BackgroundInhalation of high concentrations of zinc oxide particles (ZnO) may cause metal fume fever. In an earlier human inhalation study, no effects were observed after exposure to ZnO concentrations of 0.5 mg/m3. Further data from experimental studies with pure ZnO in the concentration range between 0.5 and 2.5 mg/m3 are not available. It was the aim of this experimental study to establish the concentration-response relationship of pure nano-sized ZnO particles.MethodsSixteen healthy subjects were exposed to filtered air and ZnO particles (0.5, 1.0 and 2.0 mg/m3) for 4 h on 4 different days, including 2 h of cycling with a low workload. The effects were assessed before, immediately after, and about 24 h after each exposure. Effect parameters were symptoms, body temperature, inflammatory markers and clotting factors in blood, and lung function.ResultsConcentration-dependent increases in symptoms, body temperature, acute phase proteins and neutrophils in blood were detected after ZnO inhalation. Significant effects were detected with ZnO concentrations of 1.0 mg/m3 or higher, with the most sensitive parameters being inflammatory markers in blood.ConclusionA concentration-response relationship with nano-sized ZnO particles in a low concentration range was demonstrated. Systemic inflammatory effects of inhaled nano-sized ZnO particles were observed at concentrations well below the occpational exposure limit for ZnO in many countries. It is recommended to reassess the exposure limit for ZnO at workplaces.

The cover picture shows the structure, determined crystallographically, of the tetrakis(trimethylstannyl)phosphonium cation that is formed with surprising ease from the reaction of P(SnMe3)3 with Me3SnOTf (OTf=OSO2CF3) and is isolated as the OTf salt. It is the first completely substituted main group organometallic phosphonium derivative, and, in contrast to the more common tetraorganic‐substituted phosphonium cations is only stable in the solid state; in solution it functions as a masked Me3Sn+ reagent. More about this chameleonlike ion and the N(SnMe3)4 cation homologue, which is equally dynamic in solution and has unusual long Sn−N bond lengths, is reported by M. Driess et al. on p. 3684 ff.

The title compound (1) was obtained by salt-metathesis reaction of iPr 3 SiPLi 2 with two molar equiv. of iPr 3 SiOTf (OTf = OSO 2 CF 3 ) in 34% yield. Surprisingly, (1) consists of an 4 : 1 mixture of the two diastereomers (1 a) and (1 b), which do not interconvert to each other even at their decomposition temperature (> 70°C). They represent different iPr-rotational isomers which are separated by an unusual high rotational barrier (> 25 kcal mol ±1 ), resulting from hindered rotations around the Si±C and C±C bonds. The unexpectedly small magnitude of the 1 J(Si, P) coupling constant of (1 a) (9.4 Hz) and (1 b) (9.0 Hz) reflects unusual electronic properties of the Si 3 P skeleton. Hitherto only (1 a) could be isolated in the form of single-crystals and its structure was determined by X-ray diffraction analysis. The Patom in (1 a) is almost planar coordinated (sum of bond angles = 359.789(3)°), but the Si±P-distance (2.264(7) A Ê ) resembles those values of related silylphosphanes with pyramidally coordinated P atoms. Although MNDO calculations revealed two other iPr-rotational isomers with similar energy, they prove that the Si 3 P skeleton prefers the trigonal-planar arrangement due to steric congestion. P(SiiPr 3 ) 3 : Das erste Trisilylphosphanderivat mit einem fast planar dreifachkoordinierten PhosphoratomInhaltsu È bersicht. Die Titelverbindung (1) wurde durch Salzmetathesereaktion von iPr 3 SiPLi 2 mit zwei Mola È quivalent iPr 3 SiOTf (OTf = OSO 2 CF 3 ) in 34% Ausbeute erhalten. Ûberraschenderweise besteht (1) aus einer 4 : 1 Mischung der zwei Diastereomere (1 a) und (1 b), die sich auch bis zu ihrer Zersetzungstemperatur (70°C) nicht ineinander umwandeln. Sie repra È sentieren verschiedene iPr-Rotamere, die durch eine ungewo È hnlich hohe Rotationsbarriere (> 25 kcalḿ ol ±1 ) voneinander getrennt sind und die von gehinderten Rotationen um die Si±C-und C±C-Bindungen herru È hren. Der unerwartet kleine Betrag der 1 J(Si, P)-Kopplungskonstante von (1 a) (9.4 Hz) und (1 b) (9.0 Hz) spiegelt die unge-wo È hnlichen elektronischen Eigenschaften des Si 3 P-Geru È sts wider. Bisher konnte nur (1 a) in einkristalliner Form isoliert werden, und seine Struktur wurde durch Ro È ntgenbeugungsanalyse bestimmt. Das P-Atom in (1 a) ist anna È hernd planar koordiniert (Summe der Bindungswinkel = 359.789(3)°), aber der Si±P-Abstand (2.264(7) A Ê ) gleicht den Werten von verwandten Silylphosphanen mit pyramidal-koordinierten P-Atomen. Obwohl MNDO-Berechnungen zwei andere Rotamere ergaben, beweisen sie, dass das Si 3 P-Geru È st die trigonal-planare Anordnung wegen der sterischen Ûberladung bevorzugt.

Only strong Lewis acidic, arene‐solvated Me3Si+ ions react with E(SiMe3)3 compounds (E=P, As) to give the crystallographically characterized E(SiMe3)4+ onium ions 1 (left hand picture), which contain highly negative polarized P and As atoms, respectively. The masked Me3Si+ ions in 1 can be easily transferred to Et2O, to give the first structurally characterized planar silyloxonium ion [Et2(Me3Si)O]+ 2 (right hand picture).

BackgroundWorkers in the zinc production and processing of galvanized sheet steel are exposed to a complex mixture of particles and gases, including zinc oxide (ZnO) that can affect human health. We aimed to study the effects of short-term controlled exposure to nano-sized ZnO on airway inflammatory markers in healthy volunteers.MethodsSixteen subjects (8 females, 8 men; age 19–42, non-smokers) were exposed to filtered air and ZnO nanoparticles (0.5, 1.0 and 2.0 mg/m3) for 4 h, including 2 h of cycling with a low workload. Induced sputum samples were collected during a medical baseline and a final examination and also about 24 h after each exposure. A number of inflammatory cellular and soluble markers were analyzed.ResultsFrequency and intensity of symptoms of airway irritation (throat irritation and cough) were increased in some subjects 24 h after ZnO exposures when compared to filtered air. The group comparison between filtered air and ZnO exposures showed statistically significant increases of neutrophils and interleukin-8 (IL-8), interleukin-6 (IL-6), matrix metalloproteinase (MMP-9) and tissue inhibitors of metalloproteinases (TIMP-1) in sputum starting at the lowest ZnO concentration of 0.5 mg/m3. However, a concentration-response relationship was absent. Effects were reversible. Strong correlations were found between neutrophil numbers and concentrations of total protein, IL-8, MMP-9, and TIMP-1.ConclusionsControlled exposures of healthy subjects to ZnO nanoparticles induce reversible airway inflammation which was observed at a concentration of 0.5 mg/m3 and higher. The lack of a concentration-response relationship warrants further studies.