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

Abstract

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 .

Understanding the Spatial Heterogeneity of Indoor OH and HO2 due to Photolysis of HONO Using Computational Fluid Dynamics Simulation

“…Based on a chamber study that measured concentrations of HONO, NO, and NO 2 due to a gas stove, emission rates were set to result in steady-state indoor concentrations of HONO at 10 ppb, NO at 180 ppb, and NO 2 at 35 ppb without any photochemical reactions. These concentrations are comparable to other measurement studies, showing 3–20 ppb for HONO, 40–300 ppb for NO, and 20–550 ppb for NO 2 . − The room average concentration of CO was 1 ppm . In parallel, constant surface emissions of TVOC from walls, floors, and ceiling were simulated according to the measurement studies , that assessed concentrations of 91 different VOCs in residential buildings, and emission rates were inputted in the model so that the resulting TVOC concentration was 100 ppb without any reactions at an air change rate of 1 h –1 .…”

Loss of NO(g) to painted surfaces and its re‐emission with indoor illumination

“…Peak indoor NO(g) concentrations are between tens to hundreds of ppbv. 6,11 During periods of activity such as cooking, NO(g) concentrations increase; for example, in a study in a New York residence, an increase in background concentration by two orders of magnitude was observed. 8 It is likely that NO will undergo a number of transformations indoors such as uptake to surfaces, reaction with other gaseous species, and heterogeneous reactions on surfaces, given the complexity of the indoor environment.…”

“…It is present indoors from combustion activities such as cooking, wood‐burning fires, candles and cigarette smoke, 8‐10 and ventilation and infiltration of outdoor air. Peak indoor NO(g) concentrations are between tens to hundreds of ppbv 6,11 . During periods of activity such as cooking, NO(g) concentrations increase; for example, in a study in a New York residence, an increase in background concentration by two orders of magnitude was observed 8 .…”

Black Carbon and Particulate Matter Concentrations in Eastern Mediterranean Urban Conditions: An Assessment Based on Integrated Stationary and Mobile Observations

“…In practice, the mobile laboratory setup has become less expensive, more compact, more widespread, and follows advances in air quality instrument technology and development of low-cost portable instruments. For example, the mobile laboratory concept was adopted in light-weight airplanes, passenger cars, on bikes, on baby strollers, and even inside backpacks [23][24][25][26][27][28][29][30]. Setups have become even more affordable and compact after introducing low-cost sensors, advanced data management, novel modelling tools, and fast communication networks [31].…”