Selenium behavior in the soil environment and its implication for human health

Abstract

Selenium (Se) is an important element that was discovered in 1817, and since the 1960s, it has been regarded as an essential micronutrient for both animals and humans, playing among other functions a relevant role in the antioxidant system of mammals. Inadequate blood Se levels in the human body is a well-known concern in many parts of the world. This malnutrition problem is often due to Se-poor diet, probably as a result of the low Se availability in soils where crops are growing. Nowadays, it is known that not only the total content, but also the inorganic and organic forms of Se contained in foods are important for human nutrition. However, paradoxically some regions of the world present high Se levels in soils causing several functional disorders and diseases in people who live in seleniferous areas. As essential micronutrient, Se should be supplied in controlled amounts to avoid harmful effects. Therefore, taking into account the importance of the soils as a way to ensure the adequate Se supply for the population, this review has dealt with Se behavior in soil environment (e.g., Se forms and adsorption and desorption reactions) and its relevance for the human health. As a final message, the further understanding of Se behavior in soils to predict its availability for crops in different systems will be a significant approach in future studies to establish forms and safe doses of Se to be added in fertilizers. Agronomic and genetic biofortification of staple crops with Se has been suggested as an important tool to improve Se intake by population in Se-poor sites.Index terms: Essential micronutrient; Se adsorption; Se availability; biofortification; human nutrition. RESUMOO selênio (Se) é um elemento importante que foi descoberto em 1817 e reconhecido como elemento essencial para os humanos e animais desde os anos 60. Esse elemento apresenta, dentre outras funções, papel relevante no sistema antioxidante dos mamíferos. Níveis inadequados de Se no corpo humano tem sido uma preocupação bem conhecida em muitas regiões do mundo. Esse problema de desnutrição com Se ocorre frequentemente devido a dietas pobres nesse elemento, o que provavelmente tem relação com a baixa disponibilidade de Se nos solos onde as culturas agrícolas estão sendo cultivadas. Atualmente, sabe-se que, além da quantidade de Se contida nos alimentos, sua forma (e.g., inorgânica ou orgânica) é importante para a nutrição humana. Apesar da deficiência de Se ser um problema em alguns locais, algumas regiões do mundo apresentam níveis altos de Se nos solos, causando várias desordens e doenças nas pessoas que moram nestas áreas consideradas seleníferas. Sendo um elemento essencial, o Se deve ser suprido em quantidades adequadas para evitar efeitos prejudiciais. Assim, levando-se em consideração a importância dos solos como um meio para garantir o suprimento adequado de Se para a população, esta revisão tem abordado o comportamento do Se no ambiente do solo (e.g., formas de Se e reações de adsorção e dessorção) e sua relevância para a saúde hu...

Adsorption of Selenite in Tropical Soils as Affected by Soil Management, Ionic Strength, and Soil Properties

“…This difference may be attributed to the fact that the Se(VI) is bound mainly by outer-sphere complex, while the Se(IV) mainly forms inner-sphere complex, being this last Se specie less available and less mobile. Lopes et al (2017) reported that differences in adsorption behavior of Se(VI) and Se(IV) reflect in different amounts of Se to be uptaken up by plant roots. So, taking into account that the Se(VI) is more available in tropical soils, studies involving agronomic biofortification of agricultural crops with Se through application of Se should give priority for this Se specie.…”

“…The concern about Se around the world has been justified due to the low Se contents found in soils in different regions worldwide (Lopes et al 2017). In Brazil, studies showed that the soils and consequently the agricultural crops and foods are poor in Se (Carvalho et al 2019;Gabos et al 2014a;Matos et al 2017).…”

Species and correlations between selenium and mercury in fishpond ecosystems

“…It exists mainly as elemental mercury, the bivalent form of Hg 2+ , and as the organic methylmercury (MeHg) in most natural environments (Arcagni et al, 2018;Coulibaly, Bamba, Yao, Zoro, & Rhazi, 2016;Harris, Pickering, & George, 2003). Selenium (Se), however, is recognized as an essential trace element for humans and mainly exists in the +4 and +6 valence oxyanions in natural environments and as organic selenium compounds in organisms (Lopes, Avila, & Guilherme, 2017;Zhang, Guan, Yang, Zeng, & Liu, 2018). The antagonistic phenomenon between selenium and mercury has earlier been reported, and numerous studies have shown that selenium supplementation counteracts the negative effects of exposure to mercury (Li, Li, & Feng, 2016;Wang & Wang, 2017;Wang et al, 2018).…”

Soil management and ionic strength on selenite retention in oxidic soils

“…The concern regarding the quality and capacity of products to supply essential nutrients, including selenium (Se), has increased in recent years. Se contents available in the soil can be absorbed and accumulated in the food for humans and animals (Lopes;Ávila;Guilherme, 2017;Wang et al, 2017).…”

“…Such action is important to increase Se natural intake by the population, and therefore it is a possible strategy to be used in Brazil. However, to succeed in this practice, studies are required in order to well understand Se sorption behavior in the soils (Lopes;Ávila;, which will assist in the definition of safe doses to be added to fertilizers, since the limit between the essentiality and the toxicity of this element is quite narrow (Sharma et al, 2017).…”