Christchurch's Air Pollution: Why So Bad?

Christchurch, New Zealand, has a problem with air pollution, particularly during the winter months. The air quality in Christchurch is measured by the Air Quality Index (AQI), which includes PM2.5, PM10, NO2, SO2, CO, and O3 levels. The main sources of air pollution in Christchurch are wood or coal burners and open fires, which contribute to 80% of the city's winter air pollution. The inversion layer caused by the nearby hills traps smog and pollutants close to the ground, affecting the residents' health. This has led to serious respiratory and cardiac issues for thousands of people, especially those already at risk.

Wood/coal burners and open fires

The health risks associated with this type of air pollution are significant. Professor Kingham notes that the high levels of particulate pollution can cause serious respiratory and cardiac issues for people who are already at risk of respiratory illness. In fact, research indicates that this type of pollution is responsible for serious health problems for several thousand people in Christchurch each year.

The geographical features of Christchurch also play a role in trapping air pollution at ground level. The presence of surrounding hills can create a temperature inversion layer, where a layer of warm air traps a layer of cool air and pollution close to the ground. This prevents the pollution from rising into the atmosphere and dispersing, further contributing to the high levels of air pollution experienced by residents.

To address the issue of wood/coal burner and open fire pollution, the Canterbury Air Regional Plan aims to meet national air quality standards by managing pollution from home heating. The plan includes a target of no daily average PM2.5 concentrations greater than 25 micrograms per cubic metre of air by 2030. While PM10 particles are a significant issue in Christchurch, the plan focuses on reducing PM2.5 concentrations as they are the main contributor to PM10 exceedances in Canterbury airsheds.

Temperature inversion

During the day, the land heats up and creates a layer of warm air. As the sun sets, the temperature of the earth begins to drop, causing the air closest to the ground to cool down. In the presence of hills, the warm air is unable to rise and escape, resulting in a warmer layer of air above a cooler layer near the surface. This inversion layer prevents the mixing of the two air masses, leading to a buildup of pollutants in the lower atmosphere.

The inversion layer can last for an extended period, exacerbating the air pollution issue. While the problem intensifies during the evenings, the smog and its associated health hazards remain present the following morning. This phenomenon has led to Christchurch experiencing very high air pollution levels, particularly during the winter months.

To address the challenges posed by temperature inversion and improve air quality, it is crucial to implement effective strategies. These may include reducing the use of wood burners and open fires, which contribute significantly to particulate matter emissions, and exploring alternative heating methods that produce fewer pollutants. Additionally, the development and adoption of technologies that can mitigate or disrupt the inversion layer could be explored to enhance the dispersion of pollutants and improve the air quality in Christchurch.

Respiratory illness

Air pollution in Christchurch, New Zealand, is a major issue, with the city experiencing very high levels of particulate air pollution during the winter months. This pollution has a direct impact on human health, particularly for those who are vulnerable or already at risk of respiratory illness.

The primary source of Christchurch's winter air pollution is the burning of wood or coal for home heating, which accounts for 80% of the city's air pollution during this period. The remaining 20% is contributed by vehicles and industry, at 10% each. The use of older and less efficient fires for home heating results in the emission of dangerous fine particulate matter, specifically PM2.5 and PM10. These particles can form a choking, brown smog that blankets the city, trapping the pollution close to the ground and preventing its dispersal into the atmosphere.

The high levels of particulate air pollution in Christchurch have severe health implications for its residents. According to Professor Simon Kingham, this pollution is responsible for causing serious health problems for several thousand people each year, including respiratory and cardiac illnesses. The fine particulate matter, especially PM10, poses the greatest risk to individuals with pre-existing respiratory conditions. For up to 50 days each winter, the level of PM10 particles in Christchurch's air exceeds the guidelines set by the Ministry for the Environment. This prolonged exposure to elevated levels of PM10 can have detrimental effects on respiratory health, exacerbating existing conditions and increasing the risk of respiratory-related hospitalisations and even deaths.

The impact of air pollution on respiratory health is not limited to the winter months. Throughout the year, residents of Christchurch may be exposed to various gaseous pollutants, such as carbon monoxide, sulphur dioxide, and nitrogen dioxide. While these pollutants may not exceed the National Environmental Standards for Air Quality, prolonged or cumulative exposure can still have adverse effects on respiratory health. Individuals with asthma, chronic obstructive pulmonary disease (COPD), or other respiratory conditions may experience worsened symptoms or increased frequency of flare-ups due to the presence of these gaseous pollutants in the air they breathe.

To mitigate the impact of air pollution on respiratory health, it is crucial for individuals in Christchurch to take proactive measures. This includes staying informed about real-time air quality levels, particularly during the winter season. Additionally, the use of air purifiers in homes and the adoption of cleaner home heating methods, such as modern, efficient fires or alternative heating sources, can help reduce exposure to harmful pollutants. By being vigilant and taking appropriate actions, residents of Christchurch can minimise the risk of respiratory illnesses associated with air pollution and protect their respiratory health.

Cardiac illness

Christchurch, New Zealand, has high levels of particulate air pollution, which is linked to cardiac illness and death. The level of PM10 particles in the air in Christchurch often exceeds Ministry for the Environment guidelines, and research indicates that this pollution is responsible for serious health problems and premature deaths from cardiac illness.

Particulate matter in the air, or particle pollution, refers to a mixture of solid particles and liquid droplets. Some particles are large enough to be seen, such as dust, dirt, soot, or smoke. Others are tiny and invisible, and can be inhaled and penetrate deep into the cardiovascular system. These particles can come from construction sites, unpaved roads, fields, smokestacks, fires, power plants, factories, automobiles, and wildfire smoke. They can remain in the atmosphere for days to weeks and can influence the air quality of regions far from the original source.

Short- and long-term exposure to particle pollution has been linked to an increased risk of cardiovascular disease, particularly in people with existing heart conditions. Research has found that exposure to increased concentrations of PM2.5 (fine particulate matter with diameters less than 2.5 µm) over a few hours to weeks can trigger cardiovascular disease-related heart attacks and death. This is especially true for people with underlying cardiovascular conditions, such as ischemic heart disease or heart failure, or those who have previously experienced cardiovascular events such as myocardial infarction or stroke.

The impact of particle pollution on cardiac health includes effects on heart rhythm, blood clotting, the build-up of plaques in arteries, and blood pressure. For example, exposure to particulate matter has been linked to a shortening of the prothrombin time, a global coagulation test, and higher plasma concentrations of the prothrombotic amino acid homocysteine, particularly in smokers. Additionally, particulate matter exposure has been associated with decreased heart rate variability, which is a well-established risk factor for arrhythmias and sudden cardiac death.

Temperature inversion, a meteorological phenomenon common in Christchurch, can also contribute to high levels of air pollution. This occurs when a layer of warm air traps a layer of cool air and pollution close to the ground, preventing it from dispersing. This further increases the concentration of pollutants that can be inhaled, affecting cardiac health.

Home heating

Professor Simon Kingham has highlighted the association between air pollution levels and respiratory health issues in Christchurch. The high levels of particulate matter in the air can have serious health consequences for residents, particularly those with pre-existing respiratory and cardiac conditions. The pollution from home heating is estimated to cause serious health problems for several thousand people each year.

To address this issue, the Canterbury Air Regional Plan has been implemented with the goal of meeting national air quality standards by 2030. The plan specifically targets the reduction of PM2.5 concentrations from home heating sources, aiming for no daily average PM2.5 concentrations greater than 25 micrograms per cubic metre of air. This is important because PM10 exceedances in Canterbury are largely due to PM2.5 particles from home heating.

While the plan focuses on managing air pollution from home heating, it also addresses other sources of pollution, such as industry, outdoor burning, dust, and odour. By taking a comprehensive approach, the plan aims to improve the overall air quality in Christchurch and reduce the health risks associated with air pollution.

To summarise, home heating is a major contributor to air pollution in Christchurch, particularly during the winter months when residents rely on wood or coal burners for warmth. The high levels of particulate matter emitted from these heating sources have significant health impacts on the local population. However, with the implementation of the Canterbury Air Regional Plan, there is a targeted effort to reduce pollution from home heating and improve the overall air quality in the region.

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