizes. As LOQ/OEL ratios increase, larger sample sizes may be required to reliably determine true exposure compliance.
Core Competencies:
Exposure Assessment
Secondary Core Competencies:
Chemical Sampling and Instrumental Analysis
Risk 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.
Exposure Assessment
Hazard communication
Regulatory Compliance
Risk assessment and management
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 study aims to provide insight into how industrial hygienists can improve the accuracy of compliance decisions based on the data they are able to collect in real-world settings.
Have you presented this information before?
No
I have read and agree to these guidelines.
Yes