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Dokumentation af sinkeffekter for tetrachlorethylen

English Summary

The purpose of the project has been to illustrate the sink effect² in connection with dry-cleaning establishments and surrounding habitations.

Selection of Localities for Measurements

For this purpose two localities were identified.

"Locality 1" was a pavilion, which for the past six months had been used as a place to hand in and pick-up tetrachloroethylene-cleaned textiles. The cleaned textiles and the remaining interior were removed immediately before the measurements were initiated.

"Locality 2" was found in an old three-storied apartment building. Locality 2 consisted of a basement, a ground floor with former dry-cleaning premises and an appartment flat on the first floor right above the dry-cleaning establishment.

Presence of Sink Effect

Measurements showed that there was a sink effect at both Localities. Concentrations of tetrachloroethylene in the indoor air exceeding criteria for air quality were found in Locality 1 and 2, respectively 40 days and more than one year after the cleaning activity had ceased. Thus, there was a long and significant desorption of tetrachloroethylene from the building materials on both premises.

Calculations made by means of the EAQX 1.0 model indicate that when a building has been affected by contaminants from dry-cleaning activities for a period of time, a sink effect will appear. This sink effect means that even months or years after the dry-cleaning activities have ceased, contamination of the indoor air exceeding the criteria for air quality can be measured.

Increase of Contamination on Sink Materials

From the measurements carried out and from the literature it can be established that the concentration of pollution that the building has been exposed to is not the only factor that is important for the length of the desorption. Also, the nature of the sink materials influences the amount of contaminants that can be absorbed. For example, building parts as bricks and concrete can generally absorb greater amounts of contaminants than plasterboard and wood. If the materials contain an organic or fat based phase this will also increase the absorption. From the results, it can be concluded that fatty foodstuffs are good sinks.

Problems

The sink effect implicates that several problems can occur in relation to among other things:

The planning of control measurements in dry-cleaning establishments after technical initiatives to reduce the emission of tetrachloroethylene Interpretations of measurements of the indoor air quality and measurements of soil gas concentrations under sections of polluted building.

The sink effect can also be expected for other environmentally hazardous substances. Consequently, similar adsorption and desorption can be expected for many of the environmentally hazardous materials used in both housing and small industries in the housing areas e.g. gas stations, paint dealers, car painters and mechanics.

The Need for further Knowledge about the Sink Effect

The presence of sink effect means that caution must be exercised when the results of the measurements in housing including the assessments of risks are interpreted. Furthermore, the sink effect must be included in the estimate to the greatest possible extent.

A proper estimate of the influence of the sink effect will however require further full-scale investigations, and principles for investigations and risk assessments should include the sink effect.