Variability in Quartz Exposure in the Construction Industry: Implications for Assessing Exposure-Response Relations

Abstract

The aims of this study were to determine implications of inter- and intraindividual variation in exposure to respirable (quartz) dust and of heterogeneity in dust characteristics for epidemiologic research in construction workers. Full-shift personal measurements (n = 67) from 34 construction workers were collected. The between-worker and day-to-day variances of quartz and respirable dust exposure were estimated using mixed models. Heterogeneity in dust characteristics was evaluated by electron microscopic analysis and electron spin resonance. A grouping strategy based on job title resulted in a 2- and 3.5-fold reduction in expected attenuation of a hypothetical exposure-response relation for respirable dust and quartz exposure, respectively, compared to an individual based approach. Material worked on explained most of the between-worker variance in respirable dust and quartz exposure. However, for risk assessment in epidemiology, grouping workers based on the materials they work on is not practical. Microscopic characterization of dust samples showed large quantities of aluminum silicates and large quantities of smaller particles, resulting in a D₅₀ between 1 and 2 μ m. For risk analysis, job title can be used to create exposure groups, although error is introduced by the heterogeneity of dust produced by different construction workers activities and by the nonuniformity of exposure groups. A grouping scheme based on materials worked on would be superior, for both exposure and risk assessment, but is not practical when assessing past exposure. In dust from construction sites, factors are present that are capable of influencing the toxicological potency.

Keywords:

• construction workers
• dust characteristics
• pneumoconiosis
• respirable dust
• quartz

ACKNOWLEDGMENTS

Arbouw, the Dutch national institute for safety and health in the construction industry in Amsterdam, partly funded the study. The authors acknowledge the construction workers who participated in the study, and their employers.

Notes

^A Number of measured workers.

^B Number of measurements.

^C Arithmetic mean.

^D Geometric mean.

^E Geometric standard deviation.

^A G = number of levels of fixed effects (determinants of exposure) in the model.

^B : restricted maximum likelihood estimates of the within- and between-worker variance components, respectively.

^C Relative to model with worker only.