Tom, a welder for 20 years, has encountered many workplace health issues throughout his career. “I know a lot of welders who have suffered from emphysema from inhaling fumes,” he says. “There used to be airborne particles running rampant all over the place, but even with the new OSHA standards I’m still concerned.”
Tom, himself a survivor of cancer his doctors believe to be related to his occupational inhalation of airborne particles, has good reason to be concerned.
During my decade-long experience in the air quality industry, I have encountered many stories like Tom’s. Employees want to be a part of a work environment where they are free to breathe without worry about the unseen airborne particles that threaten their health.
Dating back to antiquity, airborne particles have been identified as potential health hazards. With the rise of modern science, medical scientists have illustrated the relationship between the chemical and physical characteristics of airborne particles and respiratory diseases. Generally, airborne particles are categorized into three main types:
- Large particles – Particles greater than 100 microns in diameter are considered large. These particles fall quickly and include such things as hail, snow, room dust and soot aggregates. Although they can cause irritation to the eyes, nose and throat, large particles are not fine enough to reach the lungs.
- Medium particles – Particles that are between 1 and 100 microns in diameter are considered medium-sized. Settling slowly, these particles consist of pollen, large bacteria and coal dust, as well as dust produced during industrial processes including welding and grinding. These particles pose the greatest health risk, because they are able to pass through the nose and throat and penetrate the gas exchange region of the lungs where they settle.
- Small particles – Small particles are less than 1 micron in diameter and also pose serious health risks. They can be washed out by water and rain, and include viruses, small bacteria, metallurgic fumes and dust, as well as paint pigments.
Industrial workers are exposed to hazardous airborne particles on a daily basis. Given that there are an estimated 400,000 workers in the welding industry alone, it is important to understand the potential health consequences of particle inhalation.
Health Concerns
Airborne particles pose a variety of health concerns to workers in the welding industry, including increased risk for developing lung cancer; damage to nose, throat and lungs; and metal fume fever.
It has been well documented that long-term exposure to the fumes that welding on metals – such as stainless steel, high chrome alloys and chrome-coated metals – produces can lead to an increased risk for developing lung cancer.
As the most serious potential health concern, lung cancer begins with changes in the lungs caused by exposure to carcinogens. These changes are characterized by the development of abnormal cells on the lining of the bronchi (breathing tube) that multiply with increased exposure and eventually become cancerous, progressing into a tumor. Symptoms of lung cancer include chronic cough, hoarseness, chest pain, shortness of breath and repeated episodes of bronchitis and pneumonia.
The inhalation of known welding by-products such as hexavalent chromium also can damage or irritate the nose, throat and lungs. Larger airborne particles deposit in the nose and throat, contributing to coughing and sore throat, and may be eliminated by sneezing or blowing one’s nose. Smaller particles, however, collect in the tiny air sacs of the lungs, causing inflammation and swelling of the blood vessels.
Metal fume fever is an acute allergic condition that affects many welders throughout the duration of their careers. It chiefly is caused by exposure to zinc oxide, another welding fume, and produces flu-like symptoms. Welders afflicted by metal fume fever may experience headache, fever, chills, muscle aches, thirst, nausea, vomiting, chest soreness, gastrointestinal pain and weakness. These symptoms can last anywhere from 6-24 hours and complete recovery can usually be expected within 48 hours.
Control Methods
In light of these airborne health hazards, a number of control methods have been created to limit workplace exposure. Such methods include air ionizers, fume arms and downdraft tables.
Air ionizers operate by creating negative ions and changing the polarity of airborne particles. By changing polarity, particles magnetically attract together, becoming too large to remain airborne, and as a result, fall out of a worker’s breathing zone.
Fume arms, or lab hoods, are another option. These units typically are self-contained, 8-to-12 foot arms (snorkels) attached to a filtration system that can be moved from location to location. In order to absorb airborne particles, the arm is placed over the workstation, drawing up fumes and smoke.
Finally, downdraft tables are self-contained units that draw air from the workplace in a downward direction through perforated table tops. They maintain a powerful suction in an open workspace, as the filtration system filters dust, fumes and smoke away from operators’ breathing zones. Downdraft units also exhaust clean air back into the workplace.
Important Considerations
Employers seeking to improve workplace air quality and acquire the appropriate equipment for their needs undoubtedly face a difficult task. Though a complicated process, the following considerations can help ensure that both employer and worker interests are met:
- What emissions need to be captured and what filtration options are the most effective for each situation?
- Should a ventilation system be self-contained or integrated into the existing HVAC system?
- Is there a need for a source capture filtration system?
It is important to first review the emissions that need to be captured and the available filtration options. Depending on the air quality issue at hand, different filters may be needed to accomplish the desired effect.
Fumes from glue and paint, for instance, are often best absorbed by carbon filters. These filters are available in the weight increments of 2, 6, 12 and 30 pounds. Dust particulate and smoke particles, however, usually require two to three stage filter packs. The first of these filters is a pre-filter, minimum efficiency reporting value (MERV) 8 to 11, which is 40 percent efficient to the submicron level, followed by a MERV 14-15, 95 percent efficient to 0.7 microns, and finally, in those instances where the finest airborne particles are present, a high efficiency particulate air (HEPA) filter may be needed, boasting a 99.97 percent efficiency rate to 0.3 microns.
When deciding whether or not a ventilation system should be self-contained or integrated into the existing HVAC system, it is important to consider the volume of air being circulated. Most air cleaning equipment will generate 1,000 to 3,000 cubic feet of air per minute, and if the system is not self-contained, this air will need to be replaced with heated or cooled air. In an 8-hour shift, approximately 960,000 cubic feet of air will need to be heated or cooled in an integrated system, creating an additional cost that must be calculated.
Source capture filtration systems capture contaminants as they are occurring at the worksite. Many professionals prefer this method of filtration because it does not allow airborne particles to disperse and potentially endanger workers before absorption.
Due to the individual challenges each air quality problem presents, no one ventilation system can provide a universal solution. The complexities of these situations may even be such that the expertise of an air quality specialist or industrial hygienist is needed.
The responsibility of today’s maintenance and engineering managers to maintain a clean indoor air environment markedly has increased in recent decades. Employees are more concerned about health: They are more aware of allergic conditions and they have become increasingly informed about the adverse effects of hazardous airborne particles.
Faced with the substantial complexities of improving air quality, occupational safety and health professionals should carefully consider their workplace needs and available options and act on this knowledge. Doing this will help increase the health and efficiency of both workers and workplaces, and ensure ever-increasing regulatory compliance in a constantly changing industrial world.
Bruce Prather is the senior managing partner of DualDraw LLC, an established provider of air quality equipment. Bruce has 40 years of experience in manufacturing, fabrication and production and is an expert in workplace air quality. He can be contacted at (800) 977-2125 or at http://www.DualDraw.com.