3.4 Air toxics
Air toxics generally at low levels in NSW
Worldwide, there is growing concern about a number of air pollutants known as 'air toxics' or 'hazardous air pollutants', which have the potential to adversely affect human health and the environment, even at relatively low concentrations. A recent EPA study measured more than 80 air toxic compounds in NSW and found that ambient levels for most were very low. Twenty-three of the compounds were never, or rarely, detected. However, taking into account the levels detected and individual toxicities, the compounds of most significance for NSW were benzene, 1,3-butadiene and polycyclic aromatic hydrocarbons (PAHs).
As there are no Australian standards for these air toxics, the results were compared with overseas goals and standards. Benzene and 1,3-butadiene levels were well below the United Kingdom annual goals, although benzene levels at the Sydney CBD site exceeded the stringent 2010 European Commission goal. On the basis of the limited sampling program, PAH levels at some sites would meet the proposed 2005 European Commission goal, although they are likely to exceed the proposed 2010 United Kingdom goal. This was particularly the case in regional areas where there is widespread use of domestic solid fuel (wood or coal) heaters.
Status of Indicator
3.13 Air toxics levels
Levels of air toxics were found to be low or rarely detected. Benzene and 1,3-butadiene levels are below current overseas goals.
Importance of the issue
The high toxicity and low concentration of air toxics generally distinguishes them from mainstream air pollutants. Although there is debate about their precise definition, the OECD defines them as: 'gaseous, aerosol or particulate contaminants present in the ambient air in trace amounts with characteristics (toxicity, persistence) so as to be a hazard to human health, plant and animal life' (OECD 1995).
A large number of compounds are considered air toxics. The United States Environmental Protection Agency (USEPA), for example, lists 188 compounds as hazardous air pollutants. The main concerns about many of these compounds are the health effects associated with long-term exposure. Some of these compounds are known, or suspected, to have carcinogenic, mutagenic (increasing the chance of mutations) or neuro-toxic effects. Some compounds are listed as air toxics because of their environmental effects and so many of the most significant ozone-depleting substances are included in the suite of organic compounds measured.
Levels of air toxics
Between 1996 and 2001, the EPA investigated the levels of 17 dioxins, 41 organic compounds, 11 polycyclic aromatic hydrocarbons (PAHs) and 12 heavy metals (EPA 2002). More than 1400 samples were collected at 25 sites. Of the substances targeted, 29 organic compounds and nine heavy metals are listed by the USEPA as hazardous air pollutants. There are no Australian goals or standards for ambient levels of air toxics against which measured levels can be assessed, although a National Environment Protection Measure (NEPM) for air toxics is currently being developed. This may result in an agreed national approach to assessing the status of air toxics. In the interim, the EPA used what existing United Kingdom (UK) and European Commission (EC) goals were available.
The EPA study found that for most organic compounds ambient levels were very low, and well below current international standards or benchmarks. Some 23 compounds were never, or rarely, detected. Dioxin levels were very low compared with current standards in Europe and the United States. The metals measured were also below applicable overseas standards or goals, where they exist. The compounds identified by the study as of most concern in NSW were benzene, 1-3 butadiene and PAHs. The study concluded that ongoing vigilance will be needed to ensure that the currently acceptable levels of these three pollutants do not escalate in the future (EPA 2002).
Benzene and 1,3-butadiene
Benzene is a known human carcinogen and 1,3-butadiene a probable one. In the NSW urban environment, motor vehicles are the major source of both benzene and 1,3-butadiene.
Figure 3.8 presents data for two of the air toxics, benzene and 1,3-butadiene, found in the range of existing standards and therefore of most concern in NSW. They should not be considered as indicators of the levels of all air toxics.
Figure 3.8: Annual average benzene and 1,3-butadiene concentrations, Sydney Region
Source: EPA 2002
Annual average concentrations of benzene were below the UK 2003 goal of 5 parts per billion by volume (ppbV) at all sites in the Sydney region. Even the more stringent long-term European Commission 2010 annual average goal of 1.5 ppbV was met everywhere, except the city site, where high traffic volumes result in higher levels of emissions.
The levels of 1,3-butadiene were below the UK 2003 annual average goal of 1 ppbV at all sites. The highest annual average of 0.6 ppbV was measured at the Sydney CBD site in 1998.
The results for benzene and 1,3-butadiene in the EPA study are broadly consistent with the levels found in comparable overseas locations. The data shows some year-to-year variation but is not extensive enough to identify trends.
The USEPA has identified 16 priority PAHs based on concerns that they do or might cause cancer. The most toxic of the suite of PAHs, benzo(a)pyrene (BaP), is a probable human carcinogen and may cause genetic and reproductive damage in humans. The highest levels of PAHs measured in NSW during the EPA study were associated with the burning of coal and wood for domestic heating. In urban areas, particularly the Sydney CBD, motor vehicles were also a likely contributor to measured PAH levels.
Annual average standards are currently being considered overseas for BaP. The UK has proposed a goal of 0.25 nanograms per cubic metre (ng/m3) from 2010 and the EC is considering a goal of between 0.5 and 1.0 ng/m3 to be implemented in 2005.
It is not possible to directly compare the NSW data on BaP with the UK and EC goals as the sampling frequency was insufficient to calculate annual averages. Winter averages were between 0.16 and 0.46 ng/m3 in the Greater Metropolitan Region and between 1.12 and 4.21 ng/m3 in regional towns. It is estimated that an annual average goal of 1.0 ng/m3 would be met at all sites except Lithgow and most sites would probably meet a 0.5 ng/m3 goal. Some Sydney and regional sites would not meet the stringent 0.25 ng/m3 goal.
Response to the issue
The main responses to air toxics have included:
- programs to reduce emissions from motor vehicles
- regulation and financial incentives to reduce emissions from industrial sources
- education, regulation and incentives to reduce emissions from domestic solid fuel heaters
- actions aimed at specifically reducing the emissions of dioxins.
The Government's air quality management plan Action for Air contains a range of measures to achieve better air quality including reducing levels of air toxics, such as benzene and 1,3-butadiene. These include:
- the promotion of appropriate land-use planning and infrastructure development through the Integrating Land Use and Transport policy package (DUAP 2001)
- enhancements to the public transport system as set out in Action for Transport 2010
- strategies to reduce emissions from motor vehicles.
At the national level a broad reform program for vehicle performance based on European emission standards (Euro 3 and Euro 4) will lower vehicle emissions over the next 10 years. New emission standards for diesel vehicles came into effect in 2002 and petrol vehicles in 2003. Further emission reductions will be required from 2005 for petrol vehicles and 2006 for diesel vehicles. Coupled with the emission standards are cleaner fuel quality standards that will also reduce vehicle emissions. From 2006, for example, the benzene content of petrol will be limited to a maximum of 1%, compared with the current 5% maximum. This is expected to have an immediate and sustained impact on ambient benzene levels.
The NSW Government's Cleaner Vehicles Action Plan promotes the early uptake of the more stringent medium-term Euro 3 and Euro 4 emission standards. In the meantime the Roads and Traffic Authority has established two emissions testing stations at Botany and Penrith where owners can have their cars tested on a voluntary basis. The testing provides a short diagnostic report indicating the level of emissions from the vehicle compared with those in all vehicles tested to date. Almost 400 of State Transit Authority buses in Sydney are powered by compressed natural gas.
The NSW Government's targeted wood and coal smoke reduction program is lowering emissions from domestic solid fuel heaters (see Atmosphere 3.3). The Woodsmoke Reduction Program is promoting cleaner operation of heaters through education and enforcement programs on emissions. Financial incentives have been provided to assist householders to switch fuel heating sources in the most affected areas (see also Atmosphere 3.3). This should assist in reducing emissions of PAHs in the targeted areas.
The NSW Government has reduced emissions of dioxins by banning backyard burning; closing hospital incinerators; licensing and regulating industrial sources; reducing solid fuel heater emissions; and phasing out leaded petrol.
Improved information is also being developed through the National Pollutant Inventory (NPI), an internet-based presentation of estimated emissions from individual facilities and aggregated data from diffuse sources and non-reporting facilities (see Atmosphere 3.3).
Effectiveness of responses
In response to community pressure, point sources of air toxics in NSW have been strongly regulated over the last 10 years. Following the conclusion of the EPA air toxics study in 2001, a decision was made to incorporate the measurement of organic air toxics into the EPA's routine monitoring. This will provide ongoing information about the levels of 41 organic compounds including benzene and 1,3-butadiene. It is envisaged that future measurements of other air toxics will be carried out on a targeted basis.
The low concentrations of dioxins found in the EPA study indicate that strategies to reduce their emissions have been effective.
Motor vehicles are the major source of many of these pollutants. Government should continue its strategies to promote the uptake of cleaner fuel and vehicle technologies, and to reduce motor vehicle use. Industry and the community need to examine ways to reduce vehicle kilometres travelled (see Human Settlement 2.4).
Individuals can check that their wood heaters comply with relevant standards and are being used correctly. They can also consider switching to alternative heating sources.
3.3 Urban air quality