Birger Lind

Inter-individual variations of human mercury exposure biomarkers: a cross-sectional assessment

BackgroundBiomarkers for mercury (Hg) exposure have frequently been used to assess exposure and risk in various groups of the general population. We have evaluated the most frequently used biomarkers and the physiology on which they are based, to explore the inter-individual variations and their suitability for exposure assessment.MethodsConcentrations of total Hg (THg), inorganic Hg (IHg) and organic Hg (OHg, assumed to be methylmercury; MeHg) were determined in whole blood, red blood cells, plasma, hair and urine from Swedish men and women. An automated multiple injection cold vapour atomic fluorescence spectrophotometry analytical system for Hg analysis was developed, which provided high sensitivity, accuracy, and precision. The distribution of the various mercury forms in the different biological media was explored.ResultsAbout 90% of the mercury found in the red blood cells was in the form of MeHg with small inter-individual variations, and part of the IHg found in the red blood cells could be attributed to demethylated MeHg. THg in plasma was associated with both IHg and MeHg, with large inter-individual variations in the distribution between red blood cells and plasma. THg in hair reflects MeHg exposure at all exposure levels, and not IHg exposure. The small fraction of IHg in hair is most probably emanating from demethylated MeHg. The inter-individual variation in the blood to hair ratio was very large. The variability seemed to decrease with increasing OHg in blood, most probably due to more frequent fish consumption and thereby blood concentrations approaching steady state. THg in urine reflected IHg exposure, also at very low IHg exposure levels.ConclusionThe use of THg concentration in whole blood as a proxy for MeHg exposure will give rise to an overestimation of the MeHg exposure depending on the degree of IHg exposure, why speciation of mercury forms is needed. THg in RBC and hair are suitable proxies for MeHg exposure. Using THg concentration in plasma as a measure of IHg exposure can lead to significant exposure misclassification. THg in urine is a suitable proxy for IHg exposure.

Cadmium exposure from smoking cigarettes: Variations with time and country where purchased

Cadmium has been determined in 26 brands of cigarettes purchased in eight different countries throughout the world and in 16 different samples of cigarettes produced in Sweden between 1918 and 1968. In addition the amount of cadmium released from smoking one cigarette to the particulate phase collected from a smoking simulation machine, corresponding to the amount actually inhaled by a smoker, has been determined. The cadmium concentration in different brands of cigarettes ranged from 0.19 to 3.0 micrograms Cd/g dry wt, with a general tendency toward lower values in cigarettes from developing countries. No systematic change in the cadmium concentration of cigarettes with time could be revealed. The amount of cadmium inhaled from smoking one cigarette containing about 1.7 microgram Cd was estimated to be 0.14 to 0.19 microgram, corresponding to about 10% of the total cadmium content in the cigarette.

Lead and cadmium levels in blood samples from the general population of Sweden

Lead and cadmium was determined in whole blood samples obtained from 473 nonoccupationally exposed adult persons in Sweden in 1980. Analyses were performed using atomic absorption spectrophotometry equipped with an electrothermal atomization unit. Accuracy of the analysis was confirmed by the analysis of quality control samples. Blood lead concentrations were shown to be significantly influenced by sex, smoking habits, and alcohol consumption. Current male smokers had a median blood lead level of 92 micrograms Pb/liter, as compared to 77 micrograms Pb/liter for nonsmokers. For females the corresponding values were 69 micrograms Pb/liter and 57 micrograms Pb/liter for current smokers and nonsmokers, respectively. Highly significant correlations were found between stated alcohol consumption and blood lead in most of the different sex and smoking categories. People living in apartments close to streets with heavy traffic in Stockholm had slightly, but not significantly, higher blood lead levels when compared to people living in areas of this city with low traffic density. Blood cadmium levels were very strongly affected by smoking habits. A significant correlation existed between the number of cigarettes consumed daily and blood cadmium concentration. The median blood cadmium level for nonsmoking males was 0.2 micrograms Cd/liter (less than or equal to 0.2, detection limit) and for females 0.3 micrograms Cd/liter. About 90% of all nonsmokers had cadmium concentrations in blood below 0.6 micrograms Cd/liter, whereas about 90% of the current male and female smokers had cadmium concentrations in blood of 0.6 micrograms Cd/liter or more.

Mercury in human brain, blood, muscle and toenails in relation to exposure: an autopsy study

BackgroundThe main forms of mercury (Hg) exposure in the general population are methylmercury (MeHg) from seafood, inorganic mercury (I-Hg) from food, and mercury vapor (Hg0) from dental amalgam restorations. While the distribution of MeHg in the body is described by a one compartment model, the distribution of I-Hg after exposure to elemental mercury is more complex, and there is no biomarker for I-Hg in the brain. The aim of this study was to elucidate the relationships between on the one hand MeHg and I-Hg in human brain and other tissues, including blood, and on the other Hg exposure via dental amalgam in a fish-eating population. In addition, the use of blood and toenails as biological indicator media for inorganic and organic mercury (MeHg) in the tissues was evaluated.MethodsSamples of blood, brain (occipital lobe cortex), pituitary, thyroid, abdominal muscle and toenails were collected at autopsy of 30 deceased individuals, age from 47 to 91 years of age. Concentrations of total-Hg and I-Hg in blood and brain cortex were determined by cold vapor atomic fluorescence spectrometry and total-Hg in other tissues by sector field inductively coupled plasma-mass spectrometry (ICP-SFMS).ResultsThe median concentrations of MeHg (total-Hg minus I-Hg) and I-Hg in blood were 2.2 and 1.0 μg/L, and in occipital lobe cortex 4 and 5 μg/kg, respectively. There was a significant correlation between MeHg in blood and occipital cortex. Also, total-Hg in toenails correlated with MeHg in both blood and occipital lobe. I-Hg in both blood and occipital cortex, as well as total-Hg in pituitary and thyroid were strongly associated with the number of dental amalgam surfaces at the time of death.ConclusionIn a fish-eating population, intake of MeHg via the diet has a marked impact on the MeHg concentration in the brain, while exposure to dental amalgam restorations increases the I-Hg concentrations in the brain. Discrimination between mercury species is necessary to evaluate the impact on Hg in the brain of various sources of exposure, in particular, dental amalgam exposure.

Dissolution of metals by human and rabbit alveolar macrophages.

The ability of human and rabbit alveolar macrophages to dissolve 0.1-0.5 micron MnO2 particles in vitro was compared. The amount of Mn added and dissolved from the particles over periods of nought, one, and three days was determined by flame atomic absorption spectrophotometry. The amount dissolved by human and rabbit macrophages was similar; on average 43.1% and 43.9%, respectively, were dissolved within three days. But rabbit and human macrophages dissolved significantly more Mn than was dissolved in the respective culture medium without macrophages after one and three days. It is suggested that the dissolution of particles by alveolar macrophages should be one basic component in any model of alveolar clearance of inorganic particles.

Cadmium, zinc, copper, and lead in human renal cortex.

Analysis of cadmium and zinc in the renal cortex of 67 Swedish subjects disclosed the same dependence on age as in US subjects. In the 6–50 year age group, cadmium content and the cadmium-zinc ratio were correlated to age; thereafter, there was a decrease in cadmium and zinc and in the cadmium-zinc ratios. The increase in zinc paralleled the increase in cadmium. The difference between total zinc and the amount of zinc equivalent to the amount of cadmium provides a measure of the physiological zinc content of the cortex; this fraction, 160 ppm (based on dry weight of renal cortex), did not vary with age. In the age groups over 60, cadmium content was significantly lower in women than in men.

Ability of rabbit alveolar macrophages to dissolve metals.

Manganese dioxide particles, 0.1-0.5 micron, were added to samples of 2-3 X 10(6) rabbit alveolar macrophages. The amount of manganese added and dissolved from the particles, over periods of 0, 1, 3, and 5 days, was determined by flame atomic absorption spectrophotometry. Macrophages from six rabbits received about 10 micrograms of Mn, macrophages from two rabbits about 30 micrograms, and macrophages from another two rabbits about 100 micrograms. Over periods of 1, 3, and 5 days the macrophages in all three dose groups dissolved two to three times more Mn than was dissolved in control experiments. In control experiments solubility was studied in the medium without macrophages. Macrophages cultivated 3 days before the addition of MnO2 dissolved the particles within another 2 days to an extent similar to that in the control experiments. The ability of the macrophages to dissolve MnO2 particles might be related to the low pH values in the phagosomes. Studies of the ability of macrophages from various species to dissolve metal particles as well as of pH values in their phagosomes might lead to a better understanding of alveolar clearance of metal particles.

Dental amalgam and mercury

SummaryMercury concentration in intraoral air and urine of seven females with dental amalgam was measured before and after intake of one hard-boiled egg. A considerable decrease in mercury concentration in intraoral air was found. Twenty women with about equal dental amalgam status, with or without subjective symptoms related to dental amalgam, were also studied. Mercury concentrations in intraoral air and urine were measured. For all the 27 women the basal intraoral air concentration of mercury ranged over 0.6–10.4 μg/m3 (median value 4.3 μg/m3). This corresponds to a release of 0.02–0.38 ng/s (median value 0.16 ng/s). In urine, the mercury concentration varied from < 0.8–6.9 μg/g creatinine (median value 1.9 μg/g creatinine). Data from both parameters were significantly correlated to the total number of teeth areas with dental amalgam. Protein values in urine indicated no renal damage. Maximum concentrations of mercury vapour in intraoral air for the 27 women who had chewed chewing gum for 5 min varied between 2–60 μg Hg/m3 (median value 19 μg Hg/m3). This corresponds to 0.07–2.20 ng Hg/s and a median value of 0.70 ng Hg/s.

Concentrations of arsenic in urine of the general population in Sweden

The concentration of the sum of the metabolites of inorganic arsenic (inorganic arsenic, methylarsonic acid and dimethylarsinic acid) as well as the concentration of organic arsenic compounds, mainly in the form of arsenobetaine, in the urine of human subjects from two cities in Sweden have been studied. The median concentration of metabolites of inorganic arsenic was approximately 8 micrograms As/g creatinine, independent of place of residence, sex, smoking and consumption of beer and wine. However, subjects who frequently ate flatfish and crustacea had somewhat higher (1.5 times) concentrations than those who very seldom ate such food. Flatfish, mainly in the form of plaice, and crustacea were found to be the main source of organic arsenic compounds. Subjects eating this type of seafood more than once a week had approximately 40 micrograms organic As/g creatinine (median value), compared with about 12 micrograms organic As/g creatinine in subjects who very seldom ate it. Other types of seafish or freshwater fish did not give rise to elevated concentrations of arsenic in the urine. The total range of organic arsenic compounds in urine was less than 1 to 525 micrograms As/g creatinine.

Assessment of skin exposure to nickel, chromium and cobalt by acid wipe sampling and ICP‐MS

There is a great need to accurately assess skin exposure to contact allergens. We have developed a technique for assessment of skin exposure to nickel, chromium and cobalt using acid wipe sampling by cellulose wipes with 1% nitric acid. Chemical analysis was performed by inductively coupled plasma mass spectrometry (ICP‐MS). The recovery of nickel, chromium and cobalt from arms and palms was 93%. The analytical result is expressed in terms of mass per unit area (μg/cm2). The developed acid wipe sampling technique is suitable for determination of nickel, chromium and cobalt deposited on the skin. The technique may be used in workplace studies, in studies of individuals in the general population, in dermatitis patients, in identification of risk groups, as well as in developing preventive strategies and in follow‐up after intervention.