Predicting Personal Nitrogen Dioxide Exposure in an Elderly Population: Integrating Residential Indoor and Outdoor Measurements, Fixed-Site Ambient Pollution Concentrations, Modeled Pollutant Levels, and Time–Activity Patterns

Abstract

Predicting chronic exposure to air pollution at the intra-urban scale has been recognized as a priority area of research for environmental epidemiology. Exposure assessment models attempt to predict and proxy for individuals' personal exposure to ambient air pollution, and there are no studies to date that explicitly attempt to compare and cross-validate personal exposure concentrations with pollutants modeled at the intra-urban level using methods such as interpolated surfaces and land-use regression (LUR) models. This study aimed to identify how well personal exposure to NO(2) (nitrogen dioxide) can be predicted from ambient exposure measurements and intra-urban exposure estimates using LUR and what other factors contribute to predicting variations in personal exposure beyond measured pollutant levels within home. Personal, indoor and outdoor NO(2) were measured in a population of older adults (>65 yr old) living in Hamilton, Canada. Our results show that personal NO(2) was most strongly associated with contemporaneously collected indoor and outdoor concentrations of NO(2). Predicted NO(2) exposures from intra-urban LUR models were not associated with personal NO(2), whereas interpolated surfaces of particulates and ozone were modestly associated. Combinations of variables that best predicted personal NO(2) variability were derived from time-activity diaries, interpolated surfaces of ambient particulate pollutants, and a city wide temporally matched average of NO(2). The nonsignificant associations between personal NO(2) and the modeled ambient NO(2) concentrations suggest that observed associations between NO(2) generated by LUR models and health effects are probably not produced by NO(2), but by other pollutants that follow a similar spatial pattern.

A study on modeling nitrogen dioxide concentrations using land-use regression and conventionally used exposure assessment methods

“…In previous studies examining the difference in effect estimates by multiple exposure assessment methods, similar results have been observed (Hannam et al 2013, Montagne et al 2013, Meng et al 2015. However, a previous study in Canada reported that indoor and outdoor NO 2 showed high correlation with personal exposure, while LUR-modeled NO 2 did not, despite its high correlation with outdoor traffic-related exposure (Sahsuvaroglu et al 2009). Therefore, further studies comparing the validity and exposure estimates by multiple exposure assessment methods need to be conducted as no consensus on the comparability of exposure assessment methods exists.…”

“…Taking temporality into LUR models is another challenge, and multiple methods are being explored (Slama et al 2007, Mölter et al 2010, Wang et al 2013, Johnson et al 2013, Dons et al 2014, Liu et al 2015. Also, further improvement is needed in applying the outdoor air quality generated by LUR models to predict personal exposure (Sahsuvaroglu et al 2009).…”

Integrating smart-phone based momentary location tracking with fixed site air quality monitoring for personal exposure assessment

“…Some previous studies reported that personal exposures were poorly predicted by community monitors (Adams et al, 2009) or LUR-based predictions at home (Sahsuvaroglu et al, 2009). This could be because the studies employed the method of time-averaged, filterbased sampling, where a sample was collected (integrated) over a certain time period (e.g., two-weeks) (Sahsuvaroglu et al, 2009).…”

“…This could be because the studies employed the method of time-averaged, filterbased sampling, where a sample was collected (integrated) over a certain time period (e.g., two-weeks) (Sahsuvaroglu et al, 2009). Timeaveraged sampling may obscure relationships between spatial location and exposure.…”

Association between unemployment, income, education level, population size and air pollution in Czech cities: Evidence for environmental inequality? A pilot national scale analysis

“…It is obvious that using surrogates to estimate actual human exposures can be highly inaccurate and can introduce a great deal of uncertainty. However, environmental justice studies assessing actual human exposure to air pollutants by means of personal monitoring are scarce and are usually based on few or lower tens of individuals in 1 city (Perlin et al, 1995;Sexton et al, 2000;Payne-Sturges et al, 2004;Sahsuvaroglu et al, 2009).…”