Alkylation of metals and the activity of metal‐alkyls†

The biochemical basis for resistance to metal ion toxicity is emerging though it is complicated by the different resistance mechanisms. Several strategies for resistance to toxic metal ions have been identified:

1. The development of energy driven efflux pumps which keep toxic element levels low in the interior of the cell. Such mechanisms have been described for Cd(II) and As(V).

2. Oxidation (e.g. AsO^2‐ to AsO₄ ^3‐) or reduction (e.g. Hg²⁺ to Hg⁰) can enzymatically and intracellularly convert a more toxic form of an element to a less toxic form.

3. The biosynthesis of intracellular polymers which serve as traps for the removal of metal ions from solution such as traps have been described for cadmium, calcium, nickel and copper.

4. The binding of metal ions to cell surfaces.

5. The precipitation of insoluble metal complexes (e.g. metal sulfides and metal oxides) at cell surfaces.

6. Biomethylation and transport through cell‐membranes by diffusion controlled processes.

In this short review I shall discuss the implications of biomethylation as a detoxification mechanism for microorganisms as well as for certain higher organisms.     

Comments on the Carcinogenicity and Mutagenicity of metals and their compounds†

The carcinogenicity of metals has received extensive study, both epidemiologically and in the laboratory. These have included case reports of occasional human occurrence or clusters of cancer cases as well as extensive epidemiologic studies; in addition, there has been significant laboratory research on the whole animals and in vitro systems. This body of information will be examined selectively.

I will not in this paper attempt a comprehensive review of the mutagenicity and carcinogenicity of metals and their compounds. Rather, I will attempt to set forth some historical perspectives, and to comment on some current gaps and needs.

Other papers in this workshop have presented thorough and very current reviews of most of the topics briefly noted in this presentation and do not require repetition here.

The cancer issue has been studied and reported on far more extensively than that relating to heritable mutations. There has been in recent years increasing interest in the use of short term tests for mutagenicity and cell transformation. These, however, are primarily with respect to their relationship to cancer production rather than to germ cell injury. Interest in cancer from metal compounds goes back a long time; in fact, one of the earliest reports was on the carcinogenicity of arsenic not many decades after the pioneering report of Sir Perceval Pott on cancer in chimney sweeps. Since then cancer has been definitely associated in humans with chromium compounds, nickel, and with less assurance but probably definitely with beryllium and cadmium. The confirmation of these findings in laboratory animals has been uneven. In the case of arsenic, for example, there has been only limited success in the production of cancer in laboratory animals with arsenic.

Many other metals have been found in laboratory studies to produce cancer, although with most of these, evidence of production of cancer in humans is either absent or extremely uncertain.

The extensive body of recent information relating to the testing of metals with a variety of short term tests will be briefly reviewed.     

The application of analytical techniques to the understanding of chemical processes occurring in the atmosphere†

The science of atmospheric chemistry has expanded enormously over the last decade. In the stratosphere it has become apparent that small traces of a number of gases can perturb the earth's ozone layer. In the troposphere it is now realised that a general oxidation process is occurring which involves several free radicals and a large number of stable gaseous molecules containing the elements H, C, N, O, S, P, F, Cl, Br and I. In areas close to centres of large population this leads to the phenomenon of photochemical smog and in more remote areas it leads to excess acidity in rainwater.

In order to gain information on these problems and understand the underlying causes, many new analytical techniques have been developed. These are based mostly on chemilu‐minescence, laser spectroscopy, gas chromatography and mass spectrometry. Some examples of the application of these techniques will be given with emphasis placed on the role of GC/MS (gas chromatography combined with mass spectrometry).     

The cytotoxicity of nici2 for mammalian cells in culture†

The effects of NiCl₂ were studied in two human cell lines, HeLa and diploid embryonic fibroblasts as well as in V79 Chinese hamster cells and in L‐A mouse fibroblasts. NiCl₂ produces a dose‐dependent depression of proliferation, mitotic rate, and viability, accompanied by an increasing release of lactic dehydrogenase and stimulation of lactic acid production. The plating efficiency is reduced, as are DNA and protein synthesis and, to a lesser degree, RNA synthesis.

The cytotoxicity of NiCl₂ is comparable in degree to those of PbCl₂ and MnCl₂, but is weaker than those of HgCl₂ and CdCl₂. However, the different sensitivities of different cell lines must also be considered.

NiCl₂ effects are more severe in serum‐free medium than in medium containing serum or serum albumin indicating that serum constituents, notably albumin, bind the metal effectively and inhibit cellular uptake; this confirms earlier reports on the serum binding and slow uptake of NiCl₂.

Synchronized cells are most sensitive in the Gl and early S phases of the cell cycle. In the Painter test the depression of DNA synthesis persists following cessation of exposure to NiCI₂. These findings contribute an explanation for the known genotoxic effects of nickel.     

Interrelation of Cd‐lon concentrations and the growth and activities of microorganisms in two growth media†

Partitioning of native or anthropogenic heavy metals in solid and solution phases of soil is a result of network of several physico‐chemical reactions. The attainment of equilibrium between two phases is also regulated by biochemical processes. For practical purposes, the bioavailability of metal present in soil is predominantly regulated by the soil solution phase which is in dynamic equilibrium with the solid phase. The results of a model laboratory and greenhouse growth experiments have been used to investigate the effect of Cd‐ion concentrations (either in soil solution or in nutrient solution) on the growth and activities of microorganisms. The soil solution has been simulated by preparing a suspension of soil with 0.1 M NaNO₃ (1: 2.5) equilibrated for two hours. Important conclusions are as follows:

Increase in Cd‐ion concentration in soil solution or in nutrient solution induces corresponding adverse effect on the growth and activities of microorganisms. Thus, it seems that Cd‐ion concentration is a more sensitive indicator for assessing the effect of metal pollution upon the growth and activities of soil microorganisms in comparison to total Cd contents.

During active microbial growth phase, a large part of the organically bound Cd was released in the soil solution which is largely bioavailable. This process is termed as mobilisation. There was momentary increase of Cd‐ion concentration in soil solution which intoxicated the growing organisms. After this stage, the Cd ions from the solution phase were removed by the newly formed solid phase (nonviable biomass) and were transformed in non‐available form. This process is termed as immobilisation.

The consequences and importance of these results for practical agriculture and in deciding the limits or guidelines on the maximum tolerable metal load in soils are discussed.     

Effects of the Ellagic acid on the N‐Acetyltransferase activity and Acetylation of 2‐aminofluorene in the rat

The effects of the ellagic acid on the in vitro and in vivo acetylation of 2‐aminofluorene were investigated in male Sprague‐Dawley rats. For in vitro examination, cytosols with or without ellagic acid co‐treatment showed different percentage of 2‐aminofluorene acetylation. For in vivo examination, pre‐treatment of male rats with ellagic acid (10 mg/kg) 24h prior to the administration of 2‐aminofluorene (50 mg/kg) resulted in a 26% and 29%, respectively, decrease in the urinary and fecal recovery of N‐acetyl‐2‐aminofluorene, and a 37% decrease in the metabolic clearance of 2‐aminofluorene to N‐acetyl‐2‐aminofluorene. This is the first demonstration that ellagic acid decrease the N‐acetylation of carcinogens in vitro and in vivo.     

Potentiometric techniques applied to the modelling of actinide migration in natural water systems†

The utility of potentiometric techniques applied to environmental problems is discussed. The applicability of this technique to the estimation of thermodynamic quantities important for the modelling of uranium migration in natural waters is demonstrated. An experimental methodology for the determination of the UO₂(s) solubility product and the UO²⁺/U⁴⁺ redox potentials is proposed.     

The effect of cadmium upon the structure of the olfactory nerve in the young pike †

Some recent experiments have shown with autoradiographic methods the axonal transport of cadmium along the olfactory nerve of the salmon trout.² We should determine in our experiments the effect of cadmium upon the olfactory nerve at histological level using optical microscopy technics.     

Cross‐sectional epidemiological study on the lead burden of children and workers in Greece

Exposure of the general population to lead in the environment is mainly caused by motor traffic exhaust and by industrial pollution. The aim of the study in Greece was to assess lead exposure in children living in point source impacted areas (Lavrion and Aspropyrgos‐Eleusis) using the biological monitoring parameter “blood lead concentration”;.

In addition, workers of a lead smelter, a battery plant and an oil refinery were investigated in these areas at the same time.

Five hundred and thirty‐four children and 105 workers took part in this investigation.

The highest blood lead levels (mean: 24.16 μg/100ml; range: 10.40–60.49 μg/100 ml) were found in children living in a 500m‐area around the lead smelter at Lavrion. Blood lead decreases corresponded to the increasing distance from the emitter. Nevertheless the values of children living in a 1500 m distance to the smelter are significantly higher than those of children living next to other kinds of industrial lead sources.

The mean values of the children living in the two industrial towns were manifold higher than those of the control group.

The blood lead levels of the investigated workers did not exceed the German BAT‐value (Biologischer Arbeitsstoff‐Toleranzwert) of 70 μg/100ml.     

Analysis of the cyanotoxins anatoxin-a and microcystins in Lesser Flamingo feathers†

Feathers from carcasses of the Lesser Flamingo (Phoeniconaias minor), which had died after ingesting cyanobacterial toxins (cyanotoxins) contained between 0.02 and 30.0?µg microcystin-LR equivalents per gram of feather according to HPLC and ELISA analysis of feather extracts. Anatoxin-a was detected less frequently in the Lesser Flamingo feathers, up to 0.8?µg anatoxin-a per gram of feather being recorded. When feathers from different body regions were analysed and compared for microcystins and anatoxin-a, wing feathers were found to contain the highest concentrations of these cyanotoxins, the order of concentration and frequency of analytical detection being wing?>?breast?>?head. Consistent with the presence of the microcystins and anatoxin-a in gut contents and the livers of the dead birds and negligible in vitro adsorption to feathers, the cyanotoxins associated with the feathers of the dead wild flamingos are inferred to be primarily of dietary origin.     

Evaluation of the use of psychometric scales in human–wildlife interaction research to determine attitudes and tolerance toward wildlife

Studies evaluating human–wildlife interactions (HWIs) in a conservation context often include psychometric scales to measure attitudes and tolerance toward wildlife. However, data quality is at risk when such scales are used without appropriate validation or reliability testing, potentially leading to erroneous interpretation or application of findings. We used 2 online databases (ProQuest Psych Info and Web of Science) to identify published HWI studies that included attitude and tolerance. We analyzed these studies to determine the methods used to measure attitudes or tolerance toward predators and other wildlife; determine the proportion of these methods applying psychometric scales; and evaluate the rigor with which the scales were used by examining whether the psychometric properties of validity and reliability were reported. From 2007 to 2017, 114 published studies were identified. Ninety-four (82%) used questionnaires and many of these (53 [56%]) utilized a psychometric scale. Most scales (39 [74%]) had at least 1 test of reliability reported, but reliance on a single test was notable, contrary to recommended practice. Fewer studies (35 [66%]) reported a test of validity, but this was primarily restricted to structural validity rather than more comprehensive testing. Encouragingly, HWI investigators increasingly utilized the necessary psychometric tools for designing and analyzing questionnaire data, but failure to assess the validity or reliability of psychometric scales used in over one-third of published HWI attitude research warrants attention. We advocate incorporation of more robust application of psychometric scales to advance understanding of stakeholder attitudes as they relate to HWI.     

Pollution from polychlorodibenzo‐p‐dioxins and furans: The case of several foundry plants in the Lombardy region

In 1991 a co‐operation between Public Health Office (U.S.S.L.) n° 18 of Brescia and the Chemical Section Laboratories of U.S.S.L. n° 38 of Milan concerning the possible environmental impact of foundry industrial activities performing metallic scraps recovering, has been undertaken.

Soil and surfaces have been classified in conformity with the National Toxicological Consultative Commission (C.C.T.N.) recommendation dated 12/02/1988'; owing to the characteristics of the processed material, besides heavy metals, polychlorodibenzo‐p‐dioxins (PCDDs), polychlorodibenzofurans (PCDFs) and polychlorobiphenyls (PCBs) have been looked for.

The particulate matter collected from the filters positioned over the arc furnaces in 14 foundry plants has been characterized and classified, according both to C.C.T.N.¹ and to the Interministerial Board regulation dated 27/07/1985 for the first application of the Republic President Decree Law (D.P.R.) n° 915/1982, concerning wastes classification, based, in this case, on these toxic chlorinated compounds concentrations. From the very beginning, high levels of PCDDs and PCDFs have been detected, corroborating the very few literature data from foundry plants². The results obtained on 14 different foundries allow us to draw already some information, acceptable from the point of view of the statistical validity, about the pollution produced by this industry.     

Progress of the scientific expedition and research on farmland ecosystem and food security in Qinghai-Tibet Plateau北大核心CSCD

介绍第二次青藏高原综合科学考察研究任务三生态系统与生态安全专题三“农田生态系统与粮食安全”科学考察背景、总体思路、研究内容、研究目标和取得的阶段性进展.该专题针对青藏高原地区农业生产中逐渐出现的局部农田生态系统结构失稳、功能失衡、地力衰退、作物品质下降、农残渐增等问题,在区域尺度上,从耕地肥力和土壤生物、农田植被、农业生产经营管理、作物产量品质和利用、农业气象条件等方面开展科学考察研究,在青藏高原农田生态系统相关生态环境参数的时空特征、分布规律与作物开发利用等考察研究方面取得阶段性重要进展,可为青藏高原农业生态系统可持续经营管理和粮食安全提供数据及科技支撑.(图1参90)     

Voltammetric study on the interaction of the heavy metals Cd(II) and Mn(II) with transfer‐RNA,DNA and other polynucleotides

Small amounts of bivalent cations, usually provided by Mg²⁺, are in the living cell necessary for the biological activity of t‐RNA as these bivalent cations influence the tertiary and secondary structure of this globular polynucleotide.

In context with the discussed possibility of carcinogenic actions of ingested Cd it is of particular interest to check whether there exist specific strong interactions of this toxic heavy metal with nucleic acids.

Therefore, the binding of the toxic heavy metal ion Cd²⁺ and the essential heavy metal ion Mn²⁺ to t‐RNA and for comparison to DNA and the polynucleotides poly‐U, poly‐A and poly‐A‐poly‐U has been studied. Free metal ion concentrations have been determined by differential pulse polararography. Association constants and the number of binding sites have been evaluated by the Scatchard method and alternatively according to a simple electrostatic model of the polyelectrolytes. With the Scatchard method for t‐RNA and all polynucleotides with helical structure two different binding sites of different strength are observed. Those with higher association constants are assigned to the helical parts of t‐RNA. Interaction sites with low association constants correspond to the parts with no ordered tertiary structure, as their exclusive occurrence for poly‐U, having a completely stochastic coil structure, reflects. The values of the association constants for the stronger and weaker association sites are in the respective polynucleotides for both investigated bivalent metal ions of comparable magnitude. This emphasizes that the interaction is essentially of electrostatic nature and depends primarily on the charge of the interacting species.

Thus the specific strong interaction of Cd by the intercalation into the tertiary structure of nucleic acids or by chelation of their base units can be ruled out as one possibility for carcinogenity of Cd.

Moreover, under physiological conditions the high excess of competitive Mg²⁺ will suppress the interaction of Cd based on electrostatic forces.     

Assessing the fractionation and bioavailability of heavy metals in soil–rice system and the associated health risk

Environmental Geochemistry and Health - This study developed a method to build relationships between chemical fractionations of heavy metals in soils and their accumulations in rice and estimate...     

Source and Distribution of Heavy Metals in Food†

Diet is the major route of exposure to contaminants, therefore food monitoring programs are essential to estimate the degree of human risk. We present a study undertaken in Austria dealing with the total uptake of mercury, cadmium, arsenic and lead. The dates were calculated from diet as well as from commercial food. Higher contaminated foodstuffs are registered and a comparison was made between body burden of babies and adults on the basis of bodyweight. It was pointed out, that cooked or washed food ready to eat has a lower burden of lead and cadmium than non prepared food due to household processing, which may decontaminate food to some extent’ Arsenic content was not reduced, because it is bound chemically and not primarily deposited on the surface of food such as in the case of lead. It was mentioned that the type of compound plays an important role in the assessment of action of those elements on humans.

Their biological activity is not necessarily related to their concentration in food. As in the case of selenium and chromium one has to take into consideration that there is a narrow range between benefit and harm, toxicity, and minor supply.

Therefore we conclude, that due to interactions of elements, their different biological activity and due to the difference of compounds present in food, we have to relativate the terms toxicity and essentiality. Then we can get a more profound insight into the problems of trace elements in food.     

Mutagenic activity of transition‐metal complexes: Relation structure‐mutagenic and antibacterial activity for some Pd(II), Pt(II) and Rh(I) complexes†

The inhibitory and mutagenic action of some Pd(II), Pt(II) and Rh(I) complexes towards various bacterial strains has been evaluated, and some correlations have been found between the chemical behaviour of the complexes and their selective biological activity: most of the complexes cause only a DNA damage repaired by the excision repair system. Particularly, the Rh(I) complexes used in this work show selective antibacterial effects on defective but no effect on wild‐type strains.     

Project Tocoen. the fate of selected pollutants in the environment. Part XIX. the phytotoxicity of organic and inorganic pollutants‐cadmium. The effect of cadmium on the growth of germinating maize plants

The effect of increasing cadmium concentration (10, 100 and 1000 μmol dm^‐3) on the growth, leaf area, content of assimilation pigments, cadmium content and the regulatory ability of the tissue of maize plants was investigated.

The results obtained document, already after 6 days, a significant decrease of dry weight, reduction of leaf area, chlorophyll a and b as well as carotenoids in plants grown in the nutrient solution containing 1000 μmol dm ^‐3 of cadmium. A highly significant inhibition of growth, leaf area and assimilation pigments in plants growing in the nutrient solutions with 100 and 10 μmol dm^‐3 of cadmium was registered after 17 days of cultivation. In plants growing in the nutrient solution containing 100 μmol dm^‐3 of cadmium a demonstrable reduction of the content of assimilation pigments was registered after 11 days of culture.

With increasing cadmium concentration in the nutrient solution as well as in the plant tissue after 6 and 17 days of culture both the range of the regulatory zone and the extent of optimum pH increased into the acid region. The pH values of the isoelectric point decreased with increasing cadmium content in the solution.     

Planning for the monitoring of pollutants from non‐stationary combustion sources†

The most important constituents of traffic exhaust are carbon monoxide, nitrogen oxides, volatile organic compounds, polycyclic hydrocarbons and lead. Satisfactory analytical methods are available for measuring these compounds, but the required expenditure in their application to air pollution studies is quite different. Due to correlations between the concentrations of several exhaust components in road air conclusions regarding the expected level of some substances can be drawn by measurement of another emitted compound. But the selection of indicator compounds must be made under the aspect of the source‐specific relationship of emitted substances. The temporal and spatial distribution of air pollutants in street air is affected by traffic emissions more than by meteorological conditions. “Fingerprints”; of typical organic gaseous components of traffic exhaust also were found in residential areas.