SEGH Articles

Is there an environmental link to esophageal cancer in Tanzania?

07 July 2015
Scientists from the Centre for Environmental Geochemistry are helping health organisations understand why esophageal cancer is localised within specific areas of the African Rift Valley. Whilst various causal factors are now under investigation, such as high-strength kill-me-quick alcohol consumption or hot tea drinking, it is difficult to fully explain the localised nature of the burden. Here Dr Michael Watts outlines why soil around Mount Kilimanjaro could unearth some answers.

Dr Valerie McCormack from the International Agency for Research on Cancer (IARC, part of the World Health Organisation) has studied the high prevalence of esophageal cancer in the Rift Valley and identified a particularly localised incidence of cases in the Mount Kilimanjaro area of Tanzania. A hypothesis was presented that an environmental factor, such as exposure to potentially harmful elements or organics (e.g. polycyclic aromatic hydrocarbons, PAHs, from wood fires) or deficiency of essential micronutrients (e.g. zinc) that diminishes the body’s ability to recover from or buffer an event that may cause cell damage, could be contributing to this.

Kilimanjaro District

This is where the skills of the Centre for Environmental Geochemistry (CEG) team come in. The BGS Inorganic Geochemistry team assisted IARC-WHO and the Kilimanjaro Christian Medical Centre (KCMC) in designing and undertaking a detailed survey of soil, water and crop samples in the Kilimanjaro district.

Children in Masame

Our primary aim was to link geochemistry and crop data with areas in which esophageal cancer cases were prevalent.  In addition, the data will demonstrate a spatial understanding of the geochemistry of the differing climatic zones and food production areas around Mount Kilimanjaro and to provide an indication of micronutrient composition or presence of potentially harmful elements.


This increased understanding of the soil and crops in Kilimanjaro will improve baseline evidence for a differing climatic zone compared to previous work in Sub-Saharan Africa (previous blogs), to inform future experimentation of agricultural methods that could improve soil-crop transfer of micronutrients for onward health benefits. 


We also provided training to local counterparts from KCMC and the Ministry of Agriculture Kilimanjaro District Extension Office in the collection of environmental samples, recording of field data for quality assurance / data management and onward presentation in GIS maps for agricultural planning tools. It is a privilege to be able to help where our skills are needed most and it’s clear these strong working relationships will bring benefits to local populations and the wider science community. We see clear opportunities for future collaboration with all of the partners we worked with in Tanzania, including the Regional Area Secretariat from the Prime Minister’s Office.

Rombo Mkuu

In fact the CEG has already partnered again with IARC-WHO (the project leaders) on a recently gained grant from the US National Cancer Institute to study a similarly high-localised prevalence of esophageal cancer in the Eldoret region of Kenya.  Such work involves the cross-disciplinary collaboration of epidemiologists, medics, health practitioners, biostatisticians, geochemists, farmers and local agricultural extension workers and commences 2015 to 2017. Watch out for future blogs and see all our research via our CEG website - 

Dr Michael Watts
Head of Inorganic Geochemistry, Centre for Environmental Geochemistry

Suggestions for further reading:

Joy et al. (2015). Zinc enriched fertilisers as a potential public health intervention in Africa, DOI:10.1007/s11104-015-2430-8. 

Gibson RS, Wawer AA, Fairweather-Tait SJ, Hurst R, Young SD, Broadley MR, Chilimba ADC, Ander EL, Watts MJ, Kalimbira A, Bailey KB, Siyame EWP. (2015). Dietary iron intakes based on food composition data may underestimate the contribution of potentially exchangeable contaminant iron from soil, Journal of Analytical Food Research (in press).

Joy, EJM, Broadley, MR, Young, SD, Black CR, Chilimba, ADC, Ander, EL, Barlow, TS and Watts, MJ*. (2015). Soil type influences crop mineral composition in Malawi, Science Total Environment, 505, 587-595.

Joy, E, Ander, EL, Young, SD, Black, C, Watts, MJ, Chilimba, ADC, Chilima, B, Siyame, E, Kalimbira, A, Hurst, R, Fairweather-Tait, SJ, Stein, A, Gibson, RS, White, P, Broadley, M. (2014) Dietary mineral supplies in Africa, Physiologia Plantarum, 151, 208-229.

Siyame E; Hurst R; Wawer AW;Young SD; Broadley MR; Chilimba ADC Ander EL; Watts MJ; Chilima B; Gondwe J; Kang’ombe D; Kalimbira A; Fairweather-Tait SJ; Bailey KB; Gibson RS. (2014). A high prevalence of zinc but not iron deficiency among Women in Rural Malawi: a cross-sectional study, International Journal for Vitamin and Nutrition Research, 83, 3, 176-187.

Hurst, R, Siyame, E, Young, SD, Chilimba, ADC, Joy, EJM, Black, CR, Ander, EL, Watts, MJ, Chilima, B, Gondwe, J, Kang’ombe, D, Stein, AJ, Fairweather-Tait, SJ, Gibson, R, Kalimbira, A, Broadley, MR*. (2013). Soil-type influences human selenium status and underlies widespread selenium deficiency risks in Malawi, Scientific Reports, 3, 1425.

Broadley MR, Chilimba ADC, Joy, E, Young SD, Black CR, Ander EL, Watts MJ, Hurst R, Fairweather-Tait SJ, White PJ, Gibson RS. (2012). Dietary requirements for magnesium but not calcium are likely to be met in Malawi based on national food supply data, International Journal of Vitamin and Nutrition Research, 82(3), 192-199.

Joy EJM, Young SD, Black CR, Ander EL, Watts MJ and Broadley MR. (2012). Risk of dietary magnesium deficiency is low in most African countries based on food supply data, Plant and Soil, 368. 129-137.

W H Shetaya, S D Young, M J Watts, E L Ander and E H Bailey (2012). Iodine dynamics in soils, Geochemica et Cosmochimica Acta, 77, 457 – 473.
Chilimba, A.D.C., Young, S.D., Black, C.R., Ander, E.L., Watts, M.J., Lammel, J. and 

Broadley, M.R. (2011). Maize grain and soil surveys reveal suboptimal dietary selenium intake is widespread in Malawi, Scientific Reports, 1, 1 - 9.



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Latest on-line papers from the SEGH journal: Environmental Geochemistry and Health

  • Geophagy among East African Chimpanzees: consumed soils provide protection from plant secondary compounds and bioavailable iron 2019-12-01


    Geophagy, the intentional consumption of earth materials, has been recorded in humans and other animals. It has been hypothesized that geophagy is an adaptive behavior, and that clay minerals commonly found in eaten soil can provide protection from toxins and/or supplement micronutrients. To test these hypotheses, we monitored chimpanzee geophagy using camera traps in four permanent sites at the Budongo Forest Reserve, Uganda, from October 2015–October 2016. We also collected plants, and soil chimpanzees were observed eating. We analyzed 10 plant and 45 soil samples to characterize geophagic behavior and geophagic soil and determine (1) whether micronutrients are available from the soil under physiological conditions and if iron is bioavailable, (2) the concentration of phenolic compounds in plants, and (3) if consumed soils are able to adsorb these phenolics. Chimpanzees ate soil and drank clay-infused water containing 1:1 and 2:1 clay minerals and > 30% sand. Under physiological conditions, the soils released calcium, iron, and magnesium. In vitro Caco-2 experiments found that five times more iron was bioavailable from three of four soil samples found at the base of trees. Plant samples contained approximately 60 μg/mg gallic acid equivalent. Soil from one site contained 10 times more 2:1 clay minerals, which were better at removing phenolics present in their diet. We suggest that geophagy may provide bioavailable iron and protection from phenolics, which have increased in plants over the last 20 years. In summary, geophagy within the Sonso community is multifunctional and may be an important self-medicative behavior.

  • Accumulation of uranium and heavy metals in the soil–plant system in Xiazhuang uranium ore field, Guangdong Province, China 2019-12-01


    Plants that have grown for many years in the special environmental conditions prevailing in mining areas are naturally screened and show strong capacity to adapt to their environment. The present study investigated the enrichment characteristics of U and other heavy metals (As, Cu, Pb, Mn, Mo, Zn, Cd, Co, and Ni) in the soil–plant system in Xiazhuang uranium mine. Four dominant plants (Castanopsis carlesii, Rhus chinensis, Liriodendron chinense, and Sapium discolor) and soil samples were collected from the mined areas, unmined areas, and background areas away from the ore field. U, As, Cu, Pb, Mn, Mo, Zn, Cd, Co, and Ni concentrations were analyzed by ICP-MS. The results demonstrate that (1) The highest concentrations of U (4.1–206.9 mg/kg) and Pb (43.3–126.0 mg/kg) with the geoaccumulation index (Igeo) greater than 1 show that they are the main soil pollutants in the research area. (2) The biological accumulation coefficient (LBAC) values for Cd, Mn, and Cu are greater than zero in S. discolor, L. chinense, and C. carlesii and these three plants indicate that they can be used for remediation of the soil in the ore field. (3) R. chinensis inhibits the accumulation of heavy metals and shows sensitive pigment responses to the accumulation of U in the leaves. L. chinense has the strongest enrichment effect on heavy metals but exhibits weak biochemical responses under U stress. C. carlesii demonstrates strong adaptation to U and can maintain healthy pigment characteristics in case of high U enrichment. (4) S. discolor, L. chinense, C. carlesii and R. chinensis have strong tolerance to U toxicity and different biochemical responses.

  • Distribution, sources and health risk assessment of contaminations in water of urban park: A case study in Northeast China 2019-12-01


    This case study was performed to determine whether the pollutants in water of urban park could bring health risk to human engaging in water-related activities such as swimming and provide evidence demonstrating the critical need for strengthened recreational water resources management of urban park. TN, NH4+-N, TP, Cu, Mn, Zn, Se, Pb, As, Cd and Cr(VI) contents were determined to describe the spatial distribution of contaminations; sources apportionment with the method of correlation analysis, factor analysis and cluster analysis were followed by health risk assessment for swimmers of different age groups. The results reveal that element contents in all sites do not exceed Chinese standard for swimming area and European Commission standard for surface water; all detected elements except Cr(VI) have a tendency to accumulate in the location of lake crossing bridge; Mn and Zn are considered to have the same pollution source including geogenic and anthropogenic sources by multivariable analysis. Carcinogenic risks of different age groups descend in the same order with non-carcinogenic risks. Among all elements, Zn and Mn contribute the lowest non-carcinogenic risk (5.1940E-06) and the highest non-carcinogenic risk (7.9921E-04) through skin contact pathway, respectively. The total average personal risk for swimmers in swimming area is 1.9693E-03, and this site is not suitable for swimming. Overall, it is possible that swimmers are exposed to risk via the dermal route when carrying out water-related activities, it is recommended that necessary precautions and management should be taken in other similar locations around the world.