New Zealand has some of the best air quality in the world. Even so, air pollution is still a silent killer there, accounting for more than 2,300 premature deaths every year. Media reports indicate that air pollution is an issue for many cities and towns in New Zealand, especially during the winter months. To what extent air pollution in New Zealand in winter remains unclear, especially for people in other countries.
In a previous post, I 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 better understand seasonal variances of air pollution in New Zealand.
Unlike in the countries in the Northern Hemisphere, New Zealand’s winter season includes June, July, and August. According to the Real-Time Map of Air Pollution, moderate levels of air pollution (Air Quality Index > 50) covering 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 those observed in China and India in the present season.
According to the data on the Real-Time Map of Air Pollution, air pollution patterns were mainly evident in New Zealand between 8:00 a.m. and 17:00 p.m. UTC time. Converted to the local Wellington time, the patterns were evident mainly between 20:00 p.m. and 5:00 a.m. During the 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 the 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 home heating and transport are most likely to become a problem since they are less likely to be dispersed.
I have a question. What else makes outdoor air pollution 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 the main urban areas, the population density is 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 percent bigger than before 1990, even though some towns have recorded smaller median houses over recent years.
New Zealand’s experience may highlight the impact of human lifestyles on air pollution. To mitigate air pollution in New Zealand or other countries, measures against industrial activities and transportation vehicles may not be enough. In addition to renewable energy, humans’ lifestyles and behaviors should also be modified.
