Abstract:
Surface pollution is known to have both long‐term and short‐term consequences for human health. In Auckland, brown hazes appear above the city on some cool, calm mornings during winter. At the present time, it is unknown to what extent surface air pollution levels (to which people are exposed) are linked to the brown haze events that occur on the horizon. Furthermore, there has been limited research into acute health outcomes and air pollution concentrations in Auckland. Therefore, it remains unknown whether brown haze events (as a visual indicator of adverse air quality at the surface) are associated with health outcomes. This thesis addresses this issue. Part 1 of this thesis describes the relationship between surface‐level air pollution and the occurrence of brown haze above Auckland in winter using oxides of nitrogen (nitric oxide (NO) and nitrogen dioxide (NO2)) as the proxy. This is to establish whether there is indeed an association between the two. Part 2 investigates the associations between surface‐level pollutants and daily variations in cardiovascular and respiratory hospital admissions as measures of acute adverse health outcomes. Part 3 investigates associations between the occurrence of brown haze events (as a proxy for elevated air pollution levels at the surface) and daily variations in cardiovascular and respiratory hospital admissions. The surface air pollution data consist of daily averages of oxides of nitrogen (NO and NO2) concentration measurements from compliance air pollution monitoring stations operated by the Auckland Council. Meteorological data consists of temperatures, relative humidity, barometric pressure, wind direction and wind speeds obtained from the NIWA climate database. The haze data consist of a daily classification made based on a 10‐year photographic record provided by the Auckland Council. For investigating surface air pollution levels and brown haze, logistic regression models were constructed. Based on this analysis, it was found that low wind speeds coupled with cool temperatures are strongly associated with the occurrence of brown haze events, with nitric oxide (NO) the most strongly related surface‐level pollutant. For investigating air pollution levels and the occurrence of haze events with admissions to hospital, a time series analysis utilising generalised additive models was carried out; associations between daily variations in air pollution concentrations (nitrogen oxide, NO and nitrogen dioxide, NO2) and both cardiovascular and respiratory admissions to hospitals within the Auckland District Health Board were carried out. Analysis suggests that every 10μgm‐3 increase in NO2 concentrations is associated with a 1.29% (p=0.0094) increase in respiratory admissions for the general population and a 1.93% (p=0.0126) increase in cardiovascular admissions on the third lag day for the 65+ age group. The effects of NO2 are dependent on age with stronger effects seen in the young (0‐14 years) and in the elderly (65+ years). Less strong associations were found between NO and both cardiovascular and respiratory admissions. A further time series analysis was conducted to look for associations between brown haze events and hospital admissions. A brown haze event was found to be associated with a 5.54% (p=0.0157) increase in respiratory admissions on the fifth day following. Again, the results varied according to the age group being analysed. The 0‐19 year age group experienced a 7.03% (p=0.0467) increase in respiratory admissions on the day after a brown haze event while the 65+ age group showed an 11.45% (p=0.0232) increase in respiratory admissions 5 days following a brown haze event. Increases for cardiovascular admissions were observed on the third and fifth days following a brown haze event for the 65+ age group, with the largest increase being 8.51% (p=0.0357) on the 5th day. Brown haze events above Auckland are associated with elevated concentrations of air pollutants at the surface. NO2 (which is correlated with other surface pollutants) is associated with hospital admissions in Auckland. Brown haze is also associated with hospital admissions. The brown haze itself is unlikely to be the cause of increased hospital admissions as it is typically observed at 150‐350 m above the ground. However, it is suggested that the brown haze is indicative of very poor air quality at the surface and that surface air pollution is driving the associations seen between brown haze and hospital admissions. Therefore, brown haze events above Auckland provide an instant measure of the increased risk of adverse health outcomes due to poor air quality.