SEGH Articles

Exposure to Arsenic And Other Toxic Elements Through Eating Earth

01 February 2012
The practice of deliberately eating earth, known as geophagy has been common in many cultures across the world. Unfortunately, very little scientific research is being conducted in this area and its impact on human health.

 

 

The work decribed below has been published and can be accessed from the following link: http://www.ehjournal.net/content/9/1/79

The practice of deliberately eating earth, known as geophagy has been common in many cultures across the world.  It continues to be practiced today in many parts of the world including amongst certain groups within the United Kingdom.  The reason behind this practice remains unknown, although it has been suggested it is consumed for nutritional and medicinal purposes. Since geophagy is more prevalent during pregnancy, it has been suggested that eating earth may remedy deficiencies that results in anaemia in women.  However, others argue that eating earth may cause anaemia.   Unfortunately, very little scientific research is being conducted in this area and little is known about the composition of earth that is consumed in different parts of the world and their impact on human health.   The mineral content of the earth will naturally vary from region to region and the potential of exposure to toxic elements is likely.   This is a cause for concern especially in certain parts of the world where there are environmental problems resulting in the presence of elevated levels of toxic elements such as arsenic in water and the food chain.  Arsenic is a toxic element that is present at high levels in drinking water in Bangladesh and India.  Although many studies have focused on arsenic exposure in India (West Bengal) and Bangladesh through drinking water, very little work has been done to consider other sources of exposure.  Exposure to arsenic through consumption of rice and vegetables has been highlighted (Cascio et al. 2011 and references therein).  It was reported that the Bangladeshi's residing in the United Kingdom are exposed to a higher level of arsenic compared to white Caucasians (Cascio et al. 2011) due to their high intake of rice. 

Shaban Al-Rmalli is a PhD student (PhD supervisors:  Parvez Haris & Richard Jenkins, De Montfort University; Collaborator:  Michael Watts, British Geological Survey) at De Montfort and his research project was to identify the different sources of arsenic exposure in the Bangladeshi community not just from rice and vegetables.   The aim of the project is to identify sources of exposure to toxic elements that may explain the reasons underlying the disproportionately higher prevalence of different disease including diabetes, cardiovascular disease and some types of cancer amongst UK Bangladeshis (Cascio et al.  2010 & references therein).   Information obtained could be used to help modify the diet of the Bangladeshis (both in the UK and in Bangladesh) so that they avoid certain types of foods/non-foods that may contain high levels of toxic elements.  As part of his PhD project, Shaban analysed over 1,000 Bangladeshi food and non-food samples.  Amongst the samples he purchased from ethnic Bangladeshi shops in the United Kingdom was baked clay (imported from Bangladesh) that are called Sikor in Bengali (see Figure).   Discussions with the members of the Bangladeshi community and shop keepers revealed that these clay tablets are purchased mainly by Bangladeshi and African women and especially by pregnant women from these communities.  This revelation was rather alarming and further investigation into this issue revealed that in Bangladesh some women can consume as much as 500g of these clay tablets per day.   The average weight of the sikor tablets shown in the Figure is approximately 15g and most women consume between 3-4 tablets per day.  This is particularly worrying as intake of high levels of toxic elements could not only harm the health of the pregnant women but that of the unborn baby since many toxic elements including lead and arsenic can transfer from the mother to the baby through the placenta.  What was a cause for further worry is that women in Bangladesh are already being exposed to high levels of arsenic and manganese etc through drinking water and consumption of sikor may potentially lead to a further increase in exposure to these elements.   It was therefore vital that such samples are analysed to evaluate their content of arsenic as no previous studies have considered this issue.   

Sikor samples, originating from Bangladesh,  were purchased and analysed for their As, Pb, Cd, Mn, Fe and Zn levels using ICP-MS. Furthermore, detailed As speciation analysis was performed using HPLC-ICP-MS (http://www.ehjournal.net/content/9/1/79).   The levels of As (3.8-13.1 mg kg-1), Cd (0.09-0.4 mg kg-1) and Pb (21-26.7 mg kg-1) present in the sikor samples were of concern and could have detrimental effect on the health of the consumer. Speciation analysis revealed that sikor samples contained mainly the toxic inorganic As. It was calculated that modest consumption of 50 g of sikor is equivalent to ingesting 370 μg of As and 1235 μg of Pb per day, based on median concentration values. Just consuming 50g sikor per day exceeds the permitted maximum tolerable daily intake (PMTDI) of inorganic As by almost 2-fold (http://www.ehjournal.net/content/9/1/79).   The study concluded that sikor consumption can be a source of exposure to As, Cd and Pb in some Bangladeshis and in some other populations where this is consumed such as in India & Africa.   In the future, it is important to evaluate the bioavailability of As and other elements from sikor and their impact on human health.

The authors of the study recommend that those responsible for public health, act to create awareness about the potential dangers of consuming baked clay in populations where this practice is prevalent.  As a result, the United Kingdom Food Standards Agency has advised pregnant women not to eat baked clay (http://www.food.gov.uk/news/newsarchive/2011/june/clay ).  However, public health officials in other parts of the world including Bangladesh, India, Africa and other parts of the world where geophagy is more prevalent need to also act urgently to advise women about the potential dangers of eating clay.

For further details, please contact Dr P.I. Haris, E-Mail: pharis@dmu.ac.uk

References:

Al-Rmalli, S.W.,  Jenkins, R.O., Watts, M.J., and Haris, P.I. Risk of human exposure to arsenic and other toxic elements from geophagy: trace element analysis of baked clay using inductively coupled plasma mass spectrometry.  Environmental Health 2010, 9:79 (23 December 2010).

http://www.ehjournal.net/content/9/1/79

Cascio, C., Raab, A.,  Jenkins, R.O., Feldmann, J. Meharg, A.A. and Haris, P.I. (2011)  The impact of a rice based diet on urinary arsenic.  J. Environ. Monit., 2011, 13, 257-265.

Related reports 

Food Standards Agency issues warning about eating clay.

http://www.food.gov.uk/news/newsarchive/2011/june/clay

Keep up to date

Submit Content

Members can keep in touch with their colleagues through short news and events articles of interest to the SEGH community.

Science in the News

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

  • Agro-ecological suitability assessment of Chinese Medicinal Yam under future climate change 2019-10-15

    Abstract

    Chinese Medicinal Yam (CMY) has been prescribed as medicinal food for thousand years in China by Traditional Chinese Medicine (TCM) practitioners. Its medical benefits include nourishing the stomach and spleen to improve digestion, replenishing lung and kidney, etc., according to the TCM literature. As living standard rises and public health awareness improves in recent years, the potential medicinal benefits of CMY have attracted increasing attention in China. It has been found that the observed climate change in last several decades, together with the change in economic structure, has driven significant shift in the pattern of the traditional CMY planting areas. To identify suitable planting area for CMY in the near future is critical for ensuring the quality and supply quantity of CMY, guiding the layout of CMY industry, and safeguarding the sustainable development of CMY resources for public health. In this study, we first collect 30-year records of CMY varieties and their corresponding phenology and agro-meteorological observations. We then consolidate these data and use them to enrich and update the eco-physiological parameters of CMY in the agro-ecological zone (AEZ) model. The updated CMY varieties and AEZ model are validated using the historical planting area and production under observed climate conditions. After the successful validation, we use the updated AEZ model to simulate the potential yield of CMY and identify the suitable planting regions under future climate projections in China. This study shows that regions with high ecological similarity to the genuine and core producing areas of CMY mainly distribute in eastern Henan, southeastern Hebei, and western Shandong. The climate suitability of these areas will be improved due to global warming in the next 50 years, and therefore, they will continue to be the most suitable CMY planting regions.

  • Application of stable isotopes and dissolved ions for monitoring landfill leachate contamination 2019-10-15

    Abstract

    We evaluated groundwater contamination by landfill leachate at a municipal landfill and characterized isotopic and hydrogeochemical evidence of the degradation and natural attenuation of buried organic matter at the study site. Dissolved ion content was generally much higher in the leachate than in the surrounding groundwater. The leachate was characterized by highly elevated bicarbonate and ammonium levels and a lack of nitrate and sulfate, indicating generation under anoxic conditions. Leachate δD and δ13CDIC values were much higher than those of the surrounding groundwater; some groundwater samples near the landfill showed a significant contamination by the leachate plume. Hydrochemical characteristics of the groundwater suggest that aquifer geology in the study area plays a key role in controlling the natural attenuation of leachate plumes in this oxygen-limited environment.

  • Lead transfer into the vegetation layer growing naturally in a Pb-contaminated site 2019-10-10

    Abstract

    The lead was one of the main elements in the glazes used to colour ceramic tiles. Due to its presence, ceramic sludge has been a source of environmental pollution since this dangerous waste has been often spread into the soil without any measures of pollution control. These contaminated sites are often located close to industrial sites in the peri-urban areas, thus representing a considerable hazard to the human and ecosystem health. In this study, we investigated the lead transfer into the vegetation layer (Phragmites australis, Salix alba and Sambucus nigra) growing naturally along a Pb-contaminated ditch bank. The analysis showed a different lead accumulation among the species and their plant tissues. Salix trees were not affected by the Pb contamination, possibly because their roots mainly develop below the contaminated deposit. Differently, Sambucus accumulated high concentrations of lead in all plant tissues and fruits, representing a potential source of biomagnification. Phragmites accumulated large amounts of lead in the rhizomes and, considering its homogeneous distribution on the site, was used to map the contamination. Analysing the Pb concentration within plant tissues, we got at the same time information about the spread, the history of the contamination and the relative risks. Finally, we discussed the role of natural recolonizing plants for the soil pollution mitigation and their capacity on decreasing soil erosion and water run-off.