SEGH Articles

Back to the Future: Brian E Davies (Past President)

08 April 2014
Should we reduce our emphasis on the toxic elements? Is it time to go back to the future?



In 1970, when SEGH began, we talked about many ideas: is aluminium involved in dementia?; is arsenic an essential element?; is chromium involved in Type 2 diabetes?; can the incidence of gastric cancer be related to copper and zinc in the environment? By 1982, when I organised SEGH, and its first conference, in Britain, priorities had changed to environmental metals and sometimes we now appear to be a pollution society.


Have we reached the end of the metals era? For example, lead. The danger to child mental development has been recognised and quantified: the role of hand dirt is understood, paint and petrol are lead free, government regulations are in place, the environmental chemistry of lead is broadly understood. New ideas are now more likely to come from the clinical rather than the earth sciences. Or, cadmium. Little epidemiological evidence has emerged that environmental cadmium is a significant health problem. The special problems in Asia are probably because of poor iron nutrition (Simmons et al., 2003).


Death from all causes in 2012 (England and Wales) was 489,274. Accidental poisoning by ‘noxious substances’ accounted for 1,416 (0.3%) in contrast with 8,367 (1.7%) alcohol related deaths. Malignant neoplasms and diseases of the circulatory system each represented 28.8% total deaths. Morbidity data are broadly similar.



For cardiovascular diseases magnesium is a cofactor for over 300 enzyme systems and is required for energy generation and glycolysis. Magnesium is involved in nerve conduction, muscle contraction, potassium transport, and calcium channels. An environmental geochemistry link is seen in reports that deaths from heart attacks are greater where drinking water is soft. We all drink some tap water if only in tea, coffee or diluted ‘squash’.

In the next SEGH conference I plan to present a paper giving results from a desk study to establish the plausibility of a hard/soft water effect. The daily Reference Nutrient Intake (RNI) for Mg is men = 12 mmol. Nationally, solid food, pus bottled water plus alcoholic drinks for men provide (mean) 10.62 mmol Mg or 89% RNI. Adding in tap water: reservoir water contributes little Mg (total Mg intake 88.9% RNI); (mean) aquifer water Mg raises total intake to 11.85 mmol (96.5% RNI); a very hard water (North Downs chalk) raises total intake to 50.3 mmol (419% RNI). A beneficial role for Mg in hard drinking water seems plausible.

A recent paper (McKinley et al., 2013) reported a relationship between environmental exposure to trace elements in soil and cancer across Northern Ireland. Copper is an integral part of the antioxidant enzyme, copper-zinc superoxide dismutase. Copper deficiencies in animals and crops in Britain are a well attested problem. Yet we know little about any link from soil to humans.

Much reliable health data can now be accessed over the internet. Perhaps it is time to return to some of the older unanswered questions in environmental geochemistry and health. Should we reduce our emphasis on the toxic elements? Is it time to go back to the future?

By Professor Brian E Davies:


McKinley, J. M., Ofterdinger, U., Young, M., Barsby, A., & Gavin, A. (2013). Investigating local relationships between trace elements in soils and cancer data. Spatial Statistics, 5, 25–41.

Simmons, R. W., Pongsakul, P., Chaney, R. L., Saiyasitpanich, D., Klinphoklap, S., & Nobuntou, W. (2003). The relative exclusion of zinc and iron from rice grain in relation to rice grain cadmium as compared to soybean: Implications for human health. Plant and Soil, 257(1).

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

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  • Source and background threshold values of potentially toxic elements in soils by multivariate statistics and GIS-based mapping: a high density sampling survey in the Parauapebas basin, Brazilian Amazon 2019-08-10


    A high-density regional-scale soil geochemical survey comprising 727 samples (one sample per each 5 × 5 km grid) was carried out in the Parauapebas sub-basin of the Brazilian Amazonia, under the Itacaiúnas Basin Geochemical Mapping and Background Project. Samples were taken from two depths at each site: surface soil, 0–20 cm and deep soil, 30–50 cm. The ground and sieved (< 75 µm) fraction was digested using aqua regia and analyzed for 51 elements by inductively coupled plasma mass spectrometry (ICPMS). All data were used here, but the principal focus was on the potential toxic elements (PTEs) and Fe and Mn to evaluate the spatial distribution patterns and to establish their geochemical background concentrations in soils. Geochemical maps as well as principal component analysis (PCA) show that the distribution patterns of the elements are very similar between surface and deep soils. The PCA, applied on clr-transformed data, identified four major associations: Fe–Ti–V–Sc–Cu–Cr–Ni (Gp-1); Zr–Hf–U–Nb–Th–Al–P–Mo–Ga (Gp-2); K–Na–Ca–Mg–Ba–Rb–Sr (Gp-3); and La–Ce–Co–Mn–Y–Zn–Cd (Gp-4). Moreover, the distribution patterns of elements varied significantly among the three major geological domains. The whole data indicate a strong imprint of local geological setting in the geochemical associations and point to a dominant geogenic origin for the analyzed elements. Copper and Fe in Gp-1 were enriched in the Carajás basin and are associated with metavolcanic rocks and banded-iron formations, respectively. However, the spatial distribution of Cu is also highly influenced by two hydrothermal mineralized copper belts. Ni–Cr in Gp-1 are highly correlated and spatially associated with mafic and ultramafic units. The Gp-2 is partially composed of high field strength elements (Zr, Hf, Nb, U, Th) that could be linked to occurrences of A-type Neoarchean granites. The Gp-3 elements are mobile elements which are commonly found in feldspars and other rock-forming minerals being liberated by chemical weathering. The background threshold values (BTV) were estimated separately for surface and deep soils using different methods. The ‘75th percentile’, which commonly used for the estimation of the quality reference values (QRVs) following the Brazilian regulation, gave more restrictive or conservative (low) BTVs, while the ‘MMAD’ was more realistic to define high BTVs that can better represent the so-called mineralized/normal background. Compared with CONAMA Resolution (No. 420/2009), the conservative BTVs of most of the toxic elements were below the prevention limits (PV), except Cu, but when the high BTVs are considered, Cu, Co, Cr and Ni exceeded the PV limits. The degree of contamination (Cdeg), based on the conservative BTVs, indicates low contamination, except in the Carajás basin, which shows many anomalies and had high contamination mainly from Cu, Cr and Ni, but this is similar between surface and deep soils indicating that the observed high anomalies are strictly related to geogenic control. This is supported when the Cdeg is calculated using the high BTVs, which indicates low contamination. This suggests that the use of only conservative BTVs for the entire region might overestimate the significance of anthropogenic contamination; thus, we suggest the use of high BTVs for effective assessment of soil contamination in this region. The methodology and results of this study may help developing strategies for geochemical mapping in other Carajás soils or in other Amazonian soils with similar characteristics.

  • Uptake of Cd, Pb, and Ni by Origanum syriacum produced in Lebanon 2019-08-06


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