Coronary heart disease (CHD), and in particular myocardial infarction (MI), is one of the leading causes of death in Bangladesh. The BRAVE (Bangladesh Risk of Acute Vascular Events) study is a large-scale case-control study aimed at investigating the effects of environmental, genetic, lifestyle and biochemical factors on coronary heart disease in Bangladesh.

As part of the BRAVE study, toenail clippings were taken from each participant. Toenails can be used as effective biomarkers of toxic element exposure and mineral status, for several reasons, e.g. non-invasive collection, easy storage and transport, resistance to decay, limited exogenous exposure, and no fluctuation in element levels due to metabolic activities (unlike blood). The analysis of the toenail samples includes a number of procedures that aims at limiting the ambiguity of external contamination: sampling with questionnaire, washing, digestion, ICP-MS estimation of element concentrations, and interpretation with statistical analysis.

In this study, the cleaning protocol included the use of different solvents in sequence: acetone, milli-Q water and 0.5% Triton X-100 solution, a non-ionic detergent. For a number of samples, each rinse solution was retained for analysis by ICP-MS, to ensure an effective removal of exogenous contaminants. The obtained data of this study have so far showed high elemental variabilities amongst samples. Additionally, replicates have been analysed for a selection of specimens, with the analysis showing strong heterogeneity of the toenail samples, for elements such as Mn, Co and Mo. A procedure with LA-ICP-MS has been developed to investigate element distributions within nail samples, with focus given to surface and interior layers of the toenails. Future work will be focused on the analysis of the remaining batches, for total element concentration with ICP-MS and spatial element distribution in a selection of samples with LA-ICP-MS.