BIM is a concept that offers software technology application (app) that integrates digital building information for hazard identification and safety planning. It can virtual map a project lifecycle from design through procurement, construction, operation, and maintenance.
Hazard Analysis — Welding fumes
Problem:
Workers who perform flame or plasma cutting may be exposed to welding fumes.
Risk Description:
There are a number of health effects caused by exposure to welding fume, including metal fume fever, bronchitis and asthma, lung cancer, and neurological injuries that produce symptoms similar to Parkinson's disease. The hazard depends on the welding method (such as MIG, TIG, or stick), what the welding rod (electrode) is made of, the filler metals and base metals (such as mild steel and stainless steel), the paints and other coatings on the metals being welded, and ventilation.
Welding and associated processes such as arc-cutting, are routinely performed by pipefitters, ironworkers, boilermakers and sheet metal workers; other trades may also weld and perform thermal cutting of metals. This work often occurs in tanks or boilers or in other poorly ventilated settings. The fume generated during welding contains fine particles composed of the constituents in the base metal, the electrodes, fluxes, and the filler rods; these particles can deposit in the lungs or enter the blood stream by passing through the lungs. Welding can also create hazardous gases (see Table 1 below). Construction workers can be exposed to the hazards of chromium and manganese; the exposure varies with the welding process and the specific metals used. Estimates of the number of workers exposed to welding fumes range from 410,000 full-time welders to over one million workers who weld intermittently.
The American Welding Society has identified over 80 different types of welding and allied processes in commercial use. Of these processes, some of the more common types include shielded manual metal arc welding, gas metal arc welding, flux-cored arc welding, gas tungsten arc welding, and others such as submerged arc welding, plasma arc welding, and oxygas welding.
The chemical properties of welding fumes can be quite complex. Most welding materials are alloy mixtures of metals characterized by different steels that may contain iron, manganese, silica, chromium, nickel, and others. Fumes are released from the base metal and from welding rods, and gases are produced from some of the arc welding processes; see table 1.
Table 1. Hazardous Byproducts of Welding
| FUME | GASES | RADIANT ENERGY | OTHER HAZARDS |
| Aluminum | Carbon Dioxide | Ultraviolet | Heat |
| Cadmium | Carbon Monoxide | Visible | Noise |
| Chromium III & VI | Nitrogen Oxide | Infrared | Vibration |
| Copper | Nitrogen Dioxide | ||
| Fluorides | Ozone | ||
| Iron | |||
| Lead | |||
| Manganese | |||
| Magnesium | |||
| Molybdenum | |||
| Nickel | |||
| Silica | |||
| Titanium | |||
| Zinc |
There are a number of health effects caused by exposure to welding fume, including:
- metal fume fever
- COPD/bronchitis and asthma
- lung cancer
- neurological injury from manganese, like Parkinson’s disease
Metal fume fever: This is a frequent acute respiratory complaint among welders. Symptoms include flu-like symptoms like cough, shortness of breath and fever, lasting a few hours. It is caused by exposure to welding fumes that contain zinc, copper, magnesium, and cadmium.
COPD/Bronchitis: Chronic obstructive pulmonary disease (COPD) includes chronic bronchitis and emphysema. Chronic bronchitis is present when someone has a regular cough with phlegm for at least 3 months over two successive years, and there is no medical condition causing the cough. Emphysema is present when there is destruction of the walls of the airspaces of the lung. The destruction of airspaces means there is less lung surface; loss of lung surface reduced the ability of the lung to transfer oxygen into the body and transfer waste gases out.
Individuals with COPD often are in their 50s, with 20 or more years of smoking and/or occupational dust and fume exposure. A cough with phlegm starts so slowly as to be barely noticeable, first occurring only in the morning. Then someone with COPD gets frequent chest illnesses with cough, sputum, and wheezing. As the COPD gets worse, the intervals between these chest infections grow shorter. In severe COPD, loss of oxygen delivery occurs, and over time this decrease in oxygen can lead to heart failure.
Smoking is the primary cause of COPD, but smoking alone does not explain all COPD, as only 15-20% of smokers developed COPD and 10% of deaths from COPD occur in persons who never smoked. Occupational exposures to dusts and chemicals (vapors, irritants, fumes) increase the risk of developing COPD; the specific exposures associated with COPD in construction are wood dusts, cadmium, silica, welding fumes, cement dust, and possibly isocyanates.
One study, “A case-control study of airways obstruction among construction workers”, examined occupational exposures to vapors, gases, dusts and fumes (VGDF) among older construction workers between 1997 and 2013, comparing 834 workers with COPD and 1,243 controls. Approximately 18% (95% CI=2-24%) of COPD in this population can be attributed to workplace exposures associated with construction tasks. After adjusting for smoking habits in this population, the study also revealed among construction workers who never smoked, 32% (95% CI=6-42%) of COPD was attributable to the workplace.
Lung cancer: Welders have an increased risk for lung cancer, but it is not clear whether that is due to the welding emissions or to asbestos exposure which was common in construction decades ago. The International Agency for Research on Cancer has concluded that welding fumes may cause cancer, and welders of stainless steel have higher rates of lung cancer. Metal fume exposure from stainless steel welding is of particular concern because it contain chromium and nickel, both of which are known to cause cancer in workers. Recent studies show among the stainless steel welders, the risk of lung cancer increased significantly with increasing accumulative welding particulate exposure, It is still unresolved whether the mild steel welding process carries a carcinogenic risk.
Parkinson-like disease: Manganese is a component of nearly all steels and is present in many welding rods and wires. Manganese has been known to cause neurological injury for many years. The first cases were reported in 1837. A paper in 1955 on manganese poisoning among miners described “manganese madness” with mood swings followed by the development of tremor, abnormal gait, and other symptoms akin to Parkinsonism.
Parkinson’s disease occurs at a rate of 200 cases per 100,000 persons. About 2% of the population over age 65 has Parkinson’s disease. Symptoms include tremor at rest, slowing and loss of movement, stiffness, stooped posture and loss of balance. Pathologically these symptoms are due to loss of nerve cells in a specific part of the brain, the basal ganglia. Based on autopsies in humans and experiments in animals, the pattern of brain injury from manganese is somewhat different from that of Parkinsonism, but the symptoms are similar because the injury occurs in the same basic structures, areas that control movement and muscle tone.
It is clear there is a risk from manganese exposure in mining, ore extraction, and work with metals that have high manganese content. There is less information on the risk from the lower levels of Mn during welding exposures, but current research suggests a risk for Parkinson-like disease among welders. One study of Parkinsonism among welders found that the disease among welders was similar to Parkinson’s in other people, except that it occurred at a younger age. More information can be found at the NIOSH website: http://www.cdc.gov/niosh/topics/welding/.
Assessment Info:
The hazards posed by welding are dependent on the materials (e.g. base metal, electrodes and filler metals, shielding gases, etc); the welding process; and environmental conditions, such as the degree of enclosure or whether or not effective ventilation is in place. Personal air monitoring of workers conducted under the supervision of a professional industrial hygienist is used to determine whether exposure levels pose a health risk and are below legal and recommended exposure limits.
(Note) A professional industrial hygienist is a person possessing either a baccalaureate degree in engineering, chemistry, or physics or a baccalaureate degree in a closely related biological or physical science from an accredited college or university, who also has a minimum of three years of industrial hygiene experience. For more detail visit: http://www.aiha.org/Content/AboutAIHA/whatisIH.htm.
The type and magnitude of exposure will depend on the materials being welded. Stainless steel welding may generate nickel and hexavalent chromium and if stainless welding is performed with Sheilded Metal Arc Welding (SMAW) w/ Flux Cone Arc Welding (FCAW) the flux generates manganese as well. Mild steels generate manganese. Torch-cutting or welding through coated steels may generate organic vapors or fumes generated from coatings (such as lead in the case of lead painted steel). Stick (or shielded metal arc) and flux core welding typically generate the most fume and TIG welding the least.
Welding carbon steel does not necessarily produce Mn in the fume. Almost all of the Mn comes from the flux in FCAW and SMAW consumables. Gas Metal Arc Welding (GTAW) (TIG) does not use flux and one would not find Mn in that fume when used for welding carbon steel. SMAW and FCAW are the most common welding processes used on carbon steel and those processes on that metal are the primary sources of Mn over exposure in welders.
Material Safety Data Sheets (MSDS) should provide information on the hazardous components of steels, electrodes and filler metals, however, this information is not always accurate. Because of the very high temperatures associated with welding, metals containing relatively low percentages of metals (such as nickel, Hexavalent chromium and manganese) can generate hazardous levels of fume. Personal air monitoring methods used to assess welding fumes vary depending on the specific hazardous agent being addresses. Both OSHA and NIOSH publish sampling methods for specific hazardous agents such as total particulate, Hexavalent chromium and other metals including manganese and nickel.
NIOSH Manual of Analytical Methods: http://www.cdc.gov/niosh/nmam
US Department of Labor Sampling and Analytical Methods: http://www.osha.gov/dts/sltc/methods/index.html
Regulations & Standards:
Regulations adopted by a state must be at least as protective as the corresponding federal standard. Work may also be subject to rules of other federal, state and local agencies. Even where there is no hazard specific standard, OSHA prohibits employers from to work in surroundings or under working conditions which are unsanitary, hazardous, or dangerous to his health or safety.
Occupational Exposure Limits for Manganese
| Agency | Occupational Exposure Limit |
| NIOSH REL | 1 mg/m3 (TWA) and 3 mg/m3 (STEL) |
| NIOSH IDLH | 500 mg/m3 |
| OSHA PEL | 5 mg/m3 (ceiling) |
| ACGIH TLV | 0.2 mg/m3(TWA) |
PEL: permissible exposure limit
REL: recommended exposure limit
STEL: short-term exposure limit
TLV: threshold limit value
TWA: time-weighted average
REL: recommended exposure limit
STEL: short-term exposure limit
TLV: threshold limit value
TWA: time-weighted average
Federal OSHA Standards are enforced by the U.S. Department of Labor in 26 states. There are currently 22 states and jurisdictions operating complete State plans (covering both the private sector and state and local government employees) and 5 - Connecticut, Illinois, New Jersey, New York and the Virgin Islands - which cover public employees only. If you are working in one of those states or jurisdictions you should ensure that you are complying with their requirements.
