Robin Rattray

Levels of As, Cd, Pb, Cu, Se and Zn in bovine kidneys and livers in Jamaica

Paired liver and kidney samples from 100 free-range cattle in different parts of Jamaica were analyzed for essential and non-essential trace elements. We found significant enrichment of elements in the kidney (K) compared to the liver (L) with the K/L concentration ratios being 5.2 for Cd, 4.1 for Pb, 3.5 for Se and 2.1 for As, but the Cu contents of the kidney were significantly higher with the K/L ratio of 0.45. A large number of kidney and liver samples showed Cu concentrations in the ranges that were associated with deficiency effects in mammals. About 15% of the hepatic samples had Zn concentrations below 20 microg/g, suggesting that there might be zinc insufficiency in some of the animals. Positive associations were found between the metals in both the kidney and liver. On average, the intake of Cd from consumption of both bovine kidney and liver from the island was estimated to be 5.2 microg/day, equivalent to about 7% of the provisional tolerable daily intake (PTDI), although anyone who habitually consumed the few kidneys or livers with >40 microg/g cadmium may be at some risk of exceeding the PTDI. The consumption of offal from local animals did not appear to be an important dietary source of any of the essential microelements.

Blood lead levels in Jamaican school children

Blood lead levels are reported for a total of 421 schoolchildren in 13 schools in rural and urban environments in Jamaica, including one highly contaminated community. In the rural areas blood lead levels ranged from 3 to 28.5 microg dl(-1), with a median of 9.2 microg dl(-1); the range and median in the urban schools were 4-34.7 and 16.6 microg dl(-1), respectively. Forty-two percent of the rural and 71% of the urban blood lead levels exceeded the US Centers for Disease Control and Prevention intervention level of 10 microg dl(-1). Except in the contaminated area, the relationship between soil lead levels, which in Jamaica are in general typical of tropical lateritic soils, and blood lead levels is not clear-cut. Very high blood lead levels of 18 to > 60 microg dl(-1) with a median of 35 microg dl(-1) were observed among children in the contaminated area, the site of a former lead ore processing plant. These high blood lead levels were significantly reduced, by the implementation of relatively simple mitigation strategies which involved isolation of the lead, education, and a food supplementation programme, to levels similar to those observed in the urban schools. These values, however, remain higher than are desirable and unfortunately, all the sources of lead are not yet identified. The recent discontinuation of the use of leaded petrol is expected to result in significant reductions in exposure to lead.

Aerosol deposition direct sample insertion for ultra-trace elemental analysis by inductively coupled plasma mass spectrometry

Direct deposition of a liquid sample as an aerosol into an inductively heated graphite direct sample insertion probe is described as a means of preconcentration and high efficiency sample introduction for ICP-MS. A two minute deposition at 0.25 ml min–1 resulted in 3s detection limits ranging from 0.06 to 1.8 pg ml–1(0.03–0.9 pg) for the eight elements studied. These limits represent an element specific improvement averaging two orders of magnitude over the nebulizer/spray chamber-based sample introduction detection limits on the same instrument. The effect of varying several parameters related to the ICP and the deposition process was investigated. The performance of the system with samples in an ethanol matrix was also demonstrated. The deposition and insertion procedure was automated, providing RSDs of approximately 5% at the 1 ng ml–1 level. Analytical accuracy was assessed by replicate measurements of a Riverine Water Reference Material for Trace Metals (SLRS-2, National Research Council of Canada). Good agreement between calculated and certified values was obtained.

Chelation preconcentration with resin analysis by direct sample insertion inductively coupled plasma spectrometry

Batch preconcentration with Chelex-100 followed by direct analysis of the analyte-laden resin by direct sample insertion inductively coupled plasma atomic emission spectrometry (DSI-ICP-AES) is described. The performance of the technique is element specific. Quantitative retention of Cu, Zn, Cd and Pb on the resin is achieved, but only for Cu and Zn does the ratio of the signal before and after preconcentration approach the theoretical preconcentration factor. This observation is mainly caused by the adverse effect of the remnants of the resin after ashing on the excitation properties of the plasma. This is clearly shown by monitoring the ratio of the intensity of a Pb ionic line to a Pb atomic emission line. If the ashing temperature is increased, Cd and Pb are prematurely vaporized in the ashing stage, which is performed with inductive heating in the graphite DSI probe. Increasing the radiofrequency power sustaining the ICP improves the performance of the technique.

Communication. Assessment of direct solid sample analysis by graphite pellet electrothermal vaporization inductively coupled plasma mass spectrometry

Graphite pellet vaporization was evaluated as a method for solid sample introduction for ICP-MS. A detection limit of 0.1 ppb of Cd was obtained indicating that the technique might be very useful for screening. The accuracy was poor using the technique of external standards and four reference materials, suggesting that the technique of standard additions might be required if the technique was to be used for anything other than semi-quantitative measurements.

Communication. Rapid sample preconcentration by aerosol deposition for the determination of trace elements by inductively coupled plasma spectrometry

A new approach to sample preconcentration for inductively coupled plasma spectrometry has been developed. The method involves deposition of the sample solution as an aerosol into an inductively heated, graphite, direct sample insertion probe. With a deposition time of 2 min and a sample volume of 0.5 ml, detection limits for Cu, Zn, Cd and Pb were 0.05, 0.12, 0.10, and 0.07 ppb, respectively. These limits represent an improvement of almost three orders of magnitude over those obtained by conventional sample introduction in the same system. The relative standard deviation was <5% at the 10 ppb level. The conditions used and some performance characteristics are presented and discussed.

Geochemistry of an arsenic anomaly in St. Elizabeth, Jamaica

A soil arsenic anomaly with concentrations up to 400 μg As g−1 was discovered near Maggotty, St. Elizabeth, during an island‐wide geochemical survey of Jamaica. Detailed sampling and chemical analysis of soil samples confirmed the arsenic levels and led to a better definition of the size of the anomaly. The area exceeding the 95th percentile (>65 μg As g−1) of the island‐wide concentrations has been determined to be at least 10 km2. The anomalous values may be the result of an ancient hot spring environment which was responsible for the introduction and deposition of Fe–As–S as pyrite and arsenopyrite in the limestone bedrock, which were subsequently oxidised and weathered to yield the arsenic rich soils. These soils were also enhanced in elements such as Sb, Fe and Co. Despite the high soil arsenic content, the arsenic concentration in the surface water is low and there seems to be no immediate health risk to the residents. The area, however, does present a potential hazard with changing land use.

Design and characterisation of a vapour generation system for determination of mercury by atomic absorption spectrometry

A simple cold vapour generator is described that addresses problems with sample foaming, signal drift and memory effects associated with the wetting of gas–liquid separator membranes. The device is operated in continuous flow mode attached to an atomic absorption spectrometer. Method validation was carried out using BCR 186 Porcine Kidney reference material, with recovery averaging 97% with an estimated 3 s detection limit of 0.38 ppb Hg.

Peak Fitting and Deconvolution for Determination of the Impulse Response Function of the Sample Introduction System in Flow Injection Inductively Coupled Plasma Spectrometry

A technique for determining the impulse response function for an inductively coupled plasma atomic emission spectrometry sample introduction system is demonstrated. The input response function may then be useful for the determination of outputs, and consequently the performances, of flow injection or other sample treatment systems, which precede the sample introduction system. In a procedure to generate a known input response, a bolus of analyte was proceeded and followed by an air bubble, which reduced dispersion to a minimum. The impulse response function was determined and used to deconvolute other inputs of known concentration and dispersion. The deconvolution of the outputs using the impulse response function returned the expected result, indicating that the technique and impulse response function were correct. When used with an unsegmented traditional flow injection sample introduction valve, the system demonstrated clearly that significant dispersion takes place even in very compact introduction arrangements.

A Regional Perspective of Medical Geology – Cadmium in Jamaica

High levels of geogenic cadmium (Cd) have been found in some soils of Jamaica, particularly in the central part of the island. The potential health impact on residents who consumed foods grown on these soils was determined. The foods which have shown the greatest affinity for Cd uptake are mainly green leafy vegetables, tubers and root vegetables. Diet studies showed that some residents are at risk of ingesting Cd in excess of the 7 μg/kg body weight PTWI established by the WHO. Cd exposure and proximal tubular dysfunction were measured as urine Cd (U-Cd) and β2-microglobulin (β2-MG) in urine, respectively. Mean U-Cd and β2-MG concentrations of 4.6 μg Cd/g_cr and 290 μg/g_cr confirm that the population is being exposed to elevated Cd levels and there is evidence of very mild tubular proteinuria. The proteinuria detected in the population was related to Cd exposure, evidenced by the relationship between U-Cd and β2-MG. While positive results were obtained for the identification of Cd-related renal biomarkers in the study population and there was a clear association between U-Cd and β2-MG, the absolute concentrations obtained were well below critical limits for the onset of acute or chronic renal effects. Women typically ingested less Cd than men but absorbed greater amounts than males in the same cohort groups.