Section V – Mercury Pollution Controls:
4 Comparison of New Zealand and International Guidelines Values
The section sets out a number of comparisons for standards and guidelines for occupational settings and for air and water environments.
4.1 Occupational Exposure Limits
Occupational exposure limits for mercury in New Zealand and in most overseas countries tend to be based upon the guideline values recommended by the American Congress of Government and Industrial Hygienist (ACGIH). As shown in Table V-1 and Table V-2, the values for mercury and methylmercury for most jurisdictions are the same. No short term exposure limits (STEL) for either inorganic or organic mercury compounds have been set in any of the countries reviewed.
| Country | TWA (8 hour) | Ceiling |
|---|---|---|
| Australia | 0.025 | |
| Canada | ||
| - British Columbia | 0.025 | |
| - Quebec | 0.025 | |
| Denmark | 0.025 | |
| Ireland | 0.025 | |
| New Zealand | 0.025 | |
| UK | No guideline | |
| USA | ||
| - ACGIH | 0.025 | |
| - NOISH | 0.05 | 0.1 |
| - OSHA | 0.1 | 0.1 |
Note: TWA = time weighted average
| Country | TWA (8 hour) | Ceiling |
|---|---|---|
| Australia | 0.1 | |
| Canada | ||
| - British Columbia | 0.01 | |
| - Quebec | 0.01 | |
| Denmark | 0.01 | |
| Ireland | No guideline | |
| New Zealand | 0.1 | |
| UK | No guideline | |
| USA | ||
| - ACGIH | 0.01 | |
| - NOISH | 0.01 | 0.1 |
| - OSHA | 0.01 | 0.1 |
4.2 Ambient Air Quality Criteria
Ambient air quality guidelines for various jurisdictions are presented in Table V-3. There is a considerable range of values. The values from Texas and Washington State are very conservative compared with the New Zealand ambient air quality guidelines (MfE, 2002b). However, the MfE criteria are lower than the WHO ambient air quality criteria for Europe (Table V-3).
Exposure to the MfE ambient air quality criteria of 0.33 µg/m3 would result in the total intake of mercury of only 50.82 µg /week, or 0.726 µg/kg bw/week, for a 70 kg adult, which is less than 1% of the PTWI.
| Compound | 24-hour | Annual | |
|---|---|---|---|
| US - Texas Commission for Environmental Quality ESL | mercury (inorganic) | 0.25 | 0.025 |
| mercury (organic) | 0.1 | 0.01 | |
| US - Washington State Department of Ecology ASIL | mercury (divalent) | 1.03 | 9x10-3 |
| mercury (ion) | 0.95 | 8.95x10-3 | |
| NZ- MFE-Ambient Air Quality Guidelines | mercury (inorganic) | 0.33 | |
| mercury (organic) | 0.13 | ||
| WHO- Air quality guidelines for Europe | mercury | 1 |
4.3 Water Quality Criteria
In Australia and New Zealand the ANZECC (2000) guidelines provide water quality guideline trigger values for the protection of aquatic ecosystems (Section V-2.7). As can be seen in Table V-4, the Australian and New Zealand guideline values are slightly higher than the equivalent Canadian guideline value, but are significantly lower than the chronic continuous concentration (CCC) for long-term exposure to aquatic organisms and the chronic maximum concentration (CMC) for short term exposures set by the US EPA, and the Environment Quality Standards recommended by the EU. However, all four jurisdictions allow their guidelines to be adjusted upwards or downwards by the regulator authorities depending on site-specific conditions. Only Canada has set a water quality criterion for methylmercury.
| Country | Freshwater | Marine |
|---|---|---|
| Australia/New Zealand (99% protection) | 0.06 | 0.1 |
| Canada – inorganic mercury | 0.026 | 0.016 |
| Canada – methylmercury | 0.004 | |
| United States – CCC | 0.77 | 0.94 |
| United States – CMC | 1.4 | 1.8 |
| European Union | 5 | 7 |
