Minding your own business

By: David Banasiak

Perhaps the largest and most extensive busy-body in America is the federal government. At times there seems to be a regulation covering every aspect of our lives and businesses. Despite some people questioning the wisdom of all these rules and regulations, they do fulfill the need for protecting the safety and well-being of America's citizens.

However, others view these regulations as an interference. They advocate a laissez-faire government in the belief that business and commerce would be better off with little or no governmental regulations. Allowing business to regulate itself seems like a simpler solution than governmental interference; however, can the public rely on the altruism of business.

The asphalt-paving industry is one business that decided to alleviate a potential problem before the federal government stepped in to regulate. The issue is the exposure of paving crews to asphalt fumes. It has long been accepted that the heat of the fumes increases the temperature behind the paver, adding to the discomfort of the crew. The use of newer asphalt mixes also is turning up the heat. As polymers are added to asphalt, the mix becomes stiffer. To work with these mixes the temperature is increased to 325 deg, resulting in even hotter temperatures behind the paver.

There also is some concern over whether or not the fumes pose a health hazard to the crews. Leroy Mickelsen, chemical engineer for the National Institute for Occupational Safety and Health (NIOSH) comments, "We can detect minimal levels of asphalt fumes, but the levels are so low it is not known whether there is a health concern or not." While NIOSH is not ready to make a claim on the health effects, the National Asphalt Pavement Association (NAPA) says exposure to asphalt paving fumes poses no serious health threat.

Early studies on asphalt fume exposure, conducted in 1991, provided no definitive answers. Rather then wait, NAPA took a pro-active stance, and in May 1993 began working on a solution.

Robert M. Thompson, president of Thompson-McCully, a Michigan asphalt contractor, had an idea. In a 1995 interview with ROADS & BRIDGES, Thompson said, "If we eliminate the perceived problem and get the workers away from the fumes, then there is no reason for concern" (see Public/Private Partnership Studies Ways to Reduce Asphalt Fumes, May 1995).

As the chairman of NAPA's Engineering Controls Task Force, Thompson met, in 1994, with Byron Lord, then division chief in the Federal Highway Administration's (FHWA) Office of Research and Development. The FHWA helped secure funding and the cooperation of NIOSH. With the collaboration of asphalt paving contractors, equipment manufacturers and unions, NAPA, NIOSH and FHWA launched an engineering control evaluation program to test Thompson's hypothesis.

It was decided that there would be two phases to the testing: a lab test and a field test. Some of the paver manufacturers that agreed to participate in the tests include: Cedarapids, Blaw-Knox, Roadtec, Champion (formerly Ingersoll-Rand) and Barber-Green (now owned by Caterpillar).
NIOSH and the manufacturers have finished the lab portion of the tests-at each participating manufacturers' facility- and the findings are in the process of being compiled and written.

During the lab tests a tracer gas was used to simulate the release of fumes from the asphalt paver. The gas was measured with a multi-gas sampler to determine what percent was being diverted by the controls. On June 5-7, 1995 Roadtec cooperated with NIOSH in a series of lab tests. A smoke generator was used to produce theatrical smoke between the tractor and the screed around the augers. According to a NIOSH draft document, as reported in Industry Update, Roadtec's newsletter, the average indoor­p;capture efficiency was 100% with an exhaust volume near 2,600 cu ft.

The paver was then moved outside to be tested in different wind conditions. When the paver was positioned facing north with the wind blowing from the northwest at 5-10 mph, the average capture efficiency was 81%. Next, the paver was moved to face west. With the wind still coming from the northwest at 5-10 mph the efficiency remained at 81%. From these tests it was hypothesized that the controls will result in a reduction in asphalt fumes. This hypothesis was reached even though the wind reduced the efficiency of the controls when used outside. It was reasoned that the wind was responsible for removing the other 19% of the asphalt fumes.

Based on the lab results a preliminary field test was conducted in early October 1995, in Maryland, near the Washington, D.C., metropolitan area. The goal of this test was two-fold: to check the instruments' ability to measure various parameters under actual conditions and to test the engineering controls on the paver.

It was important to study the types of instruments that could be utilized in the field because asphalt-fume exposure is very low and difficult to measure. Leland Warren, design engineer for Blaw-Knox, explains, "The concentration of the fumes' contents are right on the borderline of the detection methods currently used." Tests had already been conducted in the spring, on pavers without controls, in order to determine the instruments to be used. From those tests it was decided to try particle or aerosol detectors and an FID­p;organic­p;vapor detector.

NAPA and Roadtec's preliminary field tests used an RP180-10 paver. The tests were conducted by running the paver with the controls on for a set period of time and then turning them off to see how much the aerosol concentration, in the air, changed at the rear of the paver. A total of six different areas were tested around the paver. Nontoxic sulfur hexafluoride gas also was released into the screed and auger area in order to measure how much gas is vented out of the fans. This allowed the efficiency of the hood­p;collection system to be tested.

Even after the preliminary tests, there was still some question as to what detectors to use in the field tests. Mickelsen explains, "In the past different methods were used to measure asphalt fumes, but there were mixed results because of wind velocity and the varying rates of the fumes produced." A perfect technique has not yet been devised, but NIOSH is working with a chemist to develop a method to measure asphalt­p;fume exposure. Previous methods only focused on separating individual components of the fumes. However, Mickelsen says field tests should begin in the late spring or early summer of this year. These tests will measure the fumes and temperature reduction with the controls on the paver.

Paver manufacturers are beginning to offer controls on their products. Roadtec is the first company to offer controls as a standard item on all its paver models. Named the FXS fume extraction system it consists of two suction fans that collect fumes from the auger and screed area and redirect them away from the operator and wokers on the paver, dispersing them through a single deck-mounted stack. Roadtec's Shuttle Buggy, a material- transfer vehicle, also comes with the FXS system and uses two suction fans to divert fumes from the conveyors and hopper section, exhausting them out through a pair of stacks; one is located near the operator's station and the other on the C-1 conveyor.

Caterpillar is another manufacturer participating in the tests. The company has completed its lab tests and is waiting to perform the field tests pending sched-uling. Cat has developed its own control designs; however, it is not currently available as standard equipment on pavers. The company does plan to custom offer the controls on new pavers.

Blaw-Knox's asphalt- fume controls vent the fumes away from the screed. The fumes are then dispersed or incinerated through the engine air­p; intake. The controls were exhibited at Blaw-Knox's booth at March's ConExpo­p; Con/Agg; however, the device is not yet available on the company's pavers. Pending finalization of the product, it should be ready in 60-90 days.

Cedarapids' engineers have designed and developed a fume-capture system for use with its Grayhound paver line. The system uses hood­p;blower units mounted over the left­p; and right­p;hand sections of the paver's hot­p;mix­p;auger section. The blowers suck fumes through ductwork into a muffler unit where asphalt fumes are combined with paver­p;engine ex-hausts. The muffler then vents fumes and engine exhaust into the atmosphere. Like the other manufacturers, Cedarapids' system is still under-going tests with NIOSH; however, the company's fume­p;capture system is currently available as an option on its seven Grayhound paver models. Cedarapids plans to make the system standard on all paver units in the future.

The initiative shown by NAPA in working together with government agencies and asphalt­p;industry members demonstrates its concern for the well-being of asphalt workers and the industry's willingness to address concerns, once they are identified, in lieu of regulations.