Impact of Nitrogen Dioxide on Health with Particular Emphasis on Vulnerable Groups

Abstract

Nitrogen dioxide (NO2) is a highly reactive gas and is primarily produced by the burning of fuel. It forms from emissions from cars, trucks and buses and power plants. Exposure to NO2 has been associated with adverse effects on hospital admissions for various diagnoses; decrements in measures of lung function; increases in respiratory symptoms, asthma incidence, adverse birth outcomes and mortality. In terms of outdoor ambient air quality, the main source of NO2 in Ireland is road transport. The objectives of the project were as follows: 1. Use currently available air pollution measurements, and recent research results on the influence of meteorological and source parameters (including transport vehicle characteristics and population mobility demands), to identify a set of characteristics for the locations in Ireland that are at most risk of experiencing high levels of NO2. 2. Use the Health Service Executive Primary Care Reimbursement Service (HSE-PCRS) prescribing database to establish baseline data linking NO2 levels with the prescription of drugs used to treat asthma and chronic obstructive airways disease. 3. Explore the Growing Up in Ireland (GUI) and the Irish Longitudinal Study on Ageing (TILDA) databases to investigate if relationships between the prevalence of respiratory symptoms in vulnerable groups and NO2 levels exist, within database constraints (TILDA, 2018). 4. Review policies and strategies being implemented by other countries to bring NO2 within compliance levels and identify a set of effective and efficient solutions to reduce and mitigate the impact of the transport sector on NO2 levels in Ireland, given this sector’s predominance in the output of NO2 emissions (EPA, 2019). To deliver on the project’s objectives, a range of different models and methods were required. In the case of objectives 1 and 4, an existing land use regression model was enhanced to include data describing the national distribution of vehicle characteristics, including vehicle fleet breakdown, Euro classifications and fuel types. To meet the requirements of objective 2, HSE-PCRS and NO2 data were used to link NO2 levels with the prescription of drugs used to treat asthma and chronic obstructive airways disease. Objective 3 involved the exploration of existing health databases to investigate if relationships between the prevalence of respiratory symptoms in vulnerable groups and NO2 levels exist, within database constraints. Relevant data from the TILDA database were used with modelled levels of NO2 to investigate the links between NO2 and asthma prevalence. The findings from the HSE-PCRS prescribing rate analysis suggest that, for most of the outcomes investigated, there was no association between the levels of NO2 and the prescribing rates. Although the focus of the project was on NO2, the team had the opportunity to consider particulate matter consisting of particles with diameter of 2.5 μm or less (PM2.5), in addition to NO2. PM2.5 can cause serious health problems. In most regions, there was an association between PM2.5 and the prescribing rate, taking account of the impact of winter on dispensing. This was most pronounced with oral steroids and especially in the subgroup analyses undertaken in the 0–4 years age group. The results from the TILDA analysis suggest that a 1 part per billion (ppb) increase in NO2 concentration is associated with a 0.24 percentage point increase in the probability of reporting an asthma diagnosis for those exposed to levels of < 13.1 ppb. In addition, a 1 ppb increase in NO2 concentration was associated with a 0.26 percentage point increase in the probability of requiring medication for asthma. The magnitude of association is large for both models. The enhanced wind sector land use regression model was successfully employed to assess the impact of a number of mitigation strategies on NO2 levels: (1) relocating businesses from a congested area with significant air pollution; (2) replacing diesel vehicles with electric vehicles in the public service vehicle leet; (3) introducing a low-emission zone (LEZ) in Dublin; and (4) introducing a city bypass/ring road. In absolute concentration reduction terms, none of the investigated strategies was indicated as being more successful than the others, with maximum improvements in annual average NO2 concentrations of approximately 2 μg/m3 being predicted in each case. Greater reductions in concentration could be achieved by implementing multiple strategies together.