German health-related environmental monitoring: assessing time trends of the general population's exposure to heavy metals.

The German system of a health-related environmental monitoring is based upon two instruments: The German Environmental Survey (GerES) and the Environmental Specimen Bank (ESB). The ESB is a tool to describe time trends of human exposure. Each year approx. 500 students from 4 sampling locations are analysed for their heavy metal contents in blood, blood plasma, and urine. GerES is a nationwide representative cross-sectional study that has been conducted four times up to now. Both instruments have been used to measure heavy metals over the last decades and thus provide complementary information. Both instruments are useful to describe time trends. However, combining the two has an added value, which is demonstrated for heavy metals for the first time in this paper. Major results and the changing importance of sources of exposure to heavy metals (Pb, Cd, Hg, Au, Pt, U and Ni) are shown. This leads to the following conclusion about the today's relevance of exposure in Germany. For the study participants of the city of Muenster, lead in whole blood decreased from about 70 µg/l in 1981 to levels below 15 µg/l in 2009. GerES data of young adults confirmed this time trend and GerES IV on children revealed the decreasing relevance of lead in outdoor air and in drinking water. The concentrations of mercury in urine decreased because in Germany it is no longer recommended to use amalgam fillings for children. However, GerES IV and ESB data also demonstrate that despite the decline of these heavy metals exposures to nickel and uranium originating from drinking water are still of importance.

The biocompatibility of dense and porous Nickel-Titanium produced by selective laser melting.

Nickel-Titanium shape memory alloys (NiTi-SMA) are of biomedical interest due to their unusual range of pure elastic deformability and their elastic modulus, which is closer to that of bone than any other metallic or ceramic material. Newly developed porous NiTi, produced by Selective Laser Melting (SLM), is currently under investigation as a potential carrier material for human mesenchymal stem cells (hMSC). SLM enables the production of highly complex and tailor-made implants for patients on the basis of CT data. Such implants could be used for the reconstruction of the skull, face, or pelvis. hMSC are a promising cell type for regenerative medicine and tissue engineering due to their ability to support the regeneration of critical size bone defects. Loading porous SLM-NiTi implants with autologous hMSC may enhance bone growth and healing for critical bone defects. The purpose of this study was to assess whether porous SLM-NiTi is a suitable carrier for hMSC. Specimens of varying porosity and surface structure were fabricated via SLM. hMSC were cultured for 8 days on NiTi specimens, and cell viability was analyzed using two-color fluorescence staining. Viable cells were detected on all specimens after 8 days of cell culture. Cell morphology and surface topography were analyzed by scanning electron microscopy (SEM). Cell morphology and surface topology were dependent on the orientation of the specimens during SLM production. The Nickel ion release can be reduced significantly by aligned laser processing conditions. The presented results clearly attest that both dense SLM-NiTi and porous SLM-NiTi are suitable carriers for hMSC. Nevertheless, before carrying out in vivo studies, some work on optimization of the manufacturing process and post-processing is required.

Can human mesenchymal stem cells survive on a NiTi implant material subjected to cyclic loading?

Nickel-titanium shape memory alloys (NiTi-SMAs) exhibit mechanical and chemical properties which make them attractive candidate materials for various types of biomedical applications. However, the high nickel content of NiTi-SMAs may result in adverse tissue reactions, especially when they are considered for load-bearing implants. It is generally assumed that a protective titanium oxide layer separates the metallic alloy from its environment and that this explains the good biocompatibility of NiTi. Cyclic loading may result in failure of the protective oxide layer. The scientific objective of this work was to find out whether cyclic dynamic strain, in a range relevant for orthopedic implants, diminishes the biocompatibility of NiTi-SMAs. In order to analyze the biocompatibility of NiTi-SMA surfaces subjected to cyclic loading, NiTi-SMA tensile specimens were preloaded with mesenchymal stem cells, transferred to a sterile cell culture system and fixed to the pull rods of a tensile testing machine. Eighty-six thousand and four hundred strain cycles at 2% pseudoelastic strain were performed for a period of 24 h or 7 days. Cytokines (IL-6, IL-8 and VEGF) and nickel ion release were determined within the cell culture medium. Adherent cells on the tensile specimens were stained with calcein-AM and propidium iodide to determine cell viability. Dynamic loading of the tensile specimens did not influence the viability of adherent human mesenchymal stem cells (hMSCs) after 24 h or 7 days compared with the non-strained control. Dynamic cycles of loading and unloading did not affect nickel ion release from the tensile specimens. The release of IL-6 from hMSCs cultured under dynamic conditions was significantly higher after mechanical load (873 pg ml(-1)) compared with static conditions (323 pg ml(-1)). The present work demonstrates that a new type of mechanical in vitro cell culture experiment can provide information which previously could only be obtained in large animal experiments.

Dietary intake of PCDD/F by small children with different food consumption measured by the duplicate method.

The dietary intake of PCDD/F by 42 small children, 21 boys and 21 girls in the age range 14-47 months, with different food consumption behaviour living in urban and rural areas of Germany was measured by the duplicate method with a 7 day sampling period from May to September 1998. The PCDD/F-levels in the food duplicates were in the range 39.2-325 fg I-TEq/g(dry weight) (median: 90.7; arithmetic mean: 96.6) and the doses were in the range 0.681-5.43 with a median of 1.56 and an arithmetic mean (AM) of 1.60 pg I-TEq/(kg(body weight) x d). Children living in an urban industrialized area with food consumption including products from the family owned vegetable gardens or the surrounding area and/or products from domestic animals showed no statistically significant different concentrations in the food duplicates or in the dietary intake of PCDD/F, calculated as I-TEq, than children living in a rural area with similar food consumption behavior or than children consuming exclusively food from the supermarket.

Comparison of different digestive tract models for estimating bioaccessibility of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) from red slag 'Kieselrot'.

'Kieselrot' (red slag), a highly PCDD/F-contaminated leaching residue from a copper production process, has been used as surface layer for more than 1,000 sports fields, playgrounds and pavements in Germany and neighbouring countries. Children can ingest this material directly by hand-to-mouth activities or soil-pica behaviour. Furthermore secondary contamination of farm land or kitchen gardens by drift of red slag dust may lead to an enrichment of PCDD/F within the food-chain. PCDD/F can be mobilized from contaminated materials by digestive juices and thus become bioaccessible for intestinal absorption. Two different digestive tract models were used to estimate the bioaccessibility of PCDD/F from red slag and to study the influence of food material on the mobilization of the contaminants. The bioaccessibility of PCDD/F from red slag depends on the charge of red slag material used, the bile content of the intestinal juice and on the presence of lipophilic foodstuffs. A low bioaccessibility of less than 5% was found when using a digestive tract model with a low bile content and in absence of food material. The bioaccessibility was estimated to be more than 60% when using a model with a higher bile content and in the presence of whole milk powder. A low bioaccessibility of PCDD/F from red slag in general--as assumed until now and mentioned in legal provision--was not confirmed by our study. Considering observations for the different homologue groups it is obvious that bioaccessibility is the first of several important steps to estimate human health risks arising from contaminated materials. In case red slag contaminated with PCDD/F their absorption rate in the digestive tract and/or metabolism might be at least just like important.

Dietary intake of lead, cadmium, copper and zinc by children from the German North Sea island Amrum.

The dietary intake of metals was studied in seven male and seven female children at the age of 1.5 to 5.3 years living in a remote area of Germany, the North Sea island Amrum. The dietary intake of lead and cadmium was measured by a seven-day-duplicate study using atomic absorption spectrometry. The dietary intake of copper and zinc were calculated from food diaries. The median lead and cadmium intakes were 2.1 micrograms/(kgbw x week) [range: 0.63-5.1 micrograms/(kgbw x week)] and 2.7 micrograms/(kgbw x week) [range: 1.7-4.4 micrograms/(kgbw x week)]. The median daily intake of copper and zinc were 1.1 mg/d (range: 0.54-2.5 mg/d) and 5.7 mg/d (range: 2.7-14 mg/d). Compared to the provisional tolerable weekly intake (PTWI) of 25 micrograms/(kgbw x week) proposed by the WHO the dietary intake of lead was low. The median amounted to 8.5% and the maximum to 20% of the PTWI. The cadmium intake was comparatively high. The median amounted to 39% and the maximum to 63% of the PTWI [7 micrograms/(kgbw x week)]. The median intake of copper was in the range of the values recommended by the German Society of Nutrition (0.7-1.0 mg/d and 1.0-1.5 mg/d for children at the age of 1-< 4 years and 4-< 7 years). Twenty-three percent of the calculated intakes were below these values. The median intake of zinc however did not reach the recommended dietary intake of 7 and 10 mg/d for children at the age of 1-< 4 years and 4-< 7 years.

Decrease of PCDD/F levels in human blood--trend analysis for the German population, 1991-1996.

More than 500 whole blood samples of normal subjects from Germany collected in 1991-1996 have been analyzed for polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) by capillary gas chromatography/high-resolution mass spectrometry. Over the examined time period a continuous decrease of the PCDD/F concentrations in human blood was observed. The mean levels found were about 42.7 pg I-TEq/g (lipid basis) in 1991 and 20.7 pg I-TEq/g (liquid basis) in 1996 [median: 40.8 and 19.2]. A reduction to about half was found for most congeners. Each 1-year subset of the entire collective shows a positive correlation of the PCDD/F blood levels with age for most of the congeners, the sum values, and the calculated toxicity equivalents. For statistical evaluation a multiplicative model was used: Concentration in blood = A x ageB. The correlation is mostly pronounced for lower chlorinated PCDD and for 2,3,4,7,8-PentaCDF.

Myeloperoxidase-catalyzed formation of PCDD/F from chlorophenols.

Chlorophenols (CP) are transformed in vitro to polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) by a biochemical-catalyzed oxidation. This is shown for 2,4,5-tri-, 2,3,4,6-tetra-and pentachlorophenol with myeloperoxidase recovered from human leucocytes in the presence of hydrogen peroxide. The yield, the reaction, and the PCDD/F-pattern found depend on the CP. The formation rates are in the micromol-per-mol range for all substrates. The experiments confirm the suspicion that a biochemical formation of PCDD/F from precursors such as CPs can take place in the human body and that this metabolic pathway may lead to a higher inner exposure with PCDD/F than is now assumed.

Decrease of PCDD/F levels in human blood from Germany over the past ten years (1989-1998).

744 whole blood samples of normal subjects from Germany collected in 1989-1998 have been analyzed for polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) by capillary gas chromatography/high resolution mass spectrometry. Over the examined time period a continuous decrease of the PCDD/F concentrations in human blood was observed. The mean levels found were 43.7 pg I-TEq/g (lipid basis) in 1989 and 20.7 pg I-TEq/g (lipid basis) in 1996/98 [median: 42.2 and 19.4]. The reduction to about the half was found for most congeners. Each one-year subset of the collective and the entire collective shows a positive correlation of the PCDD/F blood levels with age for most of the congeners, the sum values and the calculated toxicity equivalents. For statistical evaluation a multiplicative model was used: Concentration = A x Age(B). The correlation is mostly pronounced for lower chlorinated PCDD and for 2,3,4,7,8-PentaCDF. The PCDD/F concentrations in human blood in relation to the year of examination and the age of the subjects can be described by a linear model: I-TEq [pg/g (lipid basis)] = 6176 - 3.097 x Year + 0.6482 x Age or by a multiplicative model: I-TEq [pg/g(lipid basis)] = 10(89.08-0.04415 x Year + 0.008468 x Age).

Estimation of dioxin and furan elimination rates with a pharmacokinetic model.

Quantitative description of the pharmacokinetics of dioxins and furans in humans can be of great help for the assessment of health risks posed by these compounds. To that the elimination rates of sixteen 2,3,7,8-chlorinated dibenzodioxins and dibenzofurans are estimated from both a longitudinal and a cross-sectional data set using the model of Van der Molen et al. [Van der Molen G.W., Kooijman S.A.L.M., and Slob W. A generic toxicokinetic model for persistent lipophilic compounds in humans: an application to TCDD. Fundam Appl Toxicol 1996: 31: 83-94]. In this model the elimination rate is given by the (constant) specific elimination rate multiplied with the ratio between the lipid weight of the liver and total body lipid weight. Body composition, body weight and intake are assumed to depend on age. The elimination rate is, therefore, not constant. For 49-year-old males, the elimination rate estimates range between 0.03 per year for 1,2,3,6,7,8-hexaCDF to 1.0 per year for octaCDF. The elimination rates of the most toxic congeners, 2,3,7,8-tetraCDD, 1,2,3,7,8-pentaCDD, and 2,3,4,7,8-pentaCDF, were estimated at 0.09, 0.06, and 0.07, respectively, based on the cross-sectional data, and 0.11, 0.09, and 0.09 based on the longitudinal data. The elimination rates of dioxins decrease with age between 0.0011 per year for 1,2,3,6,7,8-hexaCDD and 0.0035 per year for 1,2,3,4,6,7,8-heptaCDD. For furans the average decrease is 0.0033 per year. The elimination rates were estimated both from a longitudinal and a cross-sectional data set, and agreed quite well with each other, after taking account of historical changes in average intake levels.

Human exposure to PCDD/Fs in the UK: the development of a modelling approach to give historical and future perspectives.

In order to assess the long-term impact of persistent organic contaminants such as polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) it is important to be able to quantify historical exposure. An understanding of past exposure is not only important to place our current body burdens in perspective, but is useful in assessing our potential future exposure. Unfortunately, very few direct measurements of our main source of exposure (i.e., food) over the past decades are available. This study attempts to reconstruct the historical exposure of the UK population to PCDD/Fs using a combination of emission estimates, information on environmental temporal trends derived from sediment cores and archived materials, and environmental/human fate modelling. Predicted adipose and blood lipid concentrations for a typical cross section of the population are derived over time (1920-2000), which is compared with measured data. The approach has been tested with two PCDDs and two PCDFs and showed encouraging agreement with measured data. Certain parts of the modelling methodology have been highlighted where there is still poor understanding of the processes governing fate and behaviour. These areas are discussed and recommendations for future improvements are made. The paper thus represents an initial modelling approach which defines both the historical (1920-present) and future (present-2020) fate of PCDD/Fs in the UK population.

Peroxidase-catalyzed in vitro formation of polychlorinated dibenzo-p-dioxins and dibenzofurans from chlorophenols.

Chlorophenols (CP) are transformed in vitro to polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) by a peroxidase-catalyzed oxidation. This is shown for 2,4,5-tri-, 2,3,4,6-tetra- and pentachlorophenol with plant horseradish peroxidase and with myeloperoxidase recovered from human leukocytes, each in the presence of hydrogen peroxide. The yield, the reaction and the PCDD/F-pattern found are dependent on the CP. The amounts of PCDD/F formed within 4 or 24 h are in the micromol/mol-range for all substrates and both peroxidases. The experiments suggest that biochemical formation of PCDD/F from precursors such as CPs can take place in the human body and that this metabolic pathway may lead to a higher inner exposure to PCDD/F than up to now assumed based on intake data for PCDD/F.

[Statistically evaluated 95% prediction ranges as alternative to reference ranges exemplified by polychlorinated dibenzo-p-dioxins/dibenzofurans and lead]. / Aus anlassbezogenen Untersuchungen statistisch berechnete 95%-Prognosebänder als Alternative zu Referenzbereichen am Beispiel von polychlorierten Dibenzo-p-dioxinen/Dibenzofuranen und Blei.

Using the 95% prediction limits of an age-related multiplicative regression model describing the datasets of blood examinations carried out on subjects suspected of having been exposed to lead and to polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/F), it was shown that the relevant curves can be used as an alternative to reference ranges describing the actual background exposure to these pollutants. The upper limit of the actual German background exposure can be estimated by the following equations: PCDD/F as International Toxicity Equivalents in the age range of 10-70 years [pg/g lipid basis] = 1.64.age0.871 and lead in the age range of 15-80 years [microgram/l] = 18.15.age0.3638.

Human fecal PCDD/F-excretion exceeds the dietary intake.

A mass balance of human dietary PCDD/F-intake and fecal PCDD/F-excretion was carried out. The participants of the study were seven male and seven female adults between the ages of 24 to 64 years, living in North Rhine-Westphalia, Germany. The PCDD/F-intake was measured using the duplicate method. Sampling time of each food duplicate covered three days. The fecal PCDD/F-excretion was measured by collecting the feces which corresponded to the food duplicates. The mean daily dietary PCDD/F-intake was 49 pg I-TEq/d (range: 23-96 pg I-TEq/d) and therewith lower than that estimated in the past. The mean daily fecal PCDD/F-excretion was 98 pg I-TEq/d (40-200 pg I-TEq/d). This is twice the amount of the PCDD/F-intake. The fecal excretion of OCDD was especially higher than the dietary intake (mean: 7 fold, range: 1.2-21 fold). The differences between PCDD/F-intake and PCDD/F-excretion may be caused by a reduction of the body burden as a consequence of decreasing PCDD/F-intake. Other explanations were additional sources of exposure to PCDD/F or de novo formation of PCDD/F in the human body.

[Blood tests for PCB in teachers at a heavily PCB-polluted school]. / Blutuntersuchungen auf PCB bei Lehrerinnen und Lehrern einer stark PCB-belasteten Schule.

The levels of PCB 28, 52, 101, 153, 138 and 180 were determined in blood samples of subjects (mainly teachers; n = 18) who had worked in a PCB-contaminated school-building for many years (average: 14.2 years). The PCB concentrations in indoor air ranged up to 13,500 ng/m3. For comparison PCB blood levels were determined in 18 teachers working in schools not contaminated by PCB. The subjects of the reference group were matched with the exposed subjects with respect to age and gender. PCB 28, 52 and 101 were not detectable in the blood samples (detection limit: 0.1 microgram/l). In the exposed subjects blood levels of PCB 153 and 138 were, on average, slightly higher and the levels of PCB 180 slightly lower when compared with the reference subjects, but the differences were not statistically significant. The levels of PCB 153, 138 and 180 increased with age. With the exception of two subjects the levels of these congeners were below the reference values proposed by Kappos et al. The results show that inhalative exposure to PCB 153, 138 and 180 is very low in comparison to PCB background exposure via food. Due to rapid metabolisation and elimination the blood levels of PCB 28, 52 and 101 are usually very low.

[PCDD/F-content in house dust]. / PCDD/F-Gehalte im Hausstaub.

The levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) were determined in house dust samples collected from 22 residential houses located in different areas of Germany. Nine houses were located in an urban and industrial area, one house in a rural and 10 houses in a contaminated residential area near to a former metal reclamation plant. Two house dust samples were collected from two old farm houses, in which large amounts of pentachlorophenol (PCP) containing wood preservatives had been used several years ago. All dust samples were collected from the dust bags of vacuum cleaners and passed through a sieve (mesh: 2.0 mm). Particles < 2.0 mm were used for analysis. The average level of PCDD/F in "normal" house dust was 101 ng I-TEq/kg (range: 7.83-332 ng I-TEq/kg). The predominant congeners and chlorohomologues were OctaCDD followed by HeptaCDD, HeptaCDF and OctaCDF. The average level of PCDD/F in house dust samples collected from a contaminated residential area was 265 ng I-TEq/kg (range: 29.9-1050 ng I-TEq/kg). When compared with "normal" residential houses significantly increased levels of lower chlorinated PCDD/F were noted in the house dust samples from this area. The house dust samples collected from a PCP-treated old farm house were found to contain 1.39 and 11.8 micrograms I-TEq/kg. The chlorohomologues patterns were typical for PCP contaminated with PCDD/F. The present study shows that the levels of PCDD/F in house dust may be used as indicators of indoor contamination by PCDD/F and as reference values for further investigations.

[Human biomonitoring--studies of arsenic, lead and PCDD/F in inhabitants of a contaminated residential area]. / Human-Biomonitoring--Untersuchungen auf Arsen, Blei und PCDD/F bei Bewohnern eines kontaminierten Wohngebietes.

The levels of arsenic in urine, lead in blood, and PCDD/F in blood fat were determined in 12 subjects living in a residential area where the soil was contaminated by arsenic, lead, PCDD/F and other pollutants. Six residents (group I, mean age 56 years) were living on the contaminated site for at least 35 years, and had consumed home-grown vegetables and fruits as well as self-produced animal products (eggs, meat). Six residents (group II, mean age 47 years) had been living on the contaminated site for an average period of 9 years, and had consumed only minor amounts of home-grown vegetables and fruits, but no self-produced animal products. Some of them had skin contact with contaminated soil during excavation and garden work. For comparison, blood and urine samples of subjects living in the same region but not exposed to soil contaminants were investigated for the above mentioned parameters. The reference subjects were selected by age and gender in order to form matched pairs with the exposed subjects. The levels of arsenic in urine and lead in blood did not differ significantly between the residents of the contaminated area and the reference subjects. With regard to PCDD/F in blood fat a significantly increased PCDD/F-body burden was found for the subjects of group I (median: 41.5 pg I-TE/g fat, range: 18.0-54.6 pg I-TE/g fat; reference group, median: 20.3 pg I-TE/g fat, range: 12.2-30.5 pg I-TE/g fat), whereas the subjects of group II had only a moderately, but not significantly increased PCDD/F-body burden (median: 23.4 pg I-TE/g fat, range 13.1-45.8 pg I-TE/g fat) when compared with the reference group (median: 13.9 pg I-TE/g fat, range: 12.1-30.5 pg I-TE/g fat). Increased PCDD/F levels in blood fat seemed to be related mainly to the consumption of self-produced animal products. From the present-day toxicological point of view, none of the subjects examined in this study had a critical body burden of PCDD/F.

Levels of PCDD/PCDF in blood fat as indices of the PCDD/PCDF body burden in humans.

The levels of PCDD/F in blood fat are similar to those in body fat and in milk fat of lactating women. Therefore, the levels of PCDD/F in blood fat can be used as an index of the individual PCDD/F body burden in humans. In order to evaluate the PCDD/F background exposure levels of the German population, blood samples collected from 95 subjects (age 12-82 years) living in a rural area of North-West Germany were analysed for PCDD/F. The median 2,3,7,8-TCDD toxicity equivalents (TE) were 40.8 pg I-TE/g blood fat and the 95th percentile was 82.1 pg I-TE/g blood fat. The TE levels in blood fat show a marked increase with age, which reflects the pronounced accumulation of PCDD/F in the human body throughout the entire lifetime. Considering single congeners, significant differences in the age-related increase were noted. Using age-specific reference values derived from this study the levels of PCDD/F in blood fat of individuals environmentally exposed to PCDD/F under different circumstances were evaluated.

[Blood PCDD/F levels in blood of residents of a former cable incineration facility]. / PCDD/F-Gehalte im Blut von Anwohnern einer früheren Kabelabbrennanlage.

Increased levels of polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofuranes (PCDF) were found in soil and roof dust of a residential area located near a metal reclamation plant in Northern Germany. In order to assess the degree of exposure of persons residing near to this plant, venous blood samples were collected from 14 subjects and analysed for PCDD/F and fat content. Furthermore, blood samples collected from the members of a farmer's family living nearby were analysed for PCDD/F. Previous studies had shown significantly increased PCDD/F levels in chicken eggs produced on this farm. Regarding the group of residents, the PCCD/F levels in blood fat were not increased when compared to background levels. However, some members of the farmer's family had increased PCDD/F levels in blood fat. The findings of these studies suggest that long-term consumption of contaminated animal products, especially chicken eggs, may result in increased PCDD/F levels in the body, whereas increased levels of PCDD/F in dust and soil do not noticeably affect the PCDD/F levels in human blood fat.