Heavy Metals in Traditionally Used Fruits Among the Lakota

Abstract

Heavy metals concentrations in soils and plants on and near Pine Ridge Reservation (PRR), SD, are a cause of concern to Oglala Lakota tribal government, particularly because of current and past uranium mining nearby, as well as familiarity with occasional selenium poisoning in livestock. In this study, concentrations of As, Ba, Pb, Se, and U were determined using ICP-OES for selected traditionally edible berries and small fruits, and the soils in which they grow. Results indicated that the heavy metals are likely of natural origin, and ingestion of these culturally important fruits at levels reported in interviews among the Lakota on nearby Rosebud Reservation generally do not exceed US CDC Minimal Risk Levels (MRLs) for chronic oral ingestion, with the possible exception of As in chokecherries and wild rosehips, and U in wild plum and wild rosehips. No US CDC MRL for Pb has been established, because they deem such a standard as inappropriate at the current state of knowledge, with which I agree. However, fruits were compared to the WHO/FAO Maximum Level (ML) permitted for berries and small fruit, with 8.5 per cent of fruit samples from PRR exceeding that standard. Results showed that fruits were generally lower in heavy metals than the soils in which they grew on PRR, with the exception of Se. Some detected concentrations of Se in fruits and other plant tissues at 9 of 15 sites indicated possible bioaccumulation. Wild rosehips on and near PRR were generally lower in heavy metals concentrations than in comparison samples from Brookings County, SD, where Pb concentrations were comparable or slightly higher, and one Se sample was unusually high. Concentrations of heavy metals in soils on PRR ranked substantially lower in As, Ba and Pb and much higher in Se and U compared to USGS arithmetic means and ranges for the conterminous United States established by Shacklette and Boerngen (1984). This study produced preliminary baseline concentrations for fruits and the soils in which they grow on and near PRR and for estimated oral exposure levels based on interviews from nearby Rosebud Reservation, against which other research may be compared