The controversy surrounding asphalt compounds used in roofing is focused on the production of very small particulates discharged as volatile organic compounds (VOCs) in the fume generated by heating asphalt. A fume is an extremely small, solid particle with a diameter of 0.1 to 0.01µ (micron). One micron is a millionth of a meter.
Any adverse health effects asphalt workers might incur are probably due to many years of exposure to these fumes. These VOCs are created by condensation from the gases resulting from the high temperature of the asphalt in the dip and pump kettles. These emissions may contain high levels of polycyclic aromatic hydrocarbons (PAHs). The benzene molecule is the basic aromatic hydrocarbon. Similarly, polycyclic (benzoidal) aromatic compounds (PACs) are also formed by combining sulfur, nitrogen and oxygen in the refinement process.
There are more than 100 different, man-made and naturally formed PAH substances and they are found almost everywhere in the environment. It is in areas of highest concentration where asphalt workers must be concerned. OSHA has established a Permissible Exposure Limit for PAH to be 5 mg/m3 averaged over an eight-hour period. The severity of harmful health effects of PAH exposure is based on a number of factors: the dosage (concentration); length of exposure; route of exposure; other chemicals to which you are exposed; and individual characteristics (age, sex, nutrition, lifestyle, family history, general health condition).
The Asphalt Institute and the Asphalt Roofing Environmental Council have instituted recommended optimum kettle temperature operating ranges for the four classes of asphalt. They suggest, for instance, that Type III be heated to 545 degrees F and applied at 395 to 420 degrees F. While heating an asphalt keg above its recommended temperature may expedite product preparation and delivery during periods of high-demand, this greatly increases the risk of reaching vapor flash point and the product's lower flammable limits. Not only could the ensuing fire spread to the kettle's combustible LPG fuel supply, but the explosive pressure in the head space of the kettle could turn the cover into deadly shrapnel during ignition.
First Aid MeasuresDecades of repeated occupational exposure to asphaltic fumes and coal tar pitch could possibly lead to some very hazardous health effects. The MSDS for most manufacturer's bitumen asphalt products indicate not only moderate potential health effects but the potential for some more serious debilitating conditions. While consultation with an occupational physician is always a primary recommendation, some of the first aid treatments suggested by the manufacturers are included here.
Skin Contact: Redness, drying and dermatitis may occur following prolonged and repeated skin contact with asphalt. Absorption is a possible route of entry. In some cases, prolonged and repeated skin exposure (in the absence of recommended hygiene practices) may result in pigmentation changes and benign skin growth. These effects may be exacerbated by "simultaneous exposure to ultraviolet light." For first aid, remove with waterless hand cleaners or soap and water. Flush with copious amounts of clean water. Avoid solvents. If eyes are contaminated, flush immediately with plenty of water or mineral spirits for at least 15 minutes. Immediately call a physician.
Inhalation: May cause upper respiratory system (nose/throat) irritation and inflammation. Prolonged exposure may lead to loss of appetite as well as depression of the central nervous system. Symptoms may include headaches, dizziness, loss of coordination, drowsiness and abnormal fatigue. High concentrations in poorly ventilated areas may cause convulsions and loss of consciousness. Some cases of lung cancer have been detected after prolonged and repeated use. For first aid, immediately remove the victim to fresh air. If not breathing, give artificial respiration. If breathing is simply difficult, give oxygen. Immediately call a physician.
Carcinogenicity: Petroleum asphalt (refined coal tar) is currently not listed as a carcinogen by OSHA, National Toxicology Program or the IARC. These agencies determined that there is "inadequate evidence that asphalt alone is carcinogenic to humans." Only NIOSH has concluded that, at much higher application temperatures, roofing asphalt fumes may be a potential occupational carcinogen. Laboratory tests have resulted in positive tests for cancer in experimental animals exposed to small amounts of PAH under simulated roofing concentrations There are also trace respirable amounts of the known carcinogens crystalline silica quartz and crystobolite in some fumes, as well as hardened asphalt when disturbed during demolition.
Hazard Prevention MethodsIt is evident that more research needs to be done concerning the threshold of prolonged exposure BUR workers must exceed before they are affected by bitumen fumes. As the consequences are still scientifically undetermined, it would be efficacious for roofers to practice as many safe work procedures as possible to mitigate the effects of such exposures. The following NIOSH/ARM4-suggested safe work guidelines may help the roofing employer reduce or mitigate the negative health effects of asphalt fumes.
1. Develop a plan. A written hazard exposure plan is a good place to start. Written by the employer to aid roofers who work with heated asphalt, these standard operating procedures would reduce exposures and instruct workers in the procedures to follow if potentially exposed to these particulates. Site-specific administrative planning is strongly recommended:
Consult with the host employer and/or property owner before work begins. Identify potential problems with building inlet doors, windows, ventilation, AC, etc. Notify ancillary workers and occupants prior to starting work. Post adequate signage to identify the potential hazards and establish an adequate controlled access zone with barrier tapes. Consider use of kettles, pumps and containers with sealed lids and vapor recovery systems to reduce fume emissions.
Schedule BUR work when occupancy is low.
Train all BUR workers in the hazards of hot asphalt application and the correct procedures to handle the products. Review all product MSDSs and the proper use of personal protective equipment for the job.
2. Assign a Competent Person. The employer should designate an on-site employee who is trained and experienced to identify existing and potential asphalt fume hazards during each shift.
The CP would be equipped to take on-site particulate grab samples or 8-hour dosimeter readings for laboratory analysis and/or 8-hourr TLV dosimeter readings for comparison with OSHA's permissible exposure limit for bitumen fumes.
The CP would have the employer's authority to take prompt corrective measures, including control over the kettle, ventilation practices, respiratory protection procedures, personal protective equipment, chemically protective clothing and personnel site evacuation if hazard control measures prove inadequate.
3. Implement safe kettle management. Have the CP develop site-specific safe work practices with and around the kettle where the asphalt fumes are source generated:
Plan kettle locations where the least number of workers will be exposed. Determine prevailing winds and normal building convection currents.
Set up adequate controlled access zone around the kettle. Choose a firm, level site and post/barrier tape as necessary Use high visibility traffic cones in vehicular zones. Insulate and label pipelines to the roof.
Select the right dip or pump kettle for the job, the right size with adequately maintained temperature controls and adequate pump size.
Have CP inspect equipment regularly and ensure proper maintenance procedures. Compliant equipment is always maintained in the condition in which it was manufactured.
Maintain a full-time, trained fire watch with a compliant, charged 10-pound minimum ABC fire extinguisher during kettle operations.
Kettlemen shall be trained in the use of and wear appropriate PPE to protect from hand/torso burns, eye/face damage, falling object hazards and respiratory exposure.
Chop the asphalt kegs into smaller sizes that are easier handled and quickly melted. Use fume-reduced (suppressed) asphalt products
Reduce the amount of time the kettle lid is opened. Fill to maximum capacity when reloading. Pump or draw asphalt through cocks whenever possible to limit dipping time. Visual emissions of asphalt fumes should be limited to 10 seconds with no more than 40 percent opacity (average optical density).
Initiate the kettle optimally at the equiviscous temperature (EVT) plus 50 degrees F and less than 25 degrees F of the flash point to melt the load. Reduce to EVT plus 25 degrees F during application. Take temperatures after skimming, transferring with hand-held infrared thermometer. Always fire the kettle or diptank with clean burning fuels.
Communicate with applicators to maintain mop bucket temperatures.
Install a windsock or flag and operate upwind of the kettle's fume cloud whenever possible. Wear NIOSH-approved combination R100/P100 particulate pre-filter with organic vapor cartridge respirator in compliance with OSHA 1910.134, NIOSH 42 CFR 83 and the employer's respiratory protection program.
In calm conditions or enclosed spaces (alley, behind penthouse) install a high cfm blower to create a fresh-air source for the kettleman. Make sure fumes blow away from workers or occupants. Be sure the electrical supply line is grounded and workers are not exposed to trip or electrical hazards.
4. Verify safe application practices. The employer should designate a CP on BUR and any hot asphalt projects to identify site-specific health hazards and ensure that the workers are taking adequate engineering, administrative and PPE control measures:
The CP should always notify building occupants prior to commencing roofing activities; schedule roofing for times when building is low occupancy; and identify all possible routes of entry for fumes during operations each shift (seal vents, close windows/doors, move kettle as necessary).
Applicators should communicate with kettleman regarding the mop bucket temperatures at point of application.
Use buckets with half-lids and do not fill more than 3/4 full
Always carry buckets on the downslope of the roof and select a route that exposes as few workers as possible to fumes.
Twist mops when removing from the bucket
Avoid time on your knees or close to the roof deck and use long-handled tools, minimizing exposure to higher concentration of fumes
Applicators shall be evaluated by the CP for the necessity of wearing respirators, eye protection and chemically protective clothing/gloves. All PPE shall be evaluated and fit-tested to the individual. Use shall be in compliance with the appropriate OSHA standards.
Utilization of adequate and appropriate PPE: Cotton long sleeved shirt (no synthetics) and long pants without cuffs; non-skid shoes with 6-inch minimum leather uppers. Leather or heat-resistant gloves with long gauntlets sealed with duct tape; eye protection; compliant particulate respirator (as required); and barrier cream on any exposed skin.
Practice good personal hygiene practices, including washing hands (no solvents) before leaving site or eating; take breaks upwind from asphalt fumes; shower after work as soon as possible; change work clothes before driving home to prevent asphalt and solvent exposure in car or house.