Selenium speciation in crops from an endemic selenium poisoning area: A case study in Naore village, Shuang'an township, China

Naore Village in Shuang'an Township, China is a rare high-Se area where incidents of Se poisoning have occurred due to the consumption of locally grown crops with high Se level. To study the content and speciation of Se in crops from Se poisoning area, a total of 95 crops samples, including 11 types of the most commonly consumed local crops, were collected in Naore Village and its surrounding areas. The contents of total Se (tSe), organic Se (orgSe), inorganic Se (inorgSe), and major enzyme-soluble Se species (SeMet, SeCys₂, MeSeCys, SeEt, Se(IV), and Se(VI)) in crop samples were analyzed. The results are as followed: 1) The tSe content in crops ranged from 0.008 to 165.645 mg∙kg^-1, with an average of 5.362 mg∙kg^-1. The tSe content within the same type of crop varied greatly, with the maximum and minimum values differing by up to 1205.57 times (in maize). 2) Different type of crops exhibited varying abilities to accumulate Se, with pakchoi showing the strongest accumulation (165.465 mg∙kg^-1 at Se poisoning site). 3) The predominant form of Se in crops was orgSe, with 95.88 % of crops having orgSe accounting for over 50 % of the tSe content. The predominant form of orgSe in crops was SeMet. 4) Consuming locally produced grains and vegetables with high Se level can lead to excessive daily Se intake. The long-term dependence on locally grown crops could increase the risk of Se poisoning. 5) At Se poisoning site, where Se poisoning cases once occurred, the intake of orgSe from locally produced grain and pakchoi exceeds the tolerable limit. The safety of orgSe may be overestimated. Our findings are expected to enhance the understanding of the potential risk of orgSe and provide a basis for the reasonable dietary intake of orgSe.