Something in the Air

There are more than 1500 petrol and service stations listed by the Yellow Pages across Victoria. In comparison, the number of petrol stations on the EPA’s priority sites list might seem minimal. But over 15% of the sites are current or former petrol stations and 2.5% are current or former petroleum storage areas.

A Department of Sustainability and Environment document says fuel storages and service stations have a ‘high’ potential to contaminate land.

The EPA’s Ruth Ward said an EPA audit of petrol stations in 2003 found that rural sites had a lower standard of environmental risk management than most metropolitan sites. “The majority of outlets used inventory control as the sole means of leak detection to prevent soil and groundwater contamination and there were many different methods of inventory control, of varying accuracy, being used. There was a high risk to surface water as a result of inadequate spill management provisions.’’

As a result of this audit, the EPA released Guidelines on the Design, Installation and Management Requirements for Underground Petroleum Storage Systems (UPSSs), which were designed to minimise the risks and provide advice to fuel operators. According to Ms Ward, “Clean up costs associated with leaking underground petroleum storage tanks can be significant, often several hundred thousand dollars or more”.

Brian Priestly, director of the Australian Centre for Human Health Risk Assessment (ACHHRA) within the Department of Epidemiology & Preventive Medicine (DEPM) at Monash University said that “whether there are health risks associated with living near disused petrol station sites depends on the exposure pathways and the extent of contamination with petroleum hydrocarbons”. According to the National Environment Protection (Assessment of Site Contamination) Measure draft report, potential pathways that pose a health risk to residents, the community and workers near contaminated land include soil ingestion or absorption if the contamination goes deeper than 60cm, or inhalation of toxins if the contamination is shallower.

A Spanish study published in the US Journal of Environmental Management in December 2010 suggested that emissions from evaporated petrol or fuel, generally when petrol is being transferred or has been spilt, contaminates the surrounding area with volatile materials, including the carcinogen benzene. This means that the atmosphere in the immediate vicinity of service stations can be contaminated up to 50 metres away. The study recommended that their findings be used to establish exclusion zones around current and future petrol stations, for the health and safety of residents and the community.

There are planning guidelines across Victoria regarding service station sites, management and positioning but these do not address distance from residents, apart from providing that a three metre landscape ‘buffer strip’ along the boundary must be maintained. As far as Dangerous Ground has found, there are no plans in Victoria currently to introduce these recommended distances.

Another study published in the US Journal of Toxicology and Environmental Health in 2009 studied the relationship between childhood leukaemia and traffic air pollution, including exposure to benzene and other hydrocarbons. The study examined childhood deaths in Taiwan from 1996 to 2006, and petrol station density in the child’s residential municipality. It concluded that there was a positive exposure-response relationship between the two.

Dr Deborah Glass, from Monash University’s Centre for Occupational and Environmental Health(MonCOEH) and Department of Epidemiology and Preventive Medicine, said research still couldn’t conclude whether benzene can be dangerous in just one exposure or whether it is a long-term issue.

“It could be a matter of one exposure, or a consistent overall prodding of the system. We don’t know the answer to the question. People say that with asbestos, one fibre can kill, but that is an exaggeration. We do know that some people are more susceptible to benzene than others.’’

According to Dr Glass, some people will ‘absorb’ benzene more slowly, and get rid of it more quickly, whereas for others the opposite can be true.  Benzene becomes dangerous when it is transformed into metabolite form in the liver or bone marrow. “Recent evidence suggests that the body is more efficient at benzene metabolism at low exposure levels than at higher levels, thus the exposure risk relationship is not linear. There is some evidence from animal studies that intermittent exposure is the most damaging.

“Benzene has stronger effects in children than in adults. For any carcinogen, the longer it has to work on the body the worse, and children have more active growing cells so more chances for things to go wrong.”

In most petrol stations, one of the signed safety precautions requires that those using the pumps must be over 16 years of age. Dr Glass said that whilst she doesn’t know the reasoning of the petrol companies, it is a sensible precaution.

“Children are more likely to be small and their noses to be at the level of the tank and be exposed to displaced vapour before it gets diluted into the atmosphere.”

EPA Priority Sites chartThere has been concern about studies which show that the atmosphere around petrol stations contains significantly higher levels of hydrocarbons and volatile organic compounds. One of the ways of dealing with this problem is the installation of Stage 1 and 2 vapour recovery devices at service stations. These devices capture petrol vapours during the transfer of fuel from place to place, limiting the chemicals that go into the atmosphere and returning them to the tank. These devices are common across the USA and Europe. Stage 1 devices are in use at most outlets around Australia, however the New South Wales government has recently begun introducing Stage 2 vapour recovery, estimated to be in most major service stations by 2013.

Stuart Clark, Regional Operations Officer for the New South Wales Office of Environment and Heritage, said the government began introducing the devices to target volatile organic compounds, but they also had the effect of dropping down benzene emissions in petrol station surroundings.

Mr Clark said that Stage 1 vapour recovery began in the early 80’s, targeting the release of vapours when trucks were delivering fuel to the underground tanks. “Upgrading at stations can reduce 50 per cent of emissions, but when you add recovery devices to the bowsers and the pumps, that can reduce emissions by an additional 40 per cent.’’

As well as reducing smog, Mr Clark said that  reducing benzene and other toxic emissions would decrease the impact on residential health.

Vapour recovery devices are not the only way to minimise the presence of benzene in our everyday lives. Dr Glass said that a study of non-occupational exposure to benzene showed that participants in Western Australia encountered lower amounts of benzene. This could be due to environmental factors, however in Western Australia restrictions reduced the amount of benzene used in fuel.

These were introduced in the 1990’s, as part of a Clean Fuel Initiative that included the phasing out of lead-based fuel. The initiative stated that, “International experience has shown that pollutants from motor vehicles can be reduced by changing the composition of the fuel”, and that by reducing benzene content in petrol, it would reduce the amount of benzene in the ambient air.

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[Reproduced from Dangerous Ground, Monash University’s online journal of the environment]

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