UNIVERSITY OF MALTA
CENTRE FOR LABOUR STUDIES
Bachelor in Occupational Health and Safety (Honours)
CLS2302 Occupational Hygiene
Critically discuss using relevant examples some of the practical measures that an occupational hygienist may recommend to effectively manage potential occupational exposures resulting from Welding.Controlling Hazardous Fume and Gases during Welding
“Welding joins materials together by melting a metal workpiece along with a filler metal to form a strong joint. The welding process produces visible smoke that contains harmful metal fume and gas by-products. This fact sheet discusses welding operations, applicable OSHA standards, and suggestions for protecting welders and coworkers from exposures to the many hazardous substances in welding fume.”(OSHA)
What is Occupational Hygiene?
Occupational Hygiene is the anticipating/ recognizing, evaluating and controlling discipline, of hazards and risks at the place of work. It is there to protect the workers’ health and well-being. (IOHA)
Occupational Hygienists can help protect employees from getting occupational illness and diseases. Thus, they can help the employer to protect the workers from ill-health by:
Identifying the health hazards
Evaluate the risk and
Take appropriate control measures.
“Every year in the UK 99% of work-related deaths are caused by occupational diseases, not by accidents!” (HSE Statistics 2014/15)
What is Occupational Health?
The term Occupational Health is used for managing the effect of an employee’s health vis-à-vis the ability on conducting own work and the effect of work on an employee. It is a two-way process.
Professional Occupational health personnel offer services in:
Health and safety risk assessment
Fitness for work assessment and
Health surveillance and rehabilitation
Occupational Health and Occupational Hygiene are different from each other. However, they overlap, as we see in the following diagram:
Harmful substances in the workplace such as asbestos and cement, dust, welding fumes and gases, spray-painting mists have to be assessed, identified and controlled by an Occupational Hygienist to protect workers’ health. ( Ann Occup Hyg. 2014)
Occupational exposures from welding:
An occupational hygienist has to make an inspection, before sampling for welding fumes. Chemical monitoring has to be done to get to know the containment of fumes and gases. Three main factors which are sampling determinants during welding activities include:
The ingredients in the welding electrode, the type of welding performed and the type of base metal welded.
Before sampling, the occupational hygienist must also take into consideration the time of exposure and the measures taken to reduce same exposure.
Equipment, media, supplies are essential to be accurately prepared by an occupational hygienist so that the sampling results will increase in accuracy.
Having said this, it is vital that an occupational hygienist develop a sampling plan while on the pre-inspection phase. Moreover, factors that will profoundly affect the sampling overall are outlined in this phase.
Material Safety Data Sheet:
It is vital to consider the safety data sheet (MSDS) for every product used in the welding operation while investigating potential health hazards concerning welding. Health hazards which associate with the use of these products are defined by the MSDS’s. Recommendations regarding preventive measures, such as engineering controls and personal protective equipment, are also provided by these documents.
Type of Welding: Tungsten inert gas welding
Tungsten inert gas (TIG) welding is one of the welding processes. It is being done by using a non-consumable tungsten electrode to produce welding. An inert shielding gas (argon or helium), protects the weld area and electrode from oxidization or atmospheric contamination; however, a filtered metal is used. Electrical energy conducted across the arc through a column of highly ionized gas and metal vapors, known as a plasma, is produced by a constant-current welding power supply.
The following are a few questions and some useful factors to consider during an on-site inspection:
An Occupational Hygienists has to make sure to have enough sampling cassettes as these might become overloaded.
Make sure that welders are making use of local exhaust ventilation (VLE), during TIG welding.
Keep in mind that the shielding gas may vary, depending on the type of welding.
What media are you using for sampling?
Number of sampling pumps
A Sampling of the exposure limits has to be done.
Are there any contaminants which have short-term exposure limits (STELs)?
If shielding gases are used, do you need to do additional sampling, according to the results? (in areas with poor ventilation, carbon dioxide, can produce carbon monoxide).
The amount of sampling time required is determined by the typical duration of welding length of exposure and an employee’s shift. Sampling is normally performed in accordance with an 8-hour shift compared to Occupational Health and Safety exposure limits results. Not all employees perform welding during all their shift hours, thus it is vital to be informed of the exact length of time welding is being performed by welders. A task-based sample together with a full-shift sample is recommended for contaminants with 8-hour time-weighted average permissible exposure limits.
The position of the sampling cassettes is much debatable. Sampling inside the helmet or outside the helmet, are required by certain situations and company policies. Both sampling methods should be aptly noted.
It is essential to make it clear that although the above mentioned pre-inspection activities are a good start, they are not the only factors to consider when preparing for an industrial hygiene sampling study. (Jackson 2013)
The atmosphere to be sampled, may be affected by a number of factors. Vapor is the result of a boiling liquid, and the quantity of vapor depends on the boiling point. The lower the boiling point of a substance, is the result of more vapor produced. Moreover, there is also the involvement of its molecular weight and structure. The production/quantity of vapor, are also affected by the surface area, air movement agitation, and splashing as well as the temperature.
According to the hierarchy of controls, the first preventive measure should be that of eliminating the hazard. If this is not possible, we opt for the substitution or reducing the hazard for an acceptable, reasonably practicable level. The provision of personal protective equipment should be the last resort.
An occupational hygienist has to make sure that preventative measures to reduce exposures should be taken before commencing with the sampling activities. Whilst on-site, intensive evaluations of current measures, will take place. The following questions might be helpful:
Is an air velocity meter needed to evaluate the type of local exhaust ventilation that is being used?
Will the Occupational Hygienist test the direction of airflow with smoke tubes?
If the worker is wearing a helmet, what type of welding helmet is he wearing and does it affect the positioning of the sampling cassette? How?
What type of respirator does the employee use, if any? And will this affect the sampling cassette? If yes, how?
Is the task being carried out in an enclosed area? If so, could any gases or byproducts of the materials be present, thus create additional hazards to the employees?
There are certain mistakes that can develop during on-site welding fume and gas sampling activities. These may be the result of neglecting to:
Having contaminants which cannot be analyzed on the same cassette and using a separate cassette to account. Hexavalent chromium and silver are included but not limited to.
Ensuring that the system works properly by testing the capture velocity of LEV during sampling
Suggestions of the Occupational Hygienist to reduce exposure to welding fume:
The hazards of the material that welders are working with, should be understood by same workers. It is very important that employers provide the welders with adequate training and relevant information on hazardous materials being used in the workplace.
Solvent residue and paint should be well cleaned off the welding surfaces so that no toxic exposure could be created.
Workers should avoid breathing fume and gases by maintaining good position. (for example, staying upwind when welding in open and outdoor environment).
To reduce fume and gas levels in the work area, a general ventilation, whether natural or forced movement of fresh air, is needed. Adequate ventilation is not guaranteed by welding outdoors or in open space. To keep fume and gases away from themselves and others, welders should use natural drafts as well as proper positioning, in areas where there are no ventilation and exhaust systems.
To remove fume and gases from the welder’s breathing zone, local exhaust ventilation system can be used. For removing the maximum amount of fume and gases, fume hoods, fume extractors, and vacuum nozzles are kept close to the plum source. To draw away fume and gases from the welder, portable or flexible exhaust system is positioned. However, exhaust ports should be kept away from other workers. There are four types of engineered local exhaust ventilation systems:
a welding bench with a fixed hood,
a down-draft bench,
a portable hood with flexible ducting, and
a fume extraction gun or gun attachments with flexible ducting.
Only when engineering controls are not technically and/or economically feasible, respiratory protection should be used.
All welders who are provided with and wear respirators, are to attend a complete respiratory training course which will include the selection, fit testing, maintenance, and inspection of same PPE.
Appropriate eye and face protection together with clothing shall be given to all welders. Depending on the level of noise, to which welders are exposed, hearing protection may also be required. Screens of sturdy opaque or translucent materials with at least 50cm bottom clearance for ventilation, are recommended mostly to prevent the welding from affecting other workers.
It is advisable to consider using a less toxic welding type or a lower fume-generating or consumable.
Welding in a confined space without ventilation is not recommended. Refer to OHSA regulations.
In the case that work practices and ventilation do not reduce exposures to safe levels, respiratory protection may be required.
The employer is required to reduce exposure below the prescribed limits, when concentrations to various constituents present in welding fumes and gases exceed specified TLVs, or when the health of the employee is at risk.
What is in welding fume?
Antimony, Arsenic, Beryllium, Cadmium, Chromium, Aluminum, Cobalt, Copper, Iron, Lead, Manganese, Vanadium, Zinc Molybdenum, Nickel, Silver, Tin, Titanium.
Shielding-Argon, Helium, Nitrogen, Carbon Dioxide
Process- Nitric Oxide, Nitrogen Dioxide, Carbon Monoxide, Ozone, Phosgene, Hydrogen Fluoride, Carbon Dioxide.
Welding fumes are classified as Group 1 carcinogens by the International Agency for Research on Cancer, as there is enough evidence that they can cause cancer in humans.
Medical surveillance program:
A qualified person should assess all welding employees for a medical surveillance program. The doctor must make particular attention to the respiratory tract, as well as their ability of how to use the respiratory protection. The program administrator must ensure that documentation is completed, before fit testing, and respirator use, to make sure that the employee does not have any physiological or psychological condition, as this may not allow him/her use the selected respirator.
Prolonged exposure to welding fumes and gases at high concentration can cause:
Siderosis (iron oxide)
Metal fume fever (zinc oxide, magnesium oxide, copper, aluminum)
Nervous system disorders (manganese)
Irritation of respiratory system
Eye, nose and throat irritation
Kidney damage (cadmium oxide, fluorides)
Cancer (cadmium oxide, nickel, chromium (VI))
Fluid in the lungs (cadmium oxide, fluorides, ozone, nitrogen oxide)
Dermatitis, eczema (nickel, chromium)
Bone and joint problems (fluorides)
Headaches and dizziness
A vast knowledge may be required to provide to provide for all aspects of health and safety, as welding considered as a complicated safety Critical operation.
By reading or training, this knowledge will not come entirely, but experience, practice, and excellent skills should include safe working practices.
A team effort policy should be considered, by having team leaders coaching their team members and team members referring to other team members who are knowledgeable about the health and safety practices. When doing a new task, this is very important! (Mahi2016)