Asbestos

Asbestos was a widely used, mineral-based material that is resistant to heat and corrosive chemicals. Typically, asbestos appears as a whitish, fibrous material that may release fibers that range in texture from coarse to silky however, the airborne fibers that can cause health damage may be too small to see with the naked eye. 

An estimated 1.3 million employees in the construction and general industry face significant asbestos exposure on the job. Heaviest exposures occur in the construction industry, particularly when removing asbestos during renovation or demolition. In the past, employees were also likely to be exposed during the manufacture of asbestos products (such as textiles, friction products, insulation, and other building materials) and during automotive brake and clutch repair work. 

Occupational Safety and Health Administration (OSHA) has issued revised regulations covering asbestos exposure in general industry and construction. Both standards set a maximum exposure limit and include provisions for engineering 

BREATHING ASBESTOS DUST MAY CAUSE LUNG DISEASE AND CANCER 

Here are some of the highlights of the revised rules in 29 CFR 1910.1001, promulgated October 11, 1994  

Permissible exposure limit (PEL) In both general industry and construction, workplace exposure must be limited to 0.1 fibers per cubic 

Methods of compliance In both general industry and construction, employers must control exposures using engineering controls, to the extent feasible. Where engineering controls are not feasible to meet the exposure limit ihey must be used to reduce employee exposures to the lowest levels attainable and must be supplemented by the use of respiratory protection. 

The Asbestos standard, 1910.1001, requires caution signs and labels warning of possible lung disease. In addition to size and location specifications, the following legend is required on all signs for areas of potential or actual asbestos overexposure  

ASBESTOS DUST HAZARD Avoid Breathing Dust Wear Assigned Protective Equipment Do Not Remain in Area Unless Your Work Requires It 

Breathing Asbestos Dust May Be Hazardous to Your Health 

Caution labels must be affixed to all materials containing asbestos, including employees contaminated protective clothing, or to their containers. This requirement is waived if the asbestos fibers have been modified in some way, and the possibility of employee overexposure to asbestos does not exist. The label must be readily visible and legible, and shall state  

Contains Asbestos Fibers Avoid Creating Dust Breathing Asbestos Dust May Cause Serious Bodily Harm 

The term asbestos is a generic designation referring usually to six types of naturally occurring mineral fibers which are or have been commercially exploited. These fibers are extracted from certain varieties of hydrated alkaline silicate minerals comprising two families serpentines and amphiboles. The serpentine group contains a single fibrous variety chrysotile five fibrous forms of amphiboles are known anthophyllite, amosite, crocidolite, tremolite, and actinolite. 

These fibrous minerals share several properties which qualify them as asbestiform fibers (/) they are found in large clusters which can be easily separated from the host matrix or cleaved into thinner fibers (1) (2) the fibers exhibit high tensile strengths (1) (3) they show high length diameter ratios, from a minimum of 20 up to 1000 (1) (4) they are sufficiendy flexible to be spun and (5) macroscopically, they resemble oiganic fibers such as cellulose (2). 

Since asbestos fibers are all silicates, they exhibit several other common properties, such as incombustibility, thermal stability, resistance to biodegradation, chemical inertia toward most chemicals, and low electrical conductivity. 

The usual definition of asbestos fiber excludes numerous other fibrous minerals which could be qualified as asbestiform following the criteria listed above. However, it appears the term asbestos has traditionally been attributed only to those varieties which are commercially exploited (1,2). 

The mineralogical designations of the various asbestos fibers, their most common alternative designations, and the main producing countries of these fibers are reported in Table 1. The fractional breakdown of the recent world production of the various fiber types shows that the industrial applications of asbestos fibers have now shifted almost exclusively to chrysotile. Two types of amphiboles, commonly designated as amosite and crocidolite are still being used, but their combined production is currently less than 2% of the total world production. The other three amphibole varieties, anthophyllite, actinolite, and tremolite, have no significant industrial applications presently. This statement excludes asbestiform amphiboles which may occur in other industrial minerals. 

1 Has survey been conducted at facility to determine whether asbestos-containing material (ACM) is present in facility  

4 Has individual written notice been issued to all employees working within the area containing asbestos  

6 Has facility been inspected for asbestos compliance by regulatory agency  

1 Asbestos is a Proposition 65 chemical. If asbestos is present at facility, please turn to Section on Proposition 65 for review. 

There has been much debate over whether it is better to remove asbestos wherever it is found as a matter of course. 

Crocidolite has been banned in practice in the UK since 1969 but is still to be found in boiler lagging, piping, older insulation boards and sheeting. Asbestos lagging installed before 1940 has a high chance of containing a measurable percentage. 

Amosite - brownish in colour unless subjected to high temperature, this form of asbestos is now considered as dangerous as crocidolite. In 1984 it was made subject to the same control limits. 

The information provided here is intended only as a summary and guide to the requirement of the Regulations, which must be studied together with the relevant Approved Codes to obtain an authoritative interpretation of the requirements. 

Importation, supply and use (and reuse) of all types of asbestos has now been banned. The main direct legislation dealing with work with asbestos is the Control of Asbestos at Work Regulations 2002 (CAWR). Anyone having a need to handle asbestos to any extent in the construction industry should obtain a copy of the current edition of the Approved Code of Practice (see page 183). Work on land contaminated by asbestos is not covered by a Code. 

Metall ic fibers are defined as fibers composed of metal, plastic-coated metal, or metal-coated plastic. Single-component metall ic fibers for textile usage are fine drawn filaments of metal which can be spun and woven on normal textile machinery. These metallic fibers possess the properties of the metal from which they are formed. Multicomponent metallic fibers are more commonly used in textiles and are usually made from flat aluminum filaments surrounded with or bonded between clear layers of polyester, cellophane, or cellulose ester or from polyester film which has been metallized through vacuum deposition of aluminum and then encapsulated in polyester. In general, the properties of these fibers resemble the properties of the plastic film used to form the multicomponent fiber. The fibers are generally weak and easily stretched but can be used for decorative purposes and for applications where electrical conductivity and heat resistance are important. Trade names for metallic fibers include Brunsmet and Lurex. 

Mineral species Other designations Main producers Wodd production, 1988, % 

Chrysotile is in the serpentine mineral group aU others are amphiboles. 

Arsine, at concentrations that induced maternal toxicity in rats and mice, did not affect end points of developmental toxicity.  

Arsine is nonirritating with a garlic-like odor. Warning properties of exposure to hazardous concentrations are inadequate.  

The 2003 ACGIH threshold limit value-time-weighted average (TLV-TWA) for arsine is 0.05ppm (0.16mg/m ). 

Arsine absence of developmental toxicity in rats and mice. Fundam Appl Toxicol 15 350-356, 1990 

NIOSH Current Intelligence Bulletin 32, Arsine (Arsenic Hydride) Poisoning in the Workplace. DHEW (NIOSH) Pub No 79-142. Cincinnati, OH, National Institute for Occupational Safety and Health, 1979 

The sample is collected with a high-volume sampler on microsorban paper. The paper is dissolved in benzene and the inorganic residue is analysed by X-ray diffraction and optical microscopy [34]. 

2 fibres per ml of air averaged over 4 hours or 0.6 fibres per ml of air averaged over 10 minutes 

Before exposing employees to asbestos, the employer must  

These Regulations are supported by HSE publication LI27 The management of asbestos in non-domestic premises . 

Refractive Index 1.53-1.56 Specific Gravity 2.5-2.6 Mohs Hardness 2.5-4 

Spinning fiber - The eleanest and longest fibers, to 12mm, are reserved for producing woven asbestos textiles. 

Asbestos cement fiber - This is the longest fiber grade that is 12mm. 

Paper/shingle fiber - This is essentially 5 mm (-4 mesh) fiber, with shingle fiber being generally shorter than paper fiber. 

Shorts/floats - These are flie shortest fibers, with most shorts or all floats 2mm (-10 mesh). 

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Some early observations on the catalytic oxidation of SO2 to SO3 on platinized asbestos catalysts led to the following observations (1) the rate was proportional to the SO2 pressure and was inversely proportional to the SO3 pressure (2) the apparent activation energy was 30 kcal/mol (3) the heats of adsorption for SO2, SO3, and O2 were 20, 25, and 30 kcal/mol, respectively. By using appropriate Langmuir equations, show that a possible explanation of the rate data is that there are two kinds of surfaces present, 5 and S2, and that the rate-determining step is... 

This form melts at 290 K, and boils at 318 K. The P form, obtained when the a form is allowed to stand for a long time at a temperature below 298 K. exists as asbestos-like, silky, felted needles and has a structure consisting ofSO tetrahedra linked together in long chains. 

Transfer the solution into the flask, add some unglazed porcelain, and support the flask over an asbestos-covered gauze. Heat the solution cautiouslv with a Bunsen flame so that the temperature... 

Place in the flask 2 g. of benzophenone, 15 ml. of isopropanol and 2 5 g. of aluminium isopropoxide. This mixture has now to be heated gently under reflux so that the temperature registered by the thermometer in the column does not exceed 80°, i.e., so that only acetone distils. For this purpose, the flask should preferably be heated in an oil-bath direct heating, even over an asbestos sheet, may cause local overheating and decomposition the use of a water-bath on the other hand may make the column undesirably damp. 

Add 4 g. of malonic acid to 4 ml. of pyridine, and then add 3 1 ml. of crotonaldehyde. Boil the mixture gently under reflux over an asbestos-covered gauze, using a small Bunsen flame, for 40 minutes and then cool it in ice-water. Meanwhile add 2 ml. of concentrated sulphuric acid carefully with shaking to 4 ml. of water, cool the diluted acid, and add it with shaking to the chilled reaction-mixture. Sorbic acid readily crystallises from the solution. Filter the sorbic acid at the pump, wash it with a small quantity of cold water and then recrystallise it from water (ca, 25 ml.). The colourless crystals, m.p. 132-133°, weigh ro-i-2 g. 

When the reaction is complete, heat the stirred mixture carefully under reflux over a Bunsen burner and asbestos gauze for I hour if the mixture becomes too thick for efficient stirring, add up to 15 mL of acetic acid. Now decant the hot mixture into 500 ml. of vigorously-stirred ice-cold water wash the residual zinc thoroughly with glacial acetic acid (2 portions each of I -2 ml.), decanting the acid also into the stirred water. 

It is best now to proceed as in the Skraup Synthesis (p. 297) and warm the mixture over an asbestos-covered gauze with a Bunsen flame until the reaction starts, and have at hand a duster soaked in cold water so that when the reaction starts, the heating can be at once removed and the duster wrapped round the shoulders of the flask to aid condensation. 

It may occasionally happen, particularly if the solution is approaching saturation, that a small quantity of the crystalline solute separates at the top of the tube H in the zone Z, i.e, immediately above the source of the heat. This may be prevented by placing a narrow oblong piece of asbestos paper, with slots cut in each end, horizontally between the tubes H and D, the slots fitting over the lower narrow ends of the condenser C and the cup F. 

The furnace and thermostatic mortar. For heating the tube packing, a small electric furnace N has been found to be more satisfactory than a row of gas burners. The type used consists of a silica tube (I s cm. in diameter and 25 cm. long) wound with nichrome wire and contained in an asbestos cylinder, the annular space being lagged the ends of the asbestos cylinder being closed by asbestos semi-circles built round the porcelain furnace tube. The furnace is controlled by a Simmerstat that has been calibrated at 680 against a bimetal pyrometer, and the furnace temperature is checked by this method from time to time. The furnace is equipped with a small steel bar attached to the asbestos and is thus mounted on an ordinary laboratory stand the Simmerstat may then be placed immediately underneath it on the baseplate of this stand, or alternatively the furnace may be built on to the top of the Simmerstat box. 

The steam-distillation is continued for 5 minutes after steam can first be seen entering the condenser the ideal rate of distillation is about 4 -5 ml. of distillate per minute, but this is not critical and may be varied within reasonable limits. The receiver J is then lowered from the lip K of the condenser and the steam-distillation continued for a further two minutes, thus ensuring that no traces of liquid containing ammonia are left on the inside of the condenser. At the end of this time any liquid on the lip K is rinsed with distilled water into J, which is then ready for titration. It is important that the receiver and its contents are kept cold during the distillation and it is advisable to interpose a piece of asbestos board or other screen so that it is not exposed to the heat from the burner under the steam generator. 

The advantages of the above air bath are (1) simplicity and cheapness of construction (2)ease of temperature control (3) rapidity of cooling of the contents of the flask effected either by removing the asbestos covers or by completely removing the air bath and (4) the contents of the flask may be inspected by removing the asbestos covers. 

Electric hot plates may also be employed for heating. These should be of substantial construction and be provided with three-way switches. The diameter of the heavy cast-iron top may vary between 5 and 10". It is usually advisable to interpose a sheet of asbestos board between the metal top and the vessel to be heated, particularly if the contents of the latter are liable to bump. ... 

Fig. 11,10, 3, depicts a housing for the apparatus of Fig. 11,10, 2, a it is easily constructed from lengths of angle iron and asbestos board. If desired, torch bulbs may be fixed in the appropriate holders in the walls, and connected with a dry battery or accumulator in order to provide illumination of the melting point apparatus. The electric bulb immediately behind the apparatus should be connected to an inde pendent micro-switch. Alternatively,... 

Several forms of apparatus employing electrical heati iig wi 11 be described. A simple form may be readily constructed from a domestic electric iron of 400-500 watts rating. The handle is removed, and two holes of 8 mm. diameter are drilled through the base (ca. 11 mm. thick) so that they meet in the centre of the block. One hole is for a 360° thermometer (small bulb) the other hole is spare and can be used for comparison with a standard thermometer. The heater is mounted on a sheet of thick asbestos board which is fixed to an appropriate wooden base. The wires from the heating unit are connected to two insulated terminals fitted on the board (Fig. 11, 11, 1). The rate of heating is controlled by either of the following methods ... 

The theory of the process is discussed in Sections 1,1-1,3. The apparatus of Fig. 11,12,1 may be used when moderate quantities of the substance are available. A is a 50 ml. distilling flask attached by a cork to a Liebig condenser B, upon the end of which an adapter C is fitted D is a receiver for collecting the distillate. The thermometer E is fitted into the neck of the distilling flask by means of a well-bored cork the bulb of the thermometer should be in the centre of the neck of the flask and slightly below (ca. 5 mm.) the level of the side tube. The flask may be heated on a wire gauze with asbestos centre or preferably in an air bath (Fig. 77, 5, 3). 

All clamps holding glass apparatus should be lined with cork, attached by means of glue or seccotine , or with asbestos paper this will reduce the danger of fracture if excessive pressure is exerted on the clamp. 

The so-called hydro-vac pump, shown in Fig. 11, 22, 2 (the upper half of the mercury reservoir and the column above it are insulated by a layer of asbestos), is an inexpensive, all-glass, mercury diffusion pump, which can be used in series either with an oil pmnp or with a water Alter pmnp (compare Fig. 11,21, 1) capable of producing a vacuum of at least 2 mm. It is accordingly of particular value in the organic laboratory for vacuum distillations, fractionations, sublimations and pyrolyses as well as for molecular distillations (see Section 11,26). The hydro-vac... 

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