Traffic-Related Air Pollution and Childhood Asthma: Recent Advances and Remaining Gaps in the Exposure Assessment Methods

Abstract

Background: Current levels of traffic-related air pollution (TRAP) are associated with the development of childhood asthma, although some inconsistencies and heterogeneity remain. An important part of the uncertainty in studies of TRAP-associated asthma originates from uncertainties in the TRAP exposure assessment and assignment methods. In this work, we aim to systematically review the exposure assessment methods used in the epidemiology of TRAP and childhood asthma, highlight recent advances, remaining research gaps and make suggestions for further research. Methods: We systematically reviewed epidemiological studies published up until 8 September 2016 and available in Embase, Ovid MEDLINE (R), and “Transport database”. We included studies which examined the association between children’s exposure to TRAP metrics and their risk of “asthma” incidence or lifetime prevalence, from birth to the age of 18 years old. Results: We found 42 studies which examined the associations between TRAP and subsequent childhood asthma incidence or lifetime prevalence, published since 1999. Land-use regression modelling was the most commonly used method and nitrogen dioxide (NO2) was the most commonly used pollutant in the exposure assessments. Most studies estimated TRAP exposure at the residential address and only a few considered the participants’ mobility. TRAP exposure was mostly assessed at the birth year and only a few studies considered different and/or multiple exposure time windows. We recommend that further work is needed including e.g., the use of new exposure metrics such as the composition of particulate matter, oxidative potential and ultra-fine particles, improved modelling e.g., by combining different exposure assessment models, including mobility of the participants, and systematically investigating different exposure time windows. Conclusions: Although our previous meta-analysis found statistically significant associations for various TRAP exposures and subsequent childhood asthma, further refinement of the exposure assessment may improve the risk estimates, and shed light on critical exposure time windows, putative agents, underlying mechanisms and drivers of heterogeneity.

Investigation on Indoor Air Pollution and Childhood Allergies in Households in Six Chinese Cities by Subjective Survey and Field Measurements

“…A growing number of studies suggest that dwelling environment, lifestyles and indoor air pollution contribute to the development of allergic disease [ 10 ]. Recent meta-analysis [ 11 , 12 ] concluded that living or attending schools near high traffic density roads with higher levels of motor vehicle air pollutants increased the incidence and prevalence of childhood asthma. Sun et al [ 13 ] declared that the lifestyle and home environment exposure undergone by children between 1–8 years are important asthma and allergy risk factors in Northeast Texas.…”

A Preliminary Spatial Analysis of the Association of Asthma and Traffic-Related Air Pollution in the Metropolitan Area of Calgary, Canada

“…Ambient air pollutants, including NO 2 , PM 2.5 , PM 10 , BC, and BTEX, have been shown to exacerbate asthma [6][7][8][9]16,19,20,22,23,25,51,52]. Although Calgary has relatively good air quality [39], this study shows that significant correlations exist between ambient pollutants and AEVRs, though there is seasonal variation.…”

“…Traffic-related air pollutants (TRAP), notably nitrogen dioxide (NO 2 ) and particulate matter with a diameter less than 2.5 micrometers (PM 2.5 ), have been widely researched and are known to both exacerbate asthma and lead to decreased lung function, increased risk of asthma onset, and increased asthma-related hospitalizations [8,9,[16][17][18][19][20][21]. Many studies have noted that consistent exposure to elevated levels of NO 2 and PM 2.5 can decrease lung function and lead to asthmatic symptoms such as wheezing through airway inflammation and oxidative stress [21][22][23].…”

“…While many studies analyze the effects of proximity to common TRAPs, such as NO 2 and PM 2.5 [20], fewer focus on the seasonal effects of other ambient air pollutants, especially PM 10 , BTEX, and BC [17,30,31]. Moreover, many studies identify the proximity to TRAP in relation to home residence, whereas individuals tend to spend time outside their residence; for example, most children spend a large amount of time at school and/or daycare, as well as outside on, or close to, school grounds [20]. Because people are exposed to air pollution beyond their residential environment, it is important to assess the possible associations between asthma exacerbation and the spatial pattern of ambient air pollutants.…”

Is a Land Use Regression Model Capable of Predicting the Cleanest Route to School?

“…For instance, Hankey S et al 2016 [21] combined facility-demand and LUR models to highlight exposure patterns during active travel suggesting that it should be possible to reduce exposure by~15% after intervening on the given scenario. Recently, several studies confirmed that the health benefits linked to active travel outweigh the risks such as exposure to air pollution or accidents, suggesting that the attempt to build more walkable and bikeable urban environments is worth the effort [22][23][24].…”