An interagency agreement between the National Institute for Occupational Safety and Health (NIOSH) and the Department of Transportation, Federal Highway Administration (FHWA) provided funding for NIOSH researchers to evaluate possible differences in the occupational exposures and potential health effects of crumb rubber modified (CRM) hot mix asphalt(HMA) and conventional HMA, as used in highway paving operations. This exposure and health evaluation has been performed through a series of seven NIOSH Health Hazard Evaluations (HHEs) conducted from 1994 through 1997. The specific objectives of the HHEs include: 1) characterization of occupational exposures to CRM asphalt and conventional asphalt using available methods; 2) development and field testing of new analytical methods to evaluate asphalt fume exposures; and 3) collection of information concerning the potential health effects associated with CRM in HMA compared with conventional HMA exposures. Additionally, this interagency agreement was amended to reflect another important goal, the development and evaluation of engineering controls to reduce road worker exposures to asphalt fume during paving operations. This engineering control research was conducted through NIOSHs Division of Physical Science and Engineering, Engineering Control and Technology Branch (DPSE, ECTB).
Crumb Rubber Related Health Risk Evaluation
As a result of the crumb rubber provisions of ISTEA, FHWA entered into this interagency agreement with NIOSH to evaluate the potential increase in environmental and human health effects associated with the use of crumb rubber modified (CRM) asphalt. To be included in the evaluation, a suitable site must 1) include both conventional and CRM hot mix asphalt (HMA) pavement that use asphalt binder from the same crude source, 2) have sufficient quantities of both mixtures to allow at least three days of monitoring, and 3) include a CRM wet process with at least 8 kg of crumb rubber per metric ton of mix. To date, site evaluations have been performed at seven paving projects around the country (Michigan, Indiana, Florida, Arizona, Massachusetts, California(2)). While NIOSH has released some preliminary data on the individual projects, a report documenting overall conclusions, risk assessments, or recommendations has not yet been issued.
The repeal of the mandated use of crumb rubber has made it difficult to find additional suitable field tests, so NIOSH's overall assessment will be made using data from the seven projects evaluated to date. A composite report of the overall findings and conclusions is currently being prepared by NIOSH. This report will address issues of sampling methods, worker exposures, and health effects associated with conventional versus CRM asphalt paving.
Engineering Controls for Asphalt Pavers
In December 1995, the Occupational Safety and Health Administration (OSHA) identified asphalt fumes as a priority for non-regulatory action. A significant step to control exposures to asphalt fumes through a non-regulatory process has been achieved by a cooperative effort between the asphalt industry, NIOSH, and FHWA. This effort has resulted in the January 1997 issuance of NIOSH's "Engineering Control Guidelines for Hot Mix Asphalt Pavers - Part 1, New Highway-Class Pavers."
The NIOSH guidelines are voluntary compliance and state that, "each paver manufacturer should develop and install exhaust ventilation systems with a minimum controlled indoor capture efficiency of 80% on all new self-propelled HMA pavers weighing 16,000 pounds or more and manufactured after July 1, 1997." Provisions are also included for testing, certifying, and maintaining the systems, as well as for training workers and inspectors in their use. On January 9, 1997, representatives from the paver manufacturers, Department of Labor, National Asphalt Paving Association (NAPA), FHWA, and the labor unions signed an agreement agreeing to the guidelines. Copies of the guidelines along with NAPA's Winter 1996 "Focus on HMA" which contains an article concerning this effort were distributed to FHWA's Region and Division Offices with a March 20, 1997 memo from FHWA's Director of the Office of Engineering.
NIOSH intends to address at a later date the application of engineering controls for non-highway-class (weighing less than 16,000 pounds) pavers and for the retrofit of all existing pavers. It is anticipated that FHWA will be involved as these guidelines are developed and issued.
On June 24, 1997, NIOSH hosted a Forum on Asphalt Fume Health Effects Research. The meeting attendees included NIOSH researchers and attorneys and representatives from OSHA, FHWA, NAPA, the Asphalt Institute, labor unions, oil companies, contractors, and consultants. The purpose of the meeting was to present an update on the research efforts completed, underway, and planned on the health effects due to exposure to asphalt fumes.
In the area of new research, two independent efforts were discussed. In the more advanced of the two, NIOSH has a new facility in Morgantown, West Virginia that houses the Health Effects Laboratory Division (HELD). Once fully staffed, this division is planning a two-year chronic bioassay study of asphalt fumes. Under this research, field, chemistry, animal (male rats), and exposure studies are planned. NIOSH assured the industry representatives present for this meeting that they would be kept involved as the specific protocols were developed.
The other planned effort is in its early stages, where representatives of the unions representing laborers and operating engineers have had discussions with NAPA about conducting a feasibility study on asphalt exposure. The Asphalt Institute has also been involved in these discussions, but work is still pending.