In 2022, CDC researchers discovered an unexpected pattern. Since 1997, seven cases of infection have emerged Bacillus group of bacteria that produce the anthrax toxin – all in metalworkers. Six of the seven were welders, hence the term “welder's anthrax,” while the remaining case involved a person who worked in a foundry grinding metal. Of the six cases where a specific Bacillus species was identified, B. tropical was to blame, also in the newly reported case.
Speculative risks
It is unclear why metalworkers, and welders in particular, are so vulnerable to this infection. In their 2022 report, CDC experts speculated that it could be a combination of a weakened immune response in the lungs after inhaling toxic metal fumes and gases created during metalworking, and increased exposure to the deadly germs in their workplace.
In the latter case, the teenager worked four hours a day, four days a week, with limited ventilation, sometimes in confined spaces, and often did not use personal protective equipment, such as a respirator. Environmental samples from his workplace showed anthrax toxin being produced Bacillus in 28 of the 254 spot samples. Other studies of anthrax cases in welders have produced similar results.
So far, all nine cases have been discovered in Louisiana or Texas. But experts note that cases are likely underreported, and modeling suggests these dangerous germs could thrive in many southern US states.
The experts also speculated that iron exposure could play a role. Bacillus bacteria need iron to live and thrive, and metalworkers can build up excess iron in their respiratory tract as they work. Iron overload can create the perfect environment for bacterial infections. In the teenager's case, he worked with electrodes made of carbon steel and carbon steel with a low hydrogen content.
For now, the precise risk factors and why the healthy teen – and no one else at his workplace – became ill remain unknown. CDC and government officials have recommended workplace changes to protect the health of metalworkers, including better use of respirators, ventilation and dust control.
There is also a vaccine against anthrax that is recommended for people who are at high risk, such as certain military personnel, laboratory workers, and livestock farmers. It is unclear whether metal workers can also be included in this risk category in the future.
