Elemental composition of Malawian rice

Abstract

Widespread potential dietary deficiencies of calcium (Ca), iron (Fe), iodine (I), selenium (Se) and zinc (Zn) have been identified in Malawi. Several deficiencies are likely to be compounded by high phytic acid (PA) consumption. Rice (Oryza sativa) is commonly consumed in some Malawian populations and its mineral micronutrient content is important for food security. The considerable irrigation requirements and flooded conditions of paddy soils can also introduce or mobilise potentially toxic elements including arsenic (As), cadmium (Cd) and lead (Pb). The aim of this study was to determine the mineral composition of rice sampled from farmers' fields and markets in Malawi.Rice was sampled from 18 Extension Planning Areas across Malawi with 21 white (i.e. polished) and 33 brown samples collected. Elemental composition was determined by inductively-coupled plasmamass spectrometry (ICP-MS). Arsenic speciation was performed using high performance liquid chromatography (HPLC)-ICP-MS. Concentration of PA was determined using a PA-total phosphorus assay.Median total concentrations (mg kg , dry-weight) in brown and white rice samples, respectively, were: As = 0.030 and 0.006; Cd = <0.002 and 0.006; Pb = 0.008 and 0.008. Approximately 95% of As was found to be inorganic As, where this could be quantified.

Comparison of on-site field measured inorganic arsenic in rice with laboratory measurements using a field deployable method: Method validation

“…Similar trends were observed by Seyfferth, Webb, Andrews, & Fendorf (2011) and Rahman & Hasegawa (2011). Mean iAs value determined in UPR using FDM (mean: 52±18 µg/kg compared well to mean iAs of 60 µg/kg reported by Joy et al (2016) for unpolished (brown) Malawian rice. The mean iAs concentration in polished Malawian rice (mean: 31±12 µg/kg; range 9 -54 µg/kg) is amongst the lowest ever reported concentrations for iAs in rice worldwide (Meharg et al, 2009;P.…”

Analysis of Blood Concentrations of Zinc, Germanium, and Lead and Relevant Environmental Factors in a Population Sample from Shandong Province, China

“…Another study from China found results similar to ours [78]. Rice is the main staple of Asians, but in current high-yielding rice varieties the supply of zinc is poor, as polishing and shelling cause a huge loss of zinc [81,82]. Other reason is possible that discrepancies in levels of trace elements between different countries are partly due to environmental factors, but specific reasons need to be explored further.…”

Global Sourcing of Low-Inorganic Arsenic Rice Grain

“…There has been limited survey of arsenic in African rice (Adeyemi et al 2017;Adomako et al 2011;Joy et al 2017). The finding that East African rice is low in arsenic confirms a study which reported that Malawian paddy rice was particularly low in total arsenic (Joy et al 2017). The underlying geology of the East African region surveyed, stretching from southern Malawi to northern Tanzania, has a diverse topology and geology (McConnell 1972), yet is universally low in inorganic arsenic.…”

“…There has been limited survey of arsenic in African rice (Adeyemi et al 2017;Adomako et al 2011;Joy et al 2017). The finding that East African rice is low in arsenic confirms a study which reported that Malawian paddy rice was particularly low in total arsenic (Joy et al 2017).…”

“…In particular, this needs integration of S. American, African and the S.E. Asian archipelago that are either under reported in the literature, or only feature in interregional comparisons to a limited extent (Adeyemi et al 2017;Adomako et al 2011;Farias et al 2015;Joy et al 2017;Otero et al 2016;Segura et al 2016). This knowledge is required to source low arsenic rice for sub-populations where the consumption of inorganic arsenic from rice is of particular concern, such as for infants and young children (Carey et al 2018).…”