How mercury ends up in humans and the environment
Mercury can cause severe damage to both health and the environment. Perhaps the most serious damage is that caused to the nervous system of humans during the foetal period and the consequent risk of impaired learning and development in children.
This is because in the aquatic environment mercury primarily exists in the form of the mercury compound methylmercury, which because it is more easily taken in and bioaccumulated by the body actually has a toxic effect greater than that of metallic mercury.
Some of the most important Danish sources are reviewed briefly below ( Environmental Project No. 808: Mass flow analysis for mercury 2001, 2003 ). It is stressed that there is a significant difference between the Danish sources and mercury sources at a global level. There are for example no chlor-alkali plants in Denmark.
One of the most important Danish sources of atmospheric emissions is combustion, which is probably due to the addition of mercury to batteries, contacts and relays, energy-saving light bulbs and other mercury-containing products that people do not dispose of appropriately.
Another important source of atmospheric emissions is coal-fired power stations. It must be stressed that there are requirements concerning the installation of filters at waste incineration plants, power stations and crematoria, considerably reducing emissions from these sources. Discharges into the aquatic environment can take place via wastewater from municipal treatment plants, which theoretically could be contaminated with mercury from dental clinics; there are however, general requirements concerning amalgam filters at dental clinics.
Discharge into the ground primarily takes place via wastewater sludge and churchyards (dental fillings). Most mercury disposed of at landfills is present in waste products from waste incineration; this form of disposal takes place abroad. Mercury and mercury-containing waste are collected in Denmark; this waste is exported.