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Elemental composition of Jamaican foods 1: A survey of five food crop

categories

Andrea Howe1, Leslie Hoo Fung1, Gerald Lalor1,2, Robin Rattray1 & Mitko Vutchkov11International Centre for Environmental and Nuclear Sciences, University of the West Indies, Mona Kingston7, Jamaica2Author for correspondence (e-mail: [email protected])

Received 7 March 2003; Accepted 30 March 2004

Key words: cadmium, food, heavy metals, jamaica, soil, trace elements

Abstract

The concentrations of 27 elements in Jamaican food categories consisting of fruit, legumes, leafy and rootvegetables and other root crops are reported. The main analytical techniques used were neutron activationanalysis 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 withsome regulatory limits. Over 75% of the results for antimony, arsenic, barium, cerium, thorium anduranium were below the respective sample detection limits but even among these, some of the maximumvalues observed indicate that further examination may be useful for those foods grown in the regions ofhighest 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, ura-nium, and zinc. Many of these elements occur at concentration levels above those reported from the othercountries but it seems unlikely that most of these will contribute significantly to public health risk. How-ever, at this stage cadmium clearly appears to be the element of greatest concern in the Jamaican foodchain. The observed range of cadmium concentrations suggests that factors such as land selection, coupledperhaps where necessary, with suitably modified agricultural practices, is a feasible way to reduce thecadmium content of certain local foods.

1. Introduction

Because of perceived effects on food quality andsafety, which are now seen as essential componentsof public health, the control of potentially haz-ardous elements in soils has become important forsustainable agriculture. Consequently, the ele-mental contents of foods are being increasinglyregulated in countries of the temperate region(OJEC 2001; FSANZ 2002) and, with increasingglobalisation, similar regulations will probablyeventually apply to all countries. This may repre-sent a non-tariff trade barrier for developingcountries for which food exports are an essentialcomponent of socio-economic development. In

addition there may, in certain circumstances, bepublic health risks. While this may be a challenge,the necessary work will provide interesting re-search opportunities, for example, in soil geo-chemistry including speciation, on soil–plantrelationships in the food chain, and on potentiallyimportant interactions between the system con-stituents. These studies are most important inthose regions where the population eats mainlylocally grown food and require the acquisition oflarge sets of accurate data on the occurrence anddistribution of a variety of elements in soils andfoods, human dietary intakes and the effectsthereof. This knowledge should in turn providebetter understanding of the role of trace elements

Environmental Geochemistry and Health 27: 19–30, 2005.� 2005 Springer. Printed in the Netherlands.

19

in life processes and support the establishment ofguidelines and regulations. In Jamaica the concernis not now due to anthropogenic pollution but, asshown by the comparisons in Table 1, to highnatural occurrences of several elements.Except for lead and zinc, the means in Table 1

exceed for example the Canadian guidelines foragricultural land use and the maxima approach orexceed the Danish cut-off criteria, at which the soilis considered too contaminated for any humancontact. The cadmium levels are exceptionally high(Lalor et al. 2000a). Some island-wide concentra-tion distributions are shown in Figure 1, whichincludes a highly simplified geological map and thedistributions of the more important areas underagriculture for non-plantation crops.The concentrations of arsenic and heavy metals

tend to be highest in the soils of central Jamaica.These are underlain by the White LimestoneGroup, the properties of which have no doubtcontributed to the bauxitisation and soil formationprocesses and hence to the concentration of theresistate elements. Such high levels of potentiallyhazardous elements in agricultural soils indicatethe need to examine foods grown thereon, as foodis the major source of trace element intake forhumans. The wide variation in the elemental soilconcentrations across the country allows the pos-sibility for zoning, if necessary, and provides anopportunity to examine conditions, including ele-mental speciation and agricultural practices, thatmay affect the soil-to-plant transfer of trace ele-ments under tropical conditions.

The overall project requires the collection oflarge numbers of soil and food samples island-wide and analyses for a wide range of elements.Even supported by a multi-elemental analyticaltechnique like neutron activation analysis andusing semi-automated atomic absorption spectro-photometry, such a programme is a major effortthat demands standardised procedures and meth-odologies with careful quality assurance to ensurecomparability over time and between laboratories.This paper reports on elemental contents for 129samples distributed amongst five categories offoods grown in central Jamaica.

2. Methodology

2.1. Sample collection and preparation

Food samples were collected from farms andmarkets in central Jamaica, placed in labelled pa-per bags and transported to the laboratory within4 days. There, the samples were brushed to removeadhering soil, washed with tap water, patted drywith paper towels and (where necessary) peeledwith a stainless steel knife to isolate the edibleportion. Each sample was cut into smaller piecesand combined by mixing on a plastic sheet. A sub-sample of at least 500 g was dried to constantweight on aluminium trays lined with aluminiumfoil in a forced draught oven at 100 �C. Aftercooling in a desiccator, the samples were groundusing an automated agate mortar and pestle to a

Table 1. Comparison of concentrations of some trace elements in Jamaican soils with soil criteria for Canada and Denmark; mg kg)1

except for mercury (lg kg)1).

Element Jamaican soilsa Canadian soilsb Danish soilsc

Maximum Mean Guideline limits for

agricultural land use

Cut-off criteria

Arsenic 373 25 12 20

Cadmium 409 20 1.4 5

Chromium 1063 309 64 1000

Copper 657 102 63 500

Lead 897 47 70 400

Mercury 830 221 6.6 3

Zinc 936 205 200 1000

a Lalor (1995).b CCME (2001).cDanish EPA (2000).

ANDREA HOWE ET AL.20

particle size of less than 50 lm. Liquid nitrogencooling was used to assist for samples that werenot otherwise readily ground.

2.2. Analysis

The analytical techniques used were neutron acti-vation analysis (NAA), atomic absorption spec-trophotometry (AAS) and flow injection analysis(FIA). Approximately 10% of the samples wereanalysed in duplicate; at least one reagent blankand a certified reference material were also in-cluded in each batch.

2.3. Neutron activation analysis

NAA was performed using the SLOWPOKE 2nuclear reactor (Lalor et al. 2000b). Approxi-mately 1 g of sample was irradiated for up to 4 h

at a flux of 1 · 1012 n cm)2 s)1, allowed to coolfor 5 days and counted for 1 h to quantify As, Br,Eu and Na. After decay for 21 days, Ba, La, Sm,U, Sb, Cr, Fe, Sr, Sc, Ce, Cs, Th, Hf and Rb weredetermined by counting for up to 3 h.Gamma ray spectroscopy was performed using

an EG&G ORTEC Poptop detector with an effi-ciency of 20% and resolution of 1.9 keV at the60Co 1332 keV gamma line and OMNIGAMsoftware. The concentrations of elements werecorrected for blank contributions and where nec-essary for spectral and nuclear interferences.

2.4. Atomic absorption spectrophotometry

Approximately 1 g of the dried ground sample wasaccurately weighed into a 70 ml graduated poly-ethylene digestion vial with a hinged cap; 20 ml ofa 3:1 mixture of nitric and hydrochloric acids

Fig. 1. Relationships between geology, small-farmer crop-growing areas and distributions of arsenic, cadmium, lead and mercury in

Jamaican soils.

ELEMENTAL COMPOSITION OF JAMAICAN FOODS 21

(Fisher Trace metal grade) was added and the vialwas covered with a polyethylene watch glass andallowed to stand overnight. The next day themixture was digested for 2 h at 115 �C. Aftercooling to room temperature, the digestate wasmade up to 50 ml. The resulting solutions wereanalysed by Flame (for Ca, Cu, K, Mg, Mn andZn) and Graphite Furnace (for Cd and Pb) AASusing a Perkin Elmer 5100PC spectrometer. Deu-terium lamp (flame) and Zeeman effect (furnace)background corrections were performed.

2.5. Flow injection analysis

Phosphorus in the digested samples was deter-mined colourimetrically as orthophosphate byFIA with a Lachat Quikchem 8000 instrumentusing the molybdenum blue method (Lachat1999).

2.6. Quality assurance

Analytical quality control was maintained byanalyses of blanks and duplicate analyses andadditionally, check analyses were performedinternally and externally by the ADAS FoodAnalysis Laboratories in the United Kingdom.The possibility of soil contamination was mon-

itored by measuring the scandium rather thantitanium (Thornton & Abrahams 1983) levels infood samples. Scandium is geologically ubiquitousin soils, scarcely absorbed by plant roots, notmobile within the plant tissue, and is easily mea-sured by NAA; the detection limit using the long-lived radionuclide 46Sc in plants is better than0.001 mg kg)1 dry weight.

3. Results and discussion

The results of analyses of the certified referencematerials are summarised in Table 2.These results provide a significant level of con-

fidence in the methods employed.The food types examined and the categories to

which these have been assigned are shown inTable 3. The botanical names are given for thosecrops for which the common names are probablynot generally known.The limits of detection (LODs), percentages of

samples with a particular element below the

detection limit, the highest values observed andsome comparisons with regulatory limits whereavailable, are shown in Table 4.The detection limits are reported as ranges in

this table because: (1) even though the AAS dryweight detection limit is essentially one number,variations in the sample moisture contents affectthe fresh weight detection limit; (2) the gammaspectrum background in NAA is matrix dependentand (3) the NAA detection limit for a particularsample depends also on the irradiation, decay andmeasurement times. This means, however, that thedetection limit is specific for each measurementand may carry more useful information about eachindividual sample than would be obtained from asingle number.The uncertainty in NAA is largely based upon

the error in the counting statistic, which is thesquare root of the background corrected counts inthe analytical peak. If this value exceeds 50% theresult is reported as a detection limit using theCurrie definition (Currie 1968) modified for thedecay process observed in NAA as shown inEquation (1),

LOD ¼ ½2:71þ 3 �ffiffiffi

Bp� � k � ½ð1� e�k�tiÞ�

e�k�td � ð1� e�k�tcÞ��1 ð1Þ

where B is the background count rate under theanalytical peak, k is the standardisation factor, ti,td, tc are the irradiation, decay and counting times;and k is the analyte radioactive decay constant.

3.1. Elements present mainly below detection limits

Seventy-five to 93% of the samples analysed con-tained concentrations of As, Ba, Ce, Hf, Pb, Sb,Th and U below the detection limits of the methodused. Among these elements the following meritfurther comment.

3.2. Arsenic

Although there are reports that As may be essen-tial in ultra-trace quantities (Anke et al. 1976;Perez-Granados & Vaquero 2002), inorganicforms of arsenic are toxic. The concentrations ofAs in crops are generally low and the As contentsfor foods in the UK, for example, range from 1.5to 5 l kg)1 (Ysart et al. 2000) similar to those


reported here. While there is no apparent cause forconcern, further work may be useful in areas with

particularly high soil arsenic concentrations (Laloret al. 1999).

Table 2. Results of analyses of certified reference materials (CRMs) (reported as mg kg)1 unless otherwise noted).

Element (units) CRM Concentration % Recovery

Certified This work (average ± SD)

As NIST 1571 10 ± 2 10.7 ± 1.85 107

Ba IAEA 336 6.4 ± 1.09a <10 –

Br NIST 1571 9.5b 9.31 ± 1.79 98

Ca (%) NIST 1570a 1.53 ± 0.04 1.5 ± 0.4 99

Cd NIST 1573a 1.52 ± 0.04 1.38 ± 0.10 91

Ce IAEA 336 1.28 ± 0.18 1.28 ± 0.15 100

Cu NIST 1570a 12.2 ± 0.6 12.1 ± 1.1 99

Cr IAEA 336 1.03 ± 0.19 1.05 ± 0.21 102

Cs IAEA 336 0.11 ± 0.01 0.099 ± 0.01 90

Eu IAEA 336 0.023a 0.0204 ± 0.002 89

Fe IAEA 336 426 ± 46.9 419 ± 32.9 98

Hf NIST 1571 0.026b 0.0273±0.003 105

K (%) NIST 1547 2.43 ± 0.03 2.18 ± 0.17 90

La IAEA 336 0.66±0.11a 0.67 ± 0.05 101

Mg NIST 1547 0.43 ± 0.01 0.41 ± 0.02 95

Mn NIST 1573a 246 ± 8 231 ± 11 94

Na (%) NIST 1570a 1.82 ± 0.04 1.87 ± 0.29 103

P (%) NIST 1573a 0.216 ± 0.004 0.19 ± 0.01 88

Pb NIST 1547 0.87 ± 0.03 0.97 ± 0.09 111

Rb IAEA 336 1.72 ± 0.21 1.78 ± 0.25 103

Sb (lg kg)1) IAEA 336 0.073 ± 0.01 0.075 ± 0.008 103

Sc NIST 1570a 0.055a 0.054 ± 0.003 98

Sm (lg kg)1) NIST 1571 0.113b 0.118 ± 0.01 104

Sr NIST 1570a 55.6 ± 0.8 60.1 ± 8.6 108

Th (lg kg)1) NIST 1570a 0.048 ± 0.003 0.047 ± 0.02 98

U NIST 1570a 0.15a 0.184 ± 0.05 123

Zn NIST 1573a 30.9 ± 0.7 28.6 ± 2.5 93

a Information only value.b Consensus value.

Table 3. Types of foods represented in categories.

Food category Types of samples

Fruit Banana, Breadfruit, Corn, Cucumber, Orange, Ortanique, Plantaina, Tomato,

Pumpkin, Squash, Sweet Pepper, Zucchini

Legumes Cow Peasb, French Bean (String Bean), Gungo Peas, Red Kidney Bean

Vegetables: leafy Broccoli, Cabbage, Callalooc, Cauliflower, Lettuce, Pak Choi, Thyme

Vegetables: root Beet Root, Carrot, Escallion, Onion, Turnip

Other root crops Cassava, Cocod, Dasheene, Ginger, Irish Potato, Sweet Potatof, Yamg

aMusa · paradisiaca, bVigna unguiculata, cAmaranthus viridis, dXanthosoma saggitifolium, eColocasia esculenta, fIpmoea batatas,gDioscorea sp.


3.3. Barium

Eighty-nine percent of the samples analysed fellbelow the detection limit, which in the variousfood types ranged between 0.21 and 11 mg kg)1.The highest barium concentration was found in ayam sample. Although barium is found in very lowlevels in Jamaican foods, other studies (ATSDR1992) have reported that some Brazilian nuts,seaweed and certain plants contain high amountsof barium. However, the amount of barium infoods is generally not high enough to be a healthconcern.

3.4. Cerium and hafnium

Cerium, the other lanthanides, and hafnium haveno known metabolic role in plants and have avery limited ability to travel up the food chain.The cerium and hafnium concentrations formost of the food samples were below the NAAdetection limit. The highest levels for cerium andhafnium were observed in callaloo (0.24 mg kg)1)and red kidney beans (0.006 mg kg)1). Interest-ingly, there are reports, that when mixed-lan-thanides are added along with conventionalfertiliser, at the appropriate stage of growth

Table 4. Limits of detection (LOD) food type with highest observed value and some regulatory limits (mg kg)1) except otherwise

stated (all fresh weight basis).

Element LOD % samples

below LOD

Food type with highest value Regulation value

(NR = not regulated)

Value Local name FSANZa EUb

As 0.001–0.016 89 0.064 Ginger 1.0

Ba 0.21–5 89 11 Yam NR NR

Br 0.001–0.005 0 20 Carrot NR NR

Ca 0.4–16 0 20160 Cabbage NR NR

Cd 0.0004–0.016 4 1.7 Callaloo 0.1 0.1–0.2

Ce 0.002–0.23 84 0.25 Callaloo NR NR

Cu 0.05–2.0 0 5.0 Cow Peas 10 NR

Cr1 0.006–0.097 42 1.1 Sweet Potato NR NR

Cs (lg kg)1) 1–24 38 127 Yam NR NR

Eu (lg kg)1) 0.26–2.05 62 2.8 Red kidney beans NR NR

Fe 3.0–14.8 11 76.5 Red kidney beans NR NR

Hf 0.0002–0.003 93 0.006 Red kidney beans NR NR

K (%) 0.00001–0.0004 0 3.8 Corn NR NR

La 0.0002–0.033 49 0.35 Callaloo NR NR

Mg 0.001–0.04 0 1621 Cow Peas NR NR

Mn 0.04–1.6 4 27 Cow Peas NR NR

Na 0.29–0.80 0 1920 Carrot NR NR

P 0.006–0.25 0 2500 Orange NR NR

Pb 0.001–0.05 67 0.25 Sweet Potato 0.5 0.1

Rb 0.044–0.144 0 7.8 Plantain NR NR

Sb (lg kg)1) 1.81–5.12 75 40 Coco 1000 NR

Sc (lg kg)1) 0.06–0.79 19 21 Turnip NR NR

Sm (lg kg)1) 0.17–0.43 45 27 Callaloo NR NR

Sr 0.15–3.68 68 16.7 Dasheen NR NR

Th (lg kg)1) 0.24–11.6 90 12.7 Turnip NR NR

U 0.006–0.072 89 0.21 Ortanique NR NR

Zn 0.02–0.8 0 76 Dasheen 150 NR

Nearest to food classification.a FSANZ (2002).bOJEC (2001).


the crop yield is significantly increased (Guo1987).

3.5. Thorium and uranium

Thorium and uranium concentrations in Jamaicansoils exceed 33 and 14 lg kg)1 respectively at the95th percentile levels (Lalor 1995). These elementsare bioavailable to plants (Morton et al. 2001) butthe concentrations so far observed in the foods arevery low and the risks from these elements in thefood should be negligible.

3.6. Elements present mainly above detection limits

The concentrations of the elements (Br, Ca, Cd,Cr, Cu, Fe, K, Mg, Mn, Na, P, Rb and Zn) aregenerally well above the respective detection limits.The summary statistics by food type for thesealong with those of Pb, an element that remains ofparticular interest, are shown in Table 5.Fruits are lowest in Cd, Cr, Fe and Zn and there

is no element measured for which the highest valueoccurs in fruit. Legumes are lowest in Br, Na andMn and highest in Cu, Fe, K, P and Zn. Leafyvegetables are lowest in Cu and K and highest inCa, Cd, Mg and Rb. The root vegetables arelowest only in Mg, and have the highest concen-trations of Br, Cd and Na; the highest Cd con-centration is the same as that of the leafyvegetables. The root crops are lowest in Ca, P andRb and highest in Cr. The high Cd concentrationsmay be of concern since root crops are a majorfeature in the Jamaican diet, but as was found inShipham (McKenzie-Parnell & Eynon 1987;Morgan & Simms 1998) there is no direct evidenceof health problems.

3.7. Country comparisons

Table 6 compares mean results for Jamaica withDenmark (Danish Veterinary and Food Admin-istration 2002), the United Kingdom (Ysart et al.2000), the United States (USDA 2002) and Nigeria(Okoye 2001).These data are very general indicators as there

are gaps that coarsen comparisons and, in the caseof the developed countries, the results may wellinclude imports. Nevertheless, even at this level theavailable data indicate some interesting trends.

3.8. Ca, Cu, Fe and Mn in foods

Figure 2 presents the concentrations, relative tothe Jamaican values, of the elements for whichdata are available from the references quoted forall the food types, except for legumes where therewere no results for Nigeria.The Nigerian values for Ca in fruit are very low.

The Ca levels for Denmark, UK, and the US areless than about one half the Jamaican levels. Thepredominantly limestone geology of the islandmay be a contributing factor to this.Cu and Fe levels in fruit from the other coun-

tries are rather similar and again about one-halfthe Jamaica value. The Mn levels for Denmarkand the US are similar, that for the UK is roughlyequal to the Jamaican value; the Mn concentra-tions vary from one-half the Jamaican value tonearly twice as high.The values from Denmark are uniformly low,

about a factor of 4 below those for Jamaica. Theother elements are similar to, or exceed theJamaican values, but by considerably less than afactor of 2. Except for Cu in the UK samples, theaverage levels of these four elements are similar inleafy vegetables, and considerably higher in theJamaican samples than those in the other coun-tries. Average Cu levels in root vegetables aresimilar in all countries except Nigeria, which isabout 50% lower. Fe and Mn levels in Jamaicanroot vegetables are about twice those from theother countries. Ca levels reported in root vege-tables from Denmark and the USA are similar toJamaica, but the values from the UK average 50%lower than Jamaican data and the Nigerian valuesare low in comparison.Ca levels in root crops in Denmark average

about 2.5 times the Jamaican value. The Nigerianfigures are very low, approximately 10% of theJamaican value. Fe and Mn are also higher for theDanish data in this food category. The Cu data donot show much variation between countries exceptfor Nigeria, where the results are consistently lowfor all four elements.

3.9. Phosphorus, potassium and magnesium

Very little variation is observed in the P or Kcontent of foods both with respect to food typeand country. For legumes, the mean P in the US ismuch higher than from the other countries, but


these US data are from peanuts only. Average Klevels are high, ranging between 0.3 and 0.7% ex-cept for the Nigerian data, which seem low; the

highest value (leafy vegetables) being only 0.08%.Magnesium levels seem higher in legumes than inthe other food categories, and the data are similar

Table 5. Summary statistics of some elements in Jamaican foods (mg kg)1 fresh weight, except where indicated).

Elements Mean and range Fruit (n = 27) Legumes (n = 6) Vegetables:

leafy (n = 14)

Vegetables:

root (n = 16)

Other root crops

(n = 46)

Br Range 0.2–2.96 0.2–0.98 0.93–8.69 2.63–20.4 0.17–9.39

Mean 1.1 0.57 3.9 7.1 1.8

Ca Range 18–4866 282–1066 20–20161 101–684 13–979

Mean 360 514 2580 390 150

Cd Range 0.001–0.157 0.018–1.21 0.02–1.71 0.02–1.39 0.002–0.95

Mean 0.029 0.33 0.4 0.4 0.2

Cr Range 0.006–0.40 0.082–0.18 0.009–0.276 0.012–0.32 0.017–1.08

Mean 0.04 0.07 0.08 0.09 0.11

Cu Range 0.1–2.0 0.3–5.0 0.1–1.9 0.2–1.14 0.5–3.2

Mean 0.8 2.80 0.6 0.7 1.6

Cs Range 0.004–0.030 0.001–0.085 0.008–0.024 0.002–0.053 0.001–0.127

Mean 0.007 0.025 0.013 0.016 0.012

Eu (lg kg)1) Range 0.29–1.56 0.700–2.83 0.27–0.66 0.38–1.08 0.33–2.05

Mean 0.6 1.09 0.3 0.5 0.7

Fe Range 3.1–30.0 4.2–76.5 1.5–43.1 1.5–56.2 3.0–36.5

Mean 6.7 30.02 15.5 12.9 9.6

K (%) Range 0.08–3.77 0.09–1.28 0.17–0.69 0.18–0.75 0.11–3.44

Mean 0.46 0.67 0.38 0.41 0.47

La Range 0.001–0.013 0.005–0.024 0.005–0.353 0.003–0.057 0.0002–0.092

Mean 0.004 0.013 0.061 0.023 0.009

Na Range 1.71–26.04 1.16–8 12.1–192 26.22–1920 2.07–403

Mean 9.8 4.16 90.1 727 48.7

Mg Range 28–1236 74–1621 93–1202 106–257 80–290

Mean 248.0 790.00 359.0 157 161

Mn Range 0.2–4.9 2.1–26.9 2.2–23.6 0.02–21.6 0.1–7.8

Mean 1.7 10.6 8.3 4.3 1.6

P (%) Range 0.005–0.25 0.010–0.180 0.010–0.104 0.012–0.045 0.012–0.049

Mean 0.032 0.097 0.042 0.027 0.027

Pb Range 0.001–0.048 0.010–0.013 0.001–0.033 0.003–0.083 0.002–0.25

Mean 0.011 0.011 0.005 0.01 0.022

Rb Range 0.25–7.83 0.15–5.95 0.69–7.29 0.65–4.22 0.71–2.81

Mean 2.5 3.15 3.7 2.1 1.7

Sc (lg kg)1) Range 0.1–1.2 0.2–1.75 0.1–14.6 0.2–21.0 0.2–3.1

Mean 0.4 0.91 3.2 3.4 1.2

Sm (lg kg)1) Range 0.32–2.53 0.35–1.630 0.14–27 0.17–10.2 0.18–7.0

Mean 0.6 0.95 4.6 2.5 0.7

Sr Range 0.15–3.51 0.38–3.68 0.15–10.42 0.35–2.05 0.71–16.7

Mean 0.48 0.82 2.2 0.74 1.47

Zn Range 0.7–32.1 1.7–38.3 1.1–7.3 2.0–6.5 1.5–75.7

Mean 2.6 16.30 4.2 3.4 5.8

Note: Numbers in bold represent LOD · 0.5 (Helsel 1990).


Table

6.Comparisonsofmeanvalues

ofelem

entalcontentoffoodforfivecountries(m

gkg)1freshweight).

Country

Element

As

Ba

Br

Ca

Cd

Cr

Cu

Fe

KMg

Mn

Na

PPb

Sb

Sr

Zn

Fruit

Jamaica

0.004

1.29

1.1

360

0.029

0.04

0.80

6.7

4600

248

1.7

9.8

320

0.011

0.003

0.48

2.6

Denmark

na

na

na

139

na

0.011

0.93

3.9

2500

177

1.06

45.7

366

na

na

na

3.2

UK

0.0014

0.35

0.7

113

0.002

0.02

0.79

2.7

na

na

2.0

na

na

0.003

0.001

0.79

0.85

USA

0.002

na

na

135

0.004

na

0.75

4.0

3183

216

1.02

13.3

311

0.001

na

na

1.9

Nigeria

na

na

na

7.65

nd

nd

2.3

13.1

32

220

4.48

35.5

na

nd

na

na

na

Legumes

Jamaica

0.003

1.61

0.57

514

0.33

0.07

2.8

30

6700

790

10.6

4.16

970

0.009

0.003

0.815

16

Denmark

na

na

na

600

na

0.012

0.6

10

2370

170

2.5

20.0

390

na

na

na

3.9

UK

0.006

56

26

na

0.059

0.14

8.5

34

na

na

15

na

na

0.01

0.001

8.6

30

USA

0.014

na

na

767

0.054

na

5.4

53

8933

1157

9.5

4850

2893*

0.001

na

na

21

Nigeria

na

na

na

na

na

na

na

na

na

na

na

na

na

na

na

na

na

Leafy

vegetables

Jamaica

0.009

1.61

3.9

2581

0.4

0.08

0.6

15.5

3800

359

8.3

90

420

0.005

0.002

2.2

4.2

Denmark

na

na

na

482

na

0.011

0.36

7.2

3334

201

2.7

216

450

na

na

na

2.9

UK

0.003

0.38

5.5

379

0.023

0.02

0.76

11

na

na

2.0

na

na

0.061

<0.001

1.6

3.9

USA

0.001

na

na

484

0.058

na

0.319

6.4

2568

168

1.7

98

380

0.006

na

na

2.5

Nigeria

na

na

na

2.50

0.2

2.1

0.2

1.8

817

40

1.6

634

na

nd

na

na

na

Rootvegetables

Jamaica

0.01

0.92

7.1

390

0.4

0.09

0.7

12.9

4100

157

4.3

727

270

0.01

0.002

0.74

3.4

Denmark

na

na

na

372

na

0.012

0.64

7.4

2688

126

2.75

266

384

na

na

na

3.8

UK

0.005

0.50

2.8

208

0.011

0.04

0.85

7.5

na

na

1.6

na

na

0.015

0.001

1.3

2.4

USA

0.001

na

na

331

0.014

na

0.7

6.6

2543

159

1.8

32

362

0.001

na

na

2.8

Nigeria

na

na

na

4.00

nd

nd

0.3

3.95

540

35

1.4

609

na

nd

na

na

na

Rootcrops

Jamaica

0.006

2.07

1.8

150

0.2

0.11

1.6

9.6

4700

161

1.6

48.7

270

0.022

0.004

1.47

5.8

Denmark

na

na

na

403

na

0.006

1.6

15

4975

360

3.06

153

450

na

na

na

2.8

UK

0.002

0.16

1.8

109

0.026

0.04

1.0

8.1

na

na

1.9

na

na

0.003

0.001

0.81

3.3

USA

0.003

na

na

170

0.018

na

1.26

5.4

4254

236

3.04

120

388

0.007

na

na

3.0

Nigeria

na

na

na

12.5

0.10

4.0

0.2

5.1

98

14

0.02

167

na

nd

na

na

na

*Peanuts

only;na:data

notavailable;nd:elem

entnotdetected.


from country to country with the exception ofNigeria, which again seems low.

3.10. Lead

Except for lead (Lalor et al. 2001) severe anthro-pogenic contamination of Jamaican soils byheavy metals is not presently an issue. Lead isusually absorbed by foods from soils in onlyvery small quantities and the concentrationsdo not vary much with food type. The values sofar observed indicate that these foods are notmajor contributors to high blood levels previouslyfound in certain regions of Jamaica (Lalor et al.2001).

3.11. Cadmium and zinc

The remarkably high levels of Cd in uncontami-nated Jamaican soils appear to be unique, and it isnot perhaps surprising that this is reflected, in thefoods, as illustrated in Figure 3.There is considerable variation between the

various food types but in every case the Jamaicandata are significantly higher, with the Nigerian,where available, about a factor of 2 lower. TheNigerian data vary greatly with food type – notdetectable in fruit and root vegetables, as high as0.2 and 0.1 mg kg)1 in leafy vegetables and rootcrops respectively. The available data for the othercountries are well below 0.1 mg kg)1.

Fig. 2. Concentrations of Ca, Cu, Fe and Mn in foods, relative to Jamaican levels, for Denmark, United Kingdom, United States and

Nigeria.


Cd in the food chain is of great concern in manycountries. This element accumulates in the bodywith the kidney and liver as the main target or-gans, and it is known mainly from occupationalstudies that it causes impairment of kidney func-tion. The Itai–itai disease in Japan was a conse-quence of significant exposure to cadmium(Nogawa 1981) and there have been effects inChina (Cai et al. 1995). Yet there are cases of highexposure to cadmium without obvious harm(McKenzie-Parnell & Eynon 1987; Morgan &Simms 1988). The adverse health effects of chronicenvironmental Cd exposure have been ascribed toa predominantly rice-based diet but, despitenumerous studies on the health effects of chronicrelatively low-level exposure to cadmium (ATSDR1999), there still seems to be room for debate.Many factors come into play and cadmium levelsin the developed world are currently so well reg-ulated that human exposures are low, and there islittle direct information on cadmium exposurefor persons with varied diets to allow good esti-mates of the levels at which toxic effects becomeapparent.

Except for the legume group which is higherthan the others, the Zn concentrations are fairlysimilar across food type and country. Zn is con-sidered to offer some protection to humans againstCd absorption (Chaney et al. 1998). Since theJamaican foods have Zn levels similar to foodsfrom other countries, the Zn/Cd ratios in Jamaicaare very much lower; this may distinguish theJamaican situation from the others with respect tocadmium bioavailability and its effects. Furtherinvestigations are underway.

4. Conclusions

The elemental concentrations in the foods studiedare generally comparable across the variouscountries. It seems unlikely that most of the ele-ments reported in this paper will contribute sig-nificantly to public health risk, although dueattention may be necessary for those foods grownin the regions of highest uptake and eaten in largeamounts. However, at this stage cadmium clearlyappears to be the element of greatest concern inthe Jamaican food chain. The observed range of

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

Jam

aica UK

US

A

Jam

aica UK

US

A

Jam

aica UK

US

A

Nig

eria

Jam

aica UK

US

A

Nig

eria

Jam

aica UK

US

A

Nig

eria

Cad

miu

m, m

g kg

-1

0

5

10

15

20

25

30

Jam

aica

Jam

aica

Jam

aica

Jam

aica

Jam

aica

UK UK

Denm

ark

Denm

ark

Denm

ark

Denm

ark

Denm

ark

USAUSA

USA UKUSA

USAUKUK

Zin

c, m

g kg

-1

FRUIT

FRUIT

LEGUMES

LEGUMES

VEGETABLES

LEAFY

VEGETABLES

LEAFY

VEGETABLES

ROOT

VEGETABLESROOT ROOT

OTHER

CROPS

ROOTOTHER

CROPS

Fig. 3. Cadmium and zinc contents of various food categories.


cadmium concentrations in the foods suggests thatland selection, coupled perhaps with suitablymodified agricultural practices, will be a feasibleway to reduce the cadmium content of foods

Acknowledgements

This study builds on previous results from projectssupported by the Government of Jamaica, theEuropean Development Fund, the Inter-AmericanDevelopment Bank, the University of the West In-dies, and the Royal Netherlands Government. Thefood project was partially supported by the PanAmerican Health Organisation, the Organisation ofAmerican States and the International Atomic En-ergy Agency. TheMinistry of Agriculture and manylocal residents provided assistance with fieldworkand by sharing their knowledge and experience; thishelp is appreciated and acknowledged.

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