Use of a work sampling method (TVEA) to characterize determinants of particulate exposure in heavy and highway construction

Particulate exposures undoubtedly play a key role in the higher rates of respiratory disease experienced by construction workers. In spite of this, the difficulties of exposure assessment in construction have contributed to a gap in understanding of the factors that influence air contaminant concentration during construction work. The overall objective of this dissertation was to identify and describe potential determinants of exposure to respirable quartz in a population of heavy and highway construction workers. The first paper describes a work sampling based approach to exposure assessment. Time Variant Exposure Analysis (TVEA) is used to systematically survey over 30 potential exposure determinants that could affect exposure to three types of particulate. Two field studies were conducted to address questions of inter-rater reliability (n = 20) and coding interval appropriateness (n = 21) for the TVEA method. Substantial inter-rater agreement was obtained for most of the TVEA determinants. Regression statistics indicated that while 30 min is an acceptable interval between observations for exposure assessment, 15 min optimizes precision and practicality. The objective of the second paper was to describe potential respirable quartz exposure during heavy and highway construction work. Processes with the potential for concrete exposure occurred for every operation (n > 4), ranging from specialized foundation work (2% of workers) to demolition where 100% of workers were observed. Results indicated that the potential exists for bystander exposures for trades not associated with concrete work as 27% of these workers were in presence of concrete processes as a bystander a median 28% of the workday. The objective of the third paper was to quantify the relationship between specific exposure determinants and respirable quartz levels. When the percent of the workday spent performing concrete work was greater than 50% more than half of the laborers had exposures greater than the NIOSH REL of 0.50 mg/m 3. The two multiple regression models developed were able to explain 50% (categorical model) and 60% (tool/machine model) of the variance in quartz exposure levels. In both models, type of enclosure (complete or partial) and environmental factors (temperature and relative humidity) were significant, highlighting the importance of considering the construction environment during exposure assessment.