SoE 2006 > Atmosphere > 3.4 Air toxics

3.4 Air toxics

Ambient concentrations of most air toxics in NSW are very low, and are well below international goals. A small number of air toxics require ongoing assessment to ensure they remain at acceptable levels in the future.

Air toxics are 'hazardous air pollutants' that have the potential to adversely affect human health and the environment, even at relatively low concentrations.

The NSW Government investigated 80 air toxics and found ambient concentrations of most are very low, and are well below international goals. Three pollutants at some sites – benzene, 1,3-butadiene and polycyclic aromatic hydrocarbons – will need to be watched to ensure they remain at acceptable levels in the future.

Significant programs to reduce benzene levels in petrol take effect from 2006 and are expected to further reduce benzene levels in air.

NSW indicators

Introduction

While there is no universally accepted definition of air toxics, the better recognised ones – published by the Organisation for Economic Cooperation and Development (OECD), the United States Environment Protection Agency (US EPA) and the World Health Organization (WHO) – share a number of common elements. Air toxics are pollutants present in the atmosphere in low concentrations that are known or suspected to cause serious health or environmental problems. Air toxics include volatile and semi-volatile organic compounds, polycyclic aromatic hydrocarbons (PAHs), heavy metals, and aldehydes. The main concerns about many air toxics are the health effects associated with long-term exposure. There is evidence that cancer, birth defects, genetic damage, immunodeficiency, and respiratory and nervous system disorders can be linked to exposure to these substances.

Air Toxics Monitoring Project

Between 1996 and 2001, the Air Toxics Monitoring Project investigated concentrations of 17 dioxins, 41 organic compounds, 11 PAHs and 12 heavy metals (EPA 2002). More than 1400 samples were collected at 25 sites. Ambient concentrations of most tested substances were very low, and well below the international goals at the time. Some 23 compounds were never, or rarely, detected. The project report recommended, however, that three pollutants at some sites – benzene, 1,3-butadiene and PAHs – will need to be watched to ensure that they remain at acceptable levels in the future.

The Air Toxics National Environment Protection Measure

In 2004 a national framework for monitoring, assessing and reporting the concentrations of selected air toxics was agreed to in the National Environment Protection (Air Toxics) Measure (Air Toxics NEPM) (NEPC 2004), complementing the established standards for ambient air quality (see Air Quality 3.3). Pollutants included in the Air Toxics NEPM were selected according to their known significance and the availability of concentration data. Although most air toxics are thought to occur at low concentrations across Australia, there are few monitoring data sets to provide a more accurate picture. Benzene, toluene, xylenes, formaldehyde and benzo(α)pyrene have been selected as being significant. The long-term goal of the Air Toxics NEPM is to collect sufficient information to support the development of national air toxics standards. The Air Toxics NEPM establishes monitoring investigation levels (MILs) for the five air toxics that are based on the protection of human health (see Table 3.1). The MILs are conservative values for exposure to these chemicals over the relevant averaging period that are considered unlikely to result in adverse health effects (NSW Health 2004c).

Table 3.1: Air Toxics NEPM monitoring investigation levels (MILs)

The Air Toxics NEPM includes a 'desktop analysis' methodology to identify, as possible monitoring sites, where potentially elevated concentrations of the five pollutants are likely to occur and where there is a likelihood of significant population exposure. Major inputs to this analysis include emissions inventory, air quality modelling and ambient monitoring data from the ATMP (Air Toxics Monitoring Project). Using this approach, a number of sites have been identified where the MILs for formaldehyde and benzo(α)pyrene may be exceeded (NEPC 2006). No sites have been identified for benzene, toluene or xylenes.

Current status and trends

Benzo(α)pyrene

Benzo(α)pyrene is a probable human carcinogen that may also cause genetic and reproductive damage in humans. Significant sources of benzo(α)pyrene are burning of coal and wood for domestic heating, and motor vehicles. It is also one of the PAHs, and is used as a marker for these compounds (see 'Other air toxics' below).

Sampling of benzo(α)pyrene for the ATMP (EPA 2002) mainly took place during winter when concentrations were expected to be greatest. At sites in the greater metropolitan region (GMR₂), winter average concentrations ranged from 0.16 to 0.46 nanograms per cubic metre (ng/m³), while for regional centres winter average concentrations ranged from 1.12 to 4.21 ng/m³. These concentrations suggest that annual average concentrations may exceed the MIL at some sites.

Formaldehyde

Formaldehyde causes irritation of the eyes and upper respiratory tract and is potentially carcinogenic. Significant sources of formaldehyde include motor vehicles and aircraft exhaust.

The availability of monitoring data for formaldehyde is very limited. The RTA has monitored formaldehyde levels in the vicinity of the M5 East tunnel stack since 2002, and has reported concentrations below the level of detection (less than 2% of the standard) (RTA 2006).

Benzene

Benzene is a known human carcinogen, and motor vehicles are the major source of it in the Australian urban environment. Benzene in petrol is currently being reduced significantly under a new national fuel quality standard. The standard limits the content of benzene in petrol to a maximum of 1%.

Annual average concentrations of benzene were below the NEPM MIL at all sites where monitoring was undertaken for the ATMP (Figure 3.11). Indeed, other than the peak central business district (CBD) site, concentrations were less than the European Commission's more stringent long-term (2010) annual average goal of 1.5 parts per billion (ppb) by volume.

Research by NSW Health has confirmed findings from other cities that users of road-based transport (such as cars and buses) have significantly higher exposure to benzene, toluene, ethylbenzene and xylenes (BTEX) air toxics than do train travellers and off-road walkers (NSW Health 2004b). While BTEX levels in motor vehicles are unlikely to be associated with acute health effects, there is some concern related to long-term exposure to these chemicals, with a World Health Organization report suggesting that increased cumulative exposure to benzene was of particular concern (WHO 2000). That study estimated that a motorist would inhale 411 mg of benzene over 40 years of typical commuting compared to 126 mg for a train commuter (NSW Health 2004b).

The California Environmental Protection Agency notes that benzene emissions from high-throughput petrol stations may result in health risks above those of regional background levels. It recommends having appropriate separation distances between different-sized service stations and sensitive land uses (such as schools, homes or workplaces) (California EPA 2005).

A 2003 Department of Environment and Heritage study considered risk factors associated with an increase in personal exposure to BTEX air toxics, and found that activities associated with motor vehicles (such as repair, machinery use and refuelling), and arts, crafts and woodwork (due to exposure to glues and solvents) significantly increased the risk of exposure (DEH 2003).

Toluene and xylenes

Toluene causes respiratory irritation and has depressant effects on the central nervous system. Xylenes cause irritation of the nose, throat and eyes. The major source of toluene and xylenes in the urban environment is motor vehicles.

Concentrations of both toluene and xylenes were very low at monitoring sites for the ATMP. The maximum annual concentrations of toluene and xylenes were less than 5% of the MILs (see Figure 3.11). Maximum 24-hour concentrations of toluene and xylenes were less than 2% and 4% of the MILs respectively.

1,3-butadiene

The probable human carcinogen 1,3-butadiene was identified by the ATMP as having concentrations potentially of concern. In the NSW urban environment, motor vehicles are its major source. Figure 3.11 shows that annual average concentrations of 1,3-butadiene were less than 60% of the current UK goal (DEFRA 2002).

Other air toxics

The ATMP found that dioxin levels in the air in NSW were very low compared to concentrations measured in overseas cities. This was confirmed by monitoring undertaken in Sydney for the National Dioxins Program in 2002–03. The program also highlighted a seasonal cycle in dioxin concentrations, with higher levels in winter most likely due to smoke from solid-fuel heaters.

When the Air Toxics NEPM was established in 2004, a national working group was set up to develop a methodology for identifying other air toxics not already incorporated in the Air Toxics NEPM that could also pose a risk to human health. Once established, this methodology will be used to build on the understanding of air toxics levels in NSW gained from the ATMP.

Figure 3.11: Maximum annual average concentrations of benzene, toluene, xylenes and 1,3-butadiene in GMR₂ (1996–2001)

Source: EPA data 2002

Response to the issue

Action for Air is the Government's broad strategy for managing air toxics and ambient air NEPM pollutants (see Atmosphere 3.3). Many of the policy and regulatory actions for addressing the six major urban air pollutants are also the key management tools for air toxics.

Industry

Licensing of industrial sources under the POEO Act is the primary tool for managing air toxics emissions from industry. The Protection of the Environment Operations (Clean Air) Regulation 2002 sets emission limits for a number of specific air toxics in relation to various industrial processes carried out by licensed premises. Assessment criteria exist for more than 80 air toxics, new industrial facilities, and significant modifications to existing facilities.

Motor vehicles

The regulation of fuels is a major tool for managing air toxics emissions from motor vehicles. For example, limits on fuel volatility in Sydney (see Atmosphere 3.3) significantly reduce air toxics emissions in the GMA. The benzene content of petrol is now limited to a maximum of 1% (compared to an average of 2.5% in 2005) under new Commonwealth fuel standards that update the Fuel Standard (Petrol) Determination 2001 from 1 January 2006. These standards, and tougher emission standards for new cars, will contribute to the projected 40% reduction in both VOC and particle emissions from motor vehicles from 2002 to 2020.

Depending on the size and locality of a service station, petrol vapours can adversely impact on the health and amenity of people living and working nearby. The Protection of the Environment Operations (Clean Air) Regulation 2002 regulates the emission of petrol vapour during fuel delivery by road tankers in NSW. The NSW Government is currently evaluating vapour recovery technology to control the emission of petrol vapours at service stations when vehicles refuel. These controls can decrease the emission of VOCs at service stations by 95% compared with an uncontrolled facility, thereby helping to protect the health and amenity of those living and working within the neighbourhood of these facilities. It can also produce regional air quality benefits by reducing VOC emissions and subsequently reducing ozone formation.

Other strategies for helping to reduce air toxics concentrations include reducing traffic congestion and promoting alternative forms of transport to the motor vehicle. The Government's initiatives to further these goals are outlined in the NSW Government's Metropolitan Strategy (see Human Settlement 2.1; DoP 2005) and Action for Air.

Commercial–domestic

Solid-fuel heaters are a source of benzo(α)pyrene and other air toxics. Policies and programs to reduce emissions from this source (such as the creation of a new offence relating to excessively smoky solid-fuel heaters) are outlined in Atmosphere 3.3. These responses address particle and air toxics emissions simultaneously.

The concentrations of air toxics are also managed by controls on backyard burning under the Protection of the Environment Operations (Clean Air) Regulation 2002 and the regulation of small-scale industrial or commercial premises by local councils.

Future directions

Current air quality management strategies are expected to adequately control most air toxics. Benzene and 1,3-butadiene concentrations in NSW, except in some localised situations, are expected to remain below health guideline levels, especially with increasingly stringent regulation of fuel and motor vehicle emissions. Monitoring of air quality in regional areas which have a high usage of solid-fuel heaters has shown elevated levels of benzo(α)pyrene, suggesting a need for continued management of this source. The Government's creation of a new offence relating to excessively smoky solid-fuel heaters could reduce emissions; however, further action on solid-fuel heaters would be needed in some local council areas to reduce concentrations below levels of concern (see Atmosphere 3.3).

Most of the air toxics discussed are emitted as a result of motor vehicle use, so an increased emphasis on encouraging the use of public transport systems rather than motor vehicles would assist in achieving reductions.