Executive Summary
This report considers health effects literature in the context of concentrations of carbon monoxide (CO), nitrogen oxides (NOx), sulphur dioxide (SO2), ozone, benzene and benzo(a)pyrene (BaP) currently measured in New Zealand. The purpose of this report is to provide an indication of the extent to which existing concentrations of air contaminants in New Zealand may compromise health. This data will be subsequently used to evaluate the health benefits of improving air quality in New Zealand through the implementation of national environmental standards. While this report also describes benzene and benzo(a)pyrene, these contaminants have not yet been selected for standards development. They may be considered in the future.
In most areas of New Zealand, concentrations of CO, NO2, SO2, and benzene are below their respective ambient air quality guideline values (Ministry for the Environment, 2002). The main exceptions are concentrations of CO in the ambient air in Christchurch as well as roadside concentrations in Auckland, Christchurch, Wellington and Dunedin and roadside concentrations of NO2 in Auckland.
There may be some health impacts as a result of exposure to CO concentrations in Christchurch and near to roadsides in Auckland and Wellington. Potential health impacts include a significant decrease in work capacity in healthy adults, decreased exercise capacity at onset of angina and increased duration of angina in people with ischaemic heart disease. Similarly prolonged exposure to concentrations measured at these sites and other sites such as those measured at Dominion Road and Khyber Pass could impact on developing foeti resulting in reduced birth weight in non-smokers.
The guideline values for NO2 for New Zealand are based on a safety factor of 50% applied to the lowest observable adverse effect level for the protection of sensitive groups including children and asthmatics and people with chronic respiratory and cardiac disorders (Ministry for the Environment, 2002). Because the maximum one-hour average NO2 concentrations measured at Khyber Pass Road are in excess of twice the guideline value, it is possible that sensitive individuals in this area will suffer health impacts as a result of NO2 exposure. It is also possible that adverse health effects may occur as a result of NO2 exposure close to other roadsides within Auckland, e.g. Dominion Road. In other areas of New Zealand, ambient air concentrations of NO2 do not breach the guideline values and is unlikely to be causing adverse health effects.
Ozone concentrations have been measured in Auckland and on the outskirts of Christchurch. An estimate of the impact of ozone concentrations on mortality in Auckland indicates that over 100 deaths per year may be attributable to exposure to ozone concentrations. Concentrations of ozone in Auckland were in excess of the ambient air quality guideline values at one monitoring site. No estimates were made for Christchurch because of the large uncertainties surrounding exposure.
Although ambient air benzene concentrations are generally within existing guideline values, there is no threshold of effects for this contaminant. Estimates of health implications for New Zealand were made based on approximate concentrations of benzene in the major urban areas. This indicated that of the existing population in each area, leukaemia as a result of ambient air exposure to benzene was likely to affect less than 10 people in Hamilton and Dunedin, less than 40 people in Christchurch and less than 70 people in Auckland. This was based on the assumption of lifetime exposure to current benzene concentrations.
The potential health impacts of exposure to ambient air BaP in New Zealand could only be assessed for Christchurch because of the limited amount of monitoring that has been carried out for this contaminant. The annual average concentrations of BaP in Christchurch were over 10 times the ambient air quality guideline value. Around 70–100 people in Christchurch could be affected by exposure to this probable carcinogen, compared to around seven people if the ambient air quality guideline value for BaP was met.
