Hemda Garelick

Arsenic Pollution Sources

Arsenic is a widely dispersed element in the Earths crust and exists at an average concentration of approximately 5 mg/kg. There are many possible routes of human exposure to arsenic from both natural and anthropogenic sources. Arsenic occurs as a constituent in more than 200 minerals, although it primarily exists as arsenopyrite and as a constituent in several other sulfide minerals. The introduction of arsenic into drinking water can occur as a result of its natural geological presence in local bedrock. Arsenic-containing bedrock formations of this sort are known in Bangladesh, West Bengal (India), and regions of China, and many cases of endemic contamination by arsenic with serious consequences to human health are known from these areas. Significant natural contamination of surface waters and soil can arise when arsenic-rich geothermal fluids come into contact with surface waters. When humans are implicated in causing or exacerbating arsenic pollution, the cause can almost always be traced to mining or mining-related activities. Arsenic exists in many oxidation states, with arsenic (III) and (V) being the most common forms. Similar to many metalloids, the prevalence of particular species of arsenic depends greatly on the pH and redox conditions of the matrix in which it exists. Speciation is also important in determining the toxicity of arsenic. Arsenic minerals exist in the environment principally as sulfides, oxides, and phosphates. In igneous rocks, only those of volcanic origin are implicated in high aqueous arsenic concentrations. Sedimentary rocks tend not to bear high arsenic loads, and common matrices such as sands and sandstones contain lower concentrations owing to the dominance of quartz and feldspars. Groundwater contamination by arsenic arises from sources of arsenopyrite, base metal sulfides, realgar and orpiment, arsenic-rich pyrite, and iron oxyhydroxide. Mechanisms by which arsenic is released from minerals are varied and are accounted for by many (bio)geochemical processes: oxidation of arsenic-bearing sulfides, desorption from oxides and hydroxides, reductive dissolution, evaporative concentration, leaching from sulfides by carbonate, and microbial mobilization. Arsenic enrichment also takes place in geothermally active areas; surface waters are more susceptible than groundwater to contamination in the vicinity of such geothermal systems, and evidence suggests that increased use of geothermal power may elevate risks of arsenic exposure in affected areas. Past and current mining activities continue to provide sources of environmental contamination by arsenic. Because gold- and arsenic-bearing minerals coexist, there is a hazard of mobilizing arsenic during gold mining activities. The Ashanti region of central Ghana currently faces this as a real risk. Historical arsenic contamination exists in Cornwall, UK; an example of a recent arsenic pollution event is that of Ron Phibun town in southern Thailand, where arsenic-related human health effects have been reported. Other important sources of arsenic exposure include coal burning in Slovakia, Turkey, and the Guizhou Province of China; use of arsenic as pesticides in Australia, New Zealand, and the US; and consumption of contaminated foodstuffs (China) and exposure to wood preserving arsenicals (Europe and North America).

A brief multi-disciplinary review on antimicrobial resistance in medicine and its linkage to the global environmental microbiota

The discovery and introduction of antimicrobial agents to clinical medicine was one of the greatest medical triumphs of the 20th century that revolutionized the treatment of bacterial infections. However, the gradual emergence of populations of antimicrobial-resistant pathogenic bacteria resulting from use, misuse, and abuse of antimicrobials has today become a major global health concern. Antimicrobial resistance (AMR) genes have been suggested to originate from environmental bacteria, as clinically relevant resistance genes have been detected on the chromosome of environmental bacteria. As only a few new antimicrobials have been developed in the last decade, the further evolution of resistance poses a serious threat to public health. Urgent measures are required not only to minimize the use of antimicrobials for prophylactic and therapeutic purposes but also to look for alternative strategies for the control of bacterial infections. This review examines the global picture of antimicrobial resistance, factors that favor its spread, strategies, and limitations for its control and the need for continuous training of all stake-holders i.e., medical, veterinary, public health, and other relevant professionals as well as human consumers, in the appropriate use of antimicrobial drugs.

An investigation into arsenic(V) removal from aqueous solutions by hydroxylapatite and bone-char

Abstract Arsenic(V) removal from aqueous solution following addition of either a mixture of synthetic hydroxylapatite and baryte or bone-char is discussed. Arsenic concentrations of 4, 10 and 100 mg/1 were investigated and additions of 0.2-10g/l of solid (hydroxylapatite, baryte or bone-char) were tested, at an initial pH of either 5 or 7. Although the mixture of hydroxylapatite and baryte had a small influence on arsenic concentrations, bone-char was found to be a very effective sorbing agent for arsenic(V). Packed-column studies to investigate the bone-char capacity, followed by leaching tests were carried out. The capacity of bone-char was found to be superior to that of granular activated carbon. The experiments presented here indicate that the mechanism involved is adsorption rather than co-precipitation.

Consideration of the bioavailability of metal/metalloid species in freshwaters: experiences regarding the implementation of biotic ligand model-based approaches in risk assessment frameworks

After the scientific development of biotic ligand models (BLMs) in recent decades, these models are now considered suitable for implementation in regulatory risk assessment of metals in freshwater bodies. The BLM approach has been described in many peer-reviewed publications, and the original complex BLMs have been applied in prospective risk assessment reports for metals and metal compounds. BLMs are now also recommended as suitable concepts for the site-specific evaluation of monitoring data in the context of the European Water Framework Directive. However, the use is hampered by the data requirements for the original BLMs (about 10 water parameters). Recently, several user-friendly BLM-based bioavailability software tools for assessing the aquatic toxicity of relevant metals (mainly copper, nickel, and zinc) became available. These tools only need a basic set of commonly determined water parameters as input (i.e., pH, hardness, dissolved organic matter, and dissolved metal concentration). Such tools seem appropriate to foster the implementation of routine site-specific water quality assessments. This work aims to review the existing bioavailability-based regulatory approaches and the application of available BLM-based bioavailability tools for this purpose. Advantages and possible drawbacks of these tools (e.g., feasibility, boundaries of validity) are discussed, and recommendations for further implementation are given.

Preparation and immunogenicity of an inactivated hepatitis A vaccine

A hepatitis A vaccine was prepared by formaldehyde inactivation of purified hepatitis A virus (HAV) LSH/S strain grown on human diploid MRC-5 cells. The vaccine was devoid of residual infectivity in vitro and failed to induce in marmoset monkeys any pathological features or variations of haematological and clinical chemistry values. Infectious HAV particles were not detected in faeces and sera of the vaccinated primates by ELISA or after passages in MRC-5 cells. The immunogenicity of the vaccine was evaluated by injecting guinea-pigs with 0.8, 0.2 or 0.05 micrograms of HAV antigen adsorbed onto 0.5 and 1 mg of Al (OH)3 or 0.3 mg of AlPO4. The antibody response, measured by a competitive radioimmunoassay, was dose- and adjuvant-dependent. One injection of 0.2 micrograms of AlPO4-adsorbed HAV antigen induced seroconversion in 100% of animals and high levels of specific and neutralizing serum antibodies. A further increase of antibody titres was observed after the second and third inoculations. These results show that this vaccine formulation is safe and immunogenic in animal models, and suggest that it should be evaluated further by human clinical studies.

Effects of arsenate (As5+) on growth and production of glutathione (GSH) and phytochelatins (PCs) in Chlorella vulgaris

The effect of arsenate (As5+) on growth and chlorophyll a production in Chlorella vulgaris, its removal by C. vulgaris and the role of glutathione (GSH) and phytochelatins (PCs) were investigated.C. vulgaris was tolerant to As5+ at up to 200 mg/L and was capable of consistently removing around 70% of the As5+ present in growth media over a wide range of exposure concentrations. Spectral analysis revealed that PCs and their arsenic-combined complexes were absent, indicating that the high bioaccumulation and tolerance to arsenic observed was not due to intracellular chelation. In contrast, GSH was found in all samples ranging from 0.8 mg/L in the control to 6.5mg/L in media containing 200 mg/L As5+ suggesting that GSH plays a more prominent role in the detoxification of As5+ in C. vulgaris than PC. At concentrations below 100 mg/L cell surface binding and other mechanisms may play the primary role in As5+ detoxification, whereas above this concentration As5+ begins to accumulate inside the algal cells and activates a number of intracellular cell defense mechanisms, such as increased production of GSH.The overall findings complement field studies which suggest C. vulgaris as an increasingly promising low cost As phytoremediation method for developing countries.

Minimum requirements for reporting analytical data for environmental samples.(IUPAC Technical Report).

In view of the significance of environmental analytical data, it is essential that the quality of both sampling strategy and analysis be assured and that procedures used, as well as all relevant additional information, are reported. There is a minimum level of information required in order to guarantee the fitness-for-use of the data. Emanating from discussions on the fundamental problems of the analysis of environmental samples for chemical or biological contaminants, a general guidance is given regarding the minimum information that should be provided to adequately describe the sampling strategy, method of sampling, sample properties, handling between sampling and analysis (including storage conditions, pretreatments, homogenization, subsampling), and the analytical methodology (including calculation and validation procedures). Special attention and specific guidance are given for the environmental compartments soil, pore water, groundwater, inland surface water, sediment, seawater, precipitation water, and air.

CONSTRUCTED WETLAND CONTROL OF BOD LEVELS IN AIRPORT RUNOFF

A surface water treatment system consisting of an aeration reservoir and pond (holding capacities 45,000 and 19,000 m3) and a network of 12 horizontal subsurface flow gravel-filled constructed wetland cells of different sizes (total surface area 2.08 ha) and planted with Phragmites australis, was commissioned at Heathrow Airport, London, United Kingdom, in the winter of 2002. Ongoing monitoring of the treatment system has shown significant reductions in the biochemical oxygen demand (BOD5) throughout the system with levels decreasing by up to 76.7% across the constructed wetland cells following high anti- and de-icing fluid applications. However, continued exposure to BOD5 concentrations exceeding the design target has resulted in anaerobic conditions in the wetland. The addition of nutrients to the treatment system has resulted in improved removal efficiency for elevated BOD5 loadings in the aerated reservoir from 25.5% to 47.5%, The addition of different nutrient dosing regimes to complementary pilot-scale planted and unplanted vertical flow columns showed average but statistically insignificant BOD5 removal percentage increases from 61.9 ± 21.1% to 70.8 ± 26.5%, respectively, in planted columns over a 7-day period. There is an overall improvement in the performance of the system, but operational reviews are continuing.

Quantitative determination of Escherichia coli in water using CHROMagar®E. coli

A new medium, CHROMagar® E. coli (CAEC), containing a combination of X-glucuronide and methyl-glucuronide for the detection of β-glucuronidase activity of Escherichia coli has been evaluated by the membrane filtration (MF) technique n fresh water samples. The CAEC agar was compared with conventional media, mFC agar and mLSB, for the enumeration of faecal coliforms. The variance analysis showed that CAEC was as sensitive as mFC agar and mLSB. A good correlation was found between E. coli versus those from faecal coliforms in the water sampling areas tested. Of 321 presumptively positive E. coli colonies (blue) and 154 presumptively negative E. coli colonies (white), only 8 (2.5%) false positive and 19 (12.4%) false negative colonies were found. Specificity of the CEAC agar in spanish samples was temperature dependent, false negative E. coli colonies occurred less frequently at 37°C (2.3%) than at 44.5°C (18.8%). The results of this study indicate that CAEC agar is efficient for the enumeration of E. coli from a wide range of environmental freshwater samples.

Enzymatic Formulation Capable of Degrading Scrapie Prion under Mild Digestion Conditions

The prion agent is notoriously resistant to common proteases and conventional sterilisation procedures. The current methods known to destroy prion infectivity such as incineration, alkaline and thermal hydrolysis are harsh, destructive, environmentally polluting and potentially hazardous, thus limit their applications for decontamination of delicate medical and laboratory devices, remediation of prion contaminated environment and for processing animal by-products including specified risk materials and carcases. Therefore, an environmentally friendly, non-destructive enzymatic degradation approach is highly desirable. A feather-degrading Bacillus licheniformis N22 keratinase has been isolated which degraded scrapie prion to undetectable level of PrPSc signals as determined by Western Blot analysis. Prion infectivity was verified by ex vivo cell-based assay. An enzymatic formulation combining N22 keratinase and biosurfactant derived from Pseudomonas aeruginosa degraded PrPSc at 65°C in 10 min to undetectable level -. A time-course degradation analysis carried out at 50°C over 2 h revealed the progressive attenuation of PrPSc intensity. Test of residual infectivity by standard cell culture assay confirmed that the enzymatic formulation reduced PrPSc infectivity to undetectable levels as compared to cells challenged with untreated standard scrapie sheep prion (SSBP/1) (p-value = 0.008 at 95% confidence interval). This novel enzymatic formulation has significant potential application for prion decontamination in various environmentally friendly systems under mild treatment conditions.