The influence of soil factors and atmospheric deposition of the cadmium and lead contents of vegetables
A comprehensive survey was undertaken in 94 allotments and gardens in nine English towns
and cities to assess the degree of contamination of soils and vegetables by lead and cadmium.
Comparisons were made with the results obtained in a smaller survey of soils and vegetables in an
old lead mining area of Derbyshire and with those found in a basket survey of retail vegetables.
The geometric mean lead concentration for the soils, 215 μg/g, was five times higher than
values found for agricultural soils while the mean cadmium concentration, 0.47 μg/g, was similar
to 'background' levels. Very much higher levels of both lead and cadmium were noted in
Lead concentrations in the vegetables ranged from <0.25 to 16.7 1ug/g dry weight and
cadmium concentrations ranged from <0.03 to 10.4 μg/g. Lead concentrations were higher than
background values reported by the Ministry of Agriculture, Fisheries and Food and than levels
found in the basket survey of retail vegetables. However, less than 1% exceeded the UK statutory
limit for lead in saleable food (1 μg/g fresh weight), whereas 13% of the Derbyshire vegetables
exceeded this value. Cadmium concentrations were generally similar to background levels but
several times lower than those found in Derbyshire vegetables.
Multivariate analysis of the urban vegetable and soil data indicated that lead concentrations
in the vegetables were largely dependent on the 'total' lead content of the soil, while soil cadmium
levels (anunonium nitrate extractable and 'total') and pH were the best predictors of vegetable
The relative importance of foliar and root uptake to the lead and cadmium content of urban
vegetables was assessed by means of two studies. A 109Cd study proved unsuccessful due to
incomplete equilibration of the added radiotracer with the stable cadmium content of the soil.
However, a control soil study indicated that soil-derived lead and cadmium contributed around
57% and 67%, respectively, to the lead and cadmium contents of leafy vegetables.