Ambulatory measurement of ambient carbon monoxide levels

Measurement of air pollutant levels in the environment is traditionally performed using monitors in fixed locations so that changes over time can be directly compared. Such measurements do not necessarily correlate with the level of exposure to the individual because of distance to the monitoring site and other factors. In the case of carbon monoxide (CO), portable personal monitors are available for industrial use, some of which do not just alarm, but also record measured values.

First, it was the purpose of this study to test the feasibility of continuously measuring ambient CO levels in an ambulatory fashion. The second objective was to compare measurements made in a country with significant air pollution to one without to determine the degree to which differences might be observed.

Ambient CO levels were measured and recorded every 10 minutes during 13 days of travel in Vietnam. A parallel study was performed in the United States for comnarison.

Continuous ambient CO levels at an individual level were successfully measured and recorded. Mean ambient CO level throughout Vietnam was 3.5 ± 4.4 ppm, as compared to 0.9 ± 0.8 ppm in the U.S. (p < 0.001). In Vietnam, 36 CO measurements (2% of total) were 15 ppm or greater vs. none in the U.S. Higher mean levels, as well as number and magnitude of peaks, were highly associated with proximity to traffic.

Personal exposures to CO can be measured easily over time and may be more relevant to the individual with underlying disease than data from fixed monitoring stations. Such information may prove useful to potential travelers. Additionally, governmental agencies may find ambulatory measurement to be complimentary to data from fixed monitoring stations when attempting to estimate how traditionally collected data relate to exposure of the individual. The technique could also be used for evaluation of vague complaints suggestive of intermittent CO exposure in the home or workplace.