Occurrence and accumulation of mercury in two species of wild grown Pleurotus mushrooms from Southeastern Nigeria

The aim of this study was to evaluate the degree of contamination and intake rates, as well as the risk of Hg contained in two wild species of Pleurotus mushrooms - Oyster Mushroom (P. ostreatus) and King Tuber Mushroom (P. tuber-regium) - which are widely consumed in southeastern Nigeria; and to also assess their potential to accumulate Hg. The mean Hg concentrations in caps of P. ostreatus from distant sites of Ekeoba, Ntigha, and Ubakala in Abia State, were 31 +/- 11, 28 +/- 8, and 29 +/- 5 ng g(-1) dry weight, respectively; while the mean concentrations for stipes were 37 +/- 5, 36 +/- 17, and 28 +/- 6 ng g(-1) dw, in the respective communities. The caps and stipes were characterized by a mean bioconcentration factor value of similar to 2, indicating that P. ostreatus is a very weak Hg accumulator and probably takes in Hg solely from the wooden substratum. Sclerotia of P. tuber-regium, purchased from five different regional markets: Ukwunwangwu (Uturu), Ekeama (Umuobiala), and Ahonta (Eluama) of Abia State; and from Abakpa market and Eke-Okigwe of Imo State; contained Hg in total range of 3.3 to 180 ng g(-1) dw. A meal consisting of 300 g of caps and stipes of P. ostreatus, or of fresh sclerotia of P. tuber-regium, would expose a consumer to <1.2, and between 0.39 and 1.2 mu g Hg, respectively; and, if eaten daily for a week, would contribute less than 0.03%, and between 0.76% and 2.3% of the provisionally tolerable weekly intake (PTWI). The consumption of P. ostreatus and sclerotia of P. tuber-regium harvested from the areas investigated, therefore, poses no toxicological or health risks to the inhabitants. (C) 2012 Elsevier Inc. All rights reserved.