The big implications tied to new manganese recommendations

A big change could be coming to air quality regulations that affect metal fabricating facilities with welding operations.

The American Conference of Governmental Industrial Hygienists (ACGIH^®) recently lowered its recommendation for exposure limits to manganese in welding fumes. The change was substantial—a tenfold decrease, from 0.2 mg/m³ to 0.02 mg/m³.

(The ACGIH recommendation is a time-weighted average (TWA). This means the exposure levels are measured over an eight-hour shift and averaged. The group’s exposure limit is officially called a “threshold limit value” (TLV^®), hence their announcement of a TLV-TWA of 0.02 mg/m³.)

The change is even more dramatic considering the Occupational Safety and Health Administration’s current standards. The latest ACGIH recommendation level is 250 times lower than the current OSHA exposure limit. Air quality experts think this new recommendation could ripple through manufacturing in the coming years.

Why the Concern Over Manganese Dust?

Manganese particles are a common component of welding fumes. Most of these particles come from the burning of welding wire during which the very high temperatures involved create extremely small particles. These dust particles—which can travel deep into the lungs because of their small size—have proven to be a serious health hazard.

While manganese is a vital part of our diet, the body can’t process the metal when inhaled. The Centers for Disease Control reports that exposure to even low levels of manganese dust can produce changes to “mood and short-term memory, altered reaction time, and reduced hand-eye coordination.” The Mayo Clinic adds that chronic exposure over several months or more to manganese dust can give rise to central nervous system problems, with increased cases of tremors and depression being possible. Excessive exposure can cause manganism, a neurological disorder with symptoms similar to Parkinson’s disease.

The ACGIH’s new recommendations on manganese exposure do not have any legal authority. They are simply recommendations by industry’s leading experts.

OSHA makes regulations regarding air quality and exposure limits. It sets personal exposure limits (PELs) for multiple toxic metals that show up in welding fumes. These limits are usually measured in milligrams per cubic meter of air. Failing to meet an OSHA standard could bring serious fines and perhaps reputational damage.

While ACGIH recommendations do not carry the force of law, they are widely respected in manufacturing. The organization’s recommendations for air quality represent something close to best practices in the industry for controlling weld fumes. Despite the ACGIH recommendations’ stringency, some leading manufacturers, such as John Deere, Honda, and Volvo, have adopted them. ACGIH standards also are the basis of many Canadian air quality regulations, which are made at the provincial level, rather than the national level.

History shows that OSHA usually follows ACGIH recommendations or shifts in that direction. OSHA is often limited in its freedom to act, however. While OSHA is guided by science and industry experience, it is limited in its reach by political considerations. Pressure groups often seek to stop or delay OSHA regulations. This makes it difficult to know exactly what OSHA is going to do in the future.

As it stands today, OSHA’s current exposure limit for manganese is 5.0 mg/m³, which is much greater than the ACGIH’s new recommendation. If OSHA changes its standard, many (if not most) metalworking facilities will have to review their air quality standards.

What OSHA might do is still a matter for speculation. The political climate is currently not very supportive of such regulations, but OSHA’s pattern of following ACGIH’s guidance would help to justify a case for a rule change.

How Metal Fabricators Might Become Compliant With a New Standard

If OSHA dramatically reduces its exposure limit for manganese in welding fumes, many plant managers will need to scramble to comply. First, they likely will need to find their TLV-TWA data for the element in question. The best method for doing this is to bring in a certified industrial hygienist to test the facility.

Surveying the air quality in a facility consists of placing air quality monitors throughout a building, particularly in places near welding areas. Monitors are placed in the breathing zone, which is roughly 5 feet off the ground or on the collars of welders. A good survey gathers data for the entire facility as well as for areas where weld fumes are the densest.

Mitigating weld fumes is done primarily by two kinds of fume capture: source capture and ambient capture. The former collects fumes close to the point of welding and is accomplished by devices such as fume arms, hoods, and fume guns. Ambient capture cleans the air in an entire facility and is done through ducted systems or large filtration units.

If a facility is having a problem with its PEL for a particular substance, such as manganese dust, source capture is the best way to address it. Grabbing the fumes coming directly off the weld point is the most direct route toward bringing a facility’s PELs into compliance.

Stay Aware and Make Plans

The change in ACGIH standards for manganese dust is a wakeup call for metal manufacturers. While it carries no immediate mandates for compliance, it is likely a harbinger of changes to come. It is unlikely OSHA will maintain an exposure level 250 times higher than ACGIH’s new number—not for long, anyway.

Fortunately, planning for air quality improvements isn’t rocket science. Well-established methods exist to capture weld fumes and achieve an air quality that stays ahead of regulations.