Elements in rice on the Swedish market: part 2. Chromium, copper, iron, manganese, platinum, rubidium, selenium and zinc.

A survey of the levels of some essential and non-essential trace elements in different types of rice available on the Swedish retail market was carried out in 2001-03. The types of rice included long and short grain, brown, white, and parboiled white. The mean levels found were: chromium (Cr) = 0.008 mg kg(-1), copper (Cu) = 1.9 mg kg(-1), iron (Fe) = 4.7 mg kg(-1), manganese (Mn) = 16 mg kg(-1), platinum (Pt) < 0.0003 mg kg(-1), rubidium (Rb) = 3.3 mg kg(-1), selenium (Se) =0.1 mg kg(-1); and zinc (Zn) = 15 mg kg(-1). Inductively coupled plasma-mass spectrometry (ICP-MS) was used for the determination of Pt, Rb, and Se, after acid digestion. All other elements were determined using atomic absorption spectrometry (AAS) after dry ashing. Intake calculations were performed and it was concluded that rice may contribute considerably to the daily requirements of the essential elements Cu, Fe, Mn, Se, and Zn if rice consumption is high. The levels of some elements, e.g. Fe and Mn, were significantly higher in brown compared with white rice.

Elements in rice from the Swedish market: 1. Cadmium, lead and arsenic (total and inorganic).

A survey of the levels of cadmium, lead and arsenic in different types of rice available on the Swedish retail market was carried out in 2001--03. The types of rice included long and short grain, brown, white, and parboiled white rice. The mean levels found were as follows: total As: 0.20 mg kg(-1), inorganic As: 0.11 mg kg(-1); Cd: 0.024 mg kg(-1); and Pb: 0.004 mg kg(-1). ICP-MS was used for the determination of As (total and inorganic) after acid digestion. Lead and cadmium were determined using graphite furnace atomic absorption spectrometry (GFAAS) after dry ashing. In countries where rice is a staple food, it may represent a significant contribution in relation to the provisional tolerable weekly intake for Cd and inorganic As.

Evaluation of results derived from the analysis of certified reference materials--a user-friendly approach based on simplicity.

Certified reference materials (CRMs) have now been in regular use for several decades. Their production and certification are regulated by international standards. But, even today there are no agreements on procedures for evaluating results obtained by the users. As a consequence, the way CRM results are treated in the literature leaves a lot to be desired. A statistical evaluation is rarely, if ever, described in published reports. The most common approach is to compare the found mean and/or range with the certified range and then state if the mean falls within the certified range, or if the two ranges overlap. If this happens, the analyst is usually satisfied. In addition, usually no regard is paid to the fact that the certified interval is based on a 95% confidence interval (CI) and the found interval on standard deviation and that this evaluation has little, if any, statistical relevance. Long-term evaluation of a CRM often consists in nothing more than producing a control chart, which relates the found results to the certified mean and CI. This paper is an attempt to improve the situation by providing a set of easy-to-use guidelines for evaluating results from CRMs. During the process we have identified different areas in which there is a need for such guidelines: 1. short-term evaluation of a single, or multiple, determination at one or several specific times; 2. identification of systematic and random errors; 3. evaluation of CRMs when used in a collaborative trial of a method; and 4. long-term evaluation for monitoring an analytical process over extended periods of time. It is important that the guidelines do not require expert competence in statistics from the analyst. Such obstacles would probably render most guidelines unused.

The influence of complexing agents on the solubility and absorption of aluminium in rats exposed to aluminium in water.

The influence of citrate (0-31 mM), fluoride (0 or 2.6 mM) and silicate (0 or 2.6 mM) on the absorption of Al (0-18 mM) was studied in rats. We tested the hypothesis that the solubility and absorption of Al increases in the gastrointestinal (GI) tract in the presence of the complexing agents. Male rats were exposed for 6 or 7 weeks to soluble Al in acidic drinking water (pH 2.5-3.0) with or without the complexing agents. At the end of exposure Al was fractionated in the stomach content, in order to study if the solubility of Al was changed after ingestion. Al absorption was estimated by Al analysis of the right femur bone. Speciation calculations indicated that citrate and fluoride caused formation of soluble Al-citrate (97%) and -fluoride (> 60%) complexes in the water. Silicate did not affect the theoretical speciation. In all cases, a large fraction of soluble Al became insoluble in the stomach after ingestion. The concentration of soluble Al increased only in the presence of citrate or a mixture of fluoride and silicate, but citrate was the only complexing agent that influenced the absorption of Al in the rat. This indicates that the form of Al may be changed in the GI tract when soluble drinking-water Al is ingested, and that the solubility of Al in drinking water and GI tract may not be good predictors of the bioavailability of Al even when chelating agents are present.

Cadmium absorption in mice: effects of broiling on bioavailability of cadmium in foods of animal origin.

The absorption and organ distribution of organic Cd from raw and broiled horse kidney was compared to that of CdCl2 at two dose levels (0.05 and 3 mg Cd/kg feed) in a feeding study in mice. The high Cd concentration in the horse kidney (raw 112 mg/kg; broiled 53 mg/kg) made it possible to mix kidney into mouse feed without marked effects on the composition of the feed. The weight of the mice, feed and water consumption, and Cd levels in the feed were determined once a week. After 9 wk of exposure, the liver and kidneys of the mice were sampled and Cd was analyzed. The Cd concentration in horse kidney was halved by broiling, and the content of soluble Cd decreased from 12% in raw kidney to 5% in broiled kidney. The majority of the soluble Cd was associated with proteins with the same molecular weight as metallothionein (MT) in both raw and broiled kidney. Broiling of the kidney had no marked effect on the fractional accumulation of organic Cd in mice. The fractional accumulation of inorganic CdCl2, on the other hand, was significantly higher than that of organic Cd in the low dose groups but not in the high dose groups. The ratio between Cd accumulation in kidney and that in liver was higher in the group receiving raw kidney compared to the ratio in the group receiving CdCl2 at both the high and low exposure levels. This indicates that the raw kidney contained a Cd form that was more preferentially distributed to the kidneys.

Cadmium and other metals in Swedish wheat and rye flours: longitudinal study, 1983-1997.

Wheat flour (sifted), wheat bran, and rye flour were sampled annually in several different areas in Sweden for 15 consecutive years (1983-1997) for a total of 105, 90, and 30 samples, respectively. These samples were analyzed for their content of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn by atomic absorption spectrophotometry with background correction after dry ashing at 450 degrees C. As part of the quality control procedures, an in-house reference material was analyzed in parallel to the samples to ensure reliability of the results. In addition, a certified reference material was analyzed to monitor accuracy of the results. The Cd level in wheat and rye flours (mean 0.029 and 0.017 mg/kg dry wt, respectively) correlated significantly with time (p < 0.05) in 2 phases, tending to increase during the first half of the period and decrease during the latter half. In wheat bran, Cd (mean 0.15 mg/kg) levels did not correlate significantly with time. In wheat flour, Cu, Mn, and Zn (means 1.7, 6.2, and 7.6 mg/kg, respectively) showed a significant linear increase (p < 0.05) in concentration over time. In rye flour, the levels of Cu, Fe, Mn, and Zn (means 3.8, 36, 30, and 28 mg/kg, respectively) all decreased significantly (p < 0.05) over time. Similarly, in wheat bran Cu (mean 14 mg/kg) increased and Pb (mean 0.027 mg/kg) decreased significantly (p < 0.05) over time, whereas Ni and Zn showed a significant curved correlation with time and peaked at about the middle of the measurement period.

Determination of metals in foods by atomic absorption spectrometry after dry ashing: NMKL Collaborative Study.

A method for determination of lead, cadmium, zinc, copper, and iron in foods by atomic absorption spectrometry (AAS) after dry ashing at 450 degrees C was collaboratively studied in 16 laboratories. The study was preceded by a practice round of familiarization samples and another round in which solutions were distributed and the metals were determined directly by AAS. The study included 5 different foods (liver paste, apple sauce, minced fish, wheat bran, and milk powder) and 2 simulated diets. A single analysis was carried out with each sample. Suitable sample combinations were used as split-level combinations for determination of the repeatability standard deviation. The reproducibility relative standard deviation for each of the elements ranged from 20 to 50% for lead concentrations of 0.040-0.25 mg/kg, from 12 to 352% for cadmium concentrations of 0.001-0.51 mg/kg, from 4 to 8% for zinc concentrations of 0.7-38 mg/kg, from 7 to 45% for copper concentrations of 0.51-45 mg/kg, and from 11 to 14% for iron concentrations of 4-216 mg/kg.

Determination of lead, cadmium, zinc, copper, and iron in foods by atomic absorption spectrometry after microwave digestion: NMKL Collaborative Study.

A method for determination of lead, cadmium, zinc, copper, and iron by atomic absorption spectrometry (AAS) after microwave digestion was subjected to a collaborative study in which 16 laboratories participated [including users of inductively coupled plasma (ICP) and ICP-mass spectrometry (MS)]. The types of samples included in the study were minced fish, wheat bran, milk powder, bovine and pig liver, mushroom, 2 simulated diets, and bovine muscle; the last 4 were certified reference materials. These were analyzed as single (4 samples), double blind (1 sample), or split level (2 samples) samples. Before the collaborative study, a pretrial was conducted in which 4 ready-made solutions and one fish tissue sample were analyzed for Pb and Cu. The reproducibility relative standard deviation (RSDR) values, for results above the detection limit, ranged from 59% at 0.155 mg/kg to 16% at 1.62 mg/kg for Pb, from 28% at 0.0124 mg/kg to 11% at 0.482 mg/kg for Cd, from 9.3% at 35.3 mg/kg to 1.7% at 147 mg/kg for Zn, from 39% at 0.241 mg/kg to 3.0% at 63.4 mg/kg for Cu, and from 17% at 7.4 mg/kg to 5.9% at 303 mg/kg for Fe. The RSDR values agreed well with the norms described by the International Union of Pure and Applied Chemistry. As a complement to the AAS determinations, a number of laboratories analyzed the samples either by ICP or by ICP-MS. The results of these analyses agreed well with the AAS results. On the basis of the results of the collaborative study, the method was adopted Official First Action by AOAC INTERNATIONAL.

Does aluminium stimulate the immune system in male rats after oral exposure?

The influence of oral aluminium exposure on the immune system was studied in rats. Male rats were exposed to soluble and labile Al in acidic drinking water (0-500 mg Al/l) for 7-9 weeks. The concentration of Al in femur bone was higher in rats exposed to 50 and 500 mg Al/l (mean concentration 277 and 599 ng Al/g) than in control rats (150 ng Al/g). The Al concentration in blood plasma could only be quantified in the 500 mg/l group (mean 2.7 ng/ml), whereas the concentrations in the control and 50 mg/l groups were low (< 2 ng Al/ml). Exposure of 4-13-weeks-old rats to the highest Al concentration caused an increased number of splenocytes, whereas exposure of 9-16-weeks-old rats to 500 mg Al/l caused an increased number of thymocytes. Moreover, the proliferative response of splenocytes to the mitogen Con A (2 micrograms/ml) was increased by exposure of the 9-16-weeks-old rats to 500 mg Al/l as compared with the controls. The results indicate that oral Al exposure caused a slight stimulation of some immune functions in the rat at Al plasma concentrations normally found in the human population (< 10 ng Al/ml).

Concentration-dependent absorption of aluminum in rats exposed to labile aluminum in drinking water.

The hypothesis was tested that the absorption of labile Al in rats will increase when the Al-binding capacity of food components in the stomach is saturated. Male rats were exposed to 0, 10, 50, or 500 mg labile Al/L in acidic drinking water (pH 3) for 9 wk. The results show that labile Al in drinking water is complexed by feed constituents in the stomach of the rat in vivo, thus causing a nondetectable absorption of Al at 10 mg Al/L. An increased absorption of Al at 50 and 500 mg Al/L was associated with a saturation of the Al-binding capacity of feed components in the lumen of the stomach, causing the appearance of labile Al. Thus, the presence of labile Al in drinking water does not necessarily result in a high Al absorption when the water is ingested, since the bioavailability of labile Al is dependent both on the amount and composition of Al-binding components present in the gastrointestinal tract at the time of ingestion of the water. It is thus not possible to predict the body burden of Al in humans just by measuring the Al concentrations in drinking water. Even a further refining of the exposure measurement to include speciation of Al in the water may not markedly improve the prediction of the Al body burden. Future epidemiological studies must therefore be based on actual measurements of Al concentration in tissues or fluids from the study subjects.

Accumulation of cadmium from wheat bran, sugar-beet fibre, carrots and cadmium chloride in the liver and kidneys of mice.

The gastrointestinal absorption and organ distribution of Cd after exposure for 9 weeks to three fibre-rich foodstuffs (wheat bran, sugar-beet fibre and carrots) were determined in mice. Groups of eight mice were given a diet containing 0.05 mg Cd/kg from wheat bran, sugar-beet fibre, carrots or CdCl2 mixed in a semi-synthetic, low-Cd (< 0.007 mg/kg) feed. A control group was fed on the low-Cd semi-synthetic feed. The water consumption, food consumption and the weight of the animals were monitored throughout the study. The feed was changed once weekly and Cd was analysed in the feed at each change. myo-Inositol phosphates (hexa-, penta-, tetra- and tri-) and Zn, Cu, Fe and Ca were also analysed in the diets. After 9 weeks, the mice were killed and liver and kidneys were sampled and analysed for Cd. The group receiving the wheat-bran diet had significantly lower fractional Cd accumulation (% total Cd intake) in the liver and kidneys than the other groups, indicating a lower fractional absorption of Cd. The wheat-bran diet had markedly higher levels of inositol hexa- and pentaphosphates (phytates) and a Zn level that was twice as high as those in the other diets. The higher levels of myo-inositol hexa- and pentaphosphates in the wheat-bran diet most probably contributed more to the lower fractional absorption of Cd than the elevated Zn level, due to the formation of insoluble Cd-phytate complexes. Compared with the wheat-bran diet, the sugar-beet-fibre and carrot diets contained very low levels of myo-inositol penta- and hexaphosphates, and consequently the fractional Cd absorption from these diets was higher.

Toxic and essential elements in fish from Nordic waters, with the results seen from the perspective of analytical quality assurance.

Fish from fresh, brackish and marine waters were analysed for their levels of Pb, Cd, Cr, Ni, Co, Zn, Cu, Mn, As and Se in muscle tissue. Various quality control procedures were implemented during the survey and the results were compared with those from several other surveys, most of which were carried out during the 1990s. It was noted that several elements varied widely both within and between studies. A systematic examination of a large number of surveys and ranking of their quality level indicated that a lack of quality control procedures often results in high or varying results. This may have serious consequences when results are used as a basis for for example, legislation or intake recommendations.

Cadmium accumulation in liver and kidney of mice exposed to the same weekly cadmium dose continuously or once a week.

Cd levels in blood, liver and kidney of female mice were measured after exposure to Cd as CdCl2 in the food, either continuously (CE group) throughout the week (300 microg Cd/kg feed) or for 24 hr/wk (2100 microg Cd/kg) for 5 wk (occasionally exposed, OE group). In a control group that received feed with Cd levels below the detection limit (< 7 microg/kg), Cd levels in blood, liver and kidneys were below the detection limit after the 5 wk of exposure. The weekly dose of Cd administered to the exposed CE and OE groups was similar (approx. 400 microg Cd/kg mice/wk). The OE group had a higher Cd level in blood and a higher fractional accumulation (% of dose) of Cd in the liver and kidneys compared with the CE group. This indicates that the fractional Cd absorption in the gastrointestinal tract is higher when high Cd doses are ingested occasionally than when low doses are ingested continuously, even if weekly doses are the same. It is hypothesized that this difference in absorption could be due to Cd-induced unspecific damage to the intestinal mucosa, changes in tight-junction permeability caused by Cd, or to a saturation of the Cd-binding capacity of the intestinal mucosa in mice exposed to high Cd levels occasionally.

Cadmium levels in kidneys from Swedish pigs in relation to environmental factors--temporal and spatial trends.

The kidney cadmium level in pigs slaughtered at the age of 5-7 months was analysed with respect to geographical and temporal trends. During the period 1984-1992, a total of 1051 samples of porcine kidney from 31 abattoirs were analysed for cadmium at the National Food Administration within the control programme for livestock production. The mean kidney cadmium level was 0.11 +/- 0.07 mg/kg wet wt. (mean +/- S.D.). Regression analysis showed that the cadmium concentration in pig kidney has increased by 2% per year. By using Geographic Information System (GIS), geographical trends in cadmium concentration of porcine kidney were analysed and correlated to cadmium levels in moss and pH in the mor layer of podsolized soil. These two parameters explained 60% of the random variation in cadmium levels in porcine kidney. There were significant differences between individual abattoirs, but no significant longitudinal or latitudinal trend was found. Variation in kidney cadmium levels within breeding stocks was investigated. Kidneys from eight stocks, with five pigs from each, were analysed for cadmium concentration. In spite of the homogeneous treatment of the pig within the same stock, kidney cadmium levels varied on average by a factor of two between individuals. There was a significant correlation between cadmium in feed and cadmium levels in porcine kidney (P = 0.002). The temporal increase in cadmium levels in porcine kidney should be further investigated. An increase in cadmium body burden in pig may be an indicator of an increase in human cadmium exposure.

Levels of certain trace elements in beef and pork imported to Sweden.

The levels of Pb, Cd, Ni, Cr, Co, Zn, Cu, Mn, As and Se were determined in beef and pork imported to Sweden from six different countries. Samples of Swedish beef and pork were included for comparison. The results of this survey showed in most cases little difference in levels of these elements between the countries and agreed well with the results from our previous studies. All results for Pb, Cd, Ni and As were below the detection limits of 0.007, 0.001, 0.016 and 0.030 mg/kg fresh weight, respectively. Chromium and cobalt were, in both beef and pork, close to, or below, the detection limits of 0.004 and 0.003 mg/kg fresh wt, respectively. The level of selenium in beef varied considerably between countries, from < 0.030 to 0.18 mg/kg fresh wt. The levels of lead and cadmium from this study differed strongly in some cases from what have been reported in surveys from several countries, among them some countries exporting to Sweden. The importance of a rigorous quality control programme is emphasized.

Characterisation of a fungus reference material, and a guide for use.

A reference material consisting of an edible fungus, Cantharellus tubaeformis, with certified levels of Pb, Cd, Zn, Cu, Mn, Cr, Ni, Co and Fe was produced, primarily for use in a project concerning metal determination in common edible fungi. The C. tubaeformis was dried, homogenised and sieved using non-contaminating equipment. It was then mixed thoroughly before bottling in polythene containers. Homogeneity was checked by multiple analysis of a number of containers, and was found to be satisfactory. Each metal was determined by at least two different methods of analysis. A total of ten laboratories participated in the certification process. All the metals analysed in this certified reference material showed good agreement with the levels found in fresh C. tubaeformis, when the difference in water content was accounted for. This indicates that no contamination of the fungus reference material occurred during the production. It is concluded that the 95% confidence interval for the true mean, as defined for the different metals, is of limited value from the user's point of view. Therefore, a more user-oriented way of presenting the results, based on the within- and between-laboratory standard deviations of the certification process, is suggested. These are 95/95% tolerance intervals within which the user's results should fall. Different intervals are given, one of which indicates the largest acceptable difference between duplicates and another for the acceptable range of future means.

Levels of some trace elements in edible fungi.

A number of common edible fungi were analysed for their contents of Pg, Cd, Cr, Ni, Co, Zn, Cu, Mn and Se. The results indicate that the Cd level in the species Rozites caperata can be as high as several mg/kg fresh weight. In Lycoperdon perlatum and Macrolepiota procera the Pb level was found to be up to 2.5 mg/kg. The Ni level was at or below 0.1 mg/kg in all species, with the exception of Albatrellus ovinus, which had a mean concentration of 0.72 mg/kg. The level of Cr was highest in M. procera with a mean of 0.091 mg/kg. In a single sample of the species Agaricus augustus, the concentration of Co was found to be exceptionally high at 0.28 mg/kg. Zn and Cu levels were highest in L. perlatum and M. procera. Mn levels were fairly similar in the different species. The results of several surveys show that there can be large differences in the concentrations of the same metal (e.g. Pb) in the same species. The Se level was found to be very high in the species Boletus edulis, as has been shown by others. In the other species analysed the level of Se was low.

Bioavailability of cadmium from crab hepatopancreas and mushroom in relation to inorganic cadmium: a 9-week feeding study in mice.

The bioavailability of Cd from boiled crab hepatopancreas and dried mushroom was studied in relation to that of inorganic Cd (CdCl2). Female Balb/c mice were fed with diets containing 0.4 ppm Cd from either boiled crab (Cancer pagurus) hepatopancreas or dried mushroom (Agaricus augustus), or as inorganic Cd (CdCl2). A control group received low Cd (< 0.007 ppm) feed, and did not accumulate detectable levels of Cd during 9 wk of exposure. Using Cd accumulation in the liver and kidney as a measure of Cd absorption, it was indicated that the bioavailability of Cd from boiled crab hepatopancreas is slightly lower than that of Cd from mushroom and inorganic Cd. Fractionation of Cd in boiled crab hepatopancreas and mushroom indicated that Cd in crab hepatopancreas mainly is associated with denaturated proteins with low solubility, whereas a large fraction of Cd in dried mushroom is associated with soluble ligands. This difference in speciation of Cd may be a reason for the lower bioavailability of crab Cd than that of mushroom Cd. The difference in bioavailability is, however, low and as a safety measure it is recommended that human consumption of both crab hepatopancreas and wild mushrooms with high Cd levels should be restricted.

Bioavailability of labile aluminium in acidic drinking water: a study in the rat.

The bioavailability of labile Al (Allab; Al3+, and monomeric hydroxo and sulfato complexes) in drinking water was studied in the rat. The hypothesis was that Allab in drinking water is more available for absorption in the gastro-intestinal tract than Al complexed in the rat feed. Male Sprague-Dawley rats were exposed to 4 mg Al/litre in acidic drinking water (pH 4-5) and 5 mg Al/kg in the feed for 10 wk. The Al intake of these rats was about twice that in a control group of rats that received Al only in the feed. Both a theoretical speciation calculation and a speciation analysis of the water in a flow injection system showed that more than 98% of the Al in the water was present as Allab. However, intake of this water did not result in increased levels of Al in the bone, liver or brain tissue of the rats. Al speciation in a simulated rat stomach indicated that Allab in drinking water is rapidly complexed by feed constituents as the water enters the acidic milieu of the stomach, resulting in a very low concentration of Allab. The concentration of dissolved Al was also low in comparison to the added amount of labile Al. The possibility of complex formation between Allab and feed components in the gastro-intestinal tract should be taken into account in further studies of the bioavailability of drinking water Al in experimental animals and in humans.

Lead and cadmium levels in human milk and blood.

Lead and cadmium levels were determined (with AAS) in blood and milk obtained at 6 weeks after delivery from women living in the vicinity of a copper and lead metal smelter and in a control area. Analysis of lead and cadmium were also performed in blood samples obtained at delivery. Accuracy of the analysis was confirmed by the analysis of quality control samples. In general, blood and milk levels of lead and cadmium were low in both areas. At 6 weeks after delivery the lead levels in blood and milk were 32 +/- 8 and 0.7 +/- 0.4 micrograms Pb/l, respectively (total mean +/- S.D., n = 75). Cadmium levels in blood and milk were 0.9 +/- 0.3 and 0.06 +/- 0.04 microgram Cd/l, respectively (n = 75). At delivery the lead levels in blood of women in the smelter area were higher, 38.7 micrograms Pb/l, than the blood lead levels in women from the control area, 32.3 micrograms Pb/l, (P < 0.001). At 6 weeks after delivery there was no difference in blood lead levels between the two groups. In contrast, the lead levels in milk were higher in women from the smelter area, 0.9 microgram Pb/l, than in women from the control area, 0.5 microgram Pb/l, (P < 0.001). No differences in blood cadmium levels were found between the two groups. Milk cadmium levels in women from the control area, 0.07 microgram Cd/l, were somewhat higher (P < 0.01) than in women from the smelter area, 0.05 microgram Cd/l.(ABSTRACT TRUNCATED AT 250 WORDS)