Hexavalent Chromium is a carcinogenic substance created from different welding and hot metalworking processes. This dust/fume can be very dangerous to employees.
What makes it dangerous, and what steps can you take to mitigate the risks? Read below to learn about how hex chrome is produced, and how to protect workers at your facility from health issues.
What is Hex Chrome?
Hex Chrome is a major byproduct of all materials made from chromium. It is formed when metalworkers are performing “hot work” such as welding on stainless steel or other alloy steels that contain chromium metal.
A study conducted by the National Institute for Occupational Safety and Health found that hex chrome is most commonly produced in carbon steel welding, stainless steel welding, painting, electroplating, steel mills, and iron and steel foundries.
Chromium is not originally hexavalent. The high temperatures involved in allow steel welding result in oxidation of the chromium that changes it to a hexavalent state.
Workers are exposed to hex chrome through inhalation, absorption through the skin or swallowing if they don’t thoroughly wash their hands.
Health Issues Resulting from Hex Chrome Exposure
Hex Chrome compounds are occupational carcinogens and can cause numerous health issues to workers if they are not protected and the facility not properly maintained.
Greater risks for lung cancer are the most dangerous health effects related to exposure. However, it can also cause nasal septum ulceration and perforations, skin ulcerations, and allergic and irritant contact dermatitis.
Once in the body, hex chrome will usually target organs, including the respiratory tract. Inhalation at high levels can cause irritation to the nose and throat, damage to mucous membranes, and perforation of septum tissue between the nostrils and nose. Over time, workers can develop asthma symptoms such as wheezing or shortness of breath.
Permissible Limits and Determining Worker Exposure
The Occupational Safety and Health Administration (OSHA) in the United States has permissible limit standards and guidelines determining exposure to protect workers from hex chrome in the workplace.
The permissible exposure limit for all hex chrome compounds is 5 micrograms per cubic meter of air (μg/m3) as a time-weighted average (TWA) in an 8-hour shift. This also includes rules related to preferred methods for controlling exposure, respiratory protection, protective work clothing and equipment, hygiene areas and practices, medical surveillance, hazard communication and record keeping.
Exposure is defined by OSHA as the concentration of contaminants to which an employee would be exposed without using personal protective equipment.
OSHA does not recommend specific technologies to mitigate risks, however, it does require companies that generate hex chrome to monitor the air to determine the 8-hour TWA exposure for each affected worker.
There are two options to determine exposure:
- A scheduled monitoring option
- A performance-oriented option
The scheduled option requires a company to perform exposure monitoring immediately and then periodically depending on certain factors. The monitoring is performed by employees wearing a small air pump and filter.
If the immediate monitoring determines that exposure is at or above the PEL of 5 μg/m3, then the company must perform an exposure monitoring test every three months. If the immediate monitoring determines that exposure is at or above 2.5 μg/m3, then the company must perform an exposure monitoring test every six months.
If the initial monitoring is below these levels, then the company does not have to perform another test unless there is a change in work processes or materials that could result in new or additional exposures to hex chrome.
The performance-oriented option allows for the estimation of exposures through any combination of air sampling, historical monitoring data or objective data.
Objective data is the air monitoring data from industry-wide surveys or calculations that is based on the composition or chemical and physical properties of a substance that demonstrates the employee exposure to hex chrome associated with a particular product or material, or a specific process, operation or activity.
This data must reflect workplace conditions that closely resemble the processes, type of material, control methods, work practices and environmental conditions in the facility’s current operations.
Mitigating Exposure Risks
The best way to control hex chrome fumes in a large space is through a high-efficiency cartridge-style dust collector. An example of this is Camfil’s Gold Series X-Flo industrial dust collector, which is built to handle all kinds of toxic and combustible dust, smoke and fumes.
Older baghouse-style dust collectors and electrostatic precipitators do not usually offer high enough filtration efficiencies to remove the fumes.
Other systems used to clean up dust and fumes in smaller settings include:
- Tip extraction systems – which capture welding fumes at the tip of the welding gun
- Source-capture systems – which use fume exhaust wielding guns, fume arms, backdraft slotted hoods or small hoods with side curtains
- Enclosures and hoods – which are positioned as close as possible to the source of the hex chrome and capture them using proper airflow
Using the MERV scale will help you choose which filter to attach to your dust collection systems. However, you can’t use that alone to ensure all of the fumes are being filtered out.
Because hex chrome can be so dangerous, we recommend using primary dust collection filters that use high efficiency nanofiber media that can deliver tested efficiency of MERV 15 or MERV 16.
We also recommend using a secondary safety monitoring filter with HEPA efficiency, preferably located on the negative pressure side of the fan. Select a HEPA filter that can provide 99.97% particle removal efficiency at 0.3 microns.
A HEPA safety monitoring filter must also be attached and should provide 99.97% particle removal efficiency at 0.3 microns.
Asking a filtration product vendor about which system is best for you is the best way to ensure that you are complying with OSHA standards. In many cases, they will provide a written guarantee.
To learn more about designing a dust collection system that will keep your employees safe and your facility in compliance, contact the experts at Camfil APC.