| Air Quality Standards and Guidelines | Waihi North Project Air Discharge Assessment - Waihi Surface Facilities | 4396626-1331619777-99 | 16/06/2022 | 26 4 Air Quality Standards and Guidelines 4.1 National Environmental Standards and Guidelines for Ambient Air Quality Ambient contaminant concentration predictions may be compared with relevant criteria to assess the potential for adverse health and environmental effects to occur. The MfE Good Practice Guide for Assessing Discharges to Air from Industry (GPG Industry)22 sets out the order of priority for the use of various air quality assessment criteria as follows: ● Air Quality Standards contained in the Resource Management (National Environmental Standards for Air Quality) Regulations 2004 (NESAQ) ● New Zealand Ambient Air Quality Guidelines (AAQG) published by MfE (2002) ● Regional Plan objectives (unless more stringent than above criteria) ● World Health Organisation (WHO) guideline concentrations (where appropriate) ● California OEHHA reference exposure levels (REL) (acute and chronic) and US EPA inhalation reference concentrations and unit risk factors (chronic) ● Texas effects screening levels (if these have been derived from toxicological data in a transparent manner). The NESAQ Regulations set out ambient air quality standards for a number of contaminants, including PM10, SO2, CO and NO2, for the protection of public health. The NESAQ and the AAQG are intended to apply where people are likely to be exposed for periods commensurate with the relevant assessment averaging period. The NESAQ and AAQG include both concentration limits and the specified number of occasions that those concentration limits may be exceeded within any year. The Regional Ambient Air Quality Guidelines for Waikato are consistent with the AAQG and are not more stringent than the NESAQ or the AAQG. The air quality criteria which are relevant to this project are summarised in Table 4-1. In February 2020, the Ministry for the Environment released a consultation document on some proposed amendments to the NESAQ23 (MfE Consultation Document), including new standards for ambient air concentrations of PM2.5 and some new controls on mercury emissions. The new standards for PM2.5 are proposed to be 25 µg/m3 (24-hour average) and 10 µg/m3 (annual average). The proposed mercury controls include the adoption of best practice emission controls on new, or substantially changed processes that discharge mercury to the atmosphere including the smelting and roasting of metals in accordance with the Minimata Convention. The discharge of mercury from the gold room and the potential effects of the discharge are discussed in Sections 3.6 and 7.7. It is emphasised that the proposed amendments to the NESAQ are in the consultation stage and do not have any regulatory status at present. However, for completeness the assessment of effects have also considered these criteria. There is no existing or proposed NESAQ ambient air quality standard for mercury. An AAQG of 0.33 μg/m3 has been published for inorganic mercury. The AAQG is comparable to the US EPA’s RfC of 0.30 μg/m3 and the US Agency for Toxic Substances and Disease Registry (ATSDR) chronic minimum risk level (MRL)24 of 22 Ministry for the Environment, 2016, “Good Practice Guide for Assessing Discharges to Air from Industry” 23 Ministry for the Environment “Proposed amendments to the National Environmental Standards for Air Quality, Particulate Matter and Mercury Emissions”, February 2020. 24 https://wwwn.cdc.gov/TSP/MRLS/mrlsListing.aspx
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