Application of the Microenvironment Monitoring Approach to Assess Human Exposure to Carbon Monoxide

This study applies the microenvironment monitoring (MEM) approach to estimate human exposure to carbon monoxide (CO), using activity time data from the Washington Urban Scale Study and CO concentration data from the CO Microenvironment Study. The estimated exposures based on the MEM approach are then compared with estimated exposures based on the personal monitoring or direct approach (the PM exposures). A substantial discrepancy appears between these exposures, the MEM exposures being about 40 percent higher. However, despite the discrepancy, the MEM exposure is found to be a powerful predictor for the PM exposure. On the log scale, the MEM exposure has the correct span relative to the PM exposure; the discrepancy between the two sets of exposure estimates is found to be a constant drift. The results reported here should be considered as an illustration and should be generalized only with caution to future exposure studies, which should give higher priority to the enhanced personal monitoring (EPM) approach when feasible. When the MEM approach is the only feasible approach, the sampling of microenvironments should be carried out using either the weighted sampling scheme or the simulated human activity scheme.