Trace Element Abundance and Human Epidemiology in Northern Ireland
: The Tellus Case Study

Student thesis: Doctoral ThesisDoctor of Philosophy


Although human health in the UK, and other parts of the world, has improvedconsiderably over the last three decades, there remains considerable social andspatial difference in ill health distribution. While causal factors have been identifiedthat explain much of this difference for certain diseases, a significant proportion ofthis difference in health burden remains unexplained. Environmental factors arelikely to be significant with regard to certain diseases. In particular, the primaryspatial abundance and bioavailabilty of key trace elements (eg. As, Ni, Pb, Cr, Cdand U) in soil and water as well as subsequent residual concentrations within thefood chain, together with the presence of relevant human exposure pathways, mayexplain the spatial variability of certain disease patterns. It has been recognizedthat besides anthropogenic impacts, the diversity of bedrock geology and mineraldeposits primarily leads to similarly diverse trace element distributions inassociated soils. The complex geology of Northern Ireland includes most rock typesencountered across the UK and Ireland and presents therefore an excellent typearea for a study of trace element abundance and human epidemiology.

The Tellus Project at GSNI provides a comprehensive data set including airbornegeophysical information as well as soil, stream sediment and stream watergeochemistry and surface water chemistry data gathered across Northern Ireland.Soil geochemistry data have been collected spatially on a regular 2 km2 grid basepattern, yielding a wealth of information regarding the detailed composition of Irishsoils. With the commencement of similar survey projects in the Republic of Ireland(Tellus Border) and continuation of the G-BASE surveys in England and Wales, thereadily available data of the completed Tellus Project provide the rare opportunityfor exploring its detailed database in conjunction with available epidemiologicaldata. The incidence of twelve different cancer types (lung, stomach, leukaemia,oesophagus, colorectal, bladder, kidney, breast, mesothelioma, melanoma and nonmelanoma both basal and squamous, were provided by the Northern IrelandCancer Registry (NICR) in the form of twenty-five coded datasets comprisingaggregates over the 12 year period from 1993 to 2006.

The research explores the spatial correlation between selected trace elementabundance in soil and epidemiological data with regard to spatial disease(particularly cancer) patterns. Interpolation techniques within a GeographicalInformation System (GIS) and geostatistics (variography and kriging) were used tomap the Tellus geochemistry data, gamma radiation dose rate and radonconcentrations provided by GSNI and the Health Protection Agency (HPA). Thisenabled the spatial distribution of the identified PTEs, gamma dose rate and radonto be examined and related to geological parent material and pedological sources.The unified BARGE bioaccessability method was used to investigate thebioaccessible fraction of the PTEs. This provided a greater understanding of possiblesources and exposure pathways. Age Stantardised Incidence Rates (ASIR)s weremapped, a local Moran's / analysis identified clustering of wards with high and lowincidences of the different cancers and outlier wards of high or low incidencessurrounded by wards exhibiting very different disease statistics. The use of ageographical weighted regression (GWR) enabled the relationship betweendifferent cancers and PTEs in the soil and radon to be investigated. The results showcomparisons of the geographical incidence of certain cancers (lung cancer and nonmelanoma skin cancer) in relation to concentrations of certain PTEs (arsenic anduranium levels in soils and radon).
Northern Ireland forms an important test case, as the complex geology is amicrocosm for that encountered across the UK and Ireland. The combination of thecomprehensive soil geochemistry data generated by the Tellus project and theaccuracy and inclusiveness of data collected and maintained by the NICR hasallowed this spatial investigation into the influence of geographical distribution,total concentration and level of bioaccessibility of trace element in soil on humanepidemiology in Northern Ireland. The indications of spatial correlations found mayhave implications outside of Northern Ireland have implications for regional humanhealth risk assessments.
Date of AwardJul 2013
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SupervisorJennifer McKinley (Supervisor), Ulrich Ofterdinger (Supervisor), Michael Young (Supervisor) & Anna Gavin (Supervisor)

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