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Engineering Controls Database

Reducing Worker Exposure to Asphalt Fumes from Roofing Kettles

Roofers, particularly kettle operators, may be exposed to asphalt fumes when asphalt is heated in roofing kettles for built-up roof construction. An estimated 46,000 roofing contractors work in the United States. These contractors are primarily small businesses that specialize in residential roofing. Approximately 50,000 on roof workers are exposed to asphalt fumes
Studies of roofers show an excess of lung, bladder, brain, liver, and digestive system cancers among roofers and workers in other occupations with the potential for exposure to asphalt. The extent to which these findings may be caused by asphalt fume exposure is unknown. Asphalt fumes have been reported to cause coughing and headaches and to irritate the mucous membranes of the eyes, nose, and respiratory tract. Observations of acute irritation in workers from airborne and dermal exposures to asphalt fumes and aerosols and the potential for chronic health effects, including cancer, warrant continued diligence in the control of exposures
NIOSH examined two engineering controls for reducing exposure to asphalt fumes: fume-suppressing asphalt and afterburner and loader systems. (1) Fume-suppressing asphalt (also known as low-fuming asphalt) contains a small amount of a polymer that, when heated, floats to the surface creating a skim layer on the asphalt in the kettle. This layer may reduce the emission of asphalt fumes from the kettle. (2) Afterburner systems reduce the amount of fumes emitted and reduce worker exposures by burning asphalt fumes from the surface of the asphalt in the kettle. This system may also be used with loading devices that allow the kettle operator to add asphalt without opening the kettle lid and releasing fumes
Workers applying hot asphalt to fiberglass felt

Workers applying hot asphalt to fiberglass felt

Kettle Operator (Courtesy of Thomas R. Sha¬nahan, National Roofing Contractors Association)

Kettle Operator (Courtesy of Thomas R. Sha¬nahan, National Roofing Contractors Association)
231-11-A; 231-13-A; 231-15-A; 231-16-A; 231-17-A; 231-18-A; 231-19-A; 231-20-A;
afterburner and loader
asphalt kettles
fume-suppressing asphalt
roofing contractors
roofing kettles
(1) The NIOSH studies showed that when fume-suppressing asphalt was used, exposures to contaminants in the asphalt fumes were reduced (by 70%–83%) for kettle operators. However, it was not certain whether exposures were reduced for roof-level workers who usually did not work near the kettle. (2) During NIOSH field studies, the afterburner and loader systems may have reduced the kettle operators’ exposures to asphalt fumes, but variables such as work practices made it difficult to interpret the results. When conditions were well controlled, the contaminants were reduced by 73%–88%. Experience has shown that any afterburner and/or loader system must be carefully designed to avoid causing ignition of asphalt fumes and explosions or fires in the kettle or kettle area.