Assessments of chromium (and other metals) in vegetables and potential bio-accumulations in humans living in areas affected by tannery wastes

- Bio-availability of metals to plants is metal, site and plant specific.
- Transfer functions are better than transfer factors to estimate Cr uptake.
- Potential Cr accumulations in humans is predictable from soil Cr bio-availability.

Chromium (Cr) commonly enters the food chain through uptake by vegetables. However, accurate prediction of plant uptake of Cr (and other metals) still remains a challenge. In this study, we evaluated 5 indices of availability for Cr (and other metals) to identify reliable predictors of metal transfer from soils to garlic, onion, bokchoy, radish and celery grown in soils impacted by tannery wastes. The potential bio-accumulation of Cr in humans was calculated from the Cr content of vegetable predicted by the best bio-availability index, amounts of vegetable consumed and recommended daily doses for Cr. Our results show that soil total Cr is the best predictor of Cr transfer from soils to onion (Cr in onion = 8.51 + 0.005 Total Cr) while Cr extractable by Synthetic Precipitation Leaching Procedure at pH 5 correlates very well with Cr uptake by bokchoy (Cr bokchoy = 5.86 + 7.32 SPLP-5 Cr) and garlic (Cr garlic = 7.63 + 2.36 SPLP-5 Cr). The uptake of Cr by radish and celery could not be reliably estimated by any of the 5 indices of availability tested in this study. Potential bio-accumulation of Cr in humans (BA-Cr) increases from soils with low Cr (BA-Cr = 11.5) to soil with high total Cr (BA-Cr = 31.3). Due to numerous soil factors affecting the behavior of Cr in soils and the physiological differences among vegetables, we suggest that the prediction of the transfer of Cr (and other metals) from soils to plants should be specific to site, metal and vegetable. Potential bio-accumulation of Cr in humans can be derived from a transfer function of Cr from soils to plants and the human consumption of vegetables.