Effects of phosphorylation of chrysotile on pleuropulmonary fibrogenicity and carcinogenicity.

As well as fibre size, fibre chemistry is a determinant of toxicity of mineral fibres. On these grounds, a few years ago, the asbestos industry in Québec developed a process to modify the surface chemistry of chrysotile asbestos by fixing phosphorous atoms. The pleuropulmonary fibrogenicity and carcinogenicity of the native and surface treated chrysotile, called chrysophosphate, were tested. Both products initiated similar pulmonary fibrogenicity in rats exposed by inhalation and sheep exposed by injection in the tracheal lobe. Tumour production in rats after long term inhalation or intrapleural injection was not different between chrysotile and chrysophosphate. These findings clearly show that modification of the phosphate surface of chrysotile fibres does not appear to alter the pleuropulmonary activities of the mineral, thus arguing against the earlier contention of less biological activity for chrysophosphate, a contention essentially based upon results of in vitro tests. This study strongly argues for in vivo testing of new fibrous materials before making definite conclusions about their biological activities

Durability of ceramic fibers in the human lung. Preliminary results

International audienceA proper understanding of the pulmonary toxicology of man-made mineral fibres (MMMF) requires information on their durability in the human lung but to date there is little information on this subject. Recently however, we have had the opportunity to document some interesting aspects of the short-term durability of ceramic fibres in human lung by analysing fibres recovered in broncho-alveolar lavage fluid obtained frorn seven men currently employed in the MMMF production industry. Fibres recovered from the lungs by lavage were characterized by analytical transmission electron microscopy. Both normal and highiy-transfonned ceramic fibres were detected. The transformed fibres exhibited a spectrum ofmorphological features and elemental compositions. Some retained a typical ceramic chemistry but were heavily coated with ironcontaining material. Others had a hollow tube morphology, made up offine iron-containing granules without any of the normal major ceramic elements. Such fibres were sometimes found lying under a bed ofsiliceous Seachate. It is hypothesized (hat the transformation process first involves a coating of the ceramic fibres with iron-containing granules, followed by a progressive dissolution of the structural elements. We conclude that some ceraraic fibres are not durable in the human lung

A millennial record of environmental change in peat deposits from the Misten bog (East Belgium).

In this study, palaeoenvironmental changes recorded in the top metre of a peat profile (Misten bog, East Belgium) were investigated using a multiproxy approach. Proxies include bulk density, Ti and Si content, pollen, macrofossils, d13C on specific Sphagnum stems, and d13Ced18O on Sphagnum leaves. A highresolution chronology was generated using 210Pb measurements and 22 14C AMS dates on carefully selected Sphagnum macrofossils. d13C only records large change in mire surface wetness. This is partly due to the fact that the core was taken from the edge of a hummock, which may make it difficult to track small isotopic changes. The d13C signal seems to be dependent upon the Sphagnum species composition. For example, a change between Sphagnum section Cuspidata towards Sphagnum imbricatum causes a significant drop in the d13C values. On the whole, the C and O isotopes record two shallow pool phases during the 8the9th and the 13th centuries. Pollen and atmospheric soil dust (ASD) fluxes records increased human occupation in the area. There may be some climatic signals in the ASD flux, but they are difficult to decipher from the increasing human impact (land clearance, agriculture) during the last millennium. The variations in the proxies are not always synchronous, suggesting different triggering factors (temperature, wetness, windiness) for each proxy. This study also emphasizes that, compared to studies dealing with pollution using geochemical proxies, palaeoclimatic inferences from peat bogs need as many proxies as possible, together with highly accurate and precise age-models, in order to better understand climate variability and their consequences during the Holocene