A comparison of anthropogenic mercury emissions reported from New Zealand, Ireland, Denmark, Canada, Australia, the United States and the United Kingdom is provided in Table II-12. The year of the inventories represents the most current information acquired as part of this study, ranging from 1994-1995 (United States), 2001 (Denmark), 2006-2007 (Ireland, Canada, Australia and United Kingdom) and 2008 (New Zealand). No natural emissions are included in the UN toolkit methodology and data on natural mercury emissions are not included in any of the above studies.
Only New Zealand and Denmark followed the protocols described in UNEP (2005) for identification and quantification of mercury releases. Mercury data reported from Ireland, Canada, Australia, the United States and the United Kingdom were originally compiled into source categories based on each individual country’s environmental governing agencies individual assessment. As part of this study, the source categories were reclassified to fit in with the source categories specified in UNEP (2005) as shown in Table II-12.
A direct comparison between countries cannot be made as different countries included different items. Mercury data reported from Ireland, Canada, Australia, the United States and the United Kingdom is based predominantly on industrial mercury emissions, whereas, those from New Zealand and Denmark also report mercury within consumer products and measuring devices.
Australia also included mercury released from emissions off paved and unpaved roads, which accounted for 47% of their reported mercury (reported as a “potential area with elevated mercury concentrations” in Table II-12). Australia is the only country to report mercury emissions from this source and no data exists in New Zealand to calculate emissions off roads. Also the UN Toolkit methodology used in this assessment does not include emissions from roads as one of the potential mercury emissions sources.
In estimating the atmospheric emissions of mercury from petroleum products combusted in the Untied States, the US EPA estimated that crude oil contained 1.5 mg/kg (1.5 ppm) of mercury (US EPA, 1997; Wilhelm, 2001). However, recent work undertaken by the US EPA to determine the mean concentration of mercury in crude oil in the United States has found that the average (arithmetic mean) concentration of mercury in crude oil is close to 0.01 mg/kg (10 ppb) (Wilhelm, 2001; Wilhelm et al, 2004). Therefore, the US EPA estimate for mercury released by Fuel/Energy source is likely to be significantly in error on the high side (Wilhelm, 2001).
Because of such differences, including methodological differences, differences in population, land areas, climate, resources, industrial activities, emission controls and technological advancement, it is difficult to justify making direct comparisons of mercury releases and uses from each of the countries evaluated during this study. On a per capita basis (Table II-12), the total mercury inventories compiled for New Zealand, Ireland, Canada, the United States and the United Kingdom are comparable (of the order of 10-4 kg/person/year), whereas that of Denmark and Australia are an order of magnitude greater (10-3 kg/person/year). Excluding mercury releases from paved and unpaved roads, a total of 6 x 10-4 kg of mercury/person/year was reportedly released into the environment in Australia.
Given the differences in compilation methodology, no significance can be given to the United Kingdom per capita value being apparently lower than New Zealand and Ireland, which have similar per capita values. New Zealand and Ireland’s per capita values are generally lower than all the other countries except the United Kingdom.
Consideration was given to making a comparison normalised by gross domestic product (GDP) in an attempt to measure mercury emissions in terms of economic activity, but given the different basis of the inventories for each country this was abandoned.