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Published: 2006-10-25 00:00:00

Hamilton residents can breathe a little easier.

Levels of the cancer-causing pollutant benzene, a chemical found in petrol, have fallen at the city’s three air quality sites monitored by Environment Waikato.

Concentrations in the 12 months to September 2006 were below the current health guideline of 10 micrograms per cubic metre of air and would now also meet the requirements of a stricter guideline due to be introduced in 2010.

Benzene is a colourless liquid that occurs naturally in crude oil and is used to boost octane ratings in petrol. The carcinogenic substance is released into the air when fuels are burnt in vehicles or heaters and can damage human DNA.

Air quality readings collected at Environment Waikato’s Peachgrove Rd, Bridge St and Claudelands Bridge monitoring sites from September 2005 to September 2006 revealed significant drops in benzene levels.

“At all three sites, benzene concentrations fell by between 23 and 32 per cent compared with the previous 12 months,” said Environment Waikato air quality scientist Jeff Smith.

“In the past, the highest annual average we’ve had is 5.8 micrograms per cubic metre at the Bridge St site, which would have exceeded the 2010 guideline of 3.6 micrograms per cubic metre. The latest annual average was 3.1 micrograms per cubic metre, so that’s good news.”

Dr Smith said restrictions on benzene content in petrol, introduced by the government in 2002, were probably the main contributor to the drop.

“A major reduction from four per cent to one per cent benzene in petrol that occurred following changes to New Zealand’s Petroleum Products Specification Regulations seems to have had a noticeable impact,” Dr Smith said.

“However, other factors such as fuel quality, vehicle technology and traffic density may affect benzene concentrations in the future.”

Should change occur, Environment Waikato will investigate interventions to meet the air quality standard.

Environment Waikato will continue to monitor air quality in Hamilton.