Modeling construction worker chemical exposures for compliance with OSHA permissible exposure limits: An investigation of lead exposures to highway bridge maintenance workers

Air monitoring to determine chemical exposures to construction workers is rarely conducted. Several OSHA standards allow the use of modeled exposure data to be substituted for required air monitoring for some compliance purposes. This paper investigates the feasibility of constructing exposure models in the highly variable construction work environment. The research gathered data for West Virginia Department of Highways bridge maintenance worker' exposure to lead during bridge maintenance and inspection. Job and task based models were generated and compared. required respiratory protection levels are estimated through the models using several summary statistics. A simulation was conducted to determine if job sampling could provide adequate data for predicting exposures assuming one job observation per hour. Modeling in this work environment can generate predictive models of exposure whose high levels of variability can be accommodated by estimating exposures using an Upper Tolerance Limit1,.95. Integrated time weighted average sampling modeled with observations of time at task can generate estimates for individual task exposures. Job sampling was able to provide adequate data for model building. It is suggested that OSHA allow modeled predictions of exposures in construction under limited circumstances when such modeling would result in increased protection for workers. OSHA should adopt objective criteria for that modeling (UTL 1,.95.) Implementation of this modeling could be assisted by development of a web based expert system for exposure modeling and the development of task exposure data bases.