At a glance
internal SOE link to larger image
Source: Photograph courtesy of The Mercury
Links to content in detail
The detailed background report and supporting indicators are available through the following links:
At a glance – the issue
This 'At a glance' section provides an overview of ambient (outdoor) air quality.
Ambient (outdoor) air quality is the condition of the air in the surrounding environment. The quality of the air in Tasmania directly affects the health of humans, the health of plants and animals, and the condition of natural systems (see, for example, Internal linkParliamentary Office of Science and Technology 2006; Internal linkDoley 2006). Significant sources of primary pollutants are emitted directly into the atmosphere from human activity such as burning of fossil fuels in industrial processes, burning of fuel for domestic purposes such as wood in wood heaters, the use of motor vehicles, and emissions from industrial manufacturing, intensive agriculture and planned burning such as forestry fuel reduction and regeneration operations (see, for example, Internal linkUS EPA 2009; Internal linkPope and Dockery 2006; Internal linkCSIRO 2005). In Tasmania, a major source of air pollutants are in the form of particles derived from sources including forestry and mining operations, industrial manufacturing, domestic wood heaters, motor vehicles and land clearing (see also (Internal linkForestry Tasmania 2009; Internal linkUniversity of Tasmania 2008). Natural sources of primary pollutants in the State include sulfates from sea spray, wind entrained dust from soils and natural wildfires. Some pollutants can chemically react in the atmosphere with already polluted air to form secondary pollutants such as ground level ozone – one of the many secondary pollutants that make up photochemical smog (Internal linkCsuros and Csuros 2002).
State of ambient air quality in Tasmania
At times, Tasmania experiences the best ambient air quality in Australia although there are some areas in the State that suffer from poor ambient air quality during some periods of the year, especially during cold clear nights in the cooler months (Internal linkDTAE 2006). Air quality measured at the Cape Grim baseline ambient air quality monitoring station on the northwest coast has recorded some of the cleanest air in Australia (see Internal linkCSIRO 2008). It appears that the quality of ambient air has remained relatively stable in the State for most pollutants since the 2003 SoE Report. A reduction in particulate concentrations has been observed in the Launceston airshed.
Air pollutants can be grouped into two broad classes: particulates and gases. Of particular significance in the State are Total Suspended Particles (TSP) that are less than 50 µm in diameter. The smaller component size range of these particles are collectively referred to as 'respirable particles' and they are small enough to remain suspended in the air for some period of time. Significant sources of respirable particles are planned burning, domestic wood heaters, and vehicle and industry emissions. These particles provide a useful indicator of air quality in urban areas and can also be used to estimate any adverse health effects of air pollution more generally. Routine air quality measurements in the Launceston and Hobart airsheds suggest that most of the Tasmanian population is exposed to annual average respirable particle concentrations of 15 to 20 µg/m-3 (micrograms per cubic metre), with daily exposures ranging from around 5 up to 80 µg/m-3 (although in the early 1990s, Launceston sometimes reached a daily average on occasion of almost 200 µg/m-3). Particles less than about 2.5 µm play a larger role in affecting human health. Other pollutants such as sulfates, nitrates, acids, metals and other toxic chemicals can be adsorbed onto their surfaces (Internal linkPope and Dockery 2006). These toxic chemicals can also be carcinogenic.
The following graphical index is included as a visual method to allow a comparison of priority issues. Further information on the index is provided at Internal linkBackground to Index. The positioning of the dials tend to reflect that, from the available information of airsheds that are actively monitored, ambient air quality appears to be relatively stable in Tasmania for most monitored pollutants although there has been a recorded reduction in the concentration of particles in the Launceston airshed. However, air quality can be highly varied with localised issues caused by settlement patterns, industry and the topography of the land affecting the concentration and dispersion of pollutants. In addition, our information and knowledge about ambient air quality continues to be variable at the State-wide scale and it is difficult to draw generalised conclusions from the data. More work is required to understand the nature and extent of emission sources, the concentration of air pollutants in the environment, how these pollutants interact with one another, and how they affect human health, agricultural activities and natural systems.
Ambient air quality Indexinternal SOE link to larger image
Condition, trends and changes
The Tasmanian Government sets State-based ambient air quality emission standards for industry. Air quality standards in the State are based upon the National Environment Protection Measure for Ambient Air Quality (the Air NEPM) and the National Environment Protection (Air Toxics) Measure (the Air Toxics NEPM) (Internal linkEPHC 2009). The assessment of ambient air quality in the State is assessed against these standards.
- The main ambient air pollution in Tasmania is particles that derives mostly from wood smoke from forest industry planned burns in autumn and domestic fuel burning in winter. In 2008, 31,000 ha were burnt in planned burning operations (Internal linkChuter 2009). Wildfires can also contribute a significant quality of smoke into the atmosphere and they are highly variable in intensity and duration are influenced by the interaction of weather conditions, topography, fuel load and forest type (Internal linkForestry Tasmania 2009). For example, in 2008, the Heemskirk Road wildfire in the Tarkine burnt about 13,400 ha.
- Launceston regularly exceeded the Air NEPM Standard for PM10 (particles smaller than 10 µm in diameter) set by the National Environment Protection Council (NEPC), from a peak in 1997 when historically 50 exceedences were recorded (Internal linkDPIPWE 2009). The overall Air NEPM target for PM10 is for less than five exceedences per year. Launceston has recently met the Air NEPM Standard for PM10 with only five days in 2007 and one day in 2008 exceeding the national standard (set at 50 µg/m3 over an averaged 24 hr period). The one exceedence recorded for 2008 was the result of a wildfire event. By 2009, there had been a substantial improvement in air quality in the Launceston airshed that has been due, in part, to the implementation of local, state and federal government programs to reduce pollution sources.
- Air quality monitoring commenced in the Hobart airshed in 2000. The monitoring station was relocated in 2005 and consequently, there is not sufficient data to determine pollution trends to date. Monitoring in the Hobart airshed has shown that the Air NEPM target for PM10 is rarely exceeded. Hobart last exceeded the Air NEPM Standard for PM10 in 2000 when six exceedences were recorded. In addition, two days in 2001, one day in 2002, three days in 2003 and one day in 2005 also exceeded the national standard (set at 50 µg/m3 over an averaged 24 hr period). It is likely there are pockets within the Derwent Valley and Huon Valley that experience significant concentrations of particles from wood smoke under very stable weather conditions in autumn and winter (Internal linkNRM South 2003).
- Reporting for PM2.5 (particles smaller than 2.5 µm in diameter) is still in the advisory phase. In 2008, monitoring indicated that PM2.5 concentrations were above the advisory reporting standard on occasions. There were nine days in Hobart where PM2.5 was recorded above the advisory reporting standard. Two of these events that occurred in April appear to be related to planned burns. Planned burn smoke is suspected as being significant contribution to a further event in May. It is estimated that 17 days were over the advisory reporting standard in Launceston. Of these events, three have been attributed to planned burns, one was attributed to emissions from a wildfire event and the remainder due to emissions from domestic wood heaters.
- Concentrations of the other key air pollutants (carbon monoxide, oxides of nitrogen, sulfur dioxide, lead and ozone) that are included in the Air NEPM are largely unknown. Monitoring for carbon monoxide was conducted in Hobart from 2001 to 2004, but was discontinued because very low levels were recorded (Internal linkEPA 2009). Monitoring for oxides of nitrogen and sulfur dioxide for industry are conducted at Rowella and George Town. Routine monitoring for lead and ozone is not conducted in Tasmania.
- There are other toxic or hazardous components that contribute to air pollution that originate from man-made emissions including benzene, formaldehyde, toluene, xylenes, polycyclic aromatic hydrocarbons and other volatile organic compounds. These compounds are scheduled toxics included in the Air Toxics NEPM. The magnitude and location of air toxics in Tasmania is uncertain. While it is likely that there are no broad-scale problems with air toxics in the State, there are potentially localised issues.
- The overall number of vehicles registered in Tasmania increased by approximately 26% between 1990 and 2008 and approximately 13% between 2003 and 2008 (Internal linkABS 2009). The increase in vehicle numbers was primarily due to increases in the numbers of cars, trucks and motorcycles. Although the impact of traffic emissions on human health and the environment is largely unknown in Tasmania, one study of traffic emissions in North Hobart, Sandy Bay and Lenah Valley found that none of the air pollutants measured, including PM10, exceeded nationally set Air NEPM standards or Air Toxics NEPM monitoring investigation levels although the benzene concentration in Sandy Bay was higher than expected (Internal linkTodd 2005). Benzene does not appear to build up to significant levels in the natural environment. However, benzene is harmful to human health; it is a known carcinogen, is harmful to the reproductive organs and can damage the blood and immune system. Emissions from motor vehicles are not considered to have a major effect on Tasmania's air quality. However, there are likely to be localised areas where increased traffic result in a higher concentration of traffic emissions.
- Data on the emission of air pollutants in Tasmania are listed in the National Pollution Inventory (NPI) (Internal linkDEWHA 2009). There are two types of reporting. Industrial facilities that emit, or may emit, a reportable substance such as the burning of large amounts of fuel or the handling of significant qualities of pollutants are required to report. Industry emission data are published annually and varies with production and changes to industry sources such as a change of fuel type or the closure of an industry. The second type of reporting covers the diffuse pollution sources such as burning activities and emissions from motor vehicles. Estimates of pollution from diffuse sources are known as aggregate emissions. These estimates are likely to be out of date because the data has not been updated since they were first published in 2001.
- The NPI database presents figures for particle emissions to the Tasmanian airshed from various sources including domestic wood heaters and forest burning (including fuel reduction burns, regeneration burns and wildfires). These figures are also quoted in the Tasmanian Air Quality Strategy 2006 (Internal linkDTAE 2006). Using NPI data from 2003–04, domestic solid fuel burning was reported to contribute 41% of the total PM10 particle emissions in the State, while forest burning contributed 3% of emissions. That is, domestic wood heaters were estimated at the time to contribute to the Tasmanian airshed about 14 times the amount of particles as forest burning. These are emissions to the Tasmanian airshed, and are not an estimate of the relative contributions to population exposure.
- Officers of the Environment Division supporting the Tasmanian Environment Protection Authority (EPA) have been investigating the current validity of these figures. Recently, the Forest Practices Authority (FPA) estimated that three million tonnes of wood were burnt in forest industry planned burns in 2008 (Internal linkChuter 2009). Data from the Forest Practices Authority indicate that approximately seven million tonnes of wood were burnt in forest industry planned burns in 2008. For a particle emission rate of 17 grams per kilogram of wood burnt, the total particle emission to the Tasmanian airshed in 2008 from forest industry planned burns is consequently estimated to be near 120,000 tonnes (Internal linkEPA 2009).
- Figures from the Australian Bureau of Statistics (ABS) for 2008 lead to an estimate of 42,000 combustion stoves and 4,300 open fireplaces in Tasmanian residences (Internal linkABS 2008). Based on these data, and assuming particle emission rates of 10 gm/kg of wood burnt for combustion stoves and 17 gm/kg of wood burnt for open fires, and assuming each domestic heater uses 10 tonnes of wood per year, leads to an estimate of approximately 5,000 tonnes of emitted particles from domestic wood heating into the Tasmanian airshed in 2008 (Internal linkEPA 2009).
- Therefore, using the 2008 figures, forestry industry planned burns contributed to the Tasmanian airshed approximately 24 times the amount of particles produced by domestic wood heaters. The revised figures indicate that the relative contribution of smoke emissions from forest industry burning compared to domestic wood heaters is over 300 times greater than presented in the Tasmanian Air Quality Strategy 2006 (note: wildfire smoke is not included in the revised calculation) (Internal linkEPA 2009). The new findings point to deficiencies in the NPI data in this area. The figures above refer only to total emissions to the airshed from these sources, and do not attempt to account for the relative contributions to population exposure. Work is in progress to further investigate these issues.
- The Hobart airshed has generally less industrial emissions than the Launceston airshed.
- General trends in key ambient air pollutants included in the Air NEPM for all airsheds in Tasmania from industrial sources for the reporting periods 2004–05 and 2007–08 were as follows: PM10 rose (2,524,194 kg/yr from 61 reporting facilities in 2004–05 to 3,165,086 kg/yr from 67 reporting facilities in 2007–08); lead rose (2,727 kg/yr from 46 reporting facilities in 2004–05 to 3,091 kg/yr from 56 reporting facilities in 2007–08); carbon monoxide and oxides of nitrogen remained relatively stable and sulfur dioxide fell.
- Each of the six air toxic emissions that are included in the Air Toxics NEPM for all airsheds in Tasmania from industrial sources for the reporting periods 2004–05 and 2007–08 generally fell. However, a peak in toluene was recorded in 2005–06 at 180,130 kg/yr from 25 reporting facilities that was similar to emissions recorded between 2001–03.
- The data available at present are not sufficient to determine where changes in fire regimes (that includes the number of fire events, ignition source and intensity) have occurred in Tasmania or what the impact of these regime changes has been on the volume of emissions of pollutants released into the atmosphere and the effect of these emissions on the environment and human health. Higher resolution fire boundary mapping that captures information about fire intensity as well as previous fire history and vegetation condition mapping are required before reporting on changes in fire regime and resultant emissions. The implementation of the EPA BLANkET smoke monitoring network aims to provide better data on smoke emissions from biomass burning, and research being conducted by the University of Tasmania on the health impacts of biomass burning is likely to provide better data on the health implications of smoke from these fire events in the future.
- There is uncertainty about the magnitude of the effects of pollutant emissions into the air, including carbon dioxide and other greenhouse gases, and their effect in terms of climate change. However, the scientific community increasingly recognises that the effects are likely to be complex and wide-ranging (see, for example, Internal linkBowman et al. 2009; Internal linkBowman 2008; Internal linkCope 2009; Internal linkCostello et al. 2009).