Translocation pathways for inhaled asbestos fibers.

We discuss the translocation of inhaled asbestos fibers based on pulmonary and pleuro-pulmonary interstitial fluid dynamics. Fibers can pass the alveolar barrier and reach the lung interstitium via the paracellular route down a mass water flow due to combined osmotic (active Na+ absorption) and hydraulic (interstitial pressure is subatmospheric) pressure gradient. Fibers can be dragged from the lung interstitium by pulmonary lymph flow (primary translocation) wherefrom they can reach the blood stream and subsequently distribute to the whole body (secondary translocation). Primary translocation across the visceral pleura and towards pulmonary capillaries may also occur if the asbestos-induced lung inflammation increases pulmonary interstitial pressure so as to reverse the trans-mesothelial and trans-endothelial pressure gradients. Secondary translocation to the pleural space may occur via the physiological route of pleural fluid formation across the parietal pleura; fibers accumulation in parietal pleura stomata (black spots) reflects the role of parietal lymphatics in draining pleural fluid. Asbestos fibers are found in all organs of subjects either occupationally exposed or not exposed to asbestos. Fibers concentration correlates with specific conditions of interstitial fluid dynamics, in line with the notion that in all organs microvascular filtration occurs from capillaries to the extravascular spaces. Concentration is high in the kidney (reflecting high perfusion pressure and flow) and in the liver (reflecting high microvascular permeability) while it is relatively low in the brain (due to low permeability of blood-brain barrier). Ultrafine fibers (length < 5 mum, diameter < 0.25 mum) can travel larger distances due to low steric hindrance (in mesothelioma about 90% of fibers are ultrafine). Fibers translocation is a slow process developing over decades of life: it is aided by high biopersistence, by inflammation-induced increase in permeability, by low steric hindrance and by fibers motion pattern at low Reynolds numbers; it is hindered by fibrosis that increases interstitial flow resistances.

[Asbestos exposure in the non-asbestos textile industry: the experience of the Lombardy Mesothelioma Registry]. / Esposizioni professionali nel settore tessile non-amianto in Lombardia: i dati del Registro Regionale.

The Lombardy Mesothelioma Registry, activated in 2000, receives more than 300 cases per year of suspected malignant mesothelioma; the standardized (age and gender) incidence rate of pleural mesothelioma is 2.4/100,000 inhabitants (CI 95% 2.0-2.7). The finding of an increasing number of cases among workers of the non-asbestos-textile industry, classified as "unknown exposure to asbestos", upheld the suspect of presence of asbestos in this compartment. Specific information about a possible asbestos exposure were collected by technicians, maintenance personnel and other experts; industrial machinery utilized in the past was thoroughly examined; direct inspections were carried out in several workplaces that had not yet undergone significant changes with respect to the past. A large amount of asbestos had been regularly used on the ceilings and also to the walls of factories in order to avoid both condensation of steam and reflection of noise. In addition, asbestos had also been widely used to insulate water and steam pipes. The braking systems of most of machines also had asbestos gaskets, and on several looms some brakes operated continuously. The population in study was composed of 119 subjects, 27 males and 92 females, median age of 72 years. Asbestos exposure was ascribed to work in 106 cases (89%). The system devised by the Lombardy Registry had brought to light an occupational hazard in a professional area previously never believed as a source of asbestos exposure. In consideration of the described experience, both environmental and clinical, it seems reasonable to consider the non-asbestos-textile as a new department at risk for asbestos exposure.

[The Lombardy Mesothelioma Register, Regional Operating Centre (ROC) of National Mesothelioma Register: organizational aspects]. / Il Registro mesoteliomi Lombardia, Centro Operativo Regionale (COR) del Registro nazionale mesoteliomi: aspetti organizzativi .

The Lombardy Mesothelioma Register (LMR) collects all incident cases of Malignant Mesothelioma (MM) occurring since January 1, 2000 in residents of the Lombardy Region. For each "possible case" reported to the Registry by Lombardy hospitals, diagnosis is ascertained through examination of clinical records (including histology reports) according to ISPESL Guidelines. For confirmed cases, a standardized questionnaire is administered to the subject or next-of-kin in order to verify the possible sources of asbestos exposure in his/her lifetime. A panel composed of industrial hygienists, occupational health physicians and occupational epidemiologists evaluate asbestos exposure in the workplace and environmental settings. Case ascertainment completeness is routinely verified using other sources such as hospital discharge records and death certificates coded as 163 (ICD IX). In the period 2000-2004, 1563 cases were collected, of whom 887 have been evaluated: the diagnosis was confirmed for 626 (70.6%) 9 out of 887 evaluated cases. The age and gender standardized incidence rate for pleural mesothelioma in the Lombardy Region, in the year 2000 (the only one with completed data), was 2.4 (males 3.7; females 1.4) per 100,000 residents/year The 70.5% of certain and probable MM has an asbestos exposure, in particular the 64.5% of cases has an occupational exposure. The experience gathered over the years by the LMR has allowed to implement an efficient information network among different institutions and health services. In addition practical skills have been gained in processing epidemiological data, a useful tool to address new scientific hypothesis and to plan ad-hoc researches. In our experience the LMR represents a potential resource transferable to the epidemiological surveillance of different occupational tumours (i.e. sino-nasal cancers).

[Asbestos fibre dimensions and mesothelioma]. / Dimensioni delle fibre di amianto e mesotelioma.

The critical considerations formulated by Tomatis et al. did not take into account all the experimental works and all the research on human pleura that from the Seventies on has unanimously indicated that asbestos fibre mesothelioma is caused by the ultrafine fibres class. These fibres that are so fine are not visible with light microscopy are mostly ultrashort, but they also include, in varying percentages, elements that are >5 microm long. The conclusions of Tomatis et al, which attribute mesothelioma to fibres of all lengths and diameters, are not confirmed in the literature. Today, mesothelioma prevention must consist of identifying and cutting down airborne ultrafine fibres, above all in urban environments. The techniques for doing so now exist and can be applied. The ultrafine class of asbestos, forgotten for decades, must be the principal target for prevention programs and must be widely monitored in work and daily life settings.