Contamination of Polycyclic Aromatic Hydrocarbons (PAH) in Apartments with Parquet Flooring
Results of a symposium on 25 March 1998 at the Federal Environmental Agency
Measurements in apartments with wood parquet flooring in Frankfurt am Main previously used by the US Forces showed increased levels of polycyclic aromatic hydrocarbons (PAH) in the house dust on the floor. PAH is the collective term for a family of chemical substances which includes numerous compounds. Some PAH are regarded as carcinogenic. PAH are generated during incineration processes, but are also found in tar and bituminous products. Indoors, tobacco smoke is a significant source. PAH can be absorbed through the air, through skin contact and in food.
In Frankfurt, widely varying concentrations of PAH were found in the house dust, principally ranging between 10 and 1000 milligrammes per kilogramme (mg/kg). The cause of the increased PAH contcentrations is the glue used to fix parquet tiles. In some cases, the measurements looked at both house dust and suspended dust in indoor air. The PAH concentrations in indoor air corresponded to those measured outdoors. To determine PAH intake, urine samples from 60 children living in apartments with parquet flooring laid using tar or bitumen glue in Frankfurt were tested for metabolites of PAH and compared with those of 23 children from other apartments.
Similar cases of increased levels of PAH have been reported in Baden-Württemberg, Bayern, Rheinland-Pfalz and Berlin.
Due to considerable public concern and the significance of the problem in a number of German states, the Federal Environmental Agency (FEA) responded to requests from the federal environment, health, construction and finance ministries by organising a symposium on 25th March 1998 in Berlin, to which scientists and officials from federal, state and municipal authorities were invited. The available data, some of it difficult to interpret, was brought together and evaluated, to create a uniform information base and arrive at a common assessment of the health risks arising from PAH contamination in apartments with parquet flooring. Because of the complexity of the problem, it was not possible at the time to formulate any concrete recommendations as to how PAH contamination could be reduced. For this reason, the experts will meet again soon to discuss the unsettled issues.
The results of the first meeting can be summed up as follows:
- Until the 1950s, the parquet glues used in housing construction contained bitumen and tar oils; subsequently, pure bituminous glues were used until the mid-1970s, when differently based glues were introduced. The PAH content of tar oils is considerably higher than that of bitumen. The use of these glues was, at the time, the best available technology. They were used almost exclusively for laying block parquet, however, and hardly ever for mosaic parquet.
- Studying the available results of analysis so far reveals that the PAH content of the glues and that in house dust vary widely. In the case of house dust, an important reason for this is the way in which samples are taken. The samples were obtained either by vacuuming the floor or by sweeping the dust together. If the parquet flooring is in poor condition, some of the glue from the substructure can end up in the sample when the floor is vacuumed. This does not happen when the floor is swept. The experts were therefore of the opinion that samples obtained by sweeping permit a better assessment of contamination.
- As regards the results of the urine analysis, the experts came to the conclusion (taking into consideration the results of the Federal Environmental Agencys Human Biomonitoring Commission, a body consisting of independent experts) that the data available so far albeit from a small sample do indicate increased contamination in children from apartments with PAH parquet glues.
- The experts also agreed that benzo(a)pyrene (BaP), which is classed as a carcinogen, should be used as the indicator for PAH. This is standard practice at both national and international level.
- BaP can be absorbed through breathing, food or skin contact. It was noted that the amount of BaP absorbed through breathing is more or less insignificant compared with that of the other absorption paths. The absorption of BaP through house dust can at times equal absorption through food, and at times can exceed it.
- There was agreement that children up to the age of six who generally play on parquet floors are particularly heavily exposed, and should therefore be given prime consideration in any health-related assessment.
- For a child, daily absorption of around 100 milligramme (one tenth of a gramme) of house dust must be assumed as a base value. In keeping with to the precautionary principle, it was assumed that the entire BaP content reaches the organism.
- To help in assessing the cancer risk associated with the BaP content of house dust, the experts used a value contained in secondary regulations under the Federal Soil Protection Act, which are in preparation (as of 16th June 1997). The substantive basis for these regulations is sketched out in a paper from the federal states, where a risk of 5 x 10-5 with life-long exposure is given as the starting point in determining test values for risk. Taking as a basis the relationship between risk and exposure to BaP published by the World Health Organization (WHO), a BaP content of 10 mg/kg house dust would correspond to a risk of 5 x 10-5. This would mean that, with a life-long daily absorption of 100 mg house dust containing 10 mg/kg BaP, five additional cases of cancer per 100,000 persons would have to be expected.
This calculation and the unresolved issues, in particular with respect to a suitable analytical procedure and the possibilities of reducing the amount of contamination, will be the subjects of discussion at a further symposium.