Public health assessment of Kenyan ASGM communities using multi-element biomonitoring, dietary and environmental evaluation.

The Kakamega gold belt's natural geological enrichment and artisanal and small-scale gold mining (ASGM) have resulted in food and environmental pollution, human exposure, and subsequent risks to health. This study aimed to characterise exposure pathways and risks among ASGM communities. Human hair, nails, urine, water, and staple food crops were collected and analysed from 144 ASGM miners and 25 people from the ASGM associated communities. Exposure to PHEs was predominantly via drinking water from mine shafts, springs and shallow-wells (for As>Pb>Cr>Al), with up to 366 µg L-1 arsenic measured in shaft waters consumed by miners. Additional exposure was via consumption of locally grown crops (for As>Ni>Pb>Cr>Cd>Hg>Al) besides inhalation of Hg vapour and dust, and direct dermal contact with Hg. Urinary elemental concentrations for both ASGM workers and wider ASGM communities were in nearly all cases above bioequivalents and reference upper thresholds for As, Cr, Hg, Ni, Pb and Sb, with median concentrations of 12.3, 0.4, 1.6, 5.1, 0.7 and 0.15 µg L-1, respectively. Urinary As concentrations showed a strong positive correlation (0.958) with As in drinking water. This study highlighted the importance of a multidisciplinary approach in integrating environmental, dietary, and public health investigations to better characterise the hazards and risks associated with ASGM and better understand the trade-offs associated with ASGM activities relating to public health and environmental sustainability. Further research is crucial, and study results have been shared with Public Health and Environmental authorities to inform mitigation efforts.

Artisanal gold mining in Kakamega and Vihiga counties, Kenya: potential human exposure and health risk.

Artisanal and small-scale gold mining (ASGM) represents 20% of gold supply and 90% of gold mining workforce globally, which operates in highly informal setups. Pollutants from mined ores and chemicals introduced during gold processing pose occupational and inadvertent health risks to the extent that has not been well elucidated in Africa. Trace and major elements were analysed using inductively coupled plasma mass spectrometry in soil, sediment and water samples from 19 ASGM villages in Kakamega and Vihiga counties. Associated health risks for residents and ASGM workers were assessed. This paper focuses on As, Cd, Cr, Hg, Ni and Pb for which 96% of soil samples from mining and ore processing sites had As concentrations up to 7937 times higher than the US EPA 12 mg kg-1 standard for residential soils. Soil Cr, Hg and Ni concentrations in 98%, 49% and 68% of the samples exceeded respective USEPA and CCME standards, with 1-72% bioaccessibility. Twenty-five percentage of community drinking water sources were higher than the WHO 10 µg L-1 drinking water guideline. Pollution indices indicated significant enrichment and pollution of soils, sediment and water in decreasing order of As > Cr > Hg > Ni > Pb > Cd. The study revealed increased risks of non-cancer health effects (98.6) and cancer in adults (4.93 × 10-2) and children (1.75 × 10-1). The findings will help environment managers and public health authorities better understand the potential health risks in ASGM and support evidence-based interventions in ASGM processes, industrial hygiene and formulation of public health policy to protect residents and ASGM workers' health in Kenya.

A new hazard assessment workflow to assess soil contamination from large and artisanal scale gold mining.

Gold mining activities are undertaken both at large and artisanal scale, often resulting in serious 'collateral' environmental issues, including environmental pollution and hazard to human and ecosystem health. Furthermore, some of these activities are poorly regulated, which can produce long-lasting damage to the environment and local livelihoods. The aim of this study was to identify a new workflow model to discriminate anthropogenic versus geogenic enrichment in soils of gold mining regions. The Kedougou region (Senegal, West Africa) was used as a case study. Ninety-four soil samples (76 topsoils and 18 bottom soils) were collected over an area of 6,742 km2 and analysed for 53 chemical elements. Robust spatial mapping, compositional and geostatistical models were employed to evaluate sources and elemental footprint associated with geology and mining activities. Multivariate approaches highlighted anomalies in arsenic (As) and mercury (Hg) distribution in several areas. However, further interpretation with enrichment factor (EFs) and index of geoaccumulation (IGeo) emphasised high contamination levels in areas approximately coinciding with the ones where artisanal and small scale mining (ASGM) activities occur, and robust compositional contamination index (RCCI) isolated potentially harmful elements (PHE) contamination levels in very specific areas of the Kedougou mining region. The study underlined the importance of complementary approaches to identify anomalies and, more significantly, contamination by hazardous material. In particular, the analyses helped to identify discrete areas that would require to be surveyed in more detail to allow a comprehensive and thorough risk assessment, to investigate potential impacts to both human and ecosystem health.

Method development to characterise elephant tail hairs by LA-ICP-MS to reflect changes in elemental chemistry.

This paper evaluated analytical methods used to generate time-series data from elephant tail hairs, which can be used to reflect changing exposure to environmental geochemistry. Elephant tail hairs were analysed by three methods sequentially, each providing data to inform subsequent analysis. Scanning Electron Microscopy (SEM) and X-ray Microanalysis visually showed the structure of the hair, specific structures such as tubules, and the mineral crusting around the edge of the hair, informing targeting of subsequent analysis by Laser Ablation-Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). LA-ICP-MS generated time-series data which informed sectioning of the tail hairs for subsequent quantitative analysis for potentially toxic elements and micronutrients using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) of dissolved tail hairs. This novel approach to characterise the tail hair enabled time-series analysis to reflect changes in environmental exposure which may result from seasonal or geochemical spatial variation and could inform elephant movement patterns. The seasonal change between wet and dry seasons was reflected down the length of the hair. Correlations were seen between LA-ICP-MS data and ICP-MS data in several elements including Mg, P, Ca, Fe, Na, Mn and U. This study provided time-series data for the analysis of elephant tail hairs by evaluating analytical challenges to obtaining quantitative data, such as improving protocols to ensure removal of extraneous material, determining where to section the tail hairs to best reflect environmental changes/exposure and ensuring representative analyses. A protocol was established to determine mineral status across a 12-18 month time period utilizing single elephant tail hairs.

Assessment of bioaccessibility and health risk of mercury within soil of artisanal gold mine sites, Niger, North-central part of Nigeria.

The occurrence of mercury (Hg) in the environment globally has been linked largely to its use for gold processing. In this research, ore samples, agricultural soil and mine wastes were taken within the vicinity of an artisanal gold mine and processing sites in Niger state, a north-central part of Nigeria to determine Hg contamination in the environment and estimate the potential hazard to health. The values of Hg measured in ore, agricultural soil and mine wastes ranged between 0.03 and 5.9, 0.002 and 5.57 and 0.19 and 20.99 mg/kg, respectively, with the majority of samples observed above the crustal average values of 0.003 mg/kg. All of the samples were 100 times greater than the USEPA residential soil screening level of 0.0023 mg/kg, but were lower than comparable mine sites within the same region. Contamination indices were used to demonstrate the potential exposure to Hg contamination in the study area which ranged from a medium to high level of contamination. Average daily dose and hazard quotient (HQ) were calculated for adults and children in the study area and decreased in the following order: ADDvapour > ADDingestion > ADDdermal > ADDinhalation. The non-carcinogenic health risk index (HI) of Hg calculated for children and adults in the study area was children: 7.42, 2.19, 1.49 and adults: 4.45, 1.26, 1.19, for mine wastes, agricultural soil and ore, respectively. All of these values were higher than a considered safe level (= 1) and therefore showed that Hg posed a serious non-carcinogenic HI for both adults and children exposed to the soil in the study area. The bioaccessible fraction as a measure of ingestion for Hg was generally < 13% across all sample matrices, suggesting a low bioaccessibility. An HQ incorporating bioaccessible data (BHQ) ranged between 0.000005 and 4.06 with a mean value of 0.62. Values for the BHQ were still > 1, threshold limit in some samples and showed that Hg could present a risk to health via ingestion, although further research is required to assess dermal and inhalation bioaccessibility to assess fully the risk to residents. However, the values were lower than the non-carcinogenic health risk index, which is assumed to be overestimated.

Online Microdialysis-High-Performance Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometry (MD-HPLC-ICP-MS) as a Novel Tool for Sampling Hexavalent Chromium in Soil Solution.

Conventional soil solution sampling of species-sensitive inorganic contaminants, such as hexavalent chromium (CrVI), may induce interconversions due to disruption of system equilibrium. The temporal resolution that these sampling methods afford may also be insufficient to capture dynamic interactions or require time-consuming and expensive analysis. Microdialysis (MD) is emerging as a minimally invasive passive sampling method in environmental science, permitting the determination of solute fluxes and concentrations at previously unobtainable spatial scales and time frames. This article presents the first use of MD coupled to high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS) for the continuous sampling and simultaneous detection of CrVI in soil solution. The performance criteria of the system were assessed using stirred solutions; good repeatability of measurement (RSD < 2.5%) was obtained for CrVI, with a detection limit of 0.2 µg L-1. The online MD-HPLC-ICP-MS setup was applied to the sampling of native CrVI in three soils with differing geochemical properties. The system sampled and analyzed fresh soil solution at 15 min intervals, offering improved temporal resolution and a significant reduction in analysis time over offline MD. Simple modifications to the chromatographic conditions could resolve additional analytes, offering a powerful tool for the study of solute fluxes in soil systems to inform research into nutrient availability or soil-to-plant transfer of potentially harmful elements.

Fate of selenium in biofortification of wheat on calcareous soil: an isotopic study.

Selenium (Se) biofortification of staple cereal crops can improve the Se nutritional status of populations. A field trial employing an enriched stable isotope of Se (77Se) was undertaken over three consecutive cropping seasons in a coarse-textured, calcareous soil in Gilgit-Baltistan, Pakistan. The objectives were to (1) assess the feasibility and efficiency of Se biofortification, (2) determine the fate of residual Se, and (3) assess the consequences for dietary Se intake. Isotopically enriched 77Se (77SeFert) was applied, either as selenate or as selenite, at three levels (0, 10, and 20 g ha-1) to a wheat crop. Residual 77SeFert availability was assessed in subsequent crops of maize and wheat without further 77SeFert addition. Loss of 77SeFert was c.35% by the first (wheat) harvest, for both selenium species, attributable to the practice of flood irrigation and low adsorption capacity of the soil. No 77SeFert was detectable in subsequent maize or wheat crops. The remaining 77SeFert in soil was almost entirely organically bound and diminished with time following a reversible (pseudo-)first-order trend. Thus, repeat applications of Se would be required to adequately biofortify grain each year. In contrast to native soil Se, there was no transfer of 77SeFert to a recalcitrant form. Grain from control plots would provide only 0.5 µg person-1 day-1 of Se. By contrast, a single application of 20 g ha-1 SeVI could provide c. 47 µg person-1 day-1 Se in wheat, sufficient to avoid deficiency when combined with dietary Se intake from other sources (c. 25 µg day-1).

Multiple geochemical factors may cause iodine and selenium deficiency in Gilgit-Baltistan, Pakistan.

Deficiencies of the micronutrients iodine and selenium are particularly prevalent where populations consume local agricultural produce grown on soils with low iodine and selenium availability. This study focussed on such an area, Gilgit-Baltistan in Pakistan, through a geochemical survey of iodine and selenium fractionation and speciation in irrigation water and arable soil. Iodine and selenium concentrations in water ranged from 0.01-1.79 µg L-1 to 0.016-2.09 µg L-1, respectively, which are smaller than levels reported in similar mountainous areas in other parts of the world. Iodate and selenate were the dominant inorganic species in all water samples. Average concentrations of iodine and selenium in soil were 685 µg kg-1 and 209 µg kg-1, respectively, much lower than global averages of 2600 and 400 µg kg-1, respectively. The 'reactive' fractions ('soluble' and 'adsorbed') of iodine and selenium accounted for < 7% and < 5% of their total concentrations in soil. More than 90% of reactive iodine was organic; iodide was the main inorganic species. By contrast, 66.9 and 39.7% of 'soluble' and 'adsorbed' selenium, respectively, were present as organic species; inorganic selenium was mainly selenite. Very low distribution coefficients (kd = adsorbed/soluble; L kg-1) for iodine (1.07) and selenium (1.27) suggested minimal buffering of available iodine and selenium against leaching losses and plant uptake. These geochemical characteristics suggest low availability of iodine and selenium in Gilgit-Baltistan, which may be reflected in locally grown crops. However, further investigation is required to ascertain the status of iodine and selenium in the Gilgit-Baltistan food supply and population.

Environmental and human iodine and selenium status: lessons from Gilgit-Baltistan, North-East Pakistan.

Iodine and selenium deficiencies are common worldwide. We assessed the iodine and selenium status of Gilgit-Baltistan, Pakistan. We determined the elemental composition (ICP-MS) of locally grown crops (n = 281), drinking water (n = 82), urine (n = 451) and salt (n = 76), correcting urinary analytes for hydration (creatinine, specific gravity). We estimated dietary iodine, selenium and salt intake. Median iodine and selenium concentrations were 11.5 (IQR 6.01, 23.2) and 8.81 (IQR 4.03, 27.6) µg/kg in crops and 0.24 (IQR 0.12, 0.72) and 0.27 (IQR 0.11, 0.46) µg/L in water, respectively. Median iodised salt iodine was 4.16 (IQR 2.99, 10.8) mg/kg. Population mean salt intake was 13.0 g/day. Population median urinary iodine (uncorrected 78 µg/L, specific gravity-corrected 83 µg/L) was below WHO guidelines; creatinine-corrected median was 114 µg/L but was unreliable. Daily selenium intake (from urinary selenium concentration) was below the EAR in the majority (46-90%) of individuals. Iodine and selenium concentrations in all crops were low, but no health-related environmental standards exist. Iodine concentration in iodised salt was below WHO-recommended minimum. Estimated population average salt intake was above WHO-recommended daily intake. Locally available food and drinking water together provide an estimated 49% and 72% of EAR for iodine (95 µg/day) and selenium (45 µg/day), respectively. Low environmental and dietary iodine and selenium place Gilgit-Baltistan residents at risk of iodine deficiency disorders despite using iodised salt. Specific gravity correction of urine analysis for hydration is more consistent than using creatinine. Health-relevant environmental standards for iodine and selenium are needed.

Crop uptake of heavy metals in response to the environment and agronomic practices on land near mine tailings in the Zambian Copperbelt Province.

A field experiment was undertaken on farmers' fields adjacent to a large mine tailings dam in the Zambian mining town of Kitwe. Experimental plots were located close to the tailings (≤ 200 m) or further away (300-400 m) within the demarcated land farmed by the same community. This study evaluated the uptake of Cd, Cu, Ni, Pb and Zn by pumpkin leaves and maize grown in soil amended with lime and manure applied at agronomic rates, and the subsequent risk of dietary exposure to the local community, typical of many similar situations across the Zambian Copperbelt. Treatments, combinations of lime and manure (present or absent), were applied to subplots selected independently and randomly within each main plot, which represented variable geochemistry across this study site as a result of windblown/rain-driven dust from the tailings. Total elemental concentrations in crops were determined by ICP-MS following microwave-assisted acid digestion. Concentrations of Cu and Pb in pumpkin leaves were above the prescribed FAO/WHO safe limits by 60-205% and by 33-133%, respectively, while all five metals were below the limit for maize grain. Concentration of metals in maize grain was not affected by the amendments. However, lime at typical agronomic application rates significantly reduced concentrations of Cd, Cu, Pb and Zn in the pumpkin leaves by 40%, 33%, 19% and 10%, respectively, and for manure Cd reduced by 16%, while Zn increased by 35%. The uptake of metals by crops in locations further from the tailings was greater than closer to the tailings because of greater retention of metals in the soil at higher soil pH closer to the tailings. Crops in season 2 had greater concentrations of Cu, Ni, Pb and Zn than in season 1 due to diminished lime applied only in season 1, in line with common applications on a biannual basis. Maize as the staple crop is safe to grow in this area while pumpkin leaves as a readily available commonly consumed leafy vegetable may present a hazard due to accumulation of Cu and Pb above recommended safe limits.

Spatial analysis of urine zinc (Zn) concentration for women of reproductive age and school age children in Malawi.

Zinc (Zn) is an essential micronutrient, and Zn deficiency remains a major global public health challenge. Recognised biomarkers of population Zn status include blood plasma or serum Zn concentration and proxy data such as dietary Zn intake and prevalence of stunting. Urine Zn concentration is rarely used to assess population Zn status. This study assessed the value of urine Zn concentration as a biomarker of population Zn status using a nationally representative sample of non-pregnant women of reproductive age (WRA) and school-aged children (SAC) in Malawi. Spot (casual) urine samples were collected from 741 WRA and 665 SAC. Urine Zn concentration was measured by inductively coupled plasma mass spectrometry with specific gravity adjustment for hydration status. Data were analysed using a linear mixed model with a spatially correlated random effect for between-cluster variation. The effect of time of sample collection (morning or afternoon), and gender (for SAC), on urine Zn concentration were examined. There was spatial dependence in urine Zn concentration between clusters among SAC but not WRA, which indicates that food system or environmental factors can influence urine Zn concentration. Mapping urine Zn concentration could potentially identify areas where the prevalence of Zn deficiency is greater and thus where further sampling or interventions might be targeted. There was no evidence for differences in urine Zn concentration between gender (P = 0.69) or time of sample collection (P = 0.85) in SAC. Urine Zn concentration was greater in afternoon samples for WRA (P = 0.003). Relationships between urine Zn concentration, serum Zn concentration, dietary Zn intake, and potential food systems covariates warrant further study.

Short-Term Iodine Dynamics in Soil Solution.

Assessing the reactions of iodine (I) in soil is critical to evaluate radioiodine exposure and understand soil-to-crop transfer rates. Our mechanistic understanding has been constrained by method limitations in assessing the dynamic interactions of iodine between soil solution and soil solid phase over short periods (hours). We use microdialysis to passively extract soil solution spiked with radioiodine (129I- and 129IO3-) to monitor short-term (≤40 h) in situ fixation and speciation changes. We observed greater instantaneous adsorption of 129IO3- compared to 129I- in all soils and the complete reduction of 129IO3- to 129I- within 5 h of addition. Loss of 129I from solution was extremely rapid; the average half-lives of 129I- and 129IO3- in soil solution were 4.06 and 10.03 h, respectively. We detected the presence of soluble organically bound iodine (org-129I) with a low molecular weight (MW) range (0.5-5 kDa) in all soils and a slower (20-40 h) time-dependent formation of larger MW org-I compounds (12-18 kDa) in some samples. This study highlights the very short window of immediate availability in which I from rainfall or irrigation remains in soil solution and available to crops, thus presenting significant challenges to phytofortification strategies in soil-based production systems.

Arsenic speciation in the bracket fungus Fomitopsis betulina from contaminated and pristine sites.

Uptake, distribution and speciation of arsenic (As) were determined in the bracket fungus Fomitopsis betulina (previously Piptoporus betulinus), commonly known as the birch polypore, collected from a woodland adjacent to a highly contaminated former mine in the Southwest UK and at an uncontaminated site in Quebec, Canada, with no past or present mining activity. The fruiting body was divided into cap, centre and pores representing the top, middle and underside to identify trends in the distribution and transformation of As. Total As, determined by inductively coupled plasma-mass spectrometry (ICP-MS), was approximately tenfold higher in the mushroom from the contaminated compared to the uncontaminated site. Overall, accumulation of As was low relative to values reported for some soil-dwelling species, with maximum levels of 1.6 mg/kg at the contaminated site. Arsenic speciation was performed on aqueous extracts via both anion and cation high-performance liquid chromatography-ICP-MS (HPLC-ICP-MS) and on whole dried samples using X-ray absorption near edge structure (XANES) analysis. Seven As species were detected in F. betulina from the contaminated site by HPLC-ICP-MS: arsenite (AsIII), arsenate (AsV), dimethylarsinate (DMAV), methylarsonate (MAV), trimethylarsine oxide (TMAO), tetramethylarsonium ion (Tetra) and trace levels of arsenobetaine (AB). The same As species were observed at the uncontaminated site with the exception of TMAO and Tetra. Arsenic species were localized throughout the fruiting body at the contaminated site, with the cap and pores containing a majority of AsV, only the cap containing TMAO, and the pores containing higher concentrations of DMAV and MAV as well as tetra and a trace of AB. XANES analysis demonstrated that the predominant form of As at the contaminated site was inorganic AsIII coordinated with sulphur or oxygen and AsV coordinated with oxygen. This is the first account of arsenic speciation in F. betulina or any fungi of the family Fomitopsidaceae.

Environmental geochemistry and cancer: a pertinent global health problem requiring interdisciplinary collaboration.

Primary prevention is a key strategy to reducing the global burden of cancer, a disease responsible for ~ 9.6 million deaths per year and predicted to top 13 million by 2030. The role of environmental geochemistry in the aetiology of many cancers-as well as other non-communicable diseases-should not be understated, particularly in low- and middle-income countries where 70% of global cancer deaths occur and reliance on local geochemistry for drinking water and subsistence crops is still widespread. This article is an expansion of a series of presentations and discussions held at the 34th International Conference of the Society for Environmental Geochemistry and Health in Livingstone, Zambia, on the value of effective collaborations between environmental geochemists and cancer epidemiologists. Key technical aspects of each field are presented, in addition to a case study of the extraordinarily high incidence rates of oesophageal cancer in the East African Rift Valley, which may have a geochemical contribution. The potential merit of veterinary studies for investigating common geochemical risk factors between human and animal disease is also highlighted.

Using human hair and nails as biomarkers to assess exposure of potentially harmful elements to populations living near mine waste dumps.

Potentially harmful elements (PHEs) manganese (Mn), cobalt (Co), copper (Cu), lead (Pb), nickel (Ni) and zinc (Zn) were measured in human hair/nails, staple crops and drinking water to ascertain the level of exposure to dust transference via wind and rain erosion for members of the Mugala community living near a mine waste dump in the Zambian Copperbelt. The mean PHE concentrations of hair in decreasing order were Zn (137 ± 21 mg/kg), Cu (38 ± 7 mg/kg), Mn (16 ± 2 mg/kg), Pb (4.3 ± 1.9 mg/kg), Ni (1.3 ± 0.2 mg/kg) and Cr (1.2 ± 0.2 mg/kg), Co (0.9 ± 0.2 mg/kg) and Cd (0.30 ± 0.02 mg/kg). Whilst for toenails the decreasing order of mean concentrations was Zn (172 ± 27 mg/kg), Cu (30 ± 5 mg/kg), Mn (12 ± 2 mg/kg), Pb (4.8 ± 0.5 mg/kg), Ni (1.7 ± 0.14 mg/kg) and Co (1.0 ± 0.02 mg/kg), Cr (0.6 ± 0.1 mg/kg) and Cd (0.1 ± 0.002 mg/kg). The concentration of these potentially harmful elements (PHEs) varied greatly among different age groups. The results showed that Mn, Co, Pb, Cd and Zn were above the interval values (Biolab in Nutritional and environmental medicine, Hair Mineral Analysis, London, 2012) at 0.2-2.0 mg/kg for Mn, 0.01-0.20 mg/kg for Co, < 2.00 mg/kg for Pb, < 0.10 mg/kg for Cd and 0.2-2.00 mg/kg for Zn, whilst Ni, Cu and Cr concentrations were within the normal range concentrations of < 1.40 mg/kg, 10-100 mg/kg and 0.1-1.5 mg/kg, respectively. Dietary intake of PHEs was assessed from the ingestion of vegetables grown in Mugala village, with estimated PHE intakes expressed on a daily basis calculated for Mn (255), Pb (48), Ni (149) and Cd (33) µg/kg bw/day. For these metals, DI via vegetables was above the proposed limits of the provisional tolerable daily intakes (PTDIs) (WHO in Evaluation of certain food additive and contaminants, Seventy-third report of the Joint FAO/WHO Expert Committee on Food Additives, 2011) for Mn at 70 µg/kg bw/day, Pb at 3 µg/kg bw/day, Ni and Cd 5 µg/kg bw/day and 1 µg/kg bw/day, respectively. The rest of the PHEs listed were within the PTDIs limits. Therefore, Mugala inhabitants are at imminent health risk due to lead, nickel and cadmium ingestion of vegetables and drinking water at this location.

Heavy metals in urban road dusts from Kolkata and Bengaluru, India: implications for human health.

Air pollution and dust pollution are major urban environmental issues, with road dust being a potential source and a pathway for human exposure. The developing megacities of India, where the population may spend a significant portion of their working lives close to the roadside, including consuming street food, have obvious source-pathway-receptor linkages. The aim of this study in Kolkata and Bengaluru, India, was to evaluate the risk to human health from inorganic components of road dust. Samples were collected and analysed from a cross section of urban environments for a wide range of anthropogenic and geogenic elements, some such as antimony showing an increase in response to vehicle activity. Calculated enrichment factors relative to crustal abundance demonstrated significant enrichment in common heavy metals and less commonly reported elements, e.g. molybdenum, antimony, that may be used as contaminant markers. Factor analysis gave multielement signatures associated with geography, vehicle traffic and local industry. The bio-accessibility of road dusts in terms of ingestion was determined using the BARGE method with more than 50% of zinc and lead being available in some cases. A formal human health risk assessment using the US EPA framework showed that lead in Kolkata and chromium in Bengaluru were the elements of most concern amongst chromium, nickel, copper, zinc and lead. However, the only risk combination (hazard index) shown to be significant was lead exposure to children in Kolkata. Ingestion dominated the risk pathways, being significantly greater than dermal and inhalation routes.

Review: mine tailings in an African tropical environment-mechanisms for the bioavailability of heavy metals in soils.

Heavy metals are of environmental significance due to their effect on human health and the ecosystem. One of the major exposure pathways of Heavy metals for humans is through food crops. It is postulated in the literature that when crops are grown in soils which have excessive concentrations of heavy metals, they may absorb elevated levels of these elements thereby endangering consumers. However, due to land scarcity, especially in urban areas of Africa, potentially contaminated land around industrial dumps such as tailings is cultivated with food crops. The lack of regulation for land-usage on or near to mine tailings has not helped this situation. Moreover, most countries in tropical Africa have not defined guideline values for heavy metals in soils for various land uses, and even where such limits exist, they are based on total soil concentrations. However, the risk of uptake of heavy metals by crops or any soil organisms is determined by the bioavailable portion and not the total soil concentration. Therefore, defining bioavailable levels of heavy metals becomes very important in HM risk assessment, but methods used must be specific for particular soil types depending on the dominant sorption phases. Geochemical speciation modelling has proved to be a valuable tool in risk assessment of heavy metal-contaminated soils. Among the notable ones is WHAM (Windermere Humic Aqueous Model). But just like most other geochemical models, it was developed and adapted on temperate soils, and because major controlling variables in soils such as SOM, temperature, redox potential and mineralogy differ between temperate and tropical soils, its predictions on tropical soils may be poor. Validation and adaptation of such models for tropical soils are thus imperative before such they can be used. The latest versions (VI and VII) of WHAM are among the few that consider binding to all major binding phases. WHAM VI and VII are assemblages of three sub-models which describe binding to organic matter, (hydr)oxides of Fe, Al and Mn and clays. They predict free ion concentration, total dissolved ion concentration and organic and inorganic metal ion complexes, in soils, which are all important components for bioavailability and leaching to groundwater ways. Both WHAM VI and VII have been applied in a good number of soils studies with reported promising results. However, all these studies have been on temperate soils and have not been tried on any typical tropical soils. Nonetheless, since WHAM VII considers binding to all major binding phases, including those which are dominant in tropical soils, it would be a valuable tool in risk assessment of heavy metals in tropical soils. A discussion of the contamination of soils with heavy metals, their subsequent bioavailability to crops that are grown in these soils and the methods used to determine various bioavailable phases of heavy metals are presented in this review, with an emphasis on prospective modelling techniques for tropical soils.

Method development for rapid quantification of Rn-222 in surface water and groundwater.

Understanding the risks of a developing unconventional hydrocarbons industry, including shale gas, to the chemical quality of surface water and groundwater involves firstly establishing baseline compositions against which any future changes can be assessed. Contaminants of geogenic origin are of particular interest and radon has been identified as one potential contaminant from shale sources. Robust measurement and monitoring of radon in water at environmental concentrations is essential for ensuring protection of water sources and maintaining public confidence. Traditional techniques for Rn-222 determination in water, such as inference by gamma spectrometry and direct alpha counting, are impractical for direct field measurement, and the relatively short half-life of Rn-222 (~ 3.82 days) means that longer analytical protocols from field to the laboratory may result in greater uncertainty for Rn-222 activity. Therefore, a rapid and low-cost method would be beneficial. We have developed and refined a laboratory procedure for Rn-222 monitoring using liquid scintillation counting (LSC). The accuracy of Rn-222 activities obtained via this procedure was evaluated by the analysis of almost 200 water samples collected from streams and boreholes as part of a detailed baseline investigation in the Vale of Pickering, Yorkshire, one potential location for future shale gas exploration. LSC was preferred for measurement of Rn-222 and had comparable accuracy to gamma spectrometry and direct alpha counting. The methodology provided a rapid, portable and low-maintenance option relative to the two established techniques and is shown to be a favourable choice for the measurement of radon in surface water and groundwater at environmental concentrations.

Iodine status in western Kenya: a community-based cross-sectional survey of urinary and drinking water iodine concentrations.

Spot urinary iodine concentrations (UIC) are presented for 248 individuals from western Kenya with paired drinking water collected between 2016 and 2018. The median UIC was 271 µg L-1, ranging from 9 to 3146 µg L-1, unadjusted for hydration status/dilution. From these data, 12% were potentially iodine deficient (< 100 µg L-1), whilst 44% were considered to have an excess iodine intake (> 300 µg L-1). The application of hydration status/urinary dilution correction methods was evaluated for UICs, using creatinine, osmolality and specific gravity. The use of specific gravity correction for spot urine samples to account for hydration status/urinary dilution presents a practical approach for studies with limited budgets, rather than relying on unadjusted UICs, 24 h sampling, use of significantly large sample size in a cross-sectional study and other reported measures to smooth out the urinary dilution effect. Urinary corrections did influence boundary assessment for deficiency-sufficiency-excess for this group of participants, ranging from 31 to 44% having excess iodine intake, albeit for a study of this size. However, comparison of the correction methods did highlight that 22% of the variation in UICs was due to urinary dilution, highlighting the need for such correction, although creatinine performed poorly, yet specific gravity as a low-cost method was comparable to osmolality corrections as the often stated 'gold standard' metric for urinary concentration. Paired drinking water samples contained a median iodine concentration of 3.2 µg L-1 (0.2-304.1 µg L-1). A weak correlation was observed between UIC and water-I concentrations (R = 0.11).

Predicting the Risk of Biological Invasions Using Environmental Similarity and Transport Network Connectedness.

Understanding the risk of biological invasions associated with particular transport pathways and source regions is critical for implementing effective biosecurity management. This may require both a model for physical connectedness between regions, and a measure of environmental similarity, so as to quantify the potential for a species to be transported from a given region and to survive at a destination region. We present an analysis of integrated biosecurity risk into Australia, based on flights and shipping data from each global geopolitical region, and an adaptation of the "range bagging" method to determine environmental matching between regions. Here, we describe global patterns of environmental matching and highlight those regions with many physical connections. We classify patterns of global invasion risk (high to low) into Australian states and territories. We validate our analysis by comparison with global presence data for 844 phytophagous insect pest species, and produce a list of high-risk species not previously known to be present in Australia. We determined that, of the insect pest species used for validation, the species most likely to be present in Australia were those also present in geopolitical regions with high transport connectivity to Australia, and those regions that were geographically close, and had similar environments.