If a nature play area with mounds, bushes and small hiding places is planned, make sure that only clean soil is used. It is both fun and educational for children to grow their own vegetables and this should be encouraged where possible. It is uncertain to what degree crops absorb heavy metals and tar from the soil but soil dust can contaminate the surface of vegetables and fruit. Therefore, health authorities advise to grow vegetables, fruit and herbs in clean soil and to rinse them thoroughly before eating. It is not enough to place a layer of clean soil on the top of contaminated soil in any garden.
Soil moves continually and the contaminated soil eventually mixes with the clean soil.
Therefore, there should be a layer of plastic sheeting between the clean and the polluted soil. Vegetables and herbs can also be grown in plant bags or in pots with clean soil. Alternatively a raised bed can be made with a plastic net in the bottom and sides and clean soil inside. The clean, non-contaminated soil layer or raised bed should be at least half a metre deep. Still not enough is known about the possible contamination content in fruit and berries that are grown in contaminated soil.