Clean air - Danish efforts
Other hazardous compounds
A series of organic compounds are hazardous in themselves. By measurements and calculations of emissions, the permissible load of these compounds in the atmospheric environment is regulated when plants are approved. In recent years a few compounds have, however, attracted special interest.
Dioxins
The so-called dioxins comprise 210 closely related polychlorinated dibenzodioxines (PCDD) and furanes (PCDF). Their transport in the environment is complicated. The main source is combustion, typically incineration of material containing chlorine, but dioxin is also formed in e.g. straw and wood stoves.
Primarily, dioxin is an air pollutant, but it is not direct inhalation, that is crucial for the impact on health. Dioxins, which are very stable, are deposited on the soil and water surfaces. As they are fat-soluble they move easily from the soil and water to the food chains and are then absorbed through the food. This also means that it can be dispersed in various ways.
Dioxins are some of the most toxic compounds known. They are carcinogenic, they may have endocrine-disrupting effects, and inflict damages to the unborn child. Special attention has been given to the content of dioxin in mother's milk.
In 1998 WHO (World Health Organisation) established a tolerable daily intake (including the related PCB) at between 1 and 4 pg/kg bodyweight, while at EU level the tolerable daily intake has been fixed at 2 pg/kg. At the same time it is estimated that the load in Europe is an average of 2-6 pg/kg. The Danish Veterinary and Food Administration has on the basis of data from other countries conservatively estimated that the Danish intake is about 5 pg/kg. Although the content of dioxin in food and mother's milk is falling, there is every reason to continue efforts to reduce the load. The Minister for the Environment has in collaboration with the Minister for Food, Agriculture and Fisheries prepared a dioxin action plan to reduce dioxin emissions and provide new knowledge on sources and pollution of food and environment.
Further, the Minister for the Environment has issued a statutory order under which the incineration plants must observe a limit value of 1.1 nanogram dioxin per cubic meter flue gas by the end of 2004. So far it appears that this is possible at about 90% of all utilities. Industry is faced with similar requirements.
Many organic compounds are hazardous. Even if they start as air pollution, they may go a long way through dispersion in the atmosphere and the food chains before the impacts appear. This may make it difficult to trace the sources and reduce emissions. Dioxin in mother's milk is a typical example.
The EU has further established limit values for a series of animal foodstuffs in particular. The objective is to reduce the total human exposure to dioxin by at least 25% in 2006.
Polycyclic organic material
Combustion of material - typically wood and oil products with cyclic hydrocarbons - generates a series of mutagenic and carcinogenic compounds. The polycyclic aromatic hydrocarbons (PAH) are the most important.
Environmental concern for these compounds dates back to the 19th century, when many incidences of skin cancer were observed in workers in the tar industry. The first carcinogenic compound, benzo(a)pyrene was identified in tar in 1933, but it was not before the 1970's that the relation with air pollution became evident. Volatile PAH is in the gaseous phase, but the heavier and carcinogenic PAH has a tendency to attach to particles. Inhalation of such particles in the working environment has been shown to cause lung cancer.
In Denmark measurements were carried out at the Copenhagen Airport in 1988-89, and concentrations of about 2 ng/mg3 were found. At the busy street H.C. Andersens Boulevard in central Copenhagen up to 10 ng/m3 were measured.
As part of the report to UNECE, emission inventories have been prepared for four compounds: Benzo(a)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene and indeno (1,2,3-cd)pyrene. Total emissions in 2000 were about 11,000 kg. There are minor contributions from traffic and mobile sources, but nearly 3/4 come from increasing combustion of wood in private fireplaces.
Benzene
As described earlier lead is now completely removed as an additive to petrol in Denmark, and, thus, lead in the air has practically disappeared. But it has not been without side-effects, because it was necessary to control the octane number of the petrol buy changing its composition.
Some years ago it appeared that urban air contained the carcinogenic hydrocarbon benzene. A closer investigation indicated that benzene solely arises from unburned components in petrol. The refineries were therefore interested in introducing quickly a new technology for production of petrol with a low content of benzene. The reduction of the content of benzene in motor fuel has been documented by analysis of samples from Statoil at Kalundborg and Shell at Fredericia. In both cases the content was reduced from 3.5% to 1% during the summer of 1998. At the same time it was shown that the content of benzene in the air at the very busy street Jagtvej in Copenhagen has within a few years been reduced from about 10 µg/m3 to 3.4 µg/m3. The EU limit value for 2005 is 5 µg/m3. The problem with benzene is therefore largely under control.
Emissions of PAH
Danish emissions of PAH (Poly Aromatic Hydrocarbons) have increased in recent decades,
when the emissions have been measured. The main source is small firing units - i.a. open
fireplaces and wood burning stoves.
(Source: NERI)
Concentration of benzene
On the very busy street Jagtvej in Copenhagen the concentration of benzene has fallen
drastically since the middle of the 1990's when a reduction of the content of benzene in
petrol was introduced.
(Source: NERI)