Waikato Regional Council has been measuring the amount of benzene in the air we breathe in Hamilton at various traffic sites since 2003.
Benzene is an air contaminant that is produced by combustion processes such as burning fuels for transportation and heating and as a result of evaporative emissions.
Small amounts of benzene are present in petrol. Benzene is also used in the manufacture of plastics, detergents, pesticides, and other chemicals.
Monitoring benzene is important because exposure to it can result in significant health impacts.
Benzene is a known carcinogen, which means exposure to benzene over a long period of time, or to high enough concentrations can increase the risk of developing cancer.
At higher concentrations, the major effect of long-term exposure to benzene is on blood. Benzene causes harmful effects on bone marrow and can cause a decrease in red blood cells leading to anaemia. It can also cause excessive bleeding and can affect the immune system, increasing the chance for infection.
Short-term exposure to high levels of benzene can cause drowsiness, dizziness, unconsciousness and death. Waikato Regional Council monitors benzene to determine people’s exposure to it in areas where the air quality is suspected to be poor.
The main sources of benzene in Hamilton city are motor vehicles and domestic fires. Waikato Regional Council measures three-month average levels of benzene at six sites in Hamilton. This indicator reports data results from these sites, collected over the period 2003-2018.
Concentrations of benzene in the air have generally decreased at all sites from 2003 to 2018.
Monitoring results show that from 2003 to 2005 benzene measured at Bridge Street and Claudelands Road, two high-density traffic sites in Hamilton, would have breached the current National Ambient Air Quality Guideline for benzene, which is 3.6 µg/m3 (annual average).
Results indicate a decreasing trend in benzene concentrations which is likely to have been caused by a reduction of benzene in petrol over this monitoring period. From 2006-2018 ambient concentrations have been lower than the guideline of 3.6 µg/m3 at all six Hamilton sites.
This indicator is updated annually.
Air quality scientist - Science and Strategy Directorate
Last updated May 2019