Aquatic ecotoxicity of lanthanum : a review and an attempt to derive water and sediment quality criteria

Rare earth elements (REE) used to be taken as tracers of geological origin for fluvial transport. Nowadays their increased applications in innovative environmental-friendly technology (e.g. in catalysts, superconductors, lasers, batteries) and medical applications (e.g. MRI contrast agent) lead to man-made, elevated levels in the environment. So far, no regulatory thresholds for REE concentrations and emissions to the environment have been set because information on risks from REE is scarce. However, evidence gathers that REE have to be acknowledged as new, emerging contaminants with manifold ways of entry into the environment, e.g. through waste water from hospitals or through industrial effluents. This paper reviews existing information on bioaccumulation and ecotoxicity of lanthanum in the aquatic environment. Lanthanum is of specific interest as one of the major lanthanides in industrial effluents. This review focuses on the freshwater and the marine environment, and tackles the water column and sediments. From these data, methods to derive quality criteria for sediment and water are discussed and preliminary suggestions are made

27Al NMR Study of the pH Dependent Hydrolysis Products of Al2(SO4)3 in Different Physiological Media

Soluble inorganic aluminium compounds like aluminium sulfate or aluminium chloride have been challenged by the European Chemical Agency to induce germ cell mutagenicity. Before conducting mutagenicity tests, the hydrolysis products in water and in physiological solutions should be determined as a function of the concentration and pH. We used different 27Al NMR spectroscopic techniques (heteronuclear Overhauser effect spectroscopy (HOESY), exchange spectroscopy (EXSY), diffusion ordered (DOSY)) in this work to gain the information to study the aluminium species in solutions with Al2(SO4)3 concentrations of 50.0, 5.0, and 0.5 g/L and their pH and time dependent transformation. At low pH, three different species were present in all physiological solutions and water: [Al(OH)n(H2O)6 − n](3 − n)+ (n = 0–2), [Al(H2O)5SO4]+, and [Al2(OH)2(H2O)8]4+. Increasing pH reduced the amounts of the two monomer species, with a complete loss at pH 5 for solutions with a concentration of 50.0 g/L and at pH 4 for solutions with a concentration of 5.0 g/L. The dimer species [Al2(OH)2(H2O)8]4+ is present in a pH range between 3 and 6. Less symmetric oligomeric and probably asymmetric aluminium species are formed at pH of 5 and 6. The pH value is the driving force for the formation of aluminium species in all media, whereas the specific medium had only minor effect. No conclusive information could be obtained at pH 7 due to signal loss related to fast quadrupole relaxation of asymmetric aluminium species. A slight reduction of the content of the symmetric aluminium species due to the formation of oligomeric species was observed over a period of 6 weeks. Reference 27Al NMR experiments conducted on saturated water solutions of AlCl3 and those with a concentration of 50 g/L show that the type of salt/counter ion at the same concentration and pH influences the hydrolysis products formed

Nine Human Epidemiological Studies on Synthetic Amorphous Silica and Respiratory Health

The respiratory health effects of Synthetic Amorphous Silica (SAS) have been studied in human epidemiological research. This article presents a historical overview and review of nine occupational worker studies that have been conducted so far on this topic. The combined study population of all of these studies included 1,172 employees, and exposure concentrations ranged from <1mg/m to 100mg/m . In two studies with a total of 293 workers, the incidence of silicosis was investigated after long-term exposure to precipitated SAS, and no cases of silicosis were found (Plunkett and Dewitt, 1962; Volk, 1960). In another study, the spirometry results of 40 workers were normal (Vitums et al., 1977). In a study of 28 workers, 4 cases of silicosis were identified, but it is possible that contamination with cristobalite occurred and detailed information about the amorphous silica origin was not provided (Mohrmann and Kahn, 1985). Ferch et al. (1987) found that lung impairment was associated with confounding factors (smoking) but not with exposure to precipitated SAS in a study of 143 workers. Choudat et al. (1990) reported a reduction in forced expiratory flow in a group exposed to precipitated SAS compared to a control group. Still, they found no correlation between the extent of exposure and pulmonary function was found in a study of 131 workers. Wilson et al. (1979) also failed to show a significant association between the degree of exposure to precipitated SAS and annual changes in lung function in a study of 165 workers. In the most recent and most extensive study (Taeger et al., 2016; Yong et al., 2022) in Germany, involving 462 factory workers, no association between inhalable or respirable SAS dust exposure and respiratory health was reported. Based on the available data, there is no evidence-base to support a relationship between SAS and respiratory health in humans

Issues in the inhalation toxicity testing and hazard assessment for low density particulate materials such as synthetic amorphous silica (SAS)

Inhalation toxicity testing of particulate materials is mandated for classification. According to CLP, particulate materials should be tested as marketed and many particulate materials are marketed as non-respirable particles. However, OECD TG 413 requires exposure to particle sizes that are respirable and reach the alveoli. The requirement for exposure of rats to respirable particles is thus in contrast to CLP and requires the application of high shear forces. The exposure to artificially small particles causes a number of issues that hamper the interpretation of the results of the testing. These issues are aerosol altering in the exposure system, assessment of the adversity of the inflammatory lung responses, inclusion of recovery groups, and extrapolation of the results to humans exposed under occupational condition. In addition, effects of many particulate materials after testing according to OECD 413 are not intrinsic properties, but a general reaction of the lung to the deposited material, show very similar NOAECs for chemical diverse materials, and often are completely reversible