Ability of Fixed Monitoring Stations to Represent Personal Carbon Monoxide Exposure

Abstract

This study investigates the ability of fixed location ambient air quality monitoring stations to represent personal environmental exposures to carbon monoxide (CO) accurately. The relationship between residential location, commuting transportation mode, employment location, and time-weighted average human exposure to CO in the metropolitan area was also explored. Personal exposure was measured by equipping 66 nonsmoking volunteers in the Boston area with portable CO samplers which employ an electrochemical sensing method. Measurements at six fixed monitoring stations operated by the Massachusetts Bureau of Air Quality control underestimated mean 1 hour personal exposure by a factor of 1.3 to 2.1. However, alveolar air samples showed no significant increase in blood carboxyhemo-globin (COHb) levels due to commuting exposure since only 1 % of thé commuting exposures approached the national ambient air quality standard (NAAQS) of 35 ppm for 1 hour. The underestimation of personal exposure by fixed stations is of public health concern in those cities where violations of the 1 hour NAAQS have been reported. Fixed location measurements were representative of 8 hour average population exposure.

Mode and route of travel were the only factors influencing commuting exposure to CO. Total travel by automobile resulted in a mean CO exposure nearly twice that of rail mass transit and approximately 1.6 times that of split mode commuting. These results indicate that the most effective strategies for reducing both 1 hour and 8 hour exposures to CO are those requiring automobile emission control, system traffic flow improvement, and those designed to decrease traffic volumes.