For the first time in years, the asphalt paving industry can sleep soundly, safe in the knowledge that the federal government isn't about to declare fumes from asphalt paving operations to be carcinogenic.

A new report from the National Institute of Occupational Safety and Health (NIOSH) is that further research in this area is needed, and that measures are indicated to minimize worker exposure while studies continue. Indeed, the industry has been taking major steps in this direction, for example, providing stack exhausting of screed fumes during paving operations.

But buried deep in December 2000 report -- Hazard Review: Health Effects of Occupational Exposure to Asphalt, DHHS (NIOSH) Publication No. 2001-110 -- were the words the industry wanted to hear: "NIOSH concludes that the collective data currently available from studies on paving asphalt provide insufficient evidence for an association between lung cancer and exposure to asphalt fumes during paving."

NIOSH, however, warns that "The available data, however, do not preclude a carcinogenic risk from asphalt fumes generated during paving operations."
 

Nearly two decades of fear

The asphalt paving industry has grappled with the asphalt fumes issue for nearly two decades. As early as 1977, NIOSH had reviewed the available data on the health effects of occupational exposure to asphalt and asphalt fumes, and determined the principal adverse health effects to be irritation of the serous [secreting] membranes of the conjunctivae [inner lining of eyelid and exposed surface of eyeball], and mucous membranes of the respiratory tract.

On the basis of this evidence, NIOSH recommended an exposure limit (REL) for asphalt fumes of 5 milligrams per cubic meter of air, measured as total particulates during any 15-minute period. 
 In 1982, the National Asphalt Pavement Association (NAPA) had to respond to NIOSH reports that tests of roofing asphalts had yielded carcinogenic compounds.

To acquire fumes, these roofing asphalts were heated to temperatures more than twice those used in the paving industry. The fumes then were collected, concentrated and used in animal experiments. The tests were challenged at once by a committee with representation from NAPA, the petroleum industry, and the roofing industry, reported the late Hugh Gillespie in NAPA's 1992 history, A Century of Progress.

The issue resurfaced in 1988 when in testimony to the Department of Labor that year, NIOSH recommended that asphalt fumes also be considered a potential danger to workers. Afterward the Occupational Safety and Health Administration (OSHA) announced coming regulations on asphalt paving.

"In 1988, NIOSH recommended to OSHA that asphalt fumes be considered a potential occupational carcinogen based on the results of an animal study in which laboratory-generated roofing asphalt fume condensates induced malignant skin tumors in mice," the new report states.

Anticipating workers dressed in moon suits, and class action suits from labor unions and neighborhoods through which paving had taken place, the industry fought back with tremendous vigor and unanimity.
 NAPA itself retained two toxicologists and sought to differentiate the properties of coal tar pitch from liquid asphalt, with which asphalt was conveniently lumped. Late in 1988 OSHA -- at least temporarily -- omitted asphalt fumes from its list of carcinogens.

"Since then, investigators have described differences in chemical composition, physical characteristics, and biological activity between asphalt fumes collected in the field and those generated in the laboratory," NIOSH said in the new report. "The relevance of these differences in ascribing adverse health effects in humans is unknown ... Data regarding the potential carcinogenicity of paving asphalt fumes in humans are limited."

NIOSH also observed that no animal studies have examined the carcinogenic potential of either field- or laboratory-generated samples of paving asphalt fume condensates, and that only the laboratory-generated fumes were "genotoxic", or genetically damaging.

Therefore, NIOSH concluded "the collective data currently available from studies on paving asphalt provide insufficient evidence for an association between lung cancer and exposure to asphalt fumes during paving," but added "[t]he available data, however, do not preclude a carcinogenic risk from asphalt fumes generated during paving operations."

NIOSH also said evidence from animal studies indicated that asphalt left on the skin for long periods of time could result in local carcinomas but that no comparable reports of these effects existed for humans.
 

Collaboration improves work environment

Well before the December 2000 report, in 1996, NIOSH, NAPA, the Asphalt Institute, the Laborers' Health and Safety Fund of North America, and the International Union of Operating Engineers, and the manufacturers Blaw-Knox, Barber-Greene/Caterpillar, Cedarapids, Roadtec, and Champion all collaborated to develop draft guidelines that could be used by contractors and manufacturers of large hot-mix asphalt (HMA) pavers to improve the work environment.

"Although the health risks from asphalt exposure are not yet fully defined, all partners agreed that prudent action was needed to reduce worker exposures," wrote NIOSH director Linda Rosenstock, M.D., in the forward to the publication, Engineering Control Guidelines for Hot Mix Asphalt Pavers, DHHS (NIOSH) Publication No. 97-105, January 1997.

"The willingness of all partners to find a workable approach should serve as a model for others who are developing occupational safety and health recommendations," she wrote. "Development of these guidelines and this document was truly a joint effort."

This landmark publication is available on the internet at http://www.cdc.gov/niosh/asphalt.html, or in pdf facsimile format at http://www.cdc.gov/niosh/pdfs/97-105.pdf.

This cooperative effort resulted in exhaust control guidelines for highway-class HMA pavers. The document recommended:

o Ventilation Systems. Each paver manufacturer should develop and install exhaust ventilation systems with a minimum controlled indoor capture efficiency of 80 percent on all new self-propelled HMA pavers weighing    16,000 pounds or more and manufactured after July 1, 1997.

o Certification. Manufacturers of highway-class HMA pavers should certify the system's performance to purchasers of new pavers.

o Operation and Maintenance. For each exhaust ventilation system, HMA paver manufacturers should provide an operator's manual that contains a maintenance schedule, in addition to detailed sketches and performance criteria for equipment owners to use in their annual assessment of the exhaust ventilation systems, and troubleshooting instructions, and

o Training. Equipment manufacturers should create or identify training manuals and instructions designed to train equipment owners in the operation, maintenance, and repair of exhaust ventilation systems for HMA pavers.

The level of cooperation evidenced in the Engineering Controls Guidelines project was such that the partnership was named as a finalist for the prestigious Innovations in American Government Award in 1998.
 

Worker hazards still acknowledged

In its new December 2000 publication NIOSH states that current findings support its 1977 assessment that exposure to asphalt fumes is associated with eye, nose, and throat irritation. "Recent studies also have found evidence of lower respiratory tract symptoms among workers exposed to asphalt fumes," NIOSH said. "Those data are being further analyzed to assess the relationship between symptoms and exposures."

The new report also discusses studies that associate asphalt exposure with potential long-term health effects, such as chronic bronchitis and lung cancer. The report reviews data from those studies that relate to potential long-term effects under different conditions of use, including exposures from paving, roofing and asphalt-based paint formulations.

NIOSH says additional studies are needed to better characterize occupational exposures to asphalt fumes, vapors and aerosols, and to further evaluate the risk of chronic disease, including lung cancer.

In the meantime, NIOSH recommends that possible health effects from exposures to asphalt, asphalt fumes and vapors, and asphalt-based paints be minimized, the report suggests, by adhering to NIOSH's current REL of 5 milligrams of asphalt per cubic meter of air over any 15-minute period, and by

o Preventing skin exposure

o Keeping the application temperature of heated asphalt as low as possible

o Using engineering controls and good work practices at all work sites to minimize worker exposure to asphalt fumes and asphalt-based paint aerosols, and

o Using appropriate respiratory protection for workers.

NIOSH and its partners also have furthered collaborative laboratory and field research, and have worked together to develop informational materials for workers and contractors on methods for reducing exposures.

In September 2000, representatives of industry, labor, government, and academia met to discuss research needed to assess completely the health risks associated with exposure to asphalt.

The December 2000 document is available on the internet at http://www.cdc.gov/niosh/01-110pd.html, or in pdf format at http://www.cdc.gov/niosh/pdfs/01-110.pdf.
 

FHWA releases new edition
of Highway Statistics

The Federal Highway Administration has released the 1999 edition of Highway Statistics, an annual publication that contains a wide range of information on America's road and highway infrastructure, and users.

The FHWA and its predecessor, the Bureau of Public Roads, have published the report every year since 1945. It contains statistical data on motor fuel, motor vehicles, driver licensing, highway-user taxation, state and local highway finance, highway mileage, federal-aid for highways, select tables and charts from the 1995 Nationwide Personal Transportation Survey, and international data.

The information also is used as the principal data in calculating each state's share of funds under the Transportation Equity Act for the 21st Century (TEA-21), the legislation that provides federal-aid funds to states.

The report is available on the agency's web site at http://www.fhwa.dot.gov/ohim/hs99/index.htm. The data tables can be viewed in PDF and downloaded as Excel spreadsheets. The report also is available in hard copy at no charge by writing to the Office of Highway Policy Information, FHWA, Room 3306, 400 7th St. SW, Washington DC 20590.