Assessment of the bioavailability of cadmium in Jamaican soils.

Extraordinary geogenic concentrations of cadmium (Cd) have been reported for some Jamaican soils. However, the bioavailability of the metal in these soils remains unknown. Here, the bioavailability of Cd in selected Jamaican soils was investigated through the determination of total and sequentially extractable concentrations in paired soil-plant (yam; Dioscorea sp.) samples (n = 24), using neutron activation analysis and atomic absorption spectroscopy as primary analytical techniques. Our results indicate that total soil Cd varied widely (2.2-148.7 mg kg(-1)), and on average, total extractable Cd accounted for ~55 % of the total soil Cd. The exchangeable and oxidizable species averaged 1.5 and 6.4 % of the total Cd, respectively, and, based on Spearman analysis, are the best predictors of yam Cd. There is also good evidence to suggest that variation in the bioavailability of the metal is in part controlled by the geochemical characteristics of the soils analyzed and is best explained by pH, cation exchange capacity (CEC) and organic matter content (% LOI).

Minimal health impact from exposure to diet-sourced cadmium on a population in central Jamaica.

Elevated concentrations of naturally occurring Cd have been found mainly in the bauxitic soils of central Jamaica at levels up to 100-1,000 times higher than typical worldwide averages. Some food crops cultivated on these soils absorb significant amounts of Cd. Autopsy studies of kidney Cd concentrations confirm elevated human exposure, and some long-term residents in central Jamaica exceed the general population average by a factor of two. Diet studies have ascertained that a population in central Jamaica is at risk of being exposed to Cd levels in excess of the Provisional Tolerable Weekly Intake (PTWI) set by the WHO of 7 µgCd/kg bodyweight/week, and the EU TWI of 2.5 µgCd/kg bodyweight/week. Elevated levels of urine cadmium (U-Cd) and beta-2 microglobulin (ß2-MG) concentrations were confirmed with a strong correlation between soil Cd and the U-Cd. Also, higher ß2-MG concentrations (>200µg/g creatinine) were found in the population with U-Cd concentrations greater than 2.5µg/L. While this identification is often taken to indicate impairment in the reabsorption capacity of the renal tubules leading to renal disease, there is no evidence in the mortality records of enhanced deaths in central Jamaica compared with the general population resulting from renal disease or diabetes related complications. The highest median age of death in the island is found in Manchester, the parish with the highest average Cd concentration. While we have identified a possible Cd linked renal dysfunction, significant indications of morbidity are not present in the general population.

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.

Elemental composition of Jamaican foods 1: a survey of five food crop categories.

The concentrations of 27 elements in Jamaican food categories consisting of fruit, legumes, leafy and root vegetables and other root crops are reported. The main analytical techniques used were neutron activation analysis and flame and graphite furnace atomic absorption spectrophotometry. The results are compared, where possible, with values from Denmark, the United Kingdom, the United States and Nigeria, and with some regulatory limits. Over 75% of the results for antimony, arsenic, barium, cerium, thorium and uranium were below the respective sample detection limits but even among these, some of the maximum values observed indicate that further examination may be useful for those foods grown in the regions of highest uptake and consumed in large amounts. The other elements reported are bromine, cadmium, calcium, caesium, cerium, chromium, copper, europium, hafnium, iron, lanthanum, lead, magnesium, manganese, phosphorus, potassium, rubidium, scandium, samarium, sodium, strontium, thorium, uranium, and zinc. Many of these elements occur at concentration levels above those reported from the other countries but it seems unlikely that most of these will contribute significantly to public health risk. However, at this stage cadmium clearly appears to be the element of greatest concern in the Jamaican food chain. The observed range of cadmium concentrations suggests that factors such as land selection, coupled perhaps where necessary, with suitably modified agricultural practices, is a feasible way to reduce the cadmium content of certain local foods.