Background: Measured or modeled levels of outdoor air pollution are being used as proxies for individual exposurein a growing number of epidemiological studies. We studied the accuracy of such approaches, in comparison withmeasured individual levels, and also combined modeled levels for each subject’s workplace with the levels at theirresidence to investigate the influence of living and working in different places on individual exposure levels.
Methods: A GIS-based dispersion model and an emissions database were used to model concentrations of NO2atthe subject’s residence. Modeled levels were then compared with measured levels of NO2. Personal exposure wasalso modeled based on levels of NO2at the subject’s residence in combination with levels of NO2at theirworkplace during working hours.
Results: There was a good agreement between measured façade levels and modeled residential NO2levels (rs = 0.8,p > 0.001); however, the agreement between measured and modeled outdoor levels and measured personalexposure was poor with overestimations at low levels and underestimation at high levels (rs = 0.5, p > 0.001 andrs = 0.4, p > 0.001) even when compensating for workplace location (rs = 0.4, p > 0.001).
Conclusion: Modeling residential levels of NO2 proved to be a useful method of estimating façade concentrations.However, the agreement between outdoor levels (both modeled and measured) and personal exposure was,although significant, rather poor even when compensating for workplace location. These results indicate thatpersonal exposure cannot be fully approximated by outdoor levels and that differences in personal activity patternsor household characteristics should be carefully considered when conducting exposure studies. This is an importantfinding that may help to correct substantial bias in epidemiological studies.
BioMed Central, 2012. Vol. 10, no 10