|Characterisation Method Name:|
|Hg air emissions impact on morbidity|
|Principal Method Name:|
|EPS: empirical method|
The characterisation factor is determined by the empirical method.
Category indicator value in system considered
Some groups of the population in North America, Europe and New Zealand eating much
locally caught fish tend to get high mercury concentrations in body tissue. This may lead
to various health effects but the one of most concern is mental retardation of children due to prenatal exposure (Kjellström et al., 1988). In a New Zealand study, 1000 out of 11000 new mothers had consumed fish more than three times a week. 73 of these had hair mercury levels above 6 mg/kg. 50% of the high mercury level children had abnormal or questionable test results in a Denver Development Screening Test, whereas only 17% of the reference children had such results. This indicates that 0.2% of a “fish eating” population like New Zealand is affected. Globally the “fish eating” population is in the order of 200 millions. 0.2% of these are 400000.
Contribution to category indicators value from a flow unit
The global anthropogenic emission of Hg is estimated to 8600 tons per year (UNEP, 1992) and the bio-geochemical is around 70000 ton (Fergusson, 1989). The atmosphere is the main transport route for mercury and the run-off from the lithosphere to the oceans is
only 3800 – 5000 ton compared to the mercury from precipitation, 25000 ton annually.
Totally the emissions contributing to the population exposure via fish is 8600+70000+4600 = 83200 ton.
Calculation of characterisation factor
The characterisation factor is thus 400000/83200000 = 4.8E-03 person-years/kg Hg.
|1. Kjellström, T., Kennedy, P. Wallis, S. and Mantell, C., “Physical and Mental Development of Children with Prenatal Exposure to Mercury from Fish”, Report 3080, National Swedish Environmental Protection Board, 1988. 2. UNEP Environmental data report 1991/92 p. 36, 1992. 3. Fergusson, J.E., “The heavy elements: Chemistry, Environmental Impact and Health Effects”, Pergamon Press, Oxford, 1990.|
|Having the global extension of the emission flow group, there will also be a global extension of the environment system. The time borders may be considerable as Hg has a tendency to "move around" in the environment. After having been deposited it may be re-emitted again as it may be chemically transformed from volatile to non-volatile compounds. The knowledge about these processes is however very limited as far as quantitative aspects are concerned. We therefore assume a "steady state" and make the analysis on one-year basis. The reference year will be the same as for emissions, 1985.|
|Characterisation Parameter||Category Indicator||Impact Indication Principle||Aspect||Substance||Quantity||Unit||Notes|