Beryllium Metal II. A Review of the Available Toxicity Data

Abstract

Beryllium metal was classified in Europe collectively with beryllium compounds, e.g. soluble salts. Toxicological equivalence was assumed despite greatly differing physicochemical properties. Following introduction of the Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) regulation, beryllium metal was classified as individual substance and more investigational efforts to appropriately characterize beryllium metal as a specific substance apart from soluble beryllium compounds was required. A literature search on toxicity of beryllium metal was conducted, and the resulting literature compiled together with the results of a recently performed study package into a comprehensive data set. Testing performed under Organisation for Economic Co-Operation and Development guidelines and Good Laboratory Practice concluded that beryllium metal was neither a skin irritant, an eye irritant, a skin sensitizer nor evoked any clinical signs of acute oral toxicity; discrepancies between the current legal classification of beryllium metal in the European Union (EU) and the experimental results were identified. Furthermore, genotoxicity and carcinogenicity were discussed in the context of the literature data and the new experimental data. It was concluded that beryllium metal is unlikely to be a classical nonthreshold mutagen. Effects on DNA repair and morphological cell transformation were observed but need further investigation to evaluate their relevance in vivo. Animal carcinogenicity studies deliver evidence of carcinogenicity in the rat; however, lung overload may be a species-specific confounding factor in the existing studies, and studies in other species do not give convincing evidence of carcinogenicity. Epidemiology has been intensively discussed over the last years and has the problem that the studies base on the same US beryllium production population and do not distinguish between metal and soluble compounds. It is noted that the correlation between beryllium exposure and carcinogenicity, even including the soluble compounds, remains under discussion in the scientific community and active research is continuing.

Reactions of Beryllium Halides in Liquid Ammonia: The Tetraammineberyllium Cation [Be(NH3)4]2+, its Hydrolysis Products, and the Action of Be2+ as a Fluoride‐Ion Acceptor

“…The cation is surrounded by six ammonia molecules and three chloride ions. The ammine ligand with atom N(2) forms three N À H···Cl hydrogen bonds to symmetry-equivalent Cl(2) anions, whereas the ammine ligand with atom N(1) displays one N À H···Cl(2) and two symmetry-independent NÀH···N hydrogen bonds to N (6) and N (9). For details of the hydrogen bond lengths and angles, see the caption to Figure S2 (8) , [56] for…”

“…The cation is stable at pH < 3, but at higher pH values condensation reactions occur. [34] Owing to its high symmetry, its 9 Be NMR signal is sharp and BeSO 4 ·4H 2 O is used as the reference in 9 Be NMR spectroscopy. The structure of the [BeA C H T U N G T R E N N U N G (H 2 O) 4 ] 2 + cation has also been established by IR and Raman spectroscopy and single-crystal structure analyses by using X-ray and even neutron diffraction data.…”

“…[13] Recently, the [Be(OH) 4 ] 2À anion was obtained through solvothermal synthesis of the compound Sr[Be(OH) 4 ]. As the compound seems to be insoluble in water under ambient conditions, no chemical shift of the 9 Be resonance was observed. [42] Liquid ammonia, the solvent properties of which are often compared to water, is a verylittle-explored solvent system for beryllium chemistry, and literature is scarce: metallic beryllium is insoluble in liquid ammonia.…”

“…[47] That BeCl 2 ·4NH 3 contains the tetraammineberyllium cation was suggested by IR spectroscopy data, [48,49] but this interpretation was heavily doubted. [50] A 9 Be NMR spectrum of BeCl 2 dissolved in liquid ammonia has only been recorded once and the observed singlet was assigned to the [BeA C H T U N G T R E N N U N G (NH 3 ) 4 ] 2 + cation, [49] but the conditions of the experiment remained unclear and no standard was used. Biltz and Messerknecht found adducts of BeCl 2 with two, four, six, and twelve molecules of ammonia in tensieudiometric measurements.…”

“…Hydrolysis products of BeCl 2 in liquid ammonia: Upon the deliberate addition of trace amounts of water to the solution of BeCl 2 in liquid ammonia, the evolution of one more singlet at 2.4 ppm and a decrease of the signal at 3.1 ppm were observed in the 9 Be NMR spectrum. With the aid of quantum chemical calculations, the singlet at 2.9 ppm has been assigned to the four-membered ring species […”