An Assessment of Traffic-Related Nitrogen Dioxide Exposure and Asthma Medication Use at Early Childhood Centres in Auckland

Abstract

In New Zealand there are no restrictions in terms of the siting of early childhood centres (ECCs) in relation to proximity to roads. For this reason, and the perceived need for such businesses to be “visible”, many ECCs are located in close proximity to busy roads, potentially exposing children to elevated levels of traffic-related pollution. Exposure to traffic pollution is known to have adverse effects on human health, especially for those with existing respiratory conditions including asthma. Despite the high levels of asthma in New Zealand compared to other OECD countries, little work has been done in New Zealand specifically relating asthma with exposure to road traffic. The purpose of this study was firstly to compare the air pollution levels in Auckland (both indoors and outdoors) at ECCs located alongside quiet roads (quiet ECCs) to ECCs located alongside busy roads (busy ECCs) through the measurement of nitrogen dioxide (NO2) and to develop a simple model for predicting NO2 concentration based on traffic flow rates and proximity to the road. Secondly, the purpose was to see if there was a difference in the rate at which asthma medication was used by children diagnosed with asthma who attend busy ECCs compared to quiet ECCs. Ten busy ECCs were selected which had an average daily traffic flow rate in excess of 13,000 vehicles per day and an outdoor play areas near as possible to 15 metres or less from the road. Eleven quiet ECCs were selected which had an average daily traffic flow rate of less than 3,000 vehicles per day. NO2 passive diffusion tubes (tubes) were deployed in pairs at each of the ECCs: two in the indoor classroom, two in the outdoor play area, two at the near side of the road and two at the far side of the road. In total, six deployments were made of approximately two-three weeks each from 20 July to 4 November 2011. The tubes were analysed according to standard procedures. The results of the NO2 measurements indicated a significantly higher mean concentration at busy ECCs (25.9 ± 4.1)μg/m3 compared to quiet ECCs (17.5 ± 1.7)μg/m3. The mean NO2 concentration at quiet ECCs for indoor classrooms was found to be (13.7 ± 2.1)μg/m3 compared to outdoor play areas at (17.4± 2.6)μg/m3. The mean NO2 concentration at busy ECCs for indoor classrooms was found to be (20.3 ± 4.3)μg/m3 compared to (24.2 ± 5.9)μg/m3 for outdoor play areas with the outdoor play area NO2 concentration significantly higher than the indoor classroom NO2 concentration. The mean NO2 concentration decreased significantly between periods from winter to spring, consistent with seasonal trends from winter to spring for NO2 generally observed at fixed monitoring stations around the Auckland region. From the data gathered, it was possible to model NO2 concentration to provide estimates of indoor classroom and outdoor play area NO2 concentration for a given traffic flow rate and distance from the road from the mid-winter to mid-spring period. While based on a limited amount of data, the model provides a simple methodology for estimating the expected NO2 concentration for the purpose of regulating the introduction of new ECCs in relation to proximity to busy roads. While the diffusion tubes were deployed, ECCs were asked to record the number of children attending the ECC who had been diagnosed with asthma and who brought asthma medication to the ECC. In addition, ECCs were asked to record the number of times asthma medication was used for each child. In the study sample, 6.8 per cent of children attending the ECCs were asthmatics who brought asthma medication to school. Of the asthmatic children, the number who used their asthma medication at their ECC was significantly higher for those attending busy ECCs compared with those attending quiet ECCs. While the sample size is small, this suggests that the proximity of an ECC to a busy road results in the exacerbation of asthma for those diagnosed with the condition.