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EXPOSURE LIMITS
- OSHA PEL: The Occupational Safety and Health Administration (OSHA) does not currently regulate welding fumes.
- NIOSH REL: The National Institute for Occupational Safety and Health (NIOSH) has established a recommended exposure limit (REL) for welding fumes (and total particulates) of the lowest feasible concentration. NIOSH considers welding fumes potential occupational carcinogens [NIOSH 1992].
- ACGIH TLV: The American Conference of Governmental Industrial Hygienists (ACGIH) has assigned welding fumes (not otherwise classified) a threshold limit value (TLV) of 5 milligrams per cubic meter (mg/m(3)) as a TWA for a normal 8-hour workday and a 40-hour workweek [ACGIH 1994, p. 36].
Rationale for Limits
The NIOSH limit is based on the risk of cancer and respiratory disease [NIOSH 1992].
The ACGIH limit is based on the risk of toxic effects caused by welding fumes [ACGIH 1991, p. 1726].
HEALTH HAZARD INFORMATION
Routes of Exposure: Exposure to welding fumes can occur through inhalation and eye contact.
SUMMARY OF TOXICOLOGY
Effects on Animals: Welding fumes can cause non-specific changes in the lungs; in addition, there is limited evidence for genotoxicity in in vitro test systems. Rats exposed by inhalation or intratracheal instillation of welding fumes from mild-steel welding showed non- specific pulmonary changes with no signs of fibrosis over a period of 450 days [IARC 1990]. The primary effects observed included particle- laden macrophage aggregates, and alveolar epithelial thickening with proliferation of granular pneumocytes [IARC 1990]. Similar changes were observed in the lungs of rats exposed to 1,000 mg/m(3) for 1 hour or to 400 mg/m(3) for 30 minutes/day, six days/week over a two-week period [IARC 1990]. Welding fumes were not associated with an increased incidence of genotoxicity in 11 of 15 in vitro assays, and in all three in vivo tests performed for genotoxicity [IARC 1990].
Effects on Humans: Exposure to welding fumes from mild steel is associated with the development of a benign pneumoconiosis, "arc welder's siderosis". This condition is a reversible pneumoconiosis and no associated respiratory signs may be present at the time the pneumoconiosis is discovered [Rom 1992]. Respiratory impairment has been observed in workers exposed to mild steel welding fumes, but these impairments may be the result of exposure to other toxicants in the working environment, such as crystalline silica [Rom 1992].
Exposure to welding fumes can result in metal fume fever; this condition resembles influenza and is characterized by fever, chills, headache, nausea, shortness of breath, muscle pain, and a metallic taste in the mouth [Rom 1992]. The respiratory effects appear to be potentiated by smoking. There is an excess of infertility among welders that led to studies on sperm quality and welding exposures. There appears to be an increased frequency of abnormalities in semen quality associated with duration of exposure. Abnormalities were highest among stainless steel welders. While hypotheses exist, the mechanism of action resulting in infertility is not known [Rom 1992; IARC 1990]. IARC concluded that there is limited evidence in humans for the carcinogenicity of welding fumes and gases [IARC 1990]. This conclusion was based primarily on a review of 11 cohort studies and 12 case-control studies on lung cancer; only three of these studies (all cohort studies) specifically examined manual metal arc welding of iron, mild steel, or aluminum.
Two of the cohort studies found no association between welding fumes and cancer. The remaining cohort studies showed an increased risk for lung cancer, which in some may have been inflated due to selection bias. Ten out of twelve case- control studies showed an association between lung cancer and exposure or employment as a welder. Two of the studies found no risk [IARC 1990]. IARC's final conclusion was that welding fumes are possibly carcinogenic to humans [IARC 1990].
Signs and symptoms of exposure
Acute exposure: Acute exposure to welding fumes can result eye, nose, and throat irritation, fever, chills, headache, nausea, shortness of breath, muscle pain, and a metallic taste in the mouth.
Chronic exposure: Chronic exposure to welding fumes can result in respiratory effects including coughing, wheezing, and decreased pulmonary function.
MEDICAL SURVEILLANCE
OSHA is currently developing requirements for medical surveillance. When these requirements are promulgated, readers should refer to them for additional information and to determine whether employers whose employees are exposed to welding fumes are required to implement medical surveillance procedures.
Medical Screening : Workers who may be exposed to chemical hazards should be monitored in a systematic program of medical surveillance that is intended to prevent occupational injury and disease. The program should include education of employers and workers about work-related hazards, early detection of adverse health effects, and referral of workers for diagnosis and treatment. The occurrence of disease or other work- related adverse health effects should prompt immediate evaluation of primary preventive measures (e.g., industrial hygiene monitoring, engineering controls, and personal protective equipment). A medical surveillance program is intended to supplement, not replace, such measures. To detect and control work-related health effects, medical evaluations should be performed (1) before job placement, (2) periodically during the term of employment, and (3) at the time of job transfer or termination.
Preplacement medical evaluation: Before a worker is placed in a job with a potential for exposure to welding fumes, a licensed health care professional should evaluate and document the worker's baseline health status with thorough medical, environmental, and occupational histories, a physical examination, and physiologic and laboratory tests appropriate for the anticipated occupational risks. These should concentrate on the function and integrity of the respiratory system. Medical surveillance for respiratory disease should be conducted using the principles and methods recommended by the American Thoracic Society.
A preplacement medical evaluation is recommended to assess medical conditions that may be aggravated or may result in increased risk when a worker is exposed to welding fumes at or below the prescribed exposure limit. The health care professional should consider the probable frequency, intensity, and duration of exposure as well as the nature and degree of any applicable medical condition. Such conditions (which should not be regarded as absolute contraindications to job placement) include a history and other findings consistent with diseases of the respiratory system.
Periodic medical evaluations: Occupational health interviews and physical examinations should be performed at regular intervals during the employment period, as mandated by any applicable Federal, State, or local standard. Where no standard exists and the hazard is minimal, evaluations should be conducted every 3 to 5 years or as frequently as recommended by an experienced occupational health physician. Additional examinations may be necessary if a worker develops symptoms attributable to welding fumes exposure. The interviews, examinations, and medical screening tests should focus on identifying the adverse effects of welding fumes on the respiratory system. Current health status should be compared with the baseline health status of the individual worker or with expected values for a suitable reference population.
Termination medical evaluations: The medical, environmental, and occupational history interviews, the physical examination, and selected physiologic or laboratory tests that were conducted at the time of placement should be repeated at the time of job transfer or termination to determine the worker's medical status at the end of his or her employment. Any changes in the worker's health status should be compared with those expected for a suitable reference population. Because occupational exposure to welding fumes may cause diseases with prolonged latent periods, the need for medical surveillance may extend well beyond the termination of employment.
Biological monitoring: Biological monitoring involves sampling and analyzing body tissues or fluids to provide an index of exposure to a toxic substance or metabolite. No biological monitoring test acceptable for routine use has yet been developed for welding fumes.
WORKPLACE MONITORING AND MEASUREMENT
Determination of a worker's exposure to airborne welding fumes is made using a mixed cellulose ester (MCE) filter, 0.8 microns. Samples are collected at a maximum flow rate of 2.0 liters/minute until a maximum collection volume of 960 liters is reached. Analysis is conducted by inductively coupled argon plasma (ICP/DCP-AES). This method (ID-125G) is described in the OSHA Computerized Information System [OSHA 1994] and is fully validated. NIOSH Method No. 7300 can also be used to determine a worker's exposure to welding fumes. This method is similar to the OSHA method described above [NIOSH 1994b].
PERSONAL HYGIENE PROCEDURES
Workers should not eat, drink, use tobacco products, apply cosmetics, or take medication in areas where welding fumes are generated.
Information from (12/12/03): OSHA
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