2 Summary

Langtidseffekten af intervention på børns eksponering for bly

In 2002 the effect of interventions on exposure of children to lead exposure was evaluated in two kindergartens. The interventions were physical changes (establishment of barrier membranes and replacement of top soil, worn down grass and other vegetation) on the most intensively used playground areas of the kindergartens. The interventions caused an immediate and significant reduction in children’s lead exposure during outdoor activities. Lead in indoor dust was not, however, reduced following interventions. Further, the evaluation immediately after the interventions did not allow for conclusions related to the durability of the interventions. The unanswered questions related to lead in indoor dust and durability of the interventions formed the background for the present study. The purposes of the study was 1) to document whether the levels of lead in the soil in the most intensively used areas of the playgrounds were unchanged and still below the quality criteria of 40 mg/kg soil; 2) to evaluate whether lead in indoor dust was reduced in comparison to measurements immediately after the interventions in 2002; and 3) to document whether the exposure of the children to lead in the kindergartens was unchanged since the most recent evaluation immediately after the interventions. The results and conclusions pertaining to the 2004 study are summarized below:

Results:

The study included children aged 3-6 years from two kindergartens (Stolemagerstien and Møllelængen), both situated on Amager in Copenhagen.
The exposure of the children to lead was evaluated through measurement of lead on hands after playing outside. The hands were wiped with a paper cloth, and the method was identical to the one validated and used in the first study from 2002.
Two significant advantages characterize measurement of lead on hands instead of the more traditional measurement of lead in a blood sample. Primarily, measurements of lead on hands after outdoor activities allow source and time-specific conclusions on lead exposure. This is in contrast to a blood sample, which will reflect exposure from a number of different sources accumulated over a longer time span. Secondly, the method is non-invasive, which eliminates blood sampling from otherwise healthy children.
The sampling period ran for two weeks in May 2004, with dry weather and temperatures between 12°C and 20°C.

Stolemagerstien

Compared to the situation following the intervention in 2002, the playground was changed as an area that was previously open soil/sand was now covered with asphalt and used for ball games. This ball area had significantly changed the playing pattern of children as they now used this area very much. A second change was that the barrier membrane established between the “old” soil and the new top soil was partly or totally removed in many places.
The average level of lead in soil at Stolemagerstien is back to the level before the intervention in 2002 (just below 100mg/kg). However, the highest concentrations in 2004 are considerably lower than the high values from 2002. This was not expected, but the most probable explanation is that the barrier membrane established between “old” soil and new top soil was removed in several places, which would allow for mixing and recontamination of the top soil.
The method of replacement of top soil after instillation of a barrier membrane, which was applied as part of the intervention at Stolemagerstien can only be recommended if larger or coherent pieces of membrane can be used. The consequence is that bushes and other minor vegetation must be removed before interventions using barrier membranes can be used.
Lead in indoor dust did not change following interventions on playground areas and is still at the pre-intervention level.
The lead exposure of the children, as evaluated through measurement of lead on hands 1½ years after the intervention, is unchanged as compared to the level immediately after intervention, and still significantly lower than before the intervention.

Møllelængen

The playground area at Møllelængen is unchanged since the intervention in 2002 except for minor areas on slopes where grass has been worn down.
At Møllelængen lead in soil is unchanged since the intervention in summer 2002. The concentration of lead in soil is thus clearly below 40 mg/kg. The soil level is therefore still some ten-times lower than before the intervention.
Lead in indoor dust did not change following interventions on playground areas and is still at the pre-intervention level.
The lead exposure of the children, as evaluated through measurement of lead on hands 1½ years after the intervention, is unchanged as compared to the level immediately after intervention, and still significantly lower than before the intervention. When evaluated through measurements of lead on hands, the exposure level at Møllelængen continues to be slightly higher than at Stolemagerstien.

Overall conclusions

Based on samples from children’s hands collected in 2004, we conclude that the exposure of the children has not changed since the intervention in 2002. The intervention from 2002 is therefore still functional. The continued low amount of lead on hands at Stolemagerstien is, however, probably more due to changed playing patterns. The changes made in 2002 at Møllelængen have worked as expected, are durable, and it is expected that comparable interventions at other kindergartens following the same focussed and cost-effective approach will be effective. In principle, more kindergartens can be renovated for the same amount of money using this focussed approach than normal using a more general intervention approach. A prerequisite is, however, that playgrounds are maintained regarding vegetation, grass coverage etc., and with special focus on a continuous and unbroken barrier membrane.
In neither of the kindergartens have the interventions caused any reduction in lead in indoor dust. We have no knowledge about the amounts of lead in indoor dust in neighbouring houses/apartments to the two kindergartens. Knowledge on this aspect could clarify whether the source of lead in indoor dust is kindergarten-specific or pertains to the neighbourhood as a whole.