New aspects in deriving health-based guidance values for bromate in swimming pool water

Bromate, classified as a EU CLP 1B carcinogen, is a typical by-product of the disinfection of drinking and swimming pool water. The aim of this study was (a) to provide data on the occurrence of bromate in pool water, (b) to re-evaluate the carcinogenic MOA of bromate in the light of existing data, (c) to assess the possible exposure to bromate via swimming pool water and (d) to inform the derivation of cancer risk-related bromate concentrations in swimming pool water. Measurements from monitoring analysis of 229 samples showed bromate concentrations in seawater pools up to 34 mg/L. A comprehensive non-systematic literature search was done and the quality of the studies on genotoxicity and carcinogenicity was assessed by Klimisch criteria (Klimisch et al., Regul Toxicol Pharmacol 25:1–5, 1997) and SciRAP tool (Beronius et al., J Appl Toxicol, 38:1460–1470, 2018) respectively. Benchmark dose (BMD) modeling was performed using the modeling average mode in BMDS 3.1 and PROAST 66.40, 67 and 69 (human cancer BMDL₁₀; EFSA 2017). For exposure assessment, data from a wide range of sources were evaluated for their reliability. Different target groups (infants/toddlers, children and adults) and exposure scenarios (recreational, sport-active swimmers, top athletes) were considered for oral, inhalation and dermal exposure. Exposure was calculated according to the frequency of swimming events and duration in water. For illustration, cancer risk-related bromate concentrations in pool water were calculated for different target groups, taking into account their exposure using the hBMDL₁₀ and a cancer risk of 1 in 100,000. Convincing evidence was obtained from a multitude of studies that bromate induces oxidative DNA damage and acts as a clastogen in vitro and in vivo. Since statistical modeling of the available genotoxicity data is compatible with both linear as well as non-linear dose–response relationships, bromate should be conservatively considered to be a non-threshold carcinogen. BMD modeling with model averaging for renal cancer studies (Kurokawa et al., J Natl. Cancer Inst, 1983 and 1986a; DeAngelo et al., Toxicol Pathol 26:587–594, 1998) resulted in a median hBMDL₁₀ of 0.65 mg bromate/kg body weight (bw) per day. Evaluation of different age and activity groups revealed that top athletes had the highest exposure, followed by sport-active children, sport-active adults, infants and toddlers, children and adults. The predominant route of exposure was oral (73–98%) by swallowing water, followed by the dermal route (2–27%), while the inhalation route was insignificant (< 0.5%). Accepting the same risk level for all population groups resulted in different guidance values due to the large variation in exposure. For example, for an additional risk of 1 in 100,000, the bromate concentrations would range between 0.011 for top athletes, 0.015 for sport-active children and 2.1 mg/L for adults. In conclusion, the present study shows that health risks due to bromate exposure by swimming pool water cannot be excluded and that large differences in risk exist depending on the individual swimming habits and water concentrations.

Long-term simulation of lead concentrations in agricultural soils in relation to human adverse health effects

Lead (Pb) exposure of consumers and the environment has been reduced over the past decades. Despite all measures taken, immission of Pb onto agricultural soils still occurs, with fertilizer application, lead shot from hunting activities, and Pb from air deposition representing major sources. Little is known about the intermediate and long-term consequences of these emissions. To gain more insight, we established a mathematical model that considers input from fertilizer, ammunition, deposition from air, uptake of Pb by crops, and wash-out to simulate the resulting Pb concentrations in soil over extended periods. In a further step, human oral exposure by crop-based food was simulated and blood concentrations were derived to estimate the margin of exposure to Pb-induced toxic effects. Simulating current farming scenarios, a new equilibrium concentration of Pb in soil would be established after several centuries. Developmental neurotoxicity represents the most critical toxicological effect of Pb for humans. According to our model, a Pb concentration of ~ 5 mg/kg in agricultural soil leads to an intake of approximately 10 µg Pb per person per day by the consumption of agricultural products, the dose corresponding to the tolerable daily intake (TDI). Therefore, 5 mg Pb/kg represents a critical concentration in soil that should not be exceeded. Starting with a soil concentration of 0.1 mg/kg, the current control level for crop fields, our simulation predicts periods of ~ 50 and ~ 175 years for two Pb immission scenarios for mass of Pb per area and year [scenario 1: ~ 400 g Pb/(ha × a); scenario 2: ~ 175 g Pb/(ha × a)], until the critical concentration of ~ 5 mg/kg Pb in soil would be reached. The two scenarios, which differ in their Pb input via fertilizer, represent relatively high but not unrealistic Pb immissions. From these scenarios, we calculated that the annual deposition of Pb onto soil should remain below ~ 100 g/(ha × a) in order not to exceed the critical soil level of 5 mg/kg. We propose as efficient measures to reduce Pb input into agricultural soil to lower the Pb content of compost and to use alternatives to Pb ammunition for hunting.

Critical evaluation of human health risks due to hydraulic fracturing in natural gas and petroleum production

The use of hydraulic fracturing (HF) to extract oil and natural gas has increased, along with intensive discussions on the associated risks to human health. Three technical processes should be differentiated when evaluating human health risks, namely (1) drilling of the borehole, (2) hydraulic stimulation, and (3) gas or oil production. During the drilling phase, emissions such as NOx, NMVOCs (non-methane volatile organic compounds) as precursors for tropospheric ozone formation, and SOx have been shown to be higher compared to the subsequent phases. In relation to hydraulic stimulation, the toxicity of frac fluids is of relevance. More than 1100 compounds have been identified as components. A trend is to use fewer, less hazardous and more biodegradable substances; however, the use of hydrocarbons, such as kerosene and diesel, is still allowed in the USA. Methane in drinking water is of low toxicological relevance but may indicate inadequate integrity of the gas well. There is a great concern regarding the contamination of ground- and surface water during the production phase. Water that flows to the surface from oil and gas wells, so-called 'produced water', represents a mixture of flow-back, the injected frac fluid returning to the surface, and the reservoir water present in natural oil and gas deposits. Among numerous hazardous compounds, produced water may contain bromide, arsenic, strontium, mercury, barium, radioactive isotopes and organic compounds, particularly benzene, toluene, ethylbenzene and xylenes (BTEX). The sewage outflow, even from specialized treatment plants, may still contain critical concentrations of barium, strontium and arsenic. Evidence suggests that the quality of groundwater and surface water may be compromised by disposal of produced water. Particularly critical is the use of produced water for watering of agricultural areas, where persistent compounds may accumulate. Air contamination can occur as a result of several HF-associated activities. In addition to BTEX, 20 HF-associated air contaminants are group 1A or 1B carcinogens according to the IARC. In the U.S., oil and gas production (including conventional production) represents the second largest source of anthropogenic methane emissions. High-quality epidemiological studies are required, especially in light of recent observations of an association between childhood leukemia and multiple myeloma in the neighborhood of oil and gas production sites. In conclusion, (1) strong evidence supports the conclusion that frac fluids can lead to local environmental contamination; (2) while changes in the chemical composition of soil, water and air are likely to occur, the increased levels are still often below threshold values for safety; (3) point source pollution due to poor maintenance of wells and pipelines can be monitored and remedied; (4) risk assessment should be based on both hazard and exposure evaluation; (5) while the concentrations of frac fluid chemicals are low, some are known carcinogens; therefore, thorough, well-designed studies are needed to assess the risk to human health with high certainty; (6) HF can represent a health risk via long-lasting contamination of soil and water, when strict safety measures are not rigorously applied.

Suitability of the Limit Dose in Evaluating Reproductive Toxicity of Substances and Preparations

An oral dose of 1000 mg/kg body weight/day is mentioned in Organisation for Economic Cooperation and Development (OECD) and European Union (EU) guidelines as a default maximum dose in limit tests for studies on reproductive toxicity. This paper investigated whether upper range human exposure data from the workplace are supportive of this limit dose as an upper limit of possible human exposure. To this end, published exposure data as well as data from the database MEGA of the German “Berufsgenossenschaften” were evaluated. These data indicate that exposure concentrations in the range of 500 to 2000 mg/m3 (time-weighted averages) can be considered high human exposures to volatile compounds. Inhalation exposure to aerosols and dermal exposure result in lower dose levels. By applying suitable extrapolation factors, it was concluded that occupational exposures up to 325 mg/m3 can reliably be assessed with limit tests using a dose level of 1000 mg/kg/day. The limit dose has been proposed for use in the EU as a starting point to derive specific concentration limits for hazard classification of preparations containing reproductive toxicants, with the objective to consider the potency of the substances. This analysis shows that for some groups of chemicals, instead of the limit dose, the putative maximum levels of human exposure should be taken into account when deriving concentration limits for the classification of preparations. Furthermore, possible deviations from a linear correlation between concentration in the preparation and exposure should be considered.

Biokinetics of Nanomaterials: the Role of Biopersistence

Nanotechnology risk management strategies and environmental regulations continue to rely on hazard and exposure assessment protocols developed for bulk materials, including larger size particles, while commercial application of nanomaterials (NMs) increases. In order to support and corroborate risk assessment of NMs for workers, consumers, and the environment it is crucial to establish the impact of biopersistence of NMs at realistic doses. In the future, such data will allow a more refined future categorization of NMs. Despite many experiments on NM characterization and numerous in vitro and in vivo studies, several questions remain unanswered including the influence of biopersistence on the toxicity of NMs. It is unclear which criteria to apply to characterize a NM as biopersistent. Detection and quantification of NMs, especially determination of their state, i.e., dissolution, aggregation, and agglomeration within biological matrices and other environments are still challenging tasks; moreover mechanisms of nanoparticle (NP) translocation and persistence remain critical gaps. This review summarizes the current understanding of NM biokinetics focusing on determinants of biopersistence. Thorough particle characterization in different exposure scenarios and biological matrices requires use of suitable analytical methods and is a prerequisite to understand biopersistence and for the development of appropriate dosimetry. Analytical tools that potentially can facilitate elucidation of key NM characteristics, such as ion beam microscopy (IBM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS), are discussed in relation to their potential to advance the understanding of biopersistent NM kinetics. We conclude that a major requirement for future nanosafety research is the development and application of analytical tools to characterize NPs in different exposure scenarios and biological matrices.

Critical evaluation of key evidence on the human health hazards of exposure to bisphenol A

Despite the fact that more than 5000 safety-related studies have been published on bisphenol A (BPA), there seems to be no resolution of the apparently deadlocked controversy as to whether exposure of the general population to BPA causes adverse effects due to its estrogenicity. Therefore, the Advisory Committee of the German Society of Toxicology reviewed the background and cutting-edge topics of this BPA controversy. The current tolerable daily intake value (TDI) of 0.05 mg/kg body weight [bw]/day, derived by the European Food Safety Authority (EFSA), is mainly based on body weight changes in two- and three-generation studies in mice and rats. Recently, these studies and the derivation of the TDI have been criticized. After having carefully considered all arguments, the Committee had to conclude that the criticism was scientifically not justified; moreover, recently published additional data further support the reliability of the two- and three-generation studies demonstrating a lack of estrogen-dependent effects at and below doses on which the current TDI is based. A frequently discussed topic is whether doses below 5 mg/kg bw/day may cause adverse health effects in laboratory animals. Meanwhile, it has become clear that positive results from some explorative studies have not been confirmed in subsequent studies with higher numbers of animals or a priori defined hypotheses. Particularly relevant are some recent studies with negative outcomes that addressed effects of BPA on the brain, behavior, and the prostate in rodents for extrapolation to the human situation. The Committee came to the conclusion that rodent data can well be used as a basis for human risk evaluation. Currently published conjectures that rats are insensitive to estrogens compared to humans can be refuted. Data from toxicokinetics studies show that the half-life of BPA in adult human subjects is less than 2 hours and BPA is completely recovered in urine as BPA-conjugates. Tissue deconjugation of BPA-glucuronide and -sulfate may occur. Because of the extremely low quantities, it is only of minor relevance for BPA toxicity. Biomonitoring studies have been used to estimate human BPA exposure and show that the daily intake of BPA is far below the TDI for the general population. Further topics addressed in this article include reasons why some studies on BPA are not reproducible; the relevance of oral versus non-oral exposure routes; the degree to which newborns are at higher systemic BPA exposure; increased BPA exposure by infusions in intensive care units; mechanisms of action other than estrogen receptor activation; and the current regulatory status in Europe, as well as in the USA, Canada, Japan, New Zealand, and Australia. Overall, the Committee concluded that the current TDI for BPA is adequately justified and that the available evidence indicates that BPA exposure represents no noteworthy risk to the health of the human population, including newborns and babies.

Advanced Thermal Processing of Semiconductor Materials by Flash Lamp Annealing

The use of flash lamp annealing for processing semiconductor materials is outlined. Specific applications include ultra-shallow junction formation and heteroepitaxial growth of improved quality thin films of cubic silicon carbide. It is demonstrated that flash lamp annealing holds great promise as a technique for fabricating novel devices.

Quantification of house dust mite allergens in ambient air

The house dust mites Dermatophagoides pteronyssinus and Dermatophagoides farinae are important sources of indoor allergens. In sensitized patients, house dust mites induce and exacerbate diseases like asthma bronchiale, rhinitis, and conjunctivitis. The most significant exposure of persons occurs overnight in bed and to a lesser extent, during the daytime while performing activities like vacuum cleaning or bed making. In general, house dust mite antigens are quantified in samples of reservoir dust of carpets or beds. Yet, assessing allergens in ambient air would better represent human exposures because inhalation is the main route of uptake, and a close correlation between levels of floor and air antigens has not yet been proved. Unfortunately, because of extremely low airborne particle concentrations, analyses are difficult to perform and depend on sophisticated sampling strategies, as well as on sensitive immunometric detection assays. Using monoclonal immunoassays, house dust mite antigens, quantified in undisturbed conditions in ambient air, are found at pg/m3 levels. The disturbance of reservoir dust by vacuum cleaning or bed making increases the airborne allergen levels up to ng/m3 concentrations. In this review, we discuss the current knowledge regarding the analysis of airborne house dust mites in both undisturbed and disturbed ambient air. The advantages and disadvantages of different sampling strategies are outlined.

Confounding variables in the environmental toxicology of arsenic

Arsenic is one of the most important global environmental toxicants. For example, in regions of West Bengal and Inner Mongolia, more than 100000 persons are chronically exposed to well water often strongly contaminated with As. Unfortunately, a toxicologically safe risk assessment and standard setting, especially for long-term and low-dose exposures to arsenic, is not possible. One reason is that the key mechanism of arsenic's tumorigenicity still is not elucidated. Experimental data indicate that either DNA repair inhibition or DNA methylation status alteration may be causal explanations. Moreover, when comparing epidemiological data, it cannot be ruled out that the susceptibility to arsenic's carcinogenicity may be different between Mexican and Taiwanese people. Some other studies indicate that some Andean populations do not develop skin cancer after long-term exposure to As. It is not known yet how this resistance could be mediated. Finally, the situation is even more complicated when taking into consideration that there are several compounds suspected to modulate the chronic environmental toxicity of arsenic, variables that may either enhance or suppress the in vivo genotoxicity and carcinogenicity of the metalloid. Among them are nutritional factors like selenium and zinc as well as drinking water co-contaminants like antimony. Further, yet unidentified factors influencing the body burden and/or the excretion of arsenic are possibly prevailing: preliminary data from own human biomonitoring studies showed a peaking of As in urine samples of non-exposed people which was not caused by elevated exposure to As through seafood consumption. The relevance of these putative confounding variables cannot be finally evaluated yet. Further experimental as well as epidemiological studies are needed to answer these questions. This would help to conduct a toxicologically improved risk assessment, especially for low-dose and long-term exposures to arsenic.

Studies on the influence of the copper content in the drinking water on the newborn copper burden and transaminases activity

INTRODUCTION

Clinical parameters for the early diagnosis of a potential development of childhood cirrhosis are not available. A cross-section study was performed to investigate whether the serum copper content and the activities of the newborn's glutamic oxalacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) may be associated with the copper contents of the drinking water and/or the maternal serum and thus could serve as early indicator of an elevated health hazard.

MATERIAL AND METHODS

The serum concentration of copper was analyzed in samples of 141 mother-newborn pairs. Additionally, in umbilical cord serum the activities of the transaminases GOT and GPT were determined. Low molecular bound or free copper was quantified in 30 randomly chosen serum filtrates. According to questionnaire data, in 62 of the 141 households the drinking water installations consisted of copper. In these cases, the element was analyzed in drinking water.

RESULTS

The copper content of the drinking water was found ranging between 0.02 and 2.5 mg Cu/l (median 0.22 mg Cu/l), the maternal serum copper content ranged from 770-3720 micrograms Cu/l (median 2275 micrograms Cu/l), the neonatal serum from 220 to 1930 micrograms Cu/l (median 500 micrograms Cu/l), respectively. GOT (6-33 U/l); median 14 U/l) and GPT (3-21 U/l; median 6 U/l) activities could be judged as reference range data. In the statistical analysis, an association between the copper content of the drinking water and the maternal or neonatal serum copper content could not be found. Pearson regression analysis revealed slight, yet significant correlations of the neonatal GOT and GPT activities with the maternal serum copper content (GPT: r2 = 0.06; p < 0.05; GOT: r2 = 0.05; p < 0.05; each n = 139). In addition, the copper content of the mother's serum filtrates was correlated with the newborns' serum filtrates (Spearman: r = 0.61; p < 0.001; n = 30).

CONCLUSIONS

The prenatal copper exposure of the infant could be mainly determined by low molecular or free serum maternal copper, which seems to be able to penetrate the placental barrier easily. The association between maternal serum copper content and neonatal transaminases activity can be judged as clinically not relevant and might be a physiologic response.

Impact of dimethyl sulfoxide and examples of combined genotoxicity in the SOS chromotest

The bacterial SOS chromotest with Escherichia coli PQ37 was used for the assessment of genotoxicity of combined xenobiotic treatments. The modulation of test compound genotoxicity by dimethyl sulfoxide (DMSO), a common solvent for test compounds, was assessed as well. It was shown that DMSO modulated SOS chromotest genotoxicity of several xenobiotics: in comparison to test compound dissolution in water, the commonly used addition of 3.2% (v/v) DMSO as solvent lead to a significant increase in the genotoxicity of K(2)RhCl(5) and beta-propiolactone (BPL). However, the effects of cisplatin decreased significantly when DMSO was added. Thus, albeit DMSO is not genotoxic in this test itself, it can interfere with SOS chromotest responses. Further experiments were performed in the absence of DMSO. BPL and cisplatin in combination showed an over-additive synergism in SOS genotoxicity as well as K(2)RhCl(5) and cisplatin did. Addition of Pd(NH(3))(4)Cl(2) and NaAsO(2), which are non-genotoxic in the SOS chromotest, did not enhance the K(2)RhCl(5)- or BPL-mediated SOS sfiA induction. Nevertheless, at the highest subcytotoxic dose of NaAsO(2) tested (200 microM), a slight yet significant suppression of BPL-mediated SOS genotoxicity was observed. These results confirm that the SOS chromotest is a useful tool for the rapid evaluation of the combined genotoxicity of compound mixtures. However, the use of DMSO as test solvent has to be taken with caution.

Arsenic(III), but not antimony(III), induces DNA-protein crosslinks

Antimony compounds are supposed to resemble to arsenicals in some toxicological features. Comparative investigations with antimony and arsenic were performed to collect data on the genotoxicity of antimony, on which the knowledge is scarce. In comparison to trivalent arsenic, trivalent antimony proved to be five times less cytotoxic in the neutral red assay and one order of magnitude less genotoxic in the cytokinesis-block micronucleus test using V79 Chinese hamster cells. The data obtained in the comet assay showed that the As(III)-mediated generation of DNA-protein crosslinks and DNA strand lesions seem to be two independent processes. In contrast, Sb(III) induced DNA strand lesions but not DNA-protein crosslinks. Further studies will have to investigate whether the genotoxicity of Sb(III) is mediated by an inhibition of DNA repair as it seems to be the case for As(III).

[Drinking water supply with reference to geogenic arsenic contamination]

Geogenic Arsenic in Drinking Water. Drinking water production of surface spring water in southern Lower Saxony (Niedersachsen, Germany) was reduced because of microbiological contaminations and unreliably variable water reserves. Surface spring water in general has a low arsenic content. As a consequence ground water has been increasingly used for drinking water. Thus, high geogenic concentrations of arsenic in the central "Buntsandstein" in southern Lower Saxony caused high arsenic contents in the groundwater. Under the regulation of the German Drinking Water Ordinance (1986) the limit for total arsenic (40 micrograms/l) was exceeded in 2% of 150 fountains, wells and sources in southern Lower Saxony. Because of the well-known cancerogenic potential of arsenic the limit for total arsenic in drinking water was reduced from 40 micrograms/l to 10 micrograms/l suspending the new standard value until January 1996. This regulation based on new calculations revealing a skin cancer risk of roughly 6:10,000 and a mortality risk of roughly 1:10(6) in respect of lifetime in case of arsenic concentrations of 10 micrograms As/l drinking water. After that limit change 40% of 150 wells and sources in southern Lower Saxony exceeded the arsenic limit of 10 micrograms/l drinking water. As a matter of fact, it became necessary for a large number of water supply works to eliminate arsenic from the drinking water by technical means or to dilute drinking water with high concentrations of arsenic.

[Biological monitoring of persons in areas with increased soil mercury, arsenic and antimony content]

Part of the northern Palatinate region in Germany is characterised by elevated levels of mercury, arsenic and antimony in the soil due to the presence of ore sources and former mercury mining activities. In a biomonitoring study, roughly 200 residents of this region were investigated for a putative increased absorption of these elements. Urine and scalp hair samples were examined. The results did not show a correlation between the mercury and antimony contents in the soil of the housing area and those in urine and hair. On the other hand, slightly but presumably non-hazardous, elevated arsenic contents in urine and scalp hair could be correlated to an increased arsenic content in the soil. According to multiple regression analysis this increase also correlated with the consumption of poultry, eggs and vegetables kept and cultivated respectively in grounds contaminated with arsenic. In urine, sex differences could be seen for antimony: male probands showing significantly higher mean urinary antimony levels than female probands. Urinary mercury contents were correlated with the amalgam area. Similarly, scalp hair of men contained significantly higher levels of arsenic and antimony in comparison to women. Mercury contents in scalp hair were correlated with the consumption of seafood. Children aged 2 to 6 years had significantly lower levels of mercury, arsenic and antimony in urine than the adult subjects. Thus, an elevated health hazard to these children by e.g. intake of contaminated soil is not expected.

Heterogeneity of the DNA damage provoked by antimony and arsenic

Data on the mechanism of antimony genotoxicity is scarce. Arsenic and antimony are proposed to share some toxicological features. Thus comparative and combined experiments with As(III) and Sb(III) were performed to gain a deeper knowledge of the mechanism of antimony genotoxicity. Trivalent arsenic proved to be five times more cytotoxic and one order of magnitude more potent in induction of micronuclei in human lymphocytes in vitro than was antimony. Significantly increased micronucleus frequencies were achieved with As(III) at a dose of 0.5 microM and with Sb(III) at a dose of 5 microM. Neither the number of micronuclei induced by As(III) nor by Sb(III) could be suppressed by co-incubation with superoxide dismutase or catalase. This suggests that induction of oxidative stress may not be a crucial step in the mechanism of DNA damage induction by arsenic and antimony. The combined genotoxicity in micronucleus test co-incubation experiments with arsenic and antimony seemed best described by simple additivity. In the single cell gel test with human lymphocytes a significant induction of DNA damage was observed with 0.01 microM As(III) and 5 microM Sb(III). In contrast to Sb(III), As(III) proved to be a very potent inducer of DNA-protein crosslinks. It may be that Sb(III) as well as As(III) causes DNA damage by inhibition of enzymes involved in DNA repair. Further investigations will have to identify the relevant sites of action.

Human biomonitoring of antimony

OBJECTIVES

The aim of the study was to test the suitability of 24-h urine, blood, and scalp-hair samples as surrogates for the determination of internal exposure to antimony in case of a strongly elevated soil contamination with antimony.

METHODS

The bio-monitoring was performed using graphite-furnace atomic absorption spectrometry. Blood and scalp-hair samples were decomposed by microwave digestion.

RESULTS

No elevated content of antimony could be detected in 24-h urine, blood, or scalp-hair samples from the study participants geogenically exposed to antimony. The results did not show a correlation between the antimony contents in the soil of the housing area and those in urine, blood, or hair. Surprisingly, the reference group (n = 47) showed a significantly higher median antimony excretion rate than did the exposed group (n = 89; 1.23 versus 0.60 micrograms Sb/24 h). Additionally, the scalp-hair contents of the reference group were also significantly higher than those of the exposed persons (0.045 versus 0.026 mg Sb/kg). Blood contents of the two study groups were 0.57 and 0.48 microgram Sb/l, respectively. The detection limit for urine and blood was 0.5 microgram Sb/l and that for scalp hair was 0.005 mg Sb/kg. Of all samples of urine, blood, and scalp hair analyzed, 31.2%, 49.3%, and 10.3%, respectively, were below the limit of analytical detection.

CONCLUSIONS

The antimony contents recorded for both study groups in urine, blood, and scalp hair can be judged as being within the normal range. The rate of transfer of antimony from the soil to humans in the exposure case described seemed to be very low. With respect to analytical practicability and validity, urine was the surrogate which deemed most useful for determination of internal exposure to antimony.

Suppression of arsenic-induced chromosome mutagenicity by antimony

Arsenic and antimony are two semimetals sharing some chemical as well as toxicological properties. Both elements are clastogenic but not point mutagenic in their trivalent state of valency. Environmental exposure to arsenic was proven to be associated with increased rates of various types of cancers. Antimony is suspected to be carcinogenic to humans. Arsenic and antimony can be found as environmental co-contaminants resulting in co-exposure to man. However, in most regions where arsenic was found in elevated environmental amounts, it was not investigated whether an additional exposure to antimony was predominating. In this study, the chromosome mutagenicity induced by arsenic(III) was significantly suppressed by antimony(III) in the micronucleus test with V79 cells. The results demonstrate the necessity to identify putative environmental co-contaminations of antimony in the regions contaminated with arsenic and to determine the impact of antimony co-exposure on arsenic genotoxicity and carcinogenicity in man in vivo.

[Mutagenicity of mixtures of halogenated aliphatic hydrocarbons and polycyclic aromatic hydrocarbons in the Ames test with TA98 and TA100]

Within the framework of the assessment of the genotoxic potential of environment samples the Salmonella-microsome-test (Ames-test) is often used as a screening-test. It is one of the most applied biotest systems and possesses a large scientific acceptance. Because most environment samples are mixtures of various substances, possible effects resulting from the combination should be taken into account with regard to the mutagenic potential. In this context we investigated eight polycyclic aromatic hydrocarbons each combined with six halogenated aliphatic hydrocarbons as to their mutagenicity in the Salmonella-microsome-test with TA98 and TA100. For an exogenous metabolizing system, Arochlor 1254 induced rat liver S9-mix was used. Benz-a-pyrene in combination with bromodichloromethane (Ames neg. in TA98 and TA100 +S9) showed an increase in the number of the revertants up to 25% in TA98 and TA100 (+S9). Carbon tetrachloride (Ames neg. in TA98 and TA100 +S9) showed in TA100 (+S9) an increase in the number of the revertants of 18% at most. In the combination 3-methylcholanthrene with dichloromethane the number of revertants in TA98 (+S9) increased by 25% and in TA100 (+S9) by 18%. Hexachloroethane (weakly mutagenic in TA98 +S9) in combination showed in TA98 (+S9) a slightly increased number of revertants with benz-a-pyrene as well with 3-methylcholanthrene. All the other substances tested (chrysene, phenanthrene, anthanthrene, dibenz-a, i-pyrene, triphenylene, fluoranthene) in combination with either tetrachloroethylene or trichloroethene did not cause an increase in mutagenicity.

[Influence of exposure to mercury, arsenic and antimony on body burden--a biomonitoring study]

Part of the northern Palatinate region in Germany is characterized by elevated levels of mercury, arsenic and antimony in the soil due to the presence of ore sources and former mercury mining activities. Today, the region is characterized by housing and agriculture. In a biomonitoring study, 218 residents (age 1-89 years) were investigated for a putatively increased absorption of these elements from the environment. 76 non-exposed subjects (age 2-84 years) of a region in south lower Saxony (Germany) were chosen as a reference group. Urine and scalp hair samples were obtained as surrogates to determine the internal exposures to mercury, arsenic and antimony. In the northern Palatinate subjects slightly, yet presumably not hazardous, elevated arsenic contents in urine and scalp hair could be correlated to an increased arsenic content in the soil. On the other hand, the results did not show a correlation between the mercury and antimony contents in the soil of the housing area and those in urine and hair. Urinary mercury contents were correlated with the total amalgam area in both study groups. Mercury contents in scalp hair and arsenic contents in urine were correlated with the consumption of seafood. Surprisingly, the geogenically non-exposed reference subjects showed significantly higher internal exposures to arsenic and antimony in urine and scalp hair. However, data of both groups correspond to normal range reference data described by others.

Arsenic and antimony: comparative approach on mechanistic toxicology

A chemico-toxicological similarity between arsenic and antimony exists and their toxicology is often seen. Indeed, both elements possess several common properties, e.g. they are clastogenic but not mutagenic in the trivalent state and they have a carcinogenic potential: trivalent arsenicals are known to be human carcinogens and antimony(III) oxide (by inhalation) has been shown to cause lung cancer in female rats. For years, arsenic has been known to be environmentally toxic. Elevated human exposure to this element, mostly caused by the intake of contaminated tap water, is associated with increased incidences of cancer at various sites. It is still not clear how arsenic compounds exert their genotoxic effect. It may be connected with an inhibition of DNA repair or the induction of oxidative stress. Little work has been done on the toxicology of antimony as it is less widely present in the environment. There is evidence that in mammals antimony, unlike arsenic, is not detoxified via methylation but it still remains unclear what mechanism is responsible for antimony's genotoxicity. In general, there is little information known about this element to accurately determine its impact on human health. Thus, the aim of this paper is to review current knowledge for future risk assessment and further scientific work.

Comparative and environmental genotoxicity of antimony and arsenic

Antimony and arsenic compounds are known to have a genotoxic potential. Soil contamination with these elements can be due to the presence of natural ore sources of fahlore (gray copper). As a result, human and animal populations may be highly exposed. The sister chromatid exchange (SCE) test is an adequate tool for the sensitive detection of antimony and arsenic genotoxicity. We used this assay to investigate the coergism of the two elements in vitro to gain data for the assessment of a putative risk from coexposure. The combinative effect of antimony and arsenic in the SCE test appeared subadditive. Additionally, the SCE served to determine the genotoxic potential in extracts of contaminated fahlore soil samples gained under mildly acidic conditions. The genotoxicity observed was very low because antimony and arsenic predominated in the pentavalent, non-genotoxic state, but, the partial antagonism observed in the in vitro experiments could be an additional explanation for the low genotoxicity.

[Establishment of a method for determining the association between Legionella sp. and Amoeba sp. using polymerase chain reaction]

With two pairs of primers for the amplification of the MIP- (macrophage infectivity potentiator) and the 5S rDNA-fragment, it was possible to establish a DNA extraction and a PCR method for the detection of Legionella sp. in water-samples and, after cultivation, in Amoeba sp. Therefore, water-samples from a warm water-system in a hospital were taken. In all samples, legionellae were detected by the PCR method and identified by cultivation and a direct immunofluorescence-method as L. pneumophila (serogroup 1). Legionellae and amoebae of the same water sample were cocultured. Legionellae were also adherent at the outer-membrane. To separate the amoebae from the legionellae, the amoebae were sedimented selectively by centrifugation at 200 x g. This washing procedure had to be repeated seven times in order to eliminate the extraamoebale legionellae for sure. After DNA-extraction of water samples and heat treatment of the intraamoebale legionellae respectively, the amplification was performed with the MIP- and 5S rDNA-primers. In 14 of 16 cocultivations growth of legionellae was found. This result and the detection of legionellae and amoebae in the same water samples suggest that an infection of amoebae may also take place in the water system of the hospital. This is important for the disinfection as a procedure to eliminate legionellae, since intraamoebale bacteria are more resistant to environmental manipulation. Because in two of the cocultivations no growth of legionellae in amoebae was found, it can be assumed that only specific subtypes of legionellae can infect amoebae species.

Genotoxicity of platinum and palladium compounds in human and bacterial cells

Platinum and palladium belong to the group of platinum elements and thus share many chemical properties. Platinum coordination complexes are known to be carcinogenic and genotoxic in mammalian and bacterial cells. However, little is known about palladium genotoxicity. This study compares and evaluates the genotoxic potential of selected platinum and palladium metal salts in mammalian and bacterial cells using the cytokinesis-block micronucleus test (MNT) with human lymphocytes and the bacterial SOS chromotest. Carboplatin, cisplatin(II), transplantin(II), PtCl4(IV), and K2PtCl4(II) caused a significantly elevated genotoxicity in the MNT and the SOS chromotest. The platinum compounds PtCl2(II) and K2PtCl6(IV), and the divalent palladium salts PdCl2(II), K2PdCl4(II), Pd(NH3)2J2(II), Pd(NH3)4Cl2(II), and transpalladium(II) were not genotoxic in the MNT nor in the SOS chromotest. Therefore, evidence for palladium genotoxicity seems to be low in mammalian and bacterial cells.

Genotoxicity of selected metal compounds in the SOS chromotest

Knowledge concerning the genotoxicity of inorganic metal compounds in the SOS chromotest is limited. Up to now, only Cr(VI), Sn(II) and the platinum antitumor compound cisplatin(II) were shown to be genotoxic in this test system. However, for Cr(VI) and Sn(II), a positive reaction could only be achieved in cytotoxic dose ranges. The aim of the present study was to provide additional data concerning metal salt genotoxicity in the SOS chromotest. Therefore, 14 metal/metalloid salt compounds of platinum, palladium, rhodium, arsenic, antimony and chromium were tested. Four platinum salts, K2PtCl4, cis-Pt(NH3)2Cl2 (cisplatin), trans-Pt(NH3)2Cl2 (transplatin) and PtCl4 as well as two rhodium compounds tested, K2RhCl5 and (NH4)3RhCl6, could be shown to be genotoxic in the chromotest using the tester strain Escherichia coli PQ37. A moderate genotoxicity was shown by the two Cr(VI) compounds K2CrO4 and K2Cr2O7. All palladium compounds and all the other metal salts tested were unable to induce a significant SOS response.

In vivo genotoxicity of selected herbicides in the mouse bone-marrow micronucleus test

The herbicides alachlor, atrazine, terbuthylazine, gluphosinate-ammonium, isoproturon, pendimethaline and trifluralin were tested for genotoxicity in the mouse bone-marrow micronucleus test (MNT). Both atrazine and trifluraline caused a significant increase in the number of micronuclei at doses of 1,400 mg/kg body weight in female mice only. Alachlor, terbuthylazine, gluphosinate-ammonium, isoproturon and pendimethaline did not have any genotoxic effect in the mouse bone-marrow micronucleus test in either female or male animals.

Genotoxicity of selected pesticides in the mouse bone-marrow micronucleus test and in the sister-chromatid exchange test with human lymphocytes in vitro

Selected pesticides (aldicarb, 1,3-dichloropropene, methidathion, parathion, triadimefon, vinclozolin) were tested for their clastogenic and aneugenic activities in the mouse bone-marrow micronucleus (MN) test in vivo and for their sister-chromatid exchange-inducing activities in human lymphocytes in vitro in the presence and absence of an exogenous metabolizing system from rat-liver S9. 1,3-Dichloropropene significantly increased the frequencies of micronucleated polychromatic erythrocytes (PCE) in bone-marrow cells of female mice from 3.3 MN/1000 PCE to 15.3 MN/1000 PCE (187 mg per kg body weight). 1,3-Dichloropropene (100 microM) induced 16.0 SCE/metaphase after 24 h of incubation as compared with the basal rate of 11.2 SCE/metaphase (-S9) and of 15.4 SCE/metaphase as compared with 10.5 SCE/metaphase of the control (+S9). These values were statistically significantly different from each other. The other pesticides tested did neither increase the rate of micronuclei significantly in polychromatic erythrocytes in male nor in female animals. Aldicarb and methidathion induced a significant increase in SCEs in human lymphocytes in vitro only without the metabolic activating system: aldicarb, 5 microM, 24 h incubation: 15.5 SCE/metaphase; control: 12.6 SCE/metaphase; methidathion, 100 microM, 24 h incubation: 15.8 SCE/metaphase, control: 11.1 SCE/metaphase. Parathion, triadimefon and vinclozolin did not have any SCE-inducing effects.

[Influence of chewing gum consumption and dental contact of amalgam fillings to different metal restorations on urine mercury content]

It had been shown previously by various authors that contact of amalgam fillings to metal fillings of different type can increase the electrochemically caused amalgam corrosion in vitro thus leading to an elevated release of mercury. So it was recommended to renounce of a dental contact of amalgam to metal fillings of other type. One aim of the present study was to evaluate possible influences of this contact in vivo on the urinary mercury contents in human volunteers. Neither approximal nor occlusal contacts had any influence on the urinary mercury excretion in comparison to a reference group with similar amalgam status. Furthermore, the influence of gum chewing on urinary mercury levels was taken into account. It could be shown that the consumption of chewing gum resulted in a significantly higher mean urinary mercury content in probands with amalgam fillings in comparison to people with similar amalgam status (gum chewers: 1.36 Hg/24 h vs. non-chewers 0.70 microgram Hg/24 h). Thus, gum chewing has to be considered as important parameter of influence on the urinary mercury levels of people with amalgam fillings.

Assessment of a possible genotoxic environmental risk in sheep bred on grounds with strongly elevated contents of mercury, arsenic and antimony

A part of Northern Palatinate country (Germany) was formerly influenced by mercury mining. Today, in many cases agricultural and housing areas are placed onto or near to former dump grounds of rubble. In the soil of these areas the concentration of mercury, arsenic and antimony was found ranging from basic natural contents up to strongly elevated levels. In a biomonitoring project, sheep bred on grounds contaminated with mercury (range 1-435 mg Hg/kg dry matter), arsenic (range 17-147 mg As/kg dry matter) and antimony (range 2-15 mg Sb/kg dry matter) were taken as example on the uptake of these elements from the environment and for possible effects of this exposure. Significantly elevated mercury levels were found in wool of one collective of exposed sheep (0.107 mg/kg mean vs. 0.048 mg/kg mean, p < 0.001, U-test). Surprisingly, the arsenic content of wool taken from sheep bred in the urban referential area was approx. 10 times higher than that of the sheep bred on the grounds contaminated with arsenic (0.57 mg/kg mean vs. 0.051 mg/kg mean, p < 0.001, U-test). In general, element concentrations in the examined blood samples were low and the differences between the collectives were small: mercury was found in concentrations ranging from 0.9 microgram/l up to 2.0 micrograms/l (means), arsenic and antimony were generally found in concentrations below 1 microgram/l. Neither in the alkaline elution technique nor in the sister chromatid exchange (SCE) analysis significant increases in the rate of DNA-damaging effects between the different sheep collectives were detected. This indicates that the transfer rate of genotoxic compounds of mercury, arsenic or antimony from the environment is too low to register effects with AFE and SCE although the soil was highly contaminated.

Isolation and characterization of a cDNA encoding rat liver cytosolic epoxide hydrolase and its functional expression in Escherichia coli

A cDNA of 1992 base pairs encoding the complete rat liver cytosolic epoxide hydrolase has been isolated using a polymerase chain reaction-derived DNA fragment (Arand, M., Knehr, M., Thomas, H., Zeller, H. D., and Oesch, F. (1991) FEBS Lett. 294, 19-22) known to represent the 3'-end of the cytosolic epoxide hydrolase mRNA. Sequence analysis revealed an open reading frame of 1662 nucleotides corresponding to 554 amino acids (M(r) = 62,268). The DNA sequence obtained did not display significant homology to the sequences of microsomal epoxide hydrolase or leukotriene A4 hydrolase or to any other DNA included in the EMBL Data Bank (release 32). On Northern blotting of rat liver RNA, a single mRNA species was detected that was strongly induced on treatment of the animal with fenofibrate, a potent peroxisome proliferator. The most significant structure of the deduced protein is a modified peroxisomal targeting signal (Ser-Lys-Ile) at the carboxyl terminus that is regarded to be responsible for the unusual dual localization of the cytosolic epoxide hydrolase in peroxisomes as well as in the cytosol. In addition, a leucine zipper-like motif was identified at the amino terminus. Its possible implication for the observed dimeric structure of cytosolic epoxide hydrolase is discussed. The isolated cDNA was expressed in bacteria to yield a catalytically active enzyme. Specific activity of the crude lysate obtained exceeded that of rat liver cytosols from maximally induced animals by a factor of 8.

Characterization of carbonyl reducing activity in continuous cell lines of human and rodent origin

Carbonyl reduction was investigated in the continuous cell lines V79, NCI-H322 and C2REV7 by using the ketone compound metyrapone as a substrate. Metyrapone reducing enzymes were characterized by evaluating the cosubstrate requirement and by testing the sensitivity of this reaction to specific inhibitors. All cell lines were found to produce metyrapol at a linear rate over a time course of at least 48 hr, when tested in cultured monolayers. In general, cytosolic metyrapone reduction exceeds microsomal activity several-fold in all three cell lines. Quercitrin turned out to be the strongest inhibitor in all fractions, except in NCI-H322 microsomes where it had no effect. Consequently, carbonyl reductase is suspected to be responsible for metyrapone reduction in the cytosol and microsomes of V79 and C2REV7 cells as well as in the cytosol of NCI-H322 cells. Simultaneous sensitivity towards quercitrin, dicoumarol, indomethacin and 5 alpha-dihydrotestosterone in some cases points to the existence of different isozymes of carbonyl reductase. In NCI-H322 microsomes only dicoumarol and indomethacin decrease metyrapol formation, thus pointing to an isozyme of NAD(P)H:quinone-oxidoreductase. Concerning cosubstrate requirements metyrapone reducing enzymes show a strong preference for NADPH, thus confirming the involvement of carbonyl reductase in this reaction. In conclusion, carbonyl reduction of metyrapone in continuous cell lines is mediated by carbonyl reductases due to the common sensitivity towards the diagnostic inhibitor quercitrin and due to the strong preference for NADPH as cosubstrate. According to its maintenance in permanent cell lines carbonyl reductase seems to be an essential and constitutive enzyme, which probably fills an important role in normal cell physiology.

Induction of the peroxisome proliferator activated receptor by fenofibrate in rat liver

The process of peroxisome proliferation in rodent liver by hypolipidemic compounds and related substances has recently been shown to be receptor-mediated. In the present study, we have examined the effect of oral administration of the strong peroxisome proliferator fenofibrate on the hepatic expression level of the peroxisome proliferator activated receptor (PPAR) in rats. Immunoblots of rat liver cytosols and nuclear extracts using antibodies raised against recombinant PPAR/beta-galactosidase fusion proteins revealed a pronounced increase in the amount of PPAR protein in response to fenofibrate treatment. This induction could also be confirmed at the level of RNA by Northern blotting. A time-course investigation showed a delayed accumulation of mRNA in response to the treatment, starting on day 2 after a latency period of at least one day. Thus, induction of the PPAR as a response to peroxisome proliferators represents one important dimension of the pleiotropic effects of peroxisome proliferators.

Carbonyl reduction of metyrapone in human liver

Carbonyl reduction was investigated in cytosolic and microsomal fractions of human liver using the ketone metyrapone as a substrate. The cytosolic enzyme has a stronger preference for NADPH over NADH than the microsomal enzyme: the former shows only 14% of the NADPH-supported activity while the latter exhibits 36% activity with NADH. Barbitone and quercitrin, the classic inhibitors of carbonyl reductases, do not affect metyrapone reduction in either fraction. Dicumarol and indomethacin, the specific inhibitors of NAD(P)H: quinone-oxidoreductase and dihydrodiol dehydrogenase, respectively, only slightly decreased metyrapol formation. In contrast, 5 alpha-dihydrotestosterone, the active form of the androgen steroid testosterone, inhibited metyrapone reduction very strongly in the microsomal fractions and is postulated to be the physiological substrate of the enzyme. This resembles the situation in mouse liver [E. Maser and K. J. Netter, Biochem Pharmacol 38: 3049-3054, 1989] where microsomal metyrapone reductase was inhibited by steroids and the purified enzyme was demonstrated to mediate androsterone oxidation. Immunoblot analysis revealed antigenic cross-reaction of antibodies against the 34 kDa metyrapone reductase from mouse liver microsomes with the homologous protein in human liver microsomes pointing to structural homologies between the respective enzymes of the two species. These results--together with previous findings, which have shown that there exist functional as well as structural relationships between microsomal mouse liver metyrapone reductase and 3 alpha-hydroxysteroid dehydrogenase from Pseudomonas testosteroni [E. Maser, U. Oppermann and K. J. Netter, Eur J Pharmacol 183:1366, 1990]--suggest that metyrapone reduction in human liver microsomes might be catalysed by a microsomal hydroxysteroid dehydrogenase.

The occurrence of carbonyl reduction in continuous cell lines emphasizes the essentiality of this metabolic pathway

Using the ketone compound metyrapone (MPON) as a substrate for carbonyl reduction it has been verified for the first time that various permanent cell lines in culture express carbonyl reducing activity. This is even true for the dedifferentiated and fibroblastoid cell line V79, emphasizing the essentiality of this metabolic pathway. MPON reducing enzyme activities are located in the endoplasmic reticulum as well as in the cytoplasm of the cells. Compared to MPON-reductase in rat liver microsomes, no immunological homology to microsomal C2REV7 rat liver hepatoma cell MPON-reductase could be detected, indicating differences in antigenic determinants between the enzymes of the solid organ and respective cells in continuous culture.