| Air Quality Standards and Guidelines | Waihi North Project Air Discharge Assessment - Waihi Surface Facilities | 4396626-1331619777-99 | 16/06/2022 | 27 0.20 μg/m3. The lowest annual guideline level for mercury of 0.03 μg/m3 is published by OEHHA25. In contrast, the WHO annual average guideline26 for mercury is 1 μg/m3. Table 4-1 Relevant air quality assessment criteria Contaminant Averaging period Threshold concentration Number of permitted exceedances Source PM10 24-hour 50 µg/m3 1 NESAQ annual 20 µg/m3 - AAQG PM2.5 24-hour 25 µg/m3 1 Proposed NESAQ annual 10 µg/m3 - Proposed NESAQ CO 1-hour 30 mg/m3 - AAQG Running 8-hour 10 mg/m3 1 NESAQ NO2 1-hour 200 µg/m3 9 NESAQ 24-hour 100 µg/m3 - AAQG Respirable silica annual 3 µg/m3 - OEHHA Hydrogen Cyanide annual 9 µg/m3 - OEHHA 1-hour 360 µg/m3 - OEHHA Mercury Annual 1.0 µg/m3 - WHO 0.33 µg/m3 - AAQG 0.30 µg/m3 - USEPA RfC 0.20 µg/m3 - ASTDR MRL 0.03 µg/m3 - OEHHA Arsenic 1-hour 0.2 µg/m3 OEHHA 8-hour 0.015 µg/m3 OEHHA annual 0.0055 µg/m3 AAQG Cadmium27 annual 0.0056 µg/m3 USEPA Chromium (VI) annual 0.0011 µg/m3 AAQG Copper 1-hour 100 µg/m3 OEHHA Manganese 8-hour 0.17 µg/m3 OEHHA annual 0.09 µg/m3 OEHHA Nickel 1-hour 0.2 µg/m3 OEHHA 8-hour 0.06 µg/m3 OEHHA annual 0.014 µg/m3 OEHHA Lead 3-month 0.2 µg/m3 AAQG Selenium annual 20 µg/m3 OEHHA 25 OEHHA TSD for Non-cancer RELs December 2008 (Updated July 2014) Appendix D. Individual Acute, 8Hour, and Chronic Reference Exposure Level Summaries. https://oehha.ca.gov/media/downloads/crnr/appendixd1final.pdf 26 https://www.euro.who.int/__data/assets/pdf_file/0004/123079/AQG2ndEd_6_9Mercury.PDF 27 Calculated from the USEPA Cancer Inhalation Unit Risk of 1.8 x 10-3 per µg/m3. Derived guideline concentration represented a 1 /100,000 risk. The same guideline was used in the 2012 assessment. The non-cancer chronic exposure guideline level published by OEHHA is 0.02 µg/m3.
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