May 21, 2024

How Models Improve Exposure Judgments

By Ed Rutkowski

The limitations of professional judgment in occupational and environmental health and safety have been well established, but many OEHS professionals still resist using modeling tools that could significantly improve the accuracy of their professional judgments. A presentation delivered by Brent Altemose, PhD, CIH, CSP, yesterday at AIHA Connect 2024 offered some explanations for the limited uptake of modeling in the profession and presented brief case studies of instances where Altemose had used modeling in his consulting practice.

A member of AIHA's Improving Exposure Judgments Advisory Group, Altemose began his presentation with references to a 2016 paper in the Journal of Occupational and Environmental Hygiene that showed how training OEHS professionals on the use of a simple checklist tool could significantly improve the accuracy of their professional judgments. Such a tool, Altemose said, forces its users to think about the factors that affect an exposure rather than simply producing a judgment based on a gut feeling.

Those gut feelings, research has shown, are often biased low, which means that they underestimate exposures and put workers at risk. But overestimating exposures is also problematic because it could impose unwarranted constraints on an operation, cause workers to use unnecessary personal protective equipment, or even result in gratuitous—and very expensive—implementations of ventilation. Tools that aid judgment force OEHS professionals to be more rigorous in their exposure assessments.

"What we want to see is a shift to a more structured approach," Altemose said.

If structured approaches offer significant benefits, why aren't they used more often? One reason, Altemose said, is that clients sometimes require quick turnarounds. OEHS professionals who are given only one day to build a sampling strategy don't have time to model exposures and will be forced to rely on their professional judgment. But more often, Altemose said, OEHS professionals resist modeling because they are overconfident or believe modeling is too complicated. "We tend to believe that our in-depth knowledge is going to make us better at qualitative judgments than we really are,” Altemose said.

The case studies Altemose presented demonstrated how relatively simple models could suit many purposes in OEHS. Models can be used as an early warning system for potentially problematic exposures or to direct attention away from trivial exposures. They can allow prospective and retrospective exposure estimates. And they can help OEHS professionals focus on the predictors of exposures.

In one case study, Altemose described how he used modeling to predict exposures to respirable crystalline silica (RCS) from a consumer wood filler product. The product contained 0.6 percent silica, and some of the silica could become aerosolized when sanded. Consumers would use the product in residences with varying air exchange rates and without engineering controls. Altemose walked his audience through the application of the "one-box model" to this scenario, showing how the model's calculations determined that even the highest potential exposures to RCS from the use of the product were at safe levels. As a result of this analysis, the state of California issued a Safe Use Determination for the product, Altemose said.

A second case study concerned the potential for an ammonia leak at a power generation facility. The facility had never experienced such a leak, and engineers discounted the possibility that, if one occurred, it would result in a flammable atmosphere. Through application of the "two-zone model," Altemose showed that an hour-long ammonia leak would not only cause a flammable atmosphere but also that concentrations would create immediately dangerous to life and health (IDLH) conditions at a significant distance from the source of the leak.

Altemose pointed attendees to several resources for improving their modeling skills, including the AIHA publications Mathematical Models for Estimating Occupational Exposure to Chemicals and A Case-Based Introduction to Modeling Occupational Inhalation Exposures to Chemicals. A series of papers on modeling published in JOEH are listed below. Other modeling resources include the free tools IHMOD and IHSkinPerm, available from the AIHA website.

Ed Rutkowski is editor in chief of The Synergist.

Read more coverage of AIHA Connect 2024.

For Further Reading

AIHA: A Strategy for Assessing and Managing Occupational Exposures, Chapter 6, "Approaches to Improving Professional Judgment Accuracy," 4th ed. (2015).

Annals of Occupational Hygiene: "Occupational Exposure Decisions: Can Limited Data Interpretation Training Help Improve Accuracy?" (April 2009).

Journal of Occupational and Environmental Hygiene: "Effect of Training on Exposure Judgment Accuracy of Industrial Hygienists" (April 2012).

Journal of Occupational and Environmental Hygiene: "Using Checklists and Algorithms to Improve Qualitative Exposure Judgment Accuracy" (March 2016).

The Synergist: "Faulty Judgment" (November 2021).

The Synergist: "Filling the Gaps: Survey Clarifies Needs for Improvement in Exposure Assessment" (January 2024).

The Synergist: "How to Improve Exposure Judgments" (December 2021).

The Synergist: "Judgment Day: How Accurate Are Industrial Hygienists' Qualitative Exposure Assessments?" (January 2014).