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Publication Number: FHWA-HRT-09-039
Date: April 2010
Pavement Marking Demonstration Project: State of Alaska and State of Tennessee-Report to Congress
Chapter 5. Environmental and Safety Issues
The objective of this part of the study was to conduct an evaluation of the potential health and environmental impacts of the alternative pavement marking systems that were included in the demonstration projects and the specific materials used in those systems. Prior to 1990, solvent-borne paint was used by many agencies for pavement marking binder material. In the early 1990s, practically all transportation agencies in the United States reduced the use of solvent-borne paint primarily due to Environmental Protection Agency (EPA) requirements on dangers due to solvents. Waterborne and latex paint have replaced the solvent-borne paints of earlier years. In addition, some new durable materials have been introduced, all of which meet the EPA requirements. However, some of the new more durable materials have specific issues associated with cleaning tanks and spray guns and with disposal of the debris resulting from grinding or hydroblasting old and worn marking materials from the roadway. If these types of products are found to be effective in terms of their durability and performance, as evaluated in the demonstration projects, then the research team will identify the environmental issues associated with their use. The most knowledgeable source of this information is the industry. Therefore, the research team plans to work with the appropriate industry representatives to identify the environmental concerns and issues, including storage of materials, proper cleaning of equipment, and proper handling of debris from marking removal efforts.
The environmental and health and safety impacts of pavement marking systems need to be considered in light of the various regulatory requirements. The following lists show where additional information can be found concerning those impacts:
The U.S. manufacturers of glass beads used in pavement markings have recently expressed concern about the importation of glass beads from Third World countries, particularly China. Overseas producers have considerably lower production costs, and U.S. producers have become concerned about competition and erosion of their markets. They have raised concerns about foreign glass beads containing significant levels of heavy metals, which could be a potential safety and environmental concern to users in the United States.
The primary elements of concern appear to be lead, arsenic, and antimony. Some glass manufacturers deliberately add lead and arsenic to glass (particularly optical glass) to impart clarity and control bubbles. Glass recycled from television sets and computer monitors are another potential source of all three elements. Many electronics recycling programs send their products overseas to be dismantled, which may be a way that these elements enter the manufacturing process. As a precaution, a number of agencies worldwide are beginning to implement specifications that limit the total heavy metal content of glass beads (see table 26).
Note: Blank cells indicate missing data.
As can be seen, the limits vary widely, and some of these standards may be hard to achieve. Most beads are made from waste glass from recycling programs, and restrictions on heavy metals may impact the environmental benefit of recycling. There is also the potential that overly restrictive limits on heavy metals may impact optical performance of beads by reducing clarity.
The magnitude of environmental and safety hazards of heavy metals in glass beads is somewhat uncertain. Heavy metals in glass beads do not appear to be leachable under the conditions of the EPA Toxicity Characteristic Leaching Procedure (TCLP) test, which defines toxicity under current hazardous waste regulations. In fact, vitrification appears to be an acceptable method of disposing of heavy metal wastes.(46) An ongoing project at Rowan University studies the total heavy metal levels in various batches of domestic and foreign sourced beads and leaching under a variety of conditions including the presence of snow and ice control chemicals.(47) This project will be completed in June 2010.
In 1994, FHWA released a memorandum describing the impact of a new EPA regulation on the use of pavement marking material. The regulation was developed to reduce architectural and industrial maintenance coating emissions by 40 percent by 2004. It led to the establishment of a 1.25 lb/gal limit by 2000 and a 0.83 lb/gal limit by 2004 on VOC content for pavement marking materials. Over the past 10 years, transportation agencies in the United States have gradually replaced conventional solvent paints with waterborne paints (that have low VOC contents) and other newer pavement marking materials.
Waterborne traffic paints are the most widely used and least expensive pavement marking materials available. Waterborne paints are single-component paints that are ready for application and do not require additional ingredients. They are environmentally friendly and much easier to handle than conventional solvent paints. They greatly decrease the safety hazard for workers given their low VOC content (typically less than 1.25 lb/gal of VOC). This reason, coupled with the low cost, are the major advantages of waterborne paints.
On February 28, 2006, OSHA published the final hexavalent chromium Cr(VI) standard. The new permissible exposure limit for Cr(VI) is 5 µg/m3. In the pavement marking arena, this is primarily an issue for agencies using thermoplastic binders. Most States have moved to lead and chromate-free specifications for thermoplastic, which is the most commonly used durable pavement marking system in the United States. New regulations make it difficult for the industry to handle lead chromate in the dry form in the manufacturing plant. Thermoplastic manufacturers are pushing for lead-free and chromium-free specifications. Some States are concerned and are specifying resin-encapsulated lead chromate pigments, which will meet the new regulations but push the problem further upstream. This means the encapsulated process is usually outsourced from the United States to avoid environmental concerns. There is still the issue of line removal when encapsulated specifications are used. The researchers are testing lead-free thermoplastics in Tennessee; the main issue is the maintained nighttime yellow color.
On October 15, 2008, the EPA strengthened the national ambient air quality standards for lead. The revised standards are 10 times more stringent than the previous standards and will improve health protection for at-risk groups, especially children. The EPA has revised the level of the primary (health-based) standard from 1.5 µg/m3 to 0.15 µg/m3, measured as total suspended particles. This change is mostly going to impact the requirements for removal of thermoplastic, as it is usually done with a grinding mechanism, creating significant quantities of dust. Grinding operators and bystanders will most likely be exposed to levels above the new EPA regulations unless proper respiratory gear is used. Waterblasting may be a technique that could be used to reduce the exposure, but it may still violate the new EPA regulations. No research has been conducted in this area; however, as manufacturers push for lead-free and chromate-free thermoplastic specifications, there will soon be lead-free and chromate-free markings. However, there are currently thousands of miles of thermoplastic markings on the roads that will be removed by grinding and/or waterblasting. The removal of these lines and the environmental concerns inherently associated with the removal process will be the largest challenge related to thermoplastic markings.
State agencies are changing to lead-free and chromate-free thermoplastic markings, thereby satisfying the most recent environmental regulations. The latest EPA airborne lead regulation may cause a concern for agencies that try to remove lead-pigmented thermoplastic pavement markings. No research has been conducted to date to determine the amount of airborne lead released when encapsulated lead-pigmented thermoplastic is removed (by grinding or waterblasting).
Some multicomponent materials tested on the Alaska and Tennessee test decks are qualified as hazardous materials. Depending on the results of the Tennessee durability information and the final recommendations made from that information, there may be other environmental concerns resulting from this effort. However, the durability test decks in Tennessee are not yet old enough to make recommendations concerning specific pavement marking materials.
An evaluation of the potential environmental and health impacts of heavy metals in glass beads used in pavement markings was beyond the scope of this study. The magnitude of environmental and safety hazards of heavy metals in glass beads is somewhat uncertain. Heavy metals in glass beads do not appear to be leachable under the conditions of the EPA TCLP test which defines toxicity under current hazardous waste regulations. In fact, vitrification is an acceptable method of disposing heavy metal wastes. An ongoing project at Rowan University is studying total heavy metal levels in various batches of domestic and foreign sourced beads and leaching under a variety of conditions, including the presence of snow and ice control chemicals. This project will be completed in June 2010.
Topics: research, safety, roadside, pavement marking
Keywords: research, safety, Acrylic waterborne paint, Durability, Environmental impacts, Pavement markings, Retroreflectivity, State bidding procedures, Wider edge lines
TRT Terms: research, Safety and security, Safety, Transportation safety