Welding Health Update
A new technical standard updates workers about pulmonary, reproductive, and other health effects of certain welding activities and materials.
- By Roger Brooks, Jr.
- Mar 01, 2004
DEVELOPING standards to protect workers' well-being is a great way to get started on the path toward a healthy and injury-free workplace. But as any safety expert will tell you, it takes dedication, perseverance, and a desire to make sure every employee is as safe as can be while on the job. That's why many standards are routinely reviewed and updated. It's why researchers continually study an old topic in markedly new ways. It's also why the American Welding Society (AWS) periodically reviews and publishes the latest health literature associated with its profession in its Effects of Welding on Health. In the recently released Volume 12, several issues continued to dominate the research on welding and health.
It indicates welders face any number of possible ailments that can be directly linked to their occupation. And while most experts believe proper ventilation and other precautions can go a long way toward protecting welders, many of the studies reviewed in this latest volume show the dangers they face.
Those dangers are controversial. All of the members of AWS's Safety and Health Committee we contacted declined to be interviewed for this story. Most of them cited ongoing litigation issues at their current employers (most committee members are volunteers). One member offered this explanation: "Many of us in the welding industry, especially within the AWS Safety and Health committee, are employed by companies that are involved in litigation in the area of exposure to welding fumes. Many of us have been witnesses or acted as experts in this litigation. That precludes me from answering some of the questions you pose without clearance from [my company's] law department."
As for AWS, the society does not commission the studies it reviews and, therefore, takes no stance on the findings.
In spite of the secrecy, many of the studies in Volume 12 reveal positive news for the welding industry. At the very least, much of the research would indicate there are ways to protect workers from some of the harmful effects attributed to welding.
Ventilation Remains Key
Ventilation of the fumes associated with welding is one of the best ways to keep a worker healthy. If the fumes do not enter the breathing zone, the chances of a welder's experiencing harmful effects are greatly reduced; the latest research on this topic supports this view. A study conducted by Fishwich, et al. concluded that using local exhaust ventilation significantly reduced acute changes in lung function. The study suggested that local exhaust ventilation--judged by the authors to be the most practical exposure reduction method--be used in any area where welding is being done.
Significantly, two variables seem to have a great impact on the effectiveness of local exhaust ventilation. In a study conducted by Ludwig, et al., the breathing zone concentrations of radioactive thorium were measured during gas tungsten arc welding (GTAW) with thoriated electrodes. The study concluded the ventilation did reduce total exposure, but the position of the worker's head in relation to the emission source determined the amount of exposure. These findings are supported by a previous study, authored by Jankovic, et al., which found local exhaust ventilation was 40 times more effective than no ventilation at reducing the radioactive aerosol while GTAW was being performed. However, the concentration inside the welder's helmet was only reduced twofold. The study concluded it is possible that "incoming air from local exhaust ventilation passed around the welder's body, creating eddy currents that could have caused portions of the fume to enter beneath the helmet."
The second variable concerns the amount of welding being performed. A study by Rappaport, et al. found the duration of welding significantly altered the effectiveness of the local exhaust ventilation systems. The systems were much more effective during intermittent welding than during continuous work. Local exhaust ventilation reduced exposure to total particulate by as much as 41 percent during intermittent welding, but only 6 percent during continuous welding. The authors said workers properly positioned the ventilation systems at the beginning of a job, but then would move without repositioning the ventilation systems. This greatly reduced the effectiveness of the systems, which most likely explains the discrepancy.
AWS, which does not conduct or commission any of the studies in the report, realizes the importance of proper ventilation and believes welders do, as well. "We think welders do what is needed to keep the smoke away from their breathing zone--which can include the use of a respirator," says one official at AWS. "But proper ventilation is the key to keeping the smoke away from the breathing zone."
Lung Function, Cancer Concerns
Researchers were just as concerned with the effects of welding on pulmonary function, asthma, and lung cancer. One study in particular found a definite decline in lung function among welders versus non-welders after finishing a work shift. Again, ventilation was key, as those who did not use a local exhaust ventilator were 22 times more likely to be faced with decreased lung function after just 15 minutes of welding.
Another study found stainless steel workers were more likely to experience decreased lung function than were mild steel welders. AWS officials could not provide precise estimates of the total number of welders and stainless steel welders working in the United States. According to the Occupational Outlook Handbook, there are more than 521,000 welders in the United States. AWS officials estimated no more than 10 percent of them would work with stainless steel.
Two Swedish studies by Toren, et al. found an increased risk for occupational asthma associated with exposure to welding fumes. Their findings were corroborated by a separate, hospital-based study completed in Italy. Welders examined by Contreras and Chan-Yeung, however, exhibited asthma-like symptoms that were later attributed to non-specific irritation, and not welding fumes.
The latest findings on lung cancer are unclear. Nine studies found an increased risk for lung cancer among welders, but only two of those studies found the risk to be statistically meaningful when the effects of cigarette smoking and exposure to asbestos were factored in. Other studies did seem to find at least a slightly elevated risk of particular types of lung cancer for welders. However, in research conducted by Becker, et al., the elevated risk was attributable to asbestos exposure, not welding.
The higher risk of cancer was not limited to the lung. Studies cited in Volume 12 found an elevated risk of cancers of the pleura, kidney, and urinary bladder in welders. In a separate research project, welders were shown to be more susceptible to cancers of the throat and larynx when they had eight years or more of exposure.
With so much conflicting evidence, it's easy to understand why more research is being done on the correlation between cancer and welding.
A study conducted by Tenkate and Collins found welders and nearby workers all received doses of electromagnetic radiation that exceed the American Conference of Governmental Industrial Hygienists' maximum permissible exposure (MPE) limit. The authors used polysulfone film dosimeters, and all doses measured on the body, ocular, and environmental badges came back over the MPE limit.
They tested four helmet designs and found none completely blocked a user's eyes from UV radiation. In some instances, the UV radiation was allowed to enter the helmet "through the opening between the edge of the shield and the side of the face." Other times, the radiation "entered from behind the head through the gap between the back of the top edge of the shield and the top of the head." This study concluded that, "because of its greater reflective surface area, a narrow helmet with a larger-than-standard filter plate permitted the greatest intensity of light to reach the eye."
The Manganism and Parkinson's Disease Dilemma
One area of great concern is the growing correlation between welding and manganism and Parkinson's disease. Both are caused by the deterioration of cells in the basal ganglia portion of the brain. This section of the brain controls the smooth and coordinated movements of the body, among other things.
With the aid of magnetic resonance imaging (MRI), excessive manganese exposure can be identified through an increase in high-intensity signals in the basal ganglia. One study found that, while an MRI showing these signals did reflect a recent exposure, it did not necessarily indicate the onset of disease. Another study concluded welders who had low-level exposure to manganese did exhibit impairments in short-term memory, some basic tremor parameters, and motor functions requiring alternating and rapid movements.
Many of the studies on Parkinson's disease and welding found no difference in the severity of symptoms for welders and non-welders. In one study in particular, the age of onset was the only meaningful discrepancy, as welders tended to develop the disease earlier. The authors concluded, "welding may be a risk factor for" the disease. There was some research conducted on the role genetics plays in the development of the disease. One study found a variant of a gene that reduces susceptibility to both Parkinson's and manganism disease, for welders and non-welders alike. Those with the genetic variant developed manganism some 10 years later than people with similar exposure levels to manganese. The authors concluded this would make it even more difficult to distinguish between the two diseases, which are very similar at onset.
The amount of research cited here suggests heightened concern about the effects of welding on the development of the two diseases. A number of the studies seemingly contradict one another. AWS has recognized the apparent risk of welding as it relates to both manganism and Parkinson's disease, commissioning its own study of the role welding fumes play in the development of Parkinson's disease.
Citing a need for "something a bit more conclusive," the society expects the study to begin this sometime this year.
This article originally appeared in the March 2004 issue of Occupational Health & Safety.