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Publication of NIOSH Criteria Documents on Welding, and Brazing,Thermal Cutting and on Radon Progeny

The National Institute for Occupational Safety and Health (NIOSH) periodically issues criteria documents that examine health risks associated with various occupations. Two such documents were recently published* and are described below.

Criteria for a Recommended Standard: Welding, Brazing, and Thermal Cutting. This document examines the occupational health risks associated with welding, brazing, and thermal cutting and provides criteria for eliminating or minimizing the risks encountered by workers in these occupations. An estimated 700,000 workers in the United States are involved in the welding of various materials. The major health concerns associated with these occupations are increased risks of lung cancer and acute or chronic respiratory diseases.

The etiologic basis for this excess risk is difficult to determine because of uncertainties about smoking habits, possible interactions among the various components of welding emissions, and possible exposures to other occupational carcinogens. For workers who weld on stainless steel, the increased risk for lung cancer appears to be associated with exposure to fumes that contain nickel and chromium.

The prevalence and severity of nonmalignant respiratory conditions are not well characterized among welders, but these conditions have been observed in both smoking and nonsmoking workers in welding-associated occupations. Excess morbidity and mortality exist among welders even when reported exposures are below current Occupational Safety and Health Administration (OSHA) permissible exposure limits (PELs) for the many individual components of welding emissions.

An occupational exposure limit for total welding emissions cannot be established because the composition of welding fumes and gases varies for different welding processes and because the various components of a welding emission may interact to produce adverse health effects. Therefore, exposures to all welding emissions should be reduced to the lowest feasible concentrations using state-of-the-art engineering controls and work practices. Any applicable exposure limits for individual chemical and physical agents associated with welding (i.e., NIOSH recommended exposure limits (RELs), OSHA PELs, or limits recommended by consensus groups) should be considered as upper boundaries of exposure.

The criteria document contains NIOSH recommendations for medical monitoring of exposed workers and for engineering controls, good work practices, and worker education. Guidelines are also provided for respiratory protection and protective clothing.

A Recommended Standard for Occupational Exposure to Radon Progeny in Underground Mines. This document examines the occupational health risks associated with exposures to radon progeny (radon and its short-lived, alpha-radiation- emitting, radioactive decay products) in underground mines, and it establishes criteria for minimizing the risks encountered by miners.

Data from studies on both humans and animals demonstrate a direct link between exposure to radon progeny and lung cancer. Epidemiologic studies provide a basis for quantitatively estimating human risk at various exposure levels. Exposure is quantified using the working level month (WLM), which is a standard measure of occupational exposure to alpha radiation. Analyses show that an exposure to radon of 4 WLM per year over a 30-year working lifetime (the current Mine Safety and Health Administration standard) poses a substantial risk of lung cancer. To determine a REL, NIOSH has weighed this evidence along with uncertainties in the data and the feasibility of controlling exposure to radon progeny in mines. The resulting REL for radon progeny is a cumulative total of 1 WLM per year and an average workshift concentration of one twelfth of 1 working level. These limits are to be considered the upper boundaries of exposure, and every effort should be made to reduce exposures to the lowest concentrations possible. In addition to the REL, the criteria document contains specific provisions for medical monitoring, recordkeeping, respiratory protection, worker education, and sampling and analytical methods. Implementation of all these recommendations will help minimize risk for exposed workers. Reported by: Div of Standards Development and Technology Transfer, National Institute for Occupational Safety and Health, CDC. *Copies of the documents can be obtained without charge from the Information Dissemination Section, Division of Standards Development and Technology Transfer, National Institute for Occupational Safety and Health, 4676 Columbia Parkway, Cincinnati, Ohio 45226; telephone: (513) 533-8287.

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