Because of its properties, asbestos was a widely used raw material, primarily in the commercial building and automotive industries. In the commercial building industry, asbestos could be found in vinyl floor tile and the associated mastic, thermal system insulation, roofing materials, ceiling and wall plasters, and fireproofing. In the automotive industry, asbestos was commonly used in brake pads. Asbestos was even used to a lesser degree in the clothing industry. But when we think about historical uses of asbestos, bridge construction probably isn’t foremost in our minds, if it registers at all. But asbestos can be found in several different locations on and around bridges. This article identifies the bridge components that may contain asbestos, and explains the impacts on worker protection and waste management on bridge rehabilitation projects where asbestos is prevalent.
Before identifying the bridge components that may contain asbestos, a brief background on asbestos may be helpful. Asbestos is a naturally occurring mineral that is still being mined today in several continents, including North America. There are several forms of asbestos – chrysotile is the most common and makes up approximately 95% of the use today. The property that makes asbestos so useful in the building construction and automotive industries is its ability to withstand heat. Other properties that make asbestos so useful are its resistance to fire, poor electrical conductivity, and high tensile strength. In fact, the word asbestos is derived from a Greek adjective meaning inextinguishable. Because of these properties, and because it is relatively inexpensive and readily available, asbestos is still used today in numerous applications – vinyl floor tile, brake pads and linings, gaskets, adhesives, roofing sealant and patching compounds, and pipe wrap; but has been banned in a number of materials (i.e., fireproofing).
Unfortunately, there are several health affects related to exposure to asbestos. The two most common diseases associated with asbestos exposure are Asbestosis and Mesothelioma. Asbestosis is a scarring of the lungs, which impairs the elasticity of the lung tissue and ultimately restricts breathing and leads to decreased lung volume. Mesothelioma is a cancer of the lining of the chest or abdominal wall. Both diseases are primarily due to exposure to airborne asbestos, and both are almost always fatal. Further, a smoker who is exposed to asbestos is at least 50 times more likely to develop lung cancer than the general public.
Asbestos was (and still is) widely used in the building construction and automotive industries. But because of the properties described earlier, asbestos has also been identified in various components on and around bridges, including:
- Paints – A coating historically used on railroad bridges was coal tar epoxy. Asbestos has been found in coal tar as a reinforcing material, and in more traditional highway bridge coatings.
- Gaskets – around electrical boxes, in mechanical rooms on lift/draw bridges, and between sections of jersey barriers
- Pads – in the felt-like paper beneath bearings at piers and abutments
- Caulking – at the base of light posts or guardrails, or in expansion joint materials
- Fireproofing material – in mechanical rooms on draw/lift bridges, and anchorage vaults on larger bridges
- Insulation – to protect communication and electrical conduit attached to the bridge
- Tar – on the bridge surface
- Cementitious material – to protect piping used to transport liquids or gases along the bridge structure
- Rubber – used as vibration dampers at expansion dividers or between concrete or steel sections
Determining the Presence of Asbestos Containing Material (ACM)
Determining the presence of asbestos in bridge components must be performed by a certified Building Inspector licensed in the state where the bridge is located. Building Inspector certification usually involves the completion of a three-day EPA approved training course, and some cities (i.e., Philadelphia) require an additional level of certification beyond state requirements. Determining whether asbestos is present in a material involves the collection and laboratory analysis of a bulk sample. To conclusively state that a bridge component material is non-asbestos containing, the EPA requires the collection of a minimum of two samples; a minimum of three samples is required if the component material is thermal system insulation or a surfacing material (i.e., a material that was either sprayed or trowel-applied). Samples of the bulk materials are analyzed in the laboratory using either polarized light microscopy or Point Count methods. While there are no laboratory certifications required to analyze for asbestos, the laboratory should participate in the National Voluntary Laboratory Accreditation Program and maintain and adhere to Standard Operating Procedures as part of an established internal quality assurance program. Laboratory technicians must be trained to properly handle ACM. Once a material has been determined, through laboratory analysis, to contain greater than 1% asbestos, that material is considered asbestos containing.
Items to Consider during Bridge Rehabilitation Projects
Since asbestos may be present in materials on and around bridges, there are several items to consider during bridge rehabilitation projects:
- Cover and protect any asbestos-containing conduit during abrasive blast cleaning operations. Rubber- wrapping and plywood encasements have been successfully used to protect the conduit from damage from the impact of the abrasive. Ideally, the utility owner should be notified prior to the start of the rehabilitation project to confirm the proposed approach to protecting the conduit is suitable.
- If the bridge is scheduled to be demolished, an assessment must be performed by a licensed Building Inspector and all existing known ACM needs to be removed. The removal must be performed by a licensed abatement contractor using trained workers.
- Some state Departments of Transportation (i.e., PennDOT) require that an assessment for asbestos-containing materials be conducted as part of the design phase of any bridge renovation project.
- Waste management – if the paint being removed contains asbestos, the disposal facility must be licensed to accept waste containing asbestos (and potentially toxic metals) and have the appropriate certifications. In fact, it is common industry practice to ask the landfill for written confirmation of their ability to accept asbestos containing waste in the pre-project submittal process.
- Worker protection – if removal of asbestos-containing material is required, the abatement must be performed in accordance with the OSHA Asbestos in Construction standard (29 CFR 1926.1101), and must be performed by abatement workers certified in the state where the abatement is occurring. If ACM removal is being performed in conjunction with lead paint removal, the PPE and respiratory protection being used to protect against exposure to toxic metals will likely provide an adequate level of protection for exposure to asbestos. Likewise, the personal hygiene practices (hand wash and/or decontamination trailer, HEPA vacuum) in place for exposures to toxic metals would be used for decontamination following exposure to ACM.
- May have to file a demolition or abatement permit with the local municipalities (city or county), or the state.
Asbestos has been widely used in the building construction and automotive industries, but there have been beneficial uses of asbestos in and around bridge structures. Assessments of bridge components for asbestos-containing materials are required if the bridge is scheduled to be demolished, and are recommended, but not required, if the bridge will be rehabilitated. If asbestos-containing materials are present, precautions related to worker protection and waste management should be taken during bridge rehabilitation projects.