Between 1960 and 1980, vinylasbestos was widely used for flooring public buildings, schools, hospitals and housing due to its mechanical characteristics, low cost, rapid installation and easy cleaning. The production of vinyl-asbestos flooring was carried outby mixing inert fillers, PVC (Polyvinyl chloride) resins, copolymers, pigments and large quantities of asbestos. The mixture was heated until ~150 °C to reach the desired plasticity and pressed to obtain the required thickness; it was then cut into tiles. The result is a coating very similar to linoleum. Asbestos added to the aggregates and PVC improved the properties of mechanical, heat and corrosion resistance.
From documents kept at the DIATI (Department of Environmental and Infrastructure Engineering) asbestos laboratory of the Politecnico di Torino, the asbestos fibers used for the production of vinylasbestos, produced in the San Vittore (Balangero, Piedmont, Italy) asbestos mine, as it is shown in the flyer of the mine products (Figure 1
) were of Grade 7 [1
].The length of the asbestos fibers of Grade 7 were <10 mesh (corresponding to <2 mm) and this was the typology of asbestos fiber with the lowest economic value. Among all the different types of asbestos of industrial use (Actinolite, Amosite, Anthophyllite, Chrysotile, Crocidolite, Tremolite, according to the experience in the DIATI asbestos laboratory of the Politecnico di Torino, after more than 500 analyses on vinyl asbestos samples, the only one asbestos detected in vinyl tiles was Chrysotile.
In the literature, there are several patents concerning the manufacture of vinyl-asbestos floors, two of which are given asexamples (see Table 1
and Table 2
In addition, according to the US patent of Petry [2
], asbestos particle parts by weight of the components and dimensions of fibrous particles are shown in Table 1
. The specific weight of this vinyl-asbestos has values of 1.85–1.90 g/m3
but can reach 1.50 g/m3
depending on the type of filler used.
The percentage of components in the US patents of Laurito and Wheeler [3
] is shown in Table 2
The Italian Ministerial Decree (M.D.) 6/9/94 [4
] established, in implementation of Article 6 of Law 257/92 [5
], the methods for the removal of products containing asbestos, as well as those for transportation, storage of asbestos waste in landfills for special and hazardous waste, treatment, packaging and covering of materials containing asbestos. Furthermore, the procedures to be adopted for asbestos remediation are defined. The three remediation methods indicated by the Decree are the following:
Removal—it is mandatory for brittle materials and compact materials in the case of damages for more than 10% of its surface.
Encapsulation—covering of the asbestos-containing materials (ACMs) with several layers of a specific encapsulation coating, producing a physical barrier between the contaminated matter and the external environment.
Over coverage—occulting and sealing the ACMs by means of the physical barrier such as panels, walls or insulation.
describes the different situations that can occur during the evaluation of ACMs in buildings and the related recommendations in these different cases required by M.D. 6/9/94 [4
The Decree [4
] also defines the criteria for choosing asbestos protection devices to be used by operators during the reclamation and methods of sampling and analysis of materials and environment to verify the presence of asbestos fibers.
In the case of encapsulation of ACMs, procedures and methods for rehabilitation and a control program maintenance are recommended instead of removal. This maintenance schedule must be periodic [4
The mapping of asbestos is compulsory for every kind of asbestos material in civil buildings; the first step is to respect the evaluation of the risk and the program of management and custodial control [4
Finally, the Lgs.D.9 April 2008 n. 81 [9
] on hygiene and safety in the workplace and subsequent modifications Lgs. D. 3 August 2009 n. 106 [10
] identify that the employer must ascertain the presence of ACMs. The employer must assess the risk of workers and act on this. Legislative Decree 81/2008 [9
] defines the exposition limits value of 0.1 fiber per air cm3
The ACM potential danger depends on possible fibers released in the air, which can be inhaled by occupants. The most important criterion to evaluate is the friability of the materials. Depending on the friability [4
], ACMs can be classified in two categories. Friable ACMs can be easily crumbled or reduced to powder by the pressure of an ordinary human hand (this category includes non-friable asbestos materials where the matrix deteriorates due to weathering, ageing or wear). Non-friable ACMs are hard materials that can be crumbled or reduced to powder only with the use of mechanical tools (abrasive discs, cutter, drills, etc.); these are no longer able to maintain the original compactness. Once released, asbestos fibers are light enough to hang in the air for hours and days, long after other dust has settled; thus, being able to be inhaled. M.D. 6/9/94 [4
] provides exposition limits aimed at protecting people from breathing airborne fibers. In Table 3
], indications on asbestos content and friability of the main building materials are given.
According to M.D. 6/9/94 [4
], asbestos vinyl flooring contains chrysotile asbestos in the percentages from 10 to 25% (the same value of the US patents of Laurito and Wheeler [3
], (Table 2
)), and has an improbable release of fibers during normal use, but the possibility of released fibers if cut, abraded or perforated.
This is confirmed in the research of Campopiano et al. [11
], on the problem of indoor asbestos in school buildings, where the sampling of airborne carried out over many years always showed a very low concentration of the asbestos fibers in asbestos vinyl tiles. Williams and Crossman [1
] investigated the release of fibers during the removal of vinyl-asbestos flooring using the RCFI (Resilient Floor Covering Institute) recommendations [12
] and noted that the release of the fibers does not occur when breaking tiles, but an important part of the asbestos is caused by abrasion between fragments of tiles and mastic and/or scraper.
Kominsky et al. [13
] evaluated the release of fibers on three conditions of vinyl flooring (poor, medium and good) during spray buffering and wet stripping. The authors demonstrated that the high level of fibers released during this maintenance on the floor in bad condition was due to the decay of the matrix englobing the asbestos fibers.
Boulanger et al. [14
] studied the presence of SAF (short asbestos fibers L < 5 micron) in air samples as an indicator of the degradation of ACM to identify pollution and anticipate health risk. Dodson et al. [15
] have asserted in their research that asbestos fiber length is related to potential pathogenicity. The Regulation does not consider this type of fiber as dangerous to health, so in this research it is not taken into account.
Eypert-Blaison et al. [16
] have shown that the notion of friable/non-friable for the Regulation was erroneous and unreliable insofar as the dust emitted by a given material depends not only on its nature but also on the removal technique and the collective protection means associated with it during work.
Perez et al. [17
] evaluated the exposure to airborne asbestos during work on floor tiles, by means of a meta-analysis of the data collected through personal sampling on worker. They found that activities that involved polishing or bluing, scoring or snapping and scraping or lifting had the highest personal phase contrast optical microscopy (PCOM) concentrations, while floor tile removal and chemical solvent removal had the lowest concentrations. However, generally these works do not produce airborne concentrations at levels that exceed the current OSHA PEL [18
According to a study conducted by Lange [19
], it was found that during the demolition of floors and mastics containing chrysotile, there is a low exposure to airborne asbestos.
The purpose of the following research is to compare two different vinyl tiles containing asbestos. A first step provides vinyl tile characterization through density, macroscopic and microscopic analysis. A second step involves three different simulation tests to obtain useful guidelines for operators who remove or carry out maintenance.
As defined by the Italian Ministerial Decree 6/9/94 [4
], the release of fibers from a vinyl-containing asbestos can only occur if it is abraded, perforated or cut, but not during its normal use, even if the vinyl floor is in place for more than 30 years. Furthermore, no clear methodologies are suggested for removal due to the installation of another floor or for confinement with a new flooring complete with maintenance.
Analyzing one case at a time, we can provide the following suggestions:
The impact and drag simulation with crampons mimics the passage of people with shoes and the effect of a small stone fragment stuck in the sole of rubber shoes, or any case the normal walking routine. The simulation led to a non-release of fibers for both types of flooring, rigid and flexible. This confirms what is indicated by legislation, that there is no release of fibers in the normal use of vinyl, due to their incorporation within the matrix, independent of ageing.
The multigrip breakage simulation of vinyl tiles, on the other hand, reports a limited release of fibers that, especially in the case of rigid, old and worn floors, can exceed the limits defined by the regulations. Therefore, when sampling or removing the vinyl flooring, if it is broken, it can cause the release of asbestos fibers. The suggestion, in this case, is, therefore, to carry out this operation in wet safety, as has also been suggested by Kominsky et al. [13
]; they state that even for normal maintenance operations, especially stripping, removal should be carried out in wet conditions and using PPE (personal protective equipment). After the removal of the floor tiles, the airborne analysis must be carried out to verify that the environment is clean from fibers. In this case, the wear and the condition of vinyl floor tiles are important for the release of fibers.
The simulation with abrasion with the two different types of abrasive sandpaper produced a remarkable release of fibers in all cases and for both floors. This once again confirms what is stated in the legislation: the abrasion, perforation or cutting could release asbestos fibers. Operations such as dragging furniture or heavy materials must be carried out with care to avoid causing abrasion of the flooring. The effect of grains stuck to the soles of shoes can also cause abrasion and, therefore, the release of asbestos fibers.
During the vinyl floor removal, part of the flooring often remains attached to the sub-floor. The cleaning of this portion of vinylasbestos, probably with glue, should be carried out with great care under wet conditions to prevent a high release of fibers. The use of solvents for the removal of the underlying glue instead of abrasion must be carefully studied, as previous studies have shown. The use of solvents can break the bonds of the glue matrix with part of asbestos fibers, thus freeing them [1