Waste incineration, with minor exceptions, is not permitted in New Zealand. A 10-year prediction is therefore not relevant.
As previously mentioned in Section II-3.2.9, the quantity of mercury-containing products reaching landfills in New Zealand cannot be measured. This is because there is insufficient information on the volume and frequency of mercury-containing products entering individual landfills.
An overall trend on mercury content in landfills over the next ten years is difficult to predict as some products that historically contained mercury have had their mercury content reduced or eliminated. However, some other products have had their mercury content increased (e.g. LFLs). In addition, variable price and consumer demand will cause variations in the volumes of mercury-containing products sold and therefore disposed of in time.
It is also difficult to predict whether in the next ten years there will be an increase in the rate of recycling of certain mercury-containing products. Currently there are not many district or city councils in New Zealand that provide lamp recycling services (Stewardship Solutions, 2008), and therefore such recycling is left to businesses like Interwaste. Suppliers such as Panasonic and Sony also offer some level of recycling for larger battery users but, although working well, this recycling is not widespread.
With respect to disposal of mercury in wastewater and ending up in biosolids, improved control of mercury being discharged from dentists and medical facilities and the possible reduction in the use of dental mercury amalgams could reduce the amount of mercury entering the wastewater system. However, it is not possible to estimate the magnitude that these changes would have on the average concentration of mercury being discharged from the wastewater treatment plants and in biosolids produced by the wastewater treatment plants.
As noted in Section II-3.2.9, no information has been obtained on the amount of mercury in the treated waste water being discharged from the wastewater treatment plants. However, since mercury forms strong complexes with organic matter, most of the mercury being discharged from treatment plants will be associated with the biosolids. To estimate the amount of mercury being discharged in the biosolids from the wastewater treatment plants the following assumptions have been made:
The 10-year prediction for mercury emission rates from biosolids discharged from wastewater treatment plants is 210 kg Hg/yr in 2018, compared to 180 kg Hg/yr in 2008.
Current mercury emissions from burial or cremating of bodies were based on the number of registered deaths for 2008 of approximately 29,200. Statistics New Zealand (2007) provides forecasts for population changes, including deaths, and recommends using its mid-range projection (referred to as Series 5). On-line tables associated with Statistic New Zealand (2007)21 provide predictions of mortality in five-year intervals. The average mortality rate for 2016 – 2021 from the series 5 projections is 26,000 per year. This is a decrease to 89% of the 2008 rate.
The 10-year predictions for mercury emission rates for burials and cremations have therefore been calculated as 89% of the 2008 rates, being 46 kg and 69 kg, respectively.
The estimate was based on 1991 WHO estimates for the number of amalgam fillings an average person has. Given New Zealand’s general long-term improvement in dental health with the widespread use of fluoridated water, it is possible that the calculated rate is an over-estimate. In addition, anecdotal evidence suggests that the use of amalgam fillings is decreasing and some people are choosing to have amalgam fillings replaced with ceramic fillings.