At a lecture given by Roberto Perez, the Cuban agronomist featured in the film ‘The Community Solution’, I asked what steps had been taken to assess or remediate soil contamination in the city of Havana. The response was that nothing had been done other than to assume the soil was suspect and to use raised beds with imported soil fortified with locally produced compost. Mr. Perez added that in cases where severe contamination was suspected, one should seal the existing soil with a liner before adding soil above.
Dr. Rule, the biogeochemist from Loyola University, recommends:
“The addition of organic matter … these materials will bind a large number of contaminants and reduce their uptake by plants. The addition of lime will also render many metal contaminants unavailable to plants. … Be careful if obtaining bulk soil to ensure the origin is from an uncontaminated area.” (Rule 2008)
A Boston Globe article recommends regarding that when gardening in lead contaminated soil to:
“… plant fruiting crops such as tomatoes, squash, peas, and corn because they take up relatively little lead … avoid planting root vegetables, potatoes, and leafy vegetables, which take up more.” (Daly 2008) See appendix #10 for more from this article.
Many metals and chemicals are to be found in soils in urban areas. Each can have an effect on the bioaccessibility of the others, not only in the soil and water but in vivo as well. See appendix #11. Research indicates in vitro testing for contamination is not very useful in determining in vivo effects of contamination or bioavailability. (Environment Agency 2007) Clearly, research into the true effects of contaminants, singly and in groups, on human health is needed. Until reliable soil guideline values (SGV) are produced based on in vivo testing, perhaps the precautionary principle should be applied; in the presence of serious threats one should not wait for scientific certainty before taking action to prevent damage.
Without evidence to the contrary, citizens within Sheffield should assume the worst of their soil and only grow in carefully sourced replacement soils or if they suspect contamination, they should use a liner above the existing soil.
Meanwhile, pressure should be put on Sheffield City Council to comply with the Environment Act of 1990 and to produce a comprehensive register of contaminated sites.