Yngvar Thomassen

Evaluation of selected trivalent metal oxides as inert markers used to estimate apparent digestibility in salmonids

Abstract Trivalent oxides of yttrium and rare earth metals were evaluated as inert markers in apparent digestibility studies with salmonids in four experiments. In Experiment 1, 100 mg kg−1 of each of 15 oxides (Dy2O3, Er2O3, Eu2O3, Gd2O3, Ho2O3, La2O3, Lu2O3, Nd2O3, Pr2O3, Sc2O3, Sm2O3, Tb(III and IV) oxide, Tm2O3, Y2O3 and Yb2O3) were included in a feed fed to rainbow trout. The ratio between each marker and Yb2O3 in stripped faeces was used as an indicator of recovery. Only Er2O3, Ho2O3 and Tm2O3 had lower recoveries than the other markers. Experiment 2 compared the excretion rates of Cr2O3 and of the selected alternative markers (La2O3, Y2O3 and Yb2O3). A feed with 7.5 g kg−1 of Cr2O3 and 750 mg kg−1 of each of the other markers was fed to Atlantic salmon for a period of 1 week. Thereafter, the fish were fed with a marker-free feed, and gastro-intestinal evacuation was evaluated by comparing the marker ratios in the feed and in the faeces sieved from the outlet water of the tanks. The results did not reveal any systematic differences in evacuation among the various markers. Experiment 3 compared in vitro solubility of Cr2O3, Dy2O3, La2O3, Y2O3 and Yb2O3 in weak acid (HCl, pH 3 as in stomach contents of Atlantic salmon), weak acid neutralised with NaOH, and in water. Cr2O3 was not dissolved. Only 1.3% of Yb2O3, 22% of Y2O3, 31% of Dy2O3, and 96% of La2O3 was soluble in weak acid, but more than 99% of the dissolved markers precipitated when neutralised, and none of the markers were soluble in water. Experiment 4 compared the estimates of apparent digestibility coefficients (ADCs) of nitrogen and fat in rainbow trout when using Cr2O3, La2O3, Y2O3 and Yb2O3 as markers. The feed contained 10 g kg−1 Cr2O3 and 100 mg kg−1 of each of the other markers. Markers in feeds and stripped faeces were dissolved for the analysis with both HCl:HNO3 and H3PO4:MnSO4. Except for Cr2O3, the markers gave similar ADCs within each acid solubilisation procedure. The ADCs of fat were similar with both procedures, but the ADCs of nitrogen were 0.2% lower with HCl:HNO3 than with H3PO4. Cr2O3 was incompletely dissolved in HCl:HNO3, resulting in low ADCs. With H3PO4, no differences were seen among the ADCs obtained with Cr2O3 and the other markers. In conclusion, trivalent metal oxides, such as La2O3, Y2O3 and Yb2O3, can substitute Cr2O3 in digestibility studies with salmonids, and can be used at lower concentrations without affecting accuracy.

The placenta as a barrier for toxic and essential elements in paired maternal and cord blood samples of South African delivering women

Environmental toxicants such as metals may be detrimental to foetus and infant development and health because of their physiological immaturity, opportunistic and differential exposures, and a longer lifetime over which disease, initiated during pregnancy and in early life, can develop. The placental mechanisms responsible for regulation of absorption and excretion of elements during pregnancy are not fully understood. The aim of this paper is to assess the correlation for selected toxic and essential elements in paired whole blood samples of delivering women and cord blood, as well as to evaluate the placental permeability for selected elements. Regression analyses used to assess this correlation in 62-paired samples of maternal and cord whole blood of delivering women show that the concentrations of mercury, lead, cobalt, arsenic and selenium in maternal and cord blood differed statistically. Lead, cobalt, arsenic and selenium appear to pass the placental barrier by a diffusion mechanism. It was also found that the mercury levels in cord blood were almost double those of the mother, suggesting that the foetus may act as a filter for the maternal mercury levels during pregnancy. Transplacental transfer for arsenic and cobalt was 80% and 45%, respectively, suggesting that the placenta modulates the rate of transfer for these elements. Cadmium, manganese, copper and zinc levels did not show statistically significant correlations between two compartments (maternal versus cord whole blood). The study confirms that most of the toxic metals measured have an ability to cross the placental barrier.

Low iron stores are related to higher blood concentrations of manganese, cobalt and cadmium in non-smoking, Norwegian women in the HUNT 2 study

Low iron (Fe) stores may influence absorption or transport of divalent metals in blood. To obtain more knowledge about such associations, the divalent metal ions cadmium (Cd), manganese (Mn), cobalt (Co), copper (Cu), zinc (Zn) and lead (Pb) and parameters of Fe metabolism (serum ferritin, haemoglobin (Hb) and transferrin) were investigated in 448 healthy, menstruating non-smoking women, age 20-55 years (mean 38 years), participating in the Norwegian HUNT 2 study. The study population was stratified for serum ferritin: 257 were iron-depleted (serum ferritin < 12 microg/L) and 84 had iron deficiency anaemia (serum ferritin < 12 microg/L and Hb < 120 g/L). The low ferritin group had increased blood concentrations of Mn, Co and Cd but normal concentrations of Cu, Zn and Pb. In multiple regression models, ferritin emerged as the main determinant of Mn, Co and Cd (p < 0.001), while no significant associations with Cu, Zn and Pb were found. Adjusted r(2) for the models were 0.28, 0.48 and 0.34, respectively. Strong positive associations between blood concentrations of Mn, Co and Cd were observed, also when controlled for their common association with ferritin. Apart from these associations, the models showed no significant interactions between the six divalent metals studied. Very mild anaemia (110 < or = Hb < 120 g/L) did not seem to have any effect independent of low ferritin. Approximately 26% of the women with iron deficiency anaemia had high concentrations of all of Mn, Co and Cd as opposed to 2.3% of iron-replete subjects. The results confirm that low serum ferritin may have an impact on body kinetics of certain divalent metal ions, but not all. Only a fraction of women with low iron status exhibited an increased blood concentration of divalent metals, providing indication of complexities in the bodys handling of these metals.

Speciation of mercury in human whole blood by capillary gas chromatography with a microwave-induced plasma emission detector system following complexometric extraction and butylation

Methyl- and inorganic mercury were extracted from human whole blood samples, as their diethyldithiocarbamate complexes, into toluene and butylated by using a Grignard reagent. The mercury species were then separated by gas chromatography (on a 12 m non-polar DB-1 capillary column) and detected by a microwave-induced plasma atomic emission spectrometric (GC-MPD) system. The accuracy and precision of the proposed method were established by the analysis of Seronorm lyophilized human whole blood standards for methyl- and inorganic mercury. No statistical difference (t-test) between the sum of these two species determined by the GC-MPD based method and the recommended total mercury concentrations in the Seronorm samples was observed. Results for the determination of methyl- and inorganic mercury in 60 controls and 90 previously occupationally exposed (to inorganic mercury) workers are presented to illustrate the practical utility of the proposed method. No significantly elevated inorganic mercury concentrations between the two groups were evident.

Direct electrothermal atomic absorption spectrometric determination of selenium in serum

Abstract The effect of copper, iron, nickel and silver ions on the thermal stability of inorganic and metabolized forms of selenium in serum was studied with radioactive 75Se. Copper and iron had no stabilizing effect but in the presence of nickel or silver the temperature could be raised to 1050°C or 1250°C, respectively, without loss of selenium. On this basis an electrothermal atomic absorption spectrometric method was developed for the direct determination of selenium in human serum; selenium is stabilized with nickel during ashing. In 12 samples of sera from unexposed individuals, the concentrations ranged from 92 pob to 140 ppb. The relative standard deviation of the method is 4%, and the detection limit is 5 ppb.

Permanent iridium modifier for electrothermal atomic absorption spectrometry

The suitability for chemical modification of a pure metal layer, deposited on the inner surface of a graphite tube by cathodic sputtering of Ir in a low pressure Ar discharge, was investigated. The characteristics of the deposited layer were studied using scanning electron microscopy and compared with those of Ir deposited from solution. The analytical performance of the modifier was assessed in the determination of Cd, Mn, Pb, Se and V. When sufficient Ir was deposited by sputtering, a homogeneous layer covering the entire tube surface was formed which changed only slightly during the entire lifetime of the graphite tube. Thus integrated absorbance remained essentially constant for more than 700 atomizations. The volatile elements Cd, Pb and Se were thermally stabilized in the absence of a matrix to 800, 1200 and 1400 °C, respectively. The rate of atomization for Mn and V was, however, unfavourably delayed in the Ir-coated tubes.

Exploration of biomarkers for total fish intake in pregnant Norwegian women

OBJECTIVE Few biomarkers for dietary intake of various food groups have been established. The aim of the present study was to explore whether selenium (Se), iodine, mercury (Hg) or arsenic may serve as a biomarker for total fish and seafood intake in addition to the traditionally used n-3 fatty acids EPA and DHA. DESIGN Intake of fish and seafood estimated by an FFQ was compared with intake assessed by a 4 d weighed food diary and with biomarkers in blood and urine. SETTING Validation study in the Norwegian Mother and Child Cohort Study (MoBa). SUBJECTS One hundred and nineteen women. RESULTS Total fish/seafood intake (median 39 g/d) calculated with the MoBa FFQ was comparable to intake calculated by the food diary (median 30 g/d, rS = 0.37, P < 0.001). Erythrocyte DHA and blood Hg, Se and arsenic concentrations were positively correlated with intake of fish and seafood, but the association for DHA was weakened by the widespread use of supplements. The main finding was the consistent positive association between the intake of fish/seafood and blood arsenic concentration. In multivariate analyses, blood arsenic was associated with blood Hg and fish and seafood intake. In these models, arsenic turned out to be the best indicator of intake of fish and seafood, both totally and in subgroups of fish/seafood intake. CONCLUSIONS While DHA reflected the intake of fatty fish and n-3 PUFA supplements, blood arsenic concentration also reflected the intake of lean fish and seafood. Blood arsenic appears to be a useful biomarker for total fish and seafood intake.

Blood lead and cadmium and birth weight among sub-arctic and arctic populations of Norway and Russia

BACKGROUND Delivering women and their newborns in the Kola Peninsula of Russia and the neighboring arctic area of Norway were studied to explore relationships between maternal cadmium and lead status and birth weight as a pregnancy outcome. METHODS Life-style information, maternal blood and cord blood specimens were collected from 50 consecutive mother-infant pairs from hospital delivery departments in three Russian and three Norwegian communities. Pregnancy outcomes were verified by consulting medical records. Lead and cadmium were determined in the blood samples by electrothermal atomic absorption spectrometry. RESULTS The median blood-cadmium concentration for the Russian mothers was 2.2 nmol/L (n = 148) versus 1.8 nmol/L in the Norwegian group (n = 114, p = 0.55). A weak association was observed between maternal cadmium and amount smoked (r = 0.30, p<0.001); no correlation was found between maternal blood cadmium and birth weight. The corresponding maternal lead values were 0.14 (Russia) and 0.06 micromol/L (Norway), p<0.001. The latter lead concentration constitutes one of the lowest adult population values reported to date. Maternal and cord blood lead levels were strongly correlated (r = 0.88, p<0.001). In a multivariate linear regression model, maternal blood lead was recognized as a negative explanatory variable (p<0.05) for birth weight and childs body mass index (BMIC), with or without adjustment for gestational age. A similar association was suggested by ANOVA-analysis of maternal blood lead by quartiles. CONCLUSION Maternal blood-lead level as an environmental factor is an apparent predictor of low birth weight and BMIC. It reduced substantially the contribution of a country factor in explaining the observed differences in birth weight.

Performance improvements in the determination of mercury species in natural gas condensate using an on-line amalgamation trap or solid-phase micro-extraction with capillary gas chromatography–microwave-induced plasma atomic emission spectrometry

An on-line amalgamation trap was constructed for the collection of mercury species separated by capillary GC for detection by microwave-induced plasma atomic emission spectrometry. For direct measurement of the column eluate, the detection limits for mercury species in natural gas condensate are elevated because of background interference from carbon compounds passed to the plasma at the same time. Carbon compounds give rise to emission that spectrally interferes with the signal from the mercury detector and can overload the plasma discharge, reducing the excitation capability. With an amalgamation trap, mercury can be selectively collected from the column eluate and subsequently passed to the plasma in a flow of pure helium. By removing the carbon background emission, the trap allows the determination of dimethylmercury in condensate down to a detection limit of 0.24 µg l–1 and derivatized (butylated) monomethyl and inorganic mercury down to a detection limit of 0.56 µg l–1 in natural gas condensate. Use of the trap is compared with some existing determination methods for mercury species in condensate and other samples. Solid-phase micro-extraction is used for dimethylmercury, which gives a poorer detection limit of around 20 µg l–1 because the analyte mass collected is small compared with liquid sample injection. Following derivatization, samples are diluted for direct methylbutylmercury and dibutylmercury determination, corresponding to methylmercury and inorganic mercury. Dilution ensures a reasonably stable background for mercury signals. Again, poorer detection limits of 3.1 and 2.3 µg l–1, respectively, are obtained owing to the reduced analyte mass. The trap permits the injection of untreated condensate, or condensate reacted with butylmagnesium chloride, into the gas chromatograph without the need for dilution or sample clean-up.

Air exposure assessment and biological monitoring of manganese and other major welding fume components in welders

In a cross-sectional study, 96 welders were compared with 96 control subjects. Also 27 former welders, all diagnosed as having manganism, were examined. Exposure to welding fumes was determined in the 96 welders, while the concentration of elements in whole blood and urine was determined in all subjects. The geometric mean (GM) concentrations of manganese (Mn) and iron in the workroom air were 97 microg m(-3) (range 3-4620 microg m(-3); n=188) and 894 microg m(-3) (range 106-20 300 microg m(-3); n=188), respectively. Thus the Mn concentration in the workroom air was on average 10.6% (GM) of that of the Fe concentration. No substantial difference was observed in the air Mn concentrations when welding mild steel as compared to welding stainless steel. The arithmetic mean (AM) concentration of Mn in whole blood (B-Mn) was about 25% higher in the welders compared to the controls (8.6 vs. 6.9 microg l(-1); p < 0.001), while the difference in the urinary Mn concentrations did not attain statistical significance. A Pearsons correlation coefficient of 0.31 (p < 0.01) was calculated between B-Mn and Mn in the workroom air that was collected the day before blood sampling. Although the exposure to welding fumes in the patients had ceased on average 5.8 years prior to the study (range 4 years-7 years), their AM B-Mn concentration was still higher than in referents of similar age (8.7 microg l(-1) vs. 7.0 microg l(-1)). However, their urinary concentrations of cobolt, iron and Mn were all statistically significantly lower.