Evaluation of the Predictive Abilities of a Qualitative Exposure Assessment Model

Abstract

Various qualitative exposure assessment models based on different underlying assumptions requiring distinct inputs and providing diverse outputs are used by occupational hygienists and risk managers to evaluate the magnitude of occupational exposures. Although a wide variety of exposure assessment models are available, most models have not been validated. This study compared the inhalation risk factor of a qualitative exposure assessment model with quantitative exposure data collected at a manufacturing facility for more than 9 years for 12 worker groups involving 24 chemical agents. A Spearman's rho correlation found no significant correlation between the model's risk factor and the maximum measured exposure (rs=0.119, p=0.496). A Fisher exact test found that the maximum measured exposure was independent of the model's inhalation risk factor (chi2=0.203, p=0.653). The model accurately classified measured exposures in 18 out of 35 cases (51%), 53% of the measured exposures classified as acceptable were correctly classified by the model (sensitivity), whereas 33% of the measured exposures classified as uncertain/unacceptable were correctly classified by the model (specificity). There was a 67% probability that the model would result in a false low classification and a 47% probability that the model would result in a false high classification. Although the model was simple to apply, the overall predictive ability for the low level exposures seen in the study were poor and inconsistent among worker groups compared.

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“…Constrained by limited budgets, time, and resources, the feasibility of quantitatively evaluating all exposures for every employee is unlikely. As a result, a qualitative assessment is often the first and sometimes only attempt at exposure assessment by some employers (Elliot et al 2007).…”

“…Modeling software is another method used to qualitatively evaluate the potential for worker exposure. The QLEA software model was developed to evaluate the risk of exposure from inhalation, dermal and ingestion routes (Elliot, et al 2007). Modeling software uses parameters such as monitoring results of other agents, previous exposure monitoring for the same agent used at other processes or statistical models that include parameters thought to affect the exposure concentrations.…”

“…The objective of modeling is to classify the exposures into categories that are based on the frequency and duration of the chemical usage, the toxicity of the chemical, and the exposure reduction controls. Computer models of estimated parameters are attractive due to ease of use and favorable cost structure over a quantitative assessment (Elliot et al 2007). The cost of collecting personal exposure samples and the associated laboratory analysis fees are eliminated, and the lack of direct monitoring is far less disruptive to production.…”

“…The cost of collecting personal exposure samples and the associated laboratory analysis fees are eliminated, and the lack of direct monitoring is far less disruptive to production. But qualitative methods are less accurate and leave the potential for employees to be exposed to hazardous chemicals and noise levels (Elliot et al 2007). The inhalation risk factor of a qualitative exposure assessment model was compared with quantitative exposure data for 24 chemical agents from a manufacturing facility.…”

“…The inhalation risk factor of a qualitative exposure assessment model was compared with quantitative exposure data for 24 chemical agents from a manufacturing facility. The model accurately classified measured exposures in only 51 % of the cases with an overall probability of 47% for overestimating exposure (Elliot et al 2007).…”