Undersøgelse af effekten af intervention på børns eksponering for bly

Study of the Results of Intervention to Reduce the Exposure of Children to Lead

1 Summary

Large areas with contaminated soil exist in the urban environment. Human risk assessment related to this exposure source is based on the oral intake of soil among young children (2-5 years). This exposure is a consequence of the mouthing behavior in young children, which exposes the children to whatever adheres to their hands or toys. In most cases, the exposure will be a mixture of contaminants including heavy metals as well as more persistent organic pollutants. This report focuses on exposure to lead, but with slight modifications the results will probably also apply to other soil contaminants. Two issues were addressed in this report. We studied whether there was proportionality between the concentration of lead in soil and the amount of lead that adhered to the hands of children playing on this soil. Secondly, we evaluated whether interventions through physical changes on the playgrounds in two of the daycare centres, in accordance with recommendations from the Danish EPA, would reduce the amount of lead on the hands of children, and thereby potential exposure. The results and conclusions are summarised below.

A relevant and suitable method for assessing lead adhering to the hands of children was applied.
The groups of children from the three participating daycare centres fulfilled the inclusion criteria regarding distribution of age and gender.
Based on information from the municipality of Copenhagen, three daycare centres were included in the study. One with low concentrations of lead in soil and two with lead concentrations within the guidance interval (lead in soil < 400 mg/kg). Subsequent analyses of lead in soil confirmed these measurements, and emphasized the significant variations in lead concentrations in soil, even within confined areas such as a daycare centre.
The interventions that were implemented in two daycare centres were clearly verified through subsequent analyses of lead in soil. The concentrations of lead in soil from the most heavily used areas of the playgrounds are now at a comparable and low level in all three daycare centres.
Changes in lead concentration in indoor dust did not directly reflect the changes in concentrations of lead in soil following intervention. The effect on indoor dust following the changes in outdoor soil concentrations may, however, be delayed.
There was a clear correlation between lead in soil and lead on hands, though the correlation was not in direct ratio.
Sampling was concentrated on dry days. Results from a single wet day indicated that children would have an increased exposure under these conditions. Consequently, our results might slightlyunderestimate the true exposure on a wider time scale including a mixture of dry and wet days.
Extensive differences in amounts of lead on hands were observed between children from the same daycare centre, probably reflecting different playing behaviors.
No gender-related differences were observed regarding lead on hands.
Following interventions in the two daycare centres, a significantly reduced median exposure, i.e., lead on hands, was observed among children. In one of the daycare centres, the exposure is now comparable to the exposure of children from the daycare centre with the initial low lead contamination.
The two interventions were focused on the areas on the playgrounds most heavily used by the children, and were accomplished with limited financial resources. Thus, the interventions did not include the traditional replacement of all soil down to 50 cm. Nevertheless, the project demonstrates that a limited but focused intervention approach has an immediate effect on hand exposure of children.
Lead in soil is the single most important source for children’s exposure to lead in Denmark. The interventions reduced exposure to lead from soil by 50 % on average and caused exposure levels to approach the exposure in the daycare centre with a low concentration of lead in soil. These improved exposure conditions are considered a promising way to achieve the authorities’ desired goal regarding reducing children’s exposure to lead from soil in a cost-effective way.
The interventions were evaluated two months after being implemented. Thus, this project gives no answers as to the durability of the interventions. The answer to this question must await further studies at a later stage.
This project was focused on daycare centres. However, equivalent interventions might be considered on public playgrounds with comparable concentrations of lead in soil. Achievement of the desired level of safety regarding children’s exposure to lead from soil from private gardens will, however, continue to depend on efficient information and advice for homeowners.