Mobile Monitoring of Personal NOx Exposures during Scripted Daily Activities in Chicago, IL

10.4209/aaqr.2017.02.0063

Jiayao Xu；Han Jiang；Haoran Zhao；Brent Stephens

Nitrogen oxides ； Human exposure ； Personal exposure ； Mobile samplers ； Indoor air pollution

Aerosol and Air Quality Research

17卷8期（2017 / 08 / 01）

1999 - 2009

英文

Elevated ambient concentrations of nitrogen oxides (NO_x), including nitric oxide (NO) and nitrogen dioxide (NO_2), are associated with a wide range of adverse human health effects. Most studies have investigated these associations using ambient NO_2/NO_x measurements from fixed-site monitors or modeled ambient NO_2/NO_x concentrations. However, the majority of personal exposures to NO_2/NO_x occur in a variety of different microenvironments in which people spend most of their time. Previous studies have reported widely varying correlations between personal exposures and ambient NO_2/NO_x concentrations over various timescales. To add to the knowledge base of how personal NO/NO_2/NO_x exposures vary spatially, temporally, and within different microenvironments in an urban environment, we conducted roll-around mobile monitoring of NO/NO_2/NO_x with 1-minute resolution during 14 days of scripted activities in and around Chicago, IL. Activities involved time spent in three primary microenvironments: outdoors, indoors inside various building types, and in multiple modes of transportation including walking, personal vehicle, and public transit. Measurement were conducted at a higher time resolution than most prior microenvironmental monitoring studies using a recently developed direct UV absorbance NO/NO_2/NO_x monitor that is designed to minimize interferences that have been observed in some field campaigns using chemiluminescence monitors. The individual microenvironmental categories with the highest median NO_x concentrations included four indoor environments and a variety of public transit environments. The individual transportation microenvironments with the highest median NO_x concentrations were found aboard regional trains, largely driven by high NO from diesel locomotives. Correlations between microenvironmental NO/NO_2/NO_x measurements and simultaneous records from the nearest ambient monitor were extremely low, with coefficients of determination below 0.05 for each NO_x constituent. These data further illustrate the limitations of relying on ambient site regulatory monitors to characterize personal NO/NO_2/NO_x exposures and provide further evidence that personal monitoring is critical for accurately assessing personal exposure to NO_x.