The measurement of boron in the environment and human hair in relation to Argentina, South America

1. The measurement of boron in the environment and human hair in relation to Argentina, South America Sarah Hill* and Neil I. Ward Chemical Sciences, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, GU2 7XH, UK Introduction • Boron deficiency in agriculture is common but toxicity is rare • The environment in San José de Jachal in San Juan, Argentina suffers from high concentrations of boron, typically x10 higher than literature values • Boron is not recognised as an essential element for animals or humans but is known to have various physiological effects1-5: • Macromineral metabolism, particularly Ca, Mg and P • Vitamin D utilisation • Inflammatory disease • Enzyme function • Many studies have investigated the effects of deficiency status and toxicity symptoms, predominantly under laboratory conditions • Little is known about agricultural and human exposure through natural environmental pathways • A preliminary study highlighted the need for further research in the human population through the monitoring of hair • Methodology needed to be established for sample collection and digestion in-house General Roca Figure 1 Map of Argentina6 Results and Discussion Preliminary study results Method development for hair digestion The results from the preliminary study are shown in Table 1. The hair samples were digested using nitric acid in a microwave and wine was simply diluted in ultrapure water. The analysis was performed by ICP-MS. General Roca in Rio Negro, Patagonia is a different region of Argentina, 550 miles to the south of San Juan (Figure 1). Three different techniques were tested using unwashed and washed hair (IAEA method) and a certified reference material GBW 07601: • Dry ashing using 5% HNO3 as an ashing aid (previously proven to reduce volatile losses for other elements8) • Wet digestion using glass digestion tubes and heating block9 with concentrated HNO3 and 30% H2O2 • Wet digestion using PTFE beakers with lids on a hotplate10 with concentrated HNO3 and 30% H2O2 Table 1 Boron concentrations in hair and wine Table 2 Boron concentrations in hair using different digestion techniques • Dry ashing consistently resulted in lower values compared with the other methods • Washing the hair reduces the mean boron level suggesting the majority of B is endogenous rather than exogenous • PTFE technique provides the best precision level and best % recovery • Reference value for GBW 07601 is 1.3 mg/kg B confirming PTFE is in good agreement The size of the data in the preliminary study was small but showed the need for further investigation. Therefore a larger sample set from San José de Jachal and General Roca were obtained. Hair samples were collected with questionnaires about lifestyle and general health. Wine (Chardonnay and Cabernet Sauvignon) was collected from grape growers and manufacturers. Due to the unavailability of the microwave, an alternative hair digestion procedure was required. Boron can also be measured by a UV/Vis assay by the formation of a complex with azomethine-H and absorbance measured at 420 nm. The colour of the wine interferes with the detection of boron therefore requiring pre-treatment to eliminate this. Method development for wine digestion Problems PTFE beakers with lids were used; 1 ml of wine and 1 ml of concentrated HNO3 were allowed to stand overnight, 30% H2O2 was added and placed on hotplate for 1 hr at 140°C, allowed to cool and diluted to 10 ml with ultrapure water, resulting in a colourless solution with no absorption at 420 nm. Spiked recoveries of 91–98% were achieved for chardonnay and 84–97% for cabernet sauvignon with this methodology. Conclusion References • Institute of Medicine (2001) Dietary Reference Intakes For Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium and Zinc, National Academic Press, Washington D.C., 510-521 • F.H. Nielsen and T.R. Shuler (1992) Biol. Trace Elem. Res. 35, 225-237 • S. Samman, M.R. Naghii, P.M. Lyons Wall and A.P.Verus (1998) Biol. Trace Elem. Res., 66(1-3), 227-235 • C.D. Hunt (1994) Environ. Health Perspect., 102(Suppl. 7), 35-43 • R.E. Newnham (1994) Environ. Health Perspect., 102(Suppl. 7), 83-85 • http://www.globosapiens.net/country/argentina_map.html • N. Hammond (2002) Elemental Status of Individuals from Rio Negro, Argentina: Use of Scalp Hair as a Biomarker of Environmental and Dietary Sources, MSc Thesis, University of Surrey • A. Stovell (1999) Trace Elements and Human Fertility, PhD Thesis, University of Surrey • G.S. Bañuelos, G.E. Cardon, T. Pflaum and S. Akohoue (1992) Comm. Soil Sci. Plant Anal., 23, 2383-2397 • C.D. Hunt and T.R. Shuler (1989) J. Micronutr. Anal., 6, 161-174 • Preliminary work and lack of literature data highlighted the need for further investigation into the levels and effects of natural exposure to boron • A suitable method for digestion of hair was established using nitric acid and hydrogen peroxide in PTFE beakers on a hotplate • The effect of washing hair prior to digestion shows endogenous incorporation into the hair fibre via body absorption and assimilation • A similar digestion approach was taken for wine, allowing boron measurement by a simple UV/Vis assay without interferences • Further work: apply these methods to real samples from Argentina