Mercury pollution in the environment can result from a number of activities. For example:
Discharges to land, water and air are controlled under the Resource Management Act (RMA) (1991) process, which allows regional councils to allow activities to occur under certain conditions (Section V-2.1). Such processes should limit the amount of mercury entering the environment from discharges where mercury is a residual component.
The use, storage, handling, transport and disposal of hazardous substances is controlled under both the RMA and the Hazardous Substances and New Organisms (HSNO) Act 1996. These two pieces of legislation aim to limit any pollution to the environment which may occur when using, handling and storing hazardous substances (Section V-2.2).
All mercury-containing products are made offshore and imported into New Zealand. The New Zealand Customs Service is responsible for enforcing the regulations around allowing certain products into the country. However the New Zealand Customs Service does not make decisions on which products are allowed over the border, rather it relies on other agencies such as the Environmental Risk Management Authority (ERMA), Ministry of Health (MoH), Ministry if Economic Development (MED), Ministry for the Environment (MfE), and the New Zealand Police to provide the regulations. Currently there are no controls on the quantity of mercury allowed in certain manufactured products that are imported into New Zealand.
The RMA 199123 (the Act) is New Zealand’s main environmental legislation, which sets out the framework for managing the effects of activities on the environment. The purpose of the act is to “promote the sustainable management of natural and physical resources”. A main principle of the Act is avoiding, remedying, or mitigating any adverse effects of activities on the environment.
Section 15 controls discharges of contaminants to the environment. Discharges of contaminants are not permitted unless allowed by a rule in a regional plan, by a resource consent or by a regulation.
The Hazardous Substances and New Organisms (HSNO) Act 199624 is an environmental and health and safety legislation, implemented and operated by ERMA and enforced by various agencies, that is designed to manage the risks of using hazardous substances in business and at home (MfE, 2001).
ERMA’s roles include making decisions on applications to import or manufacture hazardous substances in New Zealand, and setting Tolerable Exposure Limits (TELs) that limit public exposure from the use of hazardous substances and Environmental Exposure Limits (EELs), which establish the maximum concentration of an ecotoxic substance legally allowable in a particular environmental medium (e.g. water, soil or sediment). To date ERMA has not set any TELs or EELs for any mercury-containing substance.
The Local Government Act 199225 sets out the powers and responsibilities of regional and district councils in New Zealand. Section 145 provides general powers for territorial local authorities to make bylaws, with Section 146 providing specific powers for regulating, amongst other things, waste management, trade wastes and solid wastes. Many district and city councils have trade waste bylaws to control the concentrations of various hazardous substances, including mercury, entering sewers. The intent is to reduce the load on municipal wastewater treatment plants and to enable councils to meet the terms of discharge consents for their treated wastewater discharges.
The Health and Safety in Employment Act 199226 controls health and safety in the work place, including the use of hazardous substances. Section 20 of the Act provides for issuing of approved codes of practice. One of these is the Approved Code of Practice for the Management of Substances Hazardous to Health in the Place of Work, issued by the Occupational Safety and Health Service (OSH) of the Department of Labour (OSH, 1997). This sets out good practice for the storage, use and monitoring of hazardous substances. OSH has also issued Workplace Exposure Standards (WES) for atmospheric contaminants, which includes a standard for mercury (OSH, 2002).
The Health Act 195627 was amended by the Health (Drinking Water) Amendment Act in October 2007 and aims to protect public health by improving the quality of drinking-water provided to communities. The Health Act requires drinking-water suppliers to take all practicable steps to ensure they provide an adequate supply of drinking water that complies with the New Zealand Drinking-water Standards28.
These standards set maximum acceptable values (MAV) for a range of contaminants, including mercury, and monitoring requirements. The MAV for mercury in New Zealand drinking water is 0.007 mg/L (Ministry of Health, 2008), which has been derived from World Health Organisation (WHO) information.
In New Zealand, food is regulated under the Food Act 198129 and delegated legislation under that Act. Under Section 11C of the Food Act 1981, the Minister of Food Safety has the power to issue food standards that set minimum requirements for the quality and safety of food for sale.
One of the five New Zealand Food Standards made under the Food Act is the Australia New Zealand Food Standards Code. The New Zealand (Australia New Zealand Food Standards Code) Food Standards 2002 is the legal instrument that incorporates the Australia New Zealand Food Standards Code into New Zealand law. The New Zealand Food Standard (2002) sets a maximum level of mercury in fish of between 0.5 and 1 mg/kg.
There are no mercury emissions standards in New Zealand. Instead, under the RMA 1991 the impact of a discharge on its receiving environment is evaluated and controls are then set on the discharge to avoid, remedy or mitigate any adverse effects that the discharge may have.
There are four main guideline documents which are commonly used in New Zealand to assess the impact of mercury on the environment. These are:
The ANZECC (2000) guidelines provide water quality guideline trigger values for the protection of aquatic ecosystems (either fresh or marine) against toxicants. These guidelines have been derived using data from single species toxicity tests on a range of test species. High reliability trigger values were calculated from ‘chronic no observable effect concentrations’ (NOEC) data. A statistical distribution method has been used to calculate four different protection levels (99%, 95%, 90% and 80% ecosystem protection) for high reliability trigger values. The guidelines recommend that the 99% ecosystem guideline of mercury (0.06 µg/l for fresh water or 0.1 µg/l for marine water) be used to protect aquatic ecosystem due to mercury’s ability to bioaccumulate.
The ANZECC (2000) guidelines also set interim guideline values for sediment quality (ISQGs) for the protection of sediment-dwelling organisms. For each trace element (including mercury), there are two ANZECC (2000) guidelines for sediment quality. The lower guideline value is the Interim Sediment Quality Guideline-low (ISQG-low) which represents a concentration below which adverse effects are unlikely. The ISQG-low guideline value for mercury is 0.15 mg/kg. Concentrations of contaminants below the ISQG-low pose a low level of risk to aquatic organisms.
The higher guideline value is the ISQG-high, which is a median level at which adverse effects are expected in half of the exposed organisms. The ISQG-high guideline value for mercury is 1 mg/kg. Contaminant concentrations above the ISQG-high are interpreted as being reasonably likely to cause significant adverse effects on aquatic organisms. Concentrations between the ISQG-low and ISQG-high are thought to pose a moderate level of risk to aquatic organisms. The ANZECC(2000) guideline values are designed to be trigger values which, when exceeded, trigger further investigations, although they are commonly used as compliance values in consents.
The MfE Ambient Air Quality Guidelines (MfE, 2002) are the minimum requirements that outdoor air quality should meet in order to protect human health and the environment. Where air pollution levels breach guideline values, emission reduction strategies should be implemented to improve air quality. Where levels do not breach the values, efforts should be made to maintain air quality and, if possible, reduce emissions (MfE, 2002).
The MfE (2002) Ambient Air Quality Guidelines set an annual average guideline concentration for inorganic mercury of 0.33 µg/m3, and 0.13 µg/m3 for organic mercury compounds. The value for inorganic mercury is derived from the occupational health standards for inorganic mercury and the US EPA reference concentration (RfC) and the Californian Air Resources Board’s reference exposure level (REL) values (MfE, 2002). The value for organic mercury is derived from the value for inorganic mercury by scaling according to the occupational health standards (MfE, 2002).
The MfE state that the Ambient Air Quality Guidelines for mercury should be viewed as applicable where exposure to mercury is mainly through inhalation. They need to be adjusted downwards where dietary intake of mercury is significant (MfE, 2002).
The Hazardous Waste Guidelines (MfE, 2004) published by MfE set out waste acceptance criteria for two classes of landfills, Class A and Class B, as well as recommending the use of the US EPA Toxicity Characteristic Leaching Procedure (TCLP) to assess the leachability of hazardous waste material. While the guidelines are recommended for use by landfill operators in setting out which wastes are prohibited and for setting limits on acceptance of hazardous waste, they have no regulatory force unless referenced by the consents for a particular landfill or within a district plan. Many landfills were consented prior to the publishing of the guidelines and therefore may have different limits set. The landfill operator may voluntarily choose to apply the waste acceptance criteria in MfE (2004) if the criteria are more stringent than the consented limits.
The guidelines state that waste containing more than a screening limit of 4 mg/kg of mercury or a leaching test concentration of greater than 0.2 g/m3 should not be disposed of to a Class A landfill without treatment to reduce its leachability. The corresponding values for a Class B landfill are a tenth of the Class A values.
Individual items such as batteries, fluorescent lamps and thermometers will considerably exceed the screening limits for mercury set in MfE (2004). Whether such items exceed average concentrations will depend on how much other waste the items are landfilled with.
The NZWWA (2003) Guidelines for the Safe Application of Biosolids to Land in New Zealand are designed to provide a framework for biosolids management to minimises the risk of adverse effects on human health, the environment and the economy from long-term application of biosolids to land (NZWWA, 2003). The biosolids guidelines recommend that soil concentration should not exceed more than 60 mg/kg of mercury and the biosolids should not contain more than 4 mg/kg (NZWWA, 2003).