Kitchen Garden soil

The Friends of Waterlow Park committee wished, for some time, to have the kitchen garden in the Park restored to its original purpose. In  2008 Camden sent a sample of the soil from the kitchen garden for scientific analysis. The results in their report indicated that the soil contained higher than average levels of arsenic, lead and cadmium. The Friends felt that it would be a good idea to ask for an independent analysis from a toxicologist. We asked Sue Barlow, a member of the European Food Safety Authority’s Scientific Committee, to comment on Camden’s soil analysis report. We did not ask her to re-do a soil analysis but simply to comment on the results reported in the analysis. She confirmed that the levels reported there, were higher than average and explained how this kind of contamination happens over time.

How does soil get contaminated?
Most soil in urban areas and near major roads is polluted to some extent by metals such as arsenic, lead, and cadmium, and sometimes by other chemicals. Metals in soil come from several sources. These include the weathering of rocks, use of fertilisers and other agrochemicals, spreading of sewage sludge and manure, and industrial waste, but most originates from the atmosphere and gets deposited on the soil.

How can you tell if soil is contaminated?
Taking soil samples and having them analysed for chemical contamination in a laboratory can indicate roughly how much contamination may be present.

How can you find out if there may be a risk to health?

If the level of contamination in the soil by a particular chemical is below its so-called ‘Soil Guideline Value (SGV)’, then no harm is likely to occur, in other words it is a ‘safe level’. SGVs are science-based and are published by the Department for Food and Rural Affairs (DEFRA).

When contamination is above the SGV, it does not necessarily mean that there definitely is a risk to health, only that there may be a risk to health from exposure over a lengthy period.

Solutions to the problem of soil contamination
After reading the independent report, and checking with Camden’s officers, the Friends of Waterlow Park felt that the solution to the problem would be to build raised beds and to fill them with fresh, uncontaminated soil. Then, it would be possible to grow vegetables in the kitchen garden along with other fruit and flowers. Regular checks at five year periods should mean that there will be no risks from food grown there, even if it is eaten regularly.