Globally, more than 800 million people are undernourished while >2 billion people have one or more chronic micronutrient deficiencies (MNDs). More than 6% of global mortality and morbidity burdens are associated with undernourishment and MNDs. Here we show that, in 2011, 3.5 and 1.1 billion people were at risk of calcium (Ca) and zinc (Zn) deficiency respectively due to inadequate dietary supply. The global mean dietary supply of Ca and Zn in 2011 was 684 ± 211 and 16 ± 3 mgcapita⁻¹d⁻¹(±SD) respectively. Between 1992 and 2011, global risk of deficiency of Ca and Zn decreased from 76 to 51% and 22 to 16%, respectively. Approximately 90% of those at risk of Ca and Zn deficiency in 2011 were in Africa and Asia. To our knowledge, these are the first global estimates of dietary Ca deficiency risks based on food supply. We conclude that continuing to reduce Ca and Zn deficiency risks through dietary diversification and food and agricultural interventions including fortification, crop breeding and use of micronutrient fertilisers will remain a significant challenge.

Dietary micronutrient deficiencies (MNDs) are widespread, yet their prevalence can be difficult to assess. Here, we estimateMNDrisks due to inadequate intakes for seven minerals in Africa using food supply and composition data, and consider the potential of food‐based and agricultural interventions. Food Balance Sheets (FBSs) for 46 countries were integrated with food composition data to estimate per capita supply of calcium (Ca), copper (Cu), iron (Fe), iodine (I), magnesium (Mg), selenium (Se) and zinc (Zn), and also phytate. Deficiency risks were quantified using an estimated average requirement (EAR) ‘cut‐point’ approach. Deficiency risks are highest for Ca (54% of the population), followed by Zn (40%), Se (28%) and I (19%, after accounting for iodized salt consumption). The risk of Cu (1%) and Mg (<1%) deficiency are low. Deficiency risks are generally lower in the north and west of Africa. MultipleMNDrisks are high in many countries. The population‐weighted mean phytate supply is 2770 mg capita⁻¹day⁻¹. Deficiency risks for Fe are lower than expected (5%). However, ‘cut‐point’ approaches for Fe are sensitive to assumptions regarding requirements; e.g. estimates of Fe deficiency risks are 43% under very low bioavailability scenarios consistent with high‐phytate, low‐animal protein diets. Fertilization and breeding strategies could greatly reduce certainMNDs. For example, meetingHarvestPlusbreeding targets for Zn would reduce dietary Zn deficiency risk by 90% based on supply data. Dietary diversification or direct fortification is likely to be needed to address Ca deficiency risks.

Micronutrient deficiencies (MNDs) remain widespread among people in sub-Saharan Africa^1–5, where access to sufficient food from plant and animal sources that is rich in micronutrients (vitamins and minerals) is limited due to socioeconomic and geographical reasons^4–6. Here we report the micronutrient composition (calcium, iron, selenium and zinc) of staple cereal grains for most of the cereal production areas in Ethiopia and Malawi. We show that there is geospatial variation in the composition of micronutrients that is nutritionally important at subnational scales. Soil and environmental covariates of grain micronutrient concentrations included soil pH, soil organic matter, temperature, rainfall and topography, which were specific to micronutrient and crop type. For rural households consuming locally sourced food—including many smallholder farming communities—the location of residence can be the largest influencing factor in determining the dietary intake of micronutrients from cereals. Positive relationships between the concentration of selenium in grain and biomarkers of selenium dietary status occur in both countries. Surveillance of MNDs on the basis of biomarkers of status and dietary intakes from national- and regional-scale food-composition data^1–7 could be improved using subnational data on the composition of grain micronutrients. Beyond dietary diversification, interventions to alleviate MNDs, such as food fortification^8,9 and biofortification to increase the micronutrient concentrations in crops^10,11, should account for geographical effects that can be larger in magnitude than intervention outcomes.

The revised Environmental Protection Act Part 2A contaminated land Statutory Guidance (England and Wales) makes reference to 'normal' levels of contaminants in soil. The British Geological Survey has been commissioned by the United Kingdom Department for Environment, Food and Rural Affairs (Defra) to estimate contaminant levels in soil and to define what is meant by 'normal' for English soil. The Guidance states that 'normal' levels of contaminants are typical and widespread and arise from a combination of both natural and diffuse pollution contributions. Available systematically collected soil data sets for England are explored for inorganic contaminants (As, Cd, Cu, Hg, Ni and Pb) and benzo[a]pyrene (BaP). Spatial variability of contaminants is studied in the context of the underlying parent material, metalliferous mineralisation and associated mining activities, and the built (urban) environment, the latter being indicative of human activities such as industry and transportation. The most significant areas of elevated contaminant concentrations are identified as contaminant domains. Therefore, rather than estimating a single national contaminant range of concentrations, we assign an upper threshold value to contaminant domains. Our representation of this threshold is a Normal Background Concentration (NBC) defined as the upper 95% confidence limit of the 95th percentile for the soil results associated with a particular domain. Concentrations of a contaminant are considered to be typical and widespread for the identified contaminant domain up to (and including) the calculated NBC. A robust statistical methodology for determining NBCs is presented using inspection of data distribution plots and skewness testing, followed by an appropriate data transformation in order to reduce the effects of point source contamination.

Food supply and composition data can be combined to estimate micronutrient intakes and deficiency risks among populations. These estimates can be improved by using local crop composition data that can capture environmental influences including soil type. This study aimed to provide spatially resolved crop composition data for Malawi, where information is currently limited. Six hundred and fifty-two plant samples, representing 97 edible food items, were sampled from >150 sites in Malawi between 2011 and 2013. Samples were analysed by ICP-MS for up to 58 elements, including the essential minerals calcium (Ca), copper (Cu), iron (Fe), magnesium (Mg), selenium (Se) and zinc (Zn). Maize grain Ca, Cu, Fe, Mg, Se and Zn concentrations were greater from plants grown on calcareous soils than those from the more widespread low-pH soils. Leafy vegetables from calcareous soils had elevated leaf Ca, Cu, Fe and Se concentrations, but lower Zn concentrations. Several foods were found to accumulate high levels of Se, including the leaves of Moringa, a crop not previously been reported in East African food composition data sets. New estimates of national dietary mineral supplies were obtained for non-calcareous and calcareous soils. High risks of Ca (100%), Se (100%) and Zn (57%) dietary deficiencies are likely on non-calcareous soils. Deficiency risks on calcareous soils are high for Ca (97%), but lower for Se (34%) and Zn (31%). Risks of Cu, Fe and Mg deficiencies appear to be low on the basis of dietary supply levels.

We investigated changes in iodine (129I) solubility and speciation in nine soils with contrasting properties (pH, Fe/Mn oxides, organic carbon and iodine contents), incubated for nine months at 10 and 20 °C. The rate of 129I sorption was greater in soils with large organic carbon contents (%SOC), low pH and at higher temperatures. Loss of iodide (I−) from solution was extremely rapid, apparently reaching completion over minutes–hours; iodate () loss from solution was slower, typically occurring over hours–days. In all soils an apparently instantaneous sorption reaction was followed by a slower sorption process for . For iodide a faster overall reaction meant that discrimination between the two processes was less clear. Instantaneous sorption of was greater in soils with high Fe/Mn oxide content, low pH and low SOC content, whereas the rate of time-dependent sorption was greatest in soils with higher SOC contents. Phosphate extraction (0.15 M KH2PO4) of soils, ∼100 h after 129I spike addition, indicated that concentrations of sorbed inorganic iodine (129I) were very low in all soils suggesting that inorganic iodine adsorption onto oxide phases has little impact on the rate of iodine assimilation into humus. Transformation of dissolved inorganic 129 and 129I− to sorbed organic forms was modelled using a range of reaction- and diffusion-based approaches. Irreversible and reversible first order kinetic models, and a spherical diffusion model, adequately described the kinetics of both and I− loss from the soil solution but required inclusion of a distribution coefficient (kd) to allow for instantaneous adsorption. A spherical diffusion model was also collectively parameterised for all the soils studied by using pH, soil organic carbon concentration and combined Fe + Mn oxide content as determinants of the model parameters (kd and D/r2). The kinetic model parameters were not directly related to a single soil parameter; inclusion of pH, SOC, oxide content and temperature was necessary to describe the observed behaviour. From the temperature-dependence of the sorption data the activation energy (Ea) for 129 transformation to organic forms was estimated to be ∼43 kJ mol−1. The Ea value was independent of %SOC and was consistent with a reaction mechanism slower than pore diffusion or physical adsorption, but faster than most surface reactions.\ud \u