Asbestos Exposure Threshold No scientist has been able to find a threshold under which asbestos exposure does not pose a risk for developing cancer. This means there is no safe level of asbestos exposure. Historically, industrial hygienists established threshold limit values (TLVs) to limit the amount of asbestos to which workers were exposed. TLVs were intended to limit the r isk of developing asbestosis. They were not intended to protect workers from cancer. We now know that the TLVs were not even effective to prevent asbestosis. Experience has shown that even people who did not work with or around asbestos have developed asbestosis because they lived ne What is Asbestos? The term “asbestos” refers to a group of naturally occurring minerals with remarkable heat resistant qualities. There are six different types of asbestos, which are divided into two different groups: serpentine and amphibole. Some, but not all, of these asbestos types have been used commercially. The serpentine group gets it name from the curved shape of the fibers. This group includes only one type of asbestos: chrysotile. Chrysotile was also commonly called white asbestos. Most of the c hrysotile asbestos used in the United States was mined in Canada, Africa and the former USSR. Chrysotile was hugely popular with industry and accounts for more than 90 percent of the commercially used asbestos in the United States. Amphibole asbestos fibers are straight, needle-like fibers. The amphibole group includes amosite (also called cummingtonite-grunerite cummingtonite-grunerite or “brown asbestos”), crocidilite (also called riebeckite or “blue asbestos”), tremolite, anthophyllite and actinolite. Of these, only crocidilite and amosite were deliberately incorporated into commercial products. However, “noncommercial” amphibole “noncommercial” amphibole fibers (tremolite, anthophyllite and actinolite) were sometimes present as contaminants in commercially used products containing chrysotile asbestos, vermiculite and talc. The amphiboles are commonly mined in southern Africa and Australia. Asbestos is made up of microscopically small fibers, hundreds of times more fine than a human hair. If asbestos fibers are released into the air, they can remain airborne for e xtended periods of time. Sweeping or regular vacuuming can re -suspend the fibers, so small they slip right through a re gular vacuum bag and escape back into the air. Asbestos fibers are too small to be seen or felt. Source: Pathology of Asbestos-Related Diseases (Victor L. Roggli et al. eds., 2004). 2004) . Why Use Asbestos? The term “asbestos” comes from a Greek word that means “unquenchable” or “indestructible,” and indeed it is almost impervious to the effects of heat, flame, salt water, chemical corrosion or biological processes. It is also flexible and strong (high tensile strength) and has low electrical conductivity.
Asbestos can be spun or woven for blankets that are fireproof, resist tear s and provide good insulation. Asbestos fibers can also be mixed into products to make them stronger, more flexible and heat re sistant. Because of its many useful properties, asbestos has been referred to as the “magic mineral.” It has been incorporated into over 3,000 different industrial and household products. ar a mine, for example. A recent study showed elevated incidence of asbestosis among people living within 10 miles of the Belvidere Mountain asbestos mine in nor thern Vermont. And hundreds of residents of Libby, Montana have developed the disease, whether or not they worked in W.R. Grace’s nearby asbestos-contaminated vermiculite mine. In any event, the evidence from asbestos cases has repeatedly shown that workers w ere regularly exposed to asbestos at levels well above t he TLV. Asbestos fibers are so small that an individual could be exposed to a significant level of asbestos without being able to see, feel, taste or smell any evidence of it. If dust levels in the work environment were high enough that dust from asbestos products was visible, the level of exposure was very high. According to asbestos experts, if dust from asbestos products was visible, the asbestos exposure was over the TLV.
Asbestos Removal After the presence of asbestos is confirmed by testing, contractors are required by law to perform asbestos removal following guidelines set forth by the Environmental Protection Agency (EPA) at both state and federal level. The requirements are in place to protect the workers, the community and the environment. Laws may vary from state to state, but they are similar in nature and often severe in consequence for contractors who choose to ignore them. Documentation is an important step to an asbestos removal operation. The EPA requires specific paperwork including reports and inspection results be filed, and asbestos disposal have a clear chain of responsibility from job site to transportation to disposal site, dated and signed by all parties as the material changes hands. Good record keeping protects t he business from legal ramifications and keeps the EPA informed about the progress of the job. Preparing for Removal Precautions must be taken before certified asbestos contractors begin an asbestos removal, which may also be called abatement. Working from the inside out to minimize exposure, workers close windows, doors and ducts and turn off fans and heating or air conditioning to prevent circulation of dust created by the process of demolition. Warning signs are posted to alert passersby that the area is off -limits and potentially hazardous. Specially trained workers are re quired to wear protective gear from head to toe, including an approved mask, gloves, and disposable coveralls and shoe covers.
If possible, the work area is we t using a fine mister to prevent dust particles in the air, and it is kept wet for the duration of the job and t he bagging of debris. Asbestos Removal Once preparations are complete, worke rs begin stripping asbestos-containing material using techniques least likely to create dust. In the past, walls and tiles were simply pulverized and the debris shoveled into an open container and carted away to the dump. Today, workers cut mea sured sections and make piles of debris separated by material to be bagged and tagged in accordance with EPA re gulations. Ceiling tiles are lifted carefully out, and the grouting around floor tiles is removed so the tiles can be scraped out with as little crumbling as possible. Once removed, the debris is wet and stored in approved containers for disposal. Containers are required to be airtight. The least expensive and most common method of containment is double bagging using leak-proof plastic bags at least 6mm thick. Finishing the Job Once the asbestos material is removed, the area must be cleaned of dust. This may be accomplished by wetting the area and using mops or sponges to clean or using a vacuum with a special HEPA (high efficiency particulate air) filter to remove all traces of dust. The last step is to bag up all the work-related materials like mop he ads and sponges, plus the disposable clothing worn by the workers. These materials should be treated in the same way as the asbestos material: sealed in leak-proof containers, tagged and sent to a qualified disposal facility. Once the job is complete, air quality testing should be performed to ensure that the air is safe and breathable before the room is opened, the air circulation equipment is returned to service and people are allowed to return without protective gear.
What is the replacement of asbestos insulation sheets? Answer: Other fibers are often used as replacements for asbestos. Fibreglas, rock wo ll and even carbon fibers can be used, depending on the application.
Asbestos Alternative, Substitute & Replacement Materials: Sleeve, Tape, Rope, Fabric & Insulation Most fiberglass and silica based materials can be used as an alternative or replacement to asbestos. These high temperature and heat r esistant fiberglass sleeves, tapes, ropes, fabrics and insulation can provide the same protection and insulation value as asbestos. All of our high temperature, heat and flame resistant products and materials are totally 100% asbestos free: non-asbestos. More information about asbestos can be found at wikipedia and the US EPA web sites.
