ObjectiveHexavalent chromate (chromate) in cement is a well-recognised cause of allergic contact dermatitis (ACD). Consequently in January 2005, following European Union legislation (EU Directive ...2003/53/EC), the use or supply of cement containing >2 ppm of chromate was prohibited in the UK (COSHH 2004). This analysis of work-related ill-health surveillance aims to evaluate the effectiveness of this legislation.MethodChanges in the incidence of work-related ACD cases returned to The Health and Occupation Reporting network by dermatologists were analysed taking in to account attribution to chromate and occupation.ResultsThere was a significant decline in the incidence of both ACD attributed to chromate (incidence rate ratio 0.48, 95% CI 0.36 to 0.64) and ACD not-attributed chromate (0.76, 95% CI 0.69 to 0.85) between the time period preceding the EU legislation (2002–2004) and the postlegislation period (2005–2009). However, the decline in ACD attributed to chromate was significantly greater (p=0.006). This decline was further increased in workers potentially exposed to cement (incidence rate ratio 0.37, p=0.001). The majority of the decline in incidence occurred during 2005.ConclusionThe timing of this significant decline in the UK incidence of chromate attributed ACD, and the greater decline in workers potentially exposed to cement strongly suggests that the EU Directive2003/53/EC was successful in reducing exposure to chromate in cement in the UK.
In this study, an electroactive polymer (EAP), poly(2,5-bis(
-methyl-
-hexylamino)phenylene vinylene) (BAM-PPV) was investigated as a potential alternative surface pretreatment for hexavalent ...chromium (Cr(VI))-based aerospace coatings. BAM-PPV was tested as a pretreatment coating on an aerospace aluminum alloy (AA2024-T3) substrate in combination with a non-Cr(VI) epoxy primer and a polyurethane Advanced Performance Coating (APC) topcoat. This testing was undertaken to determine BAM-PPV's adhesion, corrosion-inhibition, compatibility and survivability in laboratory testing and during outdoor field-testing. BAM-PPV showed excellent adhesion and acceptable corrosion performance in laboratory testing. The BAM-PPV aerospace coating system (BAM-PPV, non-Cr(VI) epoxy primer and polyurethane APC topcoat) was field tested for one year on the rear hatch door of the United States Air Force C-5 cargo plane. After one year of field testing there was no evidence of delamination or corrosion of the BAM-PPV aerospace coating system.
In the last years the dental alloy market has undergone dramatic changes for reasons of economy and biocompatibility. Nickel based alloys have become widely used substitute for the much more ...expensive precious metal alloys.
In Europe the prevalence of nickel allergy is 10–15% for female adults and 1–3% for male adults. Despite the restrictions imposed by the EU for the protection of the general population in contact dermatitis, the use of Ni–Cr dental alloys is on the increase. Some questions have to be faced regarding the safety risk of nickel contained in dental alloys.
We have collected based on many EU markets, 8 Ni–Cr dental alloys. Microstructure characterization, corrosion resistance (generalized, crevice and pitting) in saliva and the quantities of cations released in particular nickel and CrVI have been evaluated. We have applied non parametric classification tests (Kendall rank correlation) for all chemical results. Also cytotoxicity tests and an evaluation specific to TNF-alpha have been conducted.
According to the obtained results, it was found that their behavior to corrosion was weak but that nickel release was high. The quantities of nickel released are higher than the limits imposed in the EU concerning contact with the skin or piercing.
Surprisingly the biological tests did not show any cytotoxic effect on Hela and L929 cells or any change in TNF-alpha expression in monocytic cells. The alloys did not show any proinflammatory response in endothelial cells as demonstrated by the absence of ICAM-1 induction.
We note therefore that there is really no direct relationship between the in vitro biological evaluation tests and the physico-chemical characterization of these dental alloys. Clinical and epidemiological studies are required to clarify these aspects.
► Nickel released was higher than the limits imposed in EU in contact with the skin. ► No direct relationship between the biological evaluation and chemical degradation. ► Clinical and epidemiological studies are required to clarify these aspects.
Pure ZnO and composite ZnO-CeO2 coated thin films on titania substrates were prepared using a chelating sol-gel method under controlled conditions to be used in the separation and/or rejection of ...Se(IV) and Cr(VI). XRD and SEM studies confirmed the formation of highly ordered arrays of crystalline wurtzite microstructure with mixed orientation. An increase in average particle size of the prepared membranes from 1.25 to 3 µm with increasing CeO2 percent was observed indicating the vital role of CeO2 as secondary phase in improving the crystallinity of the coated films formed. Detailed study of the separation performance of the selected membranes toward Se(IV)-Cr(VI) was studied. A high separation performance for the different membranes prepared was observed toward Se(IV) with respect to Cr(VI). The polar characteristic of ZnO thin films played an essential role in Se(IV) separation. However, a high permeation flow of Cr(VI) through the membranes was governed by the capillary pressure induced within the porous structure of the membranes.
Hexavalent chromium is a genotoxic human pulmonary carcinogen that elevates DNA oxidation, apparently through the generation of reactive DNA-damaging intermediates including CrV, CrIV and reactive ...oxygen species. We tested the hypothesis that elevation of DNA oxidation may also be through inhibition of the expression of the repair glycosylase for 8-oxo deoxyguanine (hOGG1) in cultured A549 human lung epithelial cells. Treatment with sodium dichromate (0–100 μM, 16 h) resulted in a concentration-dependent decrease in the levels of OGG1 mRNA as measured by both RT–PCR and RNase protection assay. Sodium dichromate at 25 μM and above gave a marked reduction of OGG1 mRNA expression which was not seen at 1 μM and below. No effect on the expression of the apurinic endonuclease hAPE or the house-keeping gene GAPDH was observed at any of the concentrations of sodium dichromate investigated. Treatment of cells with the pro-oxidant H2O2 (0–200 μM) for 16 h had no detectable effect on the levels of OGG1 mRNA or protein expression suggesting that the effect of sodium dichromate is not mediated by H2O2. Western blotting demonstrated that sodium dichromate (100 μM; 16 h and >25 μM; 28 h) markedly reduced levels of OGG1 protein in nuclear cell extracts. Additionally, treatment of cells with sodium dichromate (>25 μM, 28 h) resulted in a concentration-dependent decrease in the ability of nuclear extracts to nick a synthetic oligonucleotide containing 8-oxo deoxyguanine (8-oxo dG). We conclude that the elevation of 8-oxo dG levels observed in A549 cells treated with sodium dichromate may be, at least in part, due to a reduced capacity to repair endogenous and hexavalent chromium-induced 8-oxo dG.
The investigation of the environmental properties of minerals, i.e., environmental mineralogy, is a branch of science dealing with interactions between natural minerals and spheres of the Earth ...surface as well as a reflection of global change, prevention of ecological destruction, participation in biomineralogy, and remediation of environmental pollution. Pollutant treatment by natural minerals is based on the natural law and reflects natural self‐purification functions in the inorganic world, similar to that of the organic world — a biological treatment. A series of case studies related to natural self‐purification, which were mostly completed by our group, are discussed in this paper. In natural cryptomelane there is a larger pseudotetragonal tunnel than that formed by MnO6 octahedral double chains, with an aperture of 0.462–0.466 nm2, filled with K cations. Cryptomelane might be a real naturally‐occurring mineral of the active octahedral molecular sieve (OMS‐2). CrVI‐bearing wastewater can be treated by natural pyrrhotite, which is used as a reductant to reduce CrVI and as a precipitant to precipitate CrIII simultaneously. Batch experiments were conducted using the CTMAB‐Montmorillonite as an adsorbent for aromatic contaminants (phenol, aniline, benzene, toluene and xylenes), which are detected frequently in the leaching water from municipal waste deposits around China. The CTMAB modification has proved very effective to enhance the adsorption capacity of the sorbent. Expansion of vermiculite develops loose interior structures, such as pores or cracks, inside briquettes, and thus brings enough oxygen for combustion and the sulfation reaction. Effective combustion of the original carbon reduces the amount of dust in the fly ash.
Synchrotron radiation-based (SR) Fourier-transform infrared (FTIR) spectromicroscopy in the mid-infrared region is a surface analytical technique that can provide direct insights into the ...localization and real-time mechanisms for the reduction of the (CrO4)2- chromate Cr(VI) species on surfaces of geologic materials. Time-resolved SR-FTIR spectra indicate that, in the presence of endoliths (mineral-inhabiting microorganisms), microbial reduction of Cr(VI) to Cr(III) compounds on basaltic mineral surfaces is the key mechanism of Cr(VI) transformation. It proceeds in at least a two-step reaction with Cr(V) compounds as possible intermediate products, with the reduction of Cr(VI) increasing during the concomitant biodegradation of a dilute organic vapor (toluene). Analyses of spatially resolved SR-FTIR spectra show that the maximum reduction of Cr(VI) to Cr(III) compounds occurs on surfaces densely populated by microorganisms. The oxidation state of Cr(III) compounds was confirmed by micro-x-ray absorption fine-structure spectroscopy. Both the time- and space-resolved SR-FTIR spectra show that in the absence of endoliths, Cr(VI) reduction is insignificant. With this effort, the potential use of SR-FTIR spectromicroscopy in providing mechanistic information of reduction of Cr(VI) has been demonstrated. This method can now be expanded to examine other IR-amenable microbial/chemical contaminant systems.
Aluminum alloys used in the construction of modern aircraft are subject to corrosion. The principal means of controlling this corrosion in the U.S. Air Force are organic coatings. The organic coating ...system consists of a chromate conversion coat, epoxy resin primer, and polyurethane enamel topcoat. Hexavalent chromium (CrVI) is present in the conversion coat in the form of chromic acid and in the primer in the form of strontium chromate. CrVI inhalation exposures can occur when workers spray conversion coat onto bare metal and apply primer to the treated metal surface. In addition, mechanical abrasion of aircraft surfaces can generate particulates that contain chromates from previously applied primers and conversion coats. This study measured CrVI exposures during these corrosion control procedures. Mean time-weighted average (TWA) exposure to chromic acid during conversion coat treatment was 0.48 µg/m
3
, below the current American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV®) TWA of 50 µg/m
3
for water-soluble CrVI compounds. Mean TWA exposures to strontium chromate were 5.33 µg/m
3
during mechanical abrasion and 83.8 µg/m
3
during primer application. These levels are in excess of the current ACGIH TLV-TWA of 0.5 µg/m
3
for strontium chromate. In the absence of a change from chromated to nonchromated conversion coats and primers, additional control measures are needed to reduce these exposures.
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