Under the cold, calm conditions typical of a Christchurch winter, air pollution from home heating becomes trapped close to its source and can cause serious health problems. For the sake of our health, Christchurch and other areas in Canterbury must meet a National Environmental Standard, much lower than current pollution levels, by 2013. Environment Canterbury has an Air Plan to deliver cleaner air and the rules for home heating are part of that plan.
National standards for air pollution
The Ministry for the Environment has set a National Environmental Standard (NES) of 50 micrograms of PM
10 per cubic metre of air (averaged over 24 hours) with only one exceedence per year allowed by 2013.
PM
10 is particulate matter in the air that's 10 microns in diameter or less. You can't see something that's PM
10-sized without using a microscope. A microgram is a millionth of a gram.
50 micrograms of PM
10 per cubic metre of air doesn't sound like a big deal, but in fact PM
10 at that concentration is associated with significant respiratory health problems for people.
That's why the NES has been set. To meet the NES the second highest concentration of PM
10 each year has to be lower than 50 micrograms per cubic metre of air by 2013. The NES also requires regional councils to show that PM
10 concentrations are trending downwards in accordance with a “straight-line path”.
Other pollutants from home heating are carbon monoxide (CO) and sulphur dioxide (SO2). The Ministry for the Environment has also set National Environmental Standards (NES) for CO and SO2.
Carbon monoxide from home fires exceeds the NES occasionally, but sulphur dioxide from home heating does not usually exceed the NES.
What causes PM10 pollution?
In all Canterbury's "air sheds" (an air shed is all the the air above a particular place: there is an air shed for Christchurch, and another for Timaru, Ashburton, Rangiora, and so on) burning wood and coal for home heating causes most of the PM
10 pollution. Some pollution is also caused by transport and industry. The amount emitted from these sources is estimated in emissions inventories.
On calm days in winter, home heating with wood and coal can cause air pollution to build up, especially in the evening when the wind often dies down on clear nights.
Although most of the pollution happens in winter, you may still see what looks like a pollution haze at other times of the year. As PM10 pollution is measured year-round, our monitoring checks whether the concentrations during such days do not breach the NES. In the summer the haze is more likely to be caused by natural particles such as dust, sea salt and moisture.
What influence does the weather have?
The weather does not cause pollution but can influence whether pollution accumulates near its source.
On still, cold winter nights a temperature inversion can occur: when the ground is cool, the air closer to the ground can be colder than air higher up. Cold air is denser than warm air and does not rise, so cold air will stay close to the ground. This means that smoke from home chimneys will not rise or blow away, but will get trapped - causing high levels of pollution.
Temperature inversions are typically formed when there is little or no wind and the sky is clear.
If there is wind, pollution will generally be blown away and diluted and pollution levels don’t generally reach high levels. The weather forecast is therefore an important factor in forecasting air pollution.
What happens if pollution levels still exceed the NES by 2013?
If the NES is still breached in any air shed more than once a year by 2013, Environment Canterbury will not be able to issue any more air discharge consents for that particular air shed. If the exceedences are not trending downwards according to a straight-line path, Environment Canterbury may have to consider declining air discharge applications sooner than 2013. This may affect local industry but also solid fuel boilers in schools, hospitals etc. that use solid fuel burners.
What does air pollution by PM10 do to our health?
- Increases and aggravates asthma
- Creates disease in the airways of children
- Increases respiratory illness in children
- Damages the lungs
- Increases deaths from respiratory and cardiovascular disease
- Increases hospital admissions for lung and heart disease
- Causes chest pain and nausea
- Causes shortness of breath and (faster) laboured breathing
- Permanently changes lung structure.
What is Environment Canterbury doing about air pollution?
Environment Canterbury has existing and proposed rules for woodburners and open fires (see our Air Plan or Proposed Canterbury Natural Resources Regional Plan, Chapter 3: Air Quality). The rules are different depending on your situation and where in Canterbury you live.
How can you help?
Open fires are the most polluting and inefficient form of heating - up to 85% of the heat generated by an open fire goes right up the chimney and is not used to heat your home. Older solid fuel burners are also more polluting and less efficient than modern, low-emission burners. If you use an open fire or older solid fuel burner to heat your home, consider replacing it with a less polluting heating system such as a flued gas or diesel fire, electric heat pump or an approved low-emission woodburner or pellet fire.
Christchurch homeowners including landlords may qualify for subsidies or loans for insulation and replacement heating under the Clean Heat Project
Insulation will keep the heat in, meaning you will need to generate less heat, causing less pollution. Many homes have substandard insulation, where only a thin layer was installed or the insulation has deteriorated. Ideally a layer of approx. 200 mm should be installed (R3.5).
Pollution hotline
If you would like to report any pollution please call the pollution hotline on 03 366 4663 (Christchurch), 03 688 3320 (Timaru) or 0800 765588. The pollution hotline operates 24 hours a day, 7 days a week.