More than 400,000 men and women are employed in welding and related occupations in the U.S., according to estimates. Some studies suggest that occupational exposures to welding fumes may pose the risk of serious respiratory, neurological, and reproductive effects. However, the available data generally are too limited to offer conclusive answers. Thus, scientists and policymakers face a need for more and better data.

Working with partners in the welding industry, the National Institute for Occupational Safety and Health (NIOSH) is pursuing strategic research to identify areas where more comprehensive, detailed, and intricate data are necessary, and to fill in those challenging gaps.

Comprehensive Review of Health Effects

Earlier this year, NIOSH published the single most comprehensive review of scientific literature on health effects associated with welding. The article, "Health Effects of Welding," noted that past investigations have found bronchitis, airway irritation, and other respiratory illnesses in large numbers of welders. However, critical differences between the studies and a shortage of dose/response data make it difficult to compare results and confidently link given exposures with given effects.

As the article also noted, some studies have suggested that welding fumes may pose risks for lung cancer and nervous system damage. This is because such fumes may contain nickel, chromium, and manganese; nickel and hexavalent chromium are classified as potential occupational carcinogens, while studies have associated chronic exposure to manganese with a risk for a Parkinson's-like disease. But data are lacking for 1) determining whether welders are exposed to those or other fume components at levels that could trigger such effects, and 2) understanding how exposures at given levels may lead to serious, long-term effects.

Two complementary types of research are needed to fill those gaps, NIOSH suggested:

• A continuation of epidemiological studies to provide a better understanding of the role that welding fumes may play in immunosuppression, lung cancer development, neurotoxicity, skin damage, reproductive disorders, and other effects that some studies have associated with the components of welding fumes.
• Toxicology studies using state-of-the-art techniques to examine key biochemical reactions to welding fumes, at the molecular level, in laboratory experiments. With such data, scientists will have better insight into the ways in which subtle genetic and cellular changes might lead to tumor formation, nerve damage, or other adverse changes in tissues and organs.

The Long Arm of Science

In the meantime, the needs identified by NIOSH in the journal article are guiding an in-house research effort in NIOSH's Health Effects Laboratory Division in Morgantown, W.Va. With the help of welding industry partners, NIOSH scientists designed and installed a sophisticated robotic arm that can be programmed to weld at specific intensities, using specified techniques, for given durations. This device allows NIOSH to generate welding fumes under realistic conditions. An exhaust trunk in the arm collects the resulting welding fumes, which are transported to a closed chamber, diluted, and then introduced into a laboratory exposure chamber for further use in exposure tests.

Because the process is computerized and controlled, NIOSH can identify all the critical characteristics of a given sample of fume with great accuracy: what metals or other materials it contains, at what temperature it formed, and from what welding process it resulted. Having installed and tested the arm, NIOSH plans to use it initially for laboratory studies under the National Occupational Research Agenda (NORA) to examine whether exposures to fumes are followed by cell injury, DNA damage, or other reactions that may signal a risk for serious long-term effects. Those results will significantly increase scientists' certainty in answering current questions, such as the question of whether welding fumes contain levels of manganese high enough to pose a risk for damage to the nervous system.

The article "Health Effects of Welding" was published in the journal Critical Reviews in Toxicology, 33(1):61-103 (2003). For additional information on the article, the NIOSH studies, or the NIOSH computerized welding arm, contact James M. Antonini, NIOSH Health Effects Laboratory Division, at jga6@cdc.gov