New Zealand is one of the countries with the best quality of air in the world. Even so, air pollution is still a silent killer there, which accounts for more than 2300 premature deaths every year. Media reports indicate that air pollution is an issue for many cities and towns in New Zealand, especially over the winter months. To what extent is air polluted in New Zealand in winter remains unclear, especially for people living in other countries.
In a previous post, I have documented air pollution in New Zealand in late autumn (May 2018). The present post aimed to do a brief overview of air pollution in New Zealand in the winter. Screenshots of the Real-Time Map of Air Pollution, hosted at the US-based non-profit Berkeley Earth website, were used to demonstrate the extent of air pollution. Such an effort may help to better understand seasonal variances of air pollution in New Zealand.
Unlike in the countries in the Northern Hemisphere, the winter season in New Zealand includes June, July and August. According to the Real-Time Map of Air Pollution, moderate levels of air pollution (Air Quality Index > 50) with a coverage of more than two-thirds of a nation’s land area were evident in New Zealand over 24 days per month in June and July 2018. The count was 16 days in May 2018 and only 5 days in April 2018.
Unhealthy levels of air pollution for sensitive groups (AQI > 100, marked red) were frequently evident in some areas. The highest values were recorded at Wellington on June 30, 2018, with a number of 184.9 for AQI and a value of 121.2 μg/m3 for PM2.5 density. During the winter months, it seemed that PM2.5 concentration fluctuated between 50 and 100 μg/m3 in some towns and cities. The levels of air pollution seemed to be comparable to that observed in China and India in the present season.
According to the data that were available on the Real-Time Map of Air Pollution, it seemed that the air pollution patterns were mainly evident in New Zealand between 8:00 a.m. and 17:00 p.m. in UTC time. Converted to the local Wellington time, the air pollution patterns were evident mainly between 20:00 p.m. and 5:00 a.m.. During daytime, air quality in New Zealand seemed to be acceptable, possibly due to strong winds that dispersed pollutants.
New Zealand has limited heavy industry and is distance from other sources of pollution. According to media reports, the primary cause of air pollution in winter in New Zealand is domestic use of wood or coal for keeping homes warm. A report suggests that 80 to 90 percent of the source of air pollutants in winter comes from home heating. Another major source of air pollutants is related to transport, especially in urban areas near busy roads. On still and cold days, pollutants emitted from both home heating and transport are most likely to become a problem, since they are less likely to be dispersed.
A question come to my mind. What else make outdoor air pollution to be a problem in winter in New Zealand where the population density is only 17.9 people per km2, ranked 203rd in the world? Even in main urban areas in New Zealand, the population density is some 523 people per km2, much lower than that in the urban areas in other countries.
It seems that house size may play a role. The larger the house size, the more wood or coal may be consumed and more air pollutants may be emitted. Over the past two decades, new houses have been getting steadily bigger in New Zealand. It has been reported that the median size of New Auckland houses increased from 194 m2 in the early 2000s to 221 m2 in the 2010s. On average, new houses in New Zealand are now almost 61 per cent bigger than they were before 1990, even though some towns have recorded smaller median houses over recent years.
New Zealand’s experience may highlight the impact of human’s lifestyle on air pollution. To mitigate air pollution either in New Zealand or in other countries, measures against industrial activities and transportation vehicles may not be enough. In addition to renewable energy, our human’s lifestyle and behaviors should also be modified.