We have not found any data for Cambridge specifically. However, the Food standards agency recently (2004) completed a survey of soil and produce from allotments: 21 samples of fruit and veg from 12 allotment sites. Urban soils contained on average 3 times as much lead as rural and so did the produce. However, they did not find any levels presenting a risk to consumers. Also, the lead levels were much reduced from a similar survey in 1999.
Mean levels in produce from allotments:
Results reported from the UK soil and Herbage Pollutant Survey also show higher levels of lead in grass and soil from urban areas than rural.
Lead ppm in for England (as opposed to UK):
|soil mean||s.d.||herbage mean||s.d.|
However, even where there is lead in soil, plants absorb very little of it and previous studies have shown that, at least in the 1970s, more than 90% of lead contamination in plants was from lead in the air, not from the soil. This is good news because since the ban on lead in petrol (limits were first introduced in 1985) lead levels in the air have decreased greatly. There is still more lead in urban air, but this is probably because dust laid down near roads before the ban is picked up by the wind. Eventually, the lead will be washed out of the soil or dispersed.
It is recommended that fruit and veg grown in high lead soils is well washed before use.
Soil testing is available from http://www.bonlab.co.uk/BA3.html but it is expensive: £130!
Environment Agency UK Soil and Herbage Pollutant Survey
Food Survey Information Sheet 01/06