Up until 1974, asbestos had been respected and used in industry due to its excellent incombustible and refractory properties, heat-insulating properties, and sound-absorbing qualities. Normally, asbestos was incorporated on walls, pipes, and industrial equipment in schools, residences, factories, office buildings, ships, and older motor vehicles, whenever sound, heat, or fire proofing was required.
However, over time, asbestos fibers tend to become airborne, as the surface spray coated with asbestos is vibrated or an object collides against the asbestos-coated surface or when the binder used in the coating deteriorates. Often, and perhaps most commonly, asbestos fibers fill the air when a building is renovated or demolished. The problem with asbestos fibers filling the air is that the fibers are environmentally hazardous, and, if inhaled, may cause asbestosis, mesothelioma or lung cancer. Thus, there is an urgent need to remove asbestos in tens of thousands, and perhaps hundreds of thousands, of buildings nationwide. Internationally, there are many millions of buildings from which asbestos must be removed. This will lead to many cases wherein asbestos fibers become airborne, often in an enclosed room, thereby causing a health hazard to many thousands of people.
In the past, asbestos containing materials was removed by workers wearing dust respirators and dustproof clothes. There have been a number of different methods used to remove asbestos. Asbestos layer(s) were removed by rod-type scrapers or wire brushes while spraying a wetting agent or amended water on the building material to be removed in a sealed workroom made for the removal operation. Another method of asbestos removal involves solidifying the surface of the asbestos coating by the use of a resin or a liquid chemical to encapsulate. In yet another method, asbestos-coated surfaces are enclosed with boards or the like.
While the latter two methods described above are merely temporary measures, the first-mentioned method comprising physical removal of asbestos is, in fact, a permanent solution. However, the manual removal of asbestos by use of rod-type scrapers or wire brushes requires much labor and leads to high working expenses due to the need to have a person spraying a wetting agent for dust suppression for each person removing building material. Most importantly, asbestos fibers generated in the removal operation are suspended in air for a long time, and the sealed workroom must be left sealed for a long time. Forced removal of the suspended asbestos fibers requires the use of HEPA filters and a large-capacity dust collector, leading to extremely high working expenses. Additionally, the manual removal of asbestos by the workers has the problem that many portions of asbestos tend to be left unstripped, particularly at narrow areas near corners or the existing piping, and the portions of asbestos left unstripped may scale off later. Furthermore, even with the use of the dust collector, a small amount of the asbestos fibers separated from the original surface may remain in air or accumulate at the corners of the floor, the asbestos fibers being very difficult to collect.
Dust suppression is used to clean the air of particulate matter. The particulate can be inorganic material such as asbestos (chrysotile, amosite, crocidolite, tremolite, actinolite, anthrophyllite, etc.), asbestiform minerals, silica, metals, salts or manmade polymers such as nylon, plastic, fiberglass, nanoparticles, etc. Particulate matter can also originate from biological materials such as germs, insects, plants, animal based allergens, proteomic proteins of health concerns, etc. The particles can be from 1 micron to 50 microns or smaller which is measured in nanometers. 1 micron equals 1,000 nanometers.
Various dust suppressant compositions and methods are known in the art for spraying in air to reduce air-borne dust or for spraying on substances which develop dust.
U.S. Pat. No. 4,369,121 (Callahan et al.) discloses a composition for controlling dust which comprises a cellulose ether and a wetting agent such as an ethylene oxide condensate of nonyl- or octylphenol, ethylene oxide condensates of straight chain alcohol, fatty acid amides, quaternary ammonium compounds, organic phosphate esters, and sulfonic acids.
U.S. Pat. No. 4,169,170 (Doeksen) discloses a composition and method for controlling dust during coal transportation wherein the composition comprises an aqueous solution containing an asphalt emulsion or a black liquor lignin product and a water soluble ethoxylated alkyl phenol.
U.S. Pat. No. 4,425,252 (Cargle et al) discloses an aqueous coal dust abatement composition including a water soluble sulfonic acid salt and ethoxylated nonyl phenol.
U.S. Pat. No. 4,428,984 (Shimizu et al) discloses a method of preventing dusts by spreading an aqueous solution including an ethoxylated alkyl phenol, alcohol, fatty acid, amine or fatty acid amide and a polyhydric alcohol.
U.S. Pat. No. 4,487,615 (Taylor et al.) discloses a method of reducing mine dust by spraying water including a surfactant produced by reacting ethylene oxide with linear primary alcohols.
U.S. Pat. No. 4,136,050 (Brehm) and U.S. Pat. No. 4,171,276 (Brehm) disclose a dust suppression composition comprising an aqueous solution of alkyl phenoxy polyethoxy ethanol and a copolymer of ethylene oxide and propylene oxide.
U.S. Pat. No. 5,052,756 (Wada et al.) discloses a process for separation of an asbestos-containing material from a surface to which the asbestos-containing material is adhered, while preventing floating of dust of the removed asbestos-containing material. The process requires jetting of pressurized water from a plurality of nozzles to the surface at a pressure of at least 80 kg/cm.sup.2 so as to wet and remove the asbestos-containing material therefrom by the energy possessed by the pressurized water.
Dust suppression for interior spaces is generally accomplished by using a combination of engineering controls and a misting agent. Misting agents are sometimes referred to as “amended water” or water with a surfactant. The term “amended water” comes from 29 CFR 1926.1101 or the OSHA regulations for asbestos in construction. Fogging is another term used in some applications common to greenhouses and cleanrooms where pesticides are administered.
The air is misted with the misting agent. The water droplets from the misting agent adhere to the particulate material in the air that is the offending agent to health or the environment. This increases the weight of the particulate material. This forces the particulate material to drop to surfaces due to the increased weight or specific gravity. This allows the particulate materials to be removed by cleaning methods on surfaces or to be “locked down” to a surface (such as a floor or wall) with a paint or sealer so the particles are permanently adhere to the surfaces.
The problem with the first scenario is that the misting agent must not evaporate too quickly or the particulate material will become airborne again. The problem with the second scenario of the particulate materials is that the asbestos needs to be removed rather than hidden under a paint, glue or polymer film that may be disturbed during a future renovation or catastrophic event like fire, flood, etc.
In each circumstance, the offending agent or particulate is removed from the air to prevent the particulate from entering the respiratory tract and possibly the bloodstream. Environmental controls use techniques such as pressurization (positive and/or negative) differentials of a contained area and mechanically exhausted through a HEPA filter and/or water baffle. This is largely done to limit cross-contamination during the removal of the particulate material or offending agent.
Towards that end, many of the techniques involve the use of “negative air pressure differential” conditions, which are not desirable because the “amended water” droplets are pulled out of the contained area too quickly and the surfaces dry too quickly to capture particles effectively.
The contained area is usually “flooded” with amended water in an attempt to ensure particle capture. It takes a high amount of the “amended water” due to the use of the negative air pressure machines. The job site becomes awash in water that must be constantly removed. The area is saturated, sometimes causing water damage to the non-remediated areas. Microbial growth is encouraged by the high-humidity conditions brought about by traditional methods.
The above dust suppressing compositions and methods all have various disadvantages in that the compositions are not immediately effective and require an extended time for satisfactory performance or that the compositions include excessively toxic or other less biodegradable materials.
There is therefore a need for a dust suppressant composition which quickly enhances the settling of air-borne dust and which is substantially biodegradable and benign in the environment.