Lead and chromium in European road paints

Lead chromate was commonly employed as a pigment in coloured road markings until restrictions led to the development of safer alternatives. In this study, the presence and concentrations of Pb and Cr have been determined in 236 road paints of various colours sampled from streets, highways, footways and carparks from eleven European countries. According to energy-dispersive X-ray fluorescence spectrometry, Pb was detected (>10 mg kg^-1) in 148 samples at concentrations up to 17.2% by weight, and above 1000 mg kg^-1 yellow was the dominant paint colour. Lead concentrations on an area basis varied from 0.02 to 8.46 mg cm^-2 and the metal was located at different depths amongst the samples, suggesting that formulations had been painted both recently and historically (and overpainted). Chromium was detected (>5 to 50 mg kg^-1) in 81 samples at concentrations between 20 and 20,000 mg kg^-1 and most often in yellow paints, and concentrations co-varied with those of Pb. These observations, and results of scanning electron microscopy coupled with energy-dispersive X-ray spectrometry, suggested that heterogeneously dispersed PbCrO₄ was the dominant, but not the only, Pb-based pigment in the samples. Although there were significant international differences in frequency of Pb detection and median Pb concentrations, overall, and despite various, albeit complex, regulations, recent or extant road paint pigmented with Pb and Cr remains a pervasive environmental problem and a potential health risk in many European countries.

Combined in vitro and in vivo investigation of barite microcrystals in Spirogyra (Zygnematophyceae, Charophyta)

We have investigated the biomineralisation of barite ‒a useful proxy for reconstructing paleoproductivity‒ in a freshwater alga, Spirogyra, by combining in vitro and in vivo approaches to unveil the nature of its barite microcrystals. Scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDXS) observations on simply dried samples revealed that the number and size of barite crystals were related to the barium concentration in the media. Additionally, their morphology showed a crystallographic face (011), which is not normally observed, suggesting the influence of organic molecules on the growth kinetics. The critical point drying method was used to preserve the internal and external structures of Spirogyra cells for SEM imaging. Crystals were found adjacent to the cytoplasmic membrane, near chloroplasts and fibrillary network. In vivo optical microscopy and Raman tweezer microspectroscopy in living cells showed that barite microcrystals are optically visible and follow cytoplasmic streaming. These results led us to propose that barite formation in Spirogyra occurs in the cytoplasm where barium and sulphate are both available: barium supplied non-selectively through the active transport of the divalent cations needed for actin polymerisation, and sulphate because necessary for amino acid biosynthesis in chloroplasts.

Nature-Inspired Effects of Naturally Occurring Trace Element-Doped Hydroxyapatite Combined with Surface Interactions of Mineral-Apatite Single Crystals on Human Fibroblast Behavior

Innovative engineering design for biologically active hydroxyapatites requires enhancing both mechanical and physical properties, along with biocompatibility, by doping with appropriate chemical elements. Herein, the purpose of this investigation was to evaluate and elucidate the model of naturally occurring hydroxyapatite and the effects of doped trace elements on the function of normal human fibroblasts, representing the main cells of connective tissues. The substrates applied (geological apatites with hexagonal prismatic crystal habit originated from Slyudyanka, Lake Baikal, Russia (GAp) and from Imilchil, The Atlas Mountains, Morocco (YAp)) were prepared from mineral natural apatite with a chemical composition consistent with the building blocks of enamel and enriched with a significant F⁻ content. Materials in the form of powders, extracts and single-crystal plates have been investigated. Moreover, the effects on the function of fibroblasts cultured on the analyzed surfaces in the form of changes in metabolic activity, proliferation and cell morphology were evaluated. Apatite plates were also evaluated for cytotoxicity and immune cell activation capacity. The results suggest that a moderate amount of F⁻ has a positive effect on cell proliferation, whereas an inhibitory effect was attributed to the Cl⁻ concentration. It was found that for (100) GAp plate, fibroblast proliferation was significantly increased, whereas for (001) YAp plate, it was significantly reduced, with no cytotoxic effect and no immune response from macrophages exposed to these materials. The study of the interaction of fibroblasts with apatite crystal surfaces provides a characterization relevant to medical applications and may contribute to the design of biomaterials suitable for medical applications and the evaluation of their bioavailability.

Kohl containing lead (and other toxic elements) is widely available in Europe

Kohl is an eye cosmetic that was traditionally used in many Asian and African countries but that is now more widely available. Ingredients of kohl reported in previous studies seem to be rather variable but mention is frequently made of minerals based on Pb whose use in cosmetic products is prohibited in Europe. We purchased 23 products of kohl from retail outlets in five different European countries and over the internet and analysed their chemical composition by XRF and SEM-EDXS. The majority of the products (n = 17) did not conform with European legislation based on the presence of Pb (often as galena), whose concentrations ranged from a few mg kg^-1 to over 400000 mg kg^-1. Cadmium, another element prohibited in cosmetic products in Europe, was also present as a contaminant in 13 products at concentrations up to a few hundred mg kg^-1. In addition to heavy metals, minerals of other metals (e.g. Fe and Zn) appeared to be present in the nano-size range and might represent an additional health hazard. Clearly, the lack of quality control in the manufacture of kohl results in the widespread occurrence of toxic and unwanted elements and the trade of illegal products in Europe. In principle, shop sales would be relatively straightforward to prevent, but products traded through internet are more difficult to regulate.