In 2022, CDC investigators identified an unexpected trend. From 1997 onward, seven infections caused by Bacillus group bacteria that produce the anthrax toxin were reported — all involved metalworkers. Six of those seven were welders, which led to the label “welder’s anthrax,” while the other case was in a foundry worker who ground metal. In the six instances where the specific Bacillus species was determined, B. tropicus was responsible, including in the newly documented case.
Speculating risks
Why metalworkers, and welders in particular, appear especially susceptible is not clear. In their 2022 report linking the cases, CDC authors suggested it could be a mix of lung immune weakening after inhaling toxic metal fumes and gases produced during metalwork and greater exposure to the dangerous bacteria at work.
In the most recent case, the teenager performed welding about four hours a day, four days a week, often in poorly ventilated or confined spaces and frequently without personal protective equipment like a respirator. Environmental testing at his job site detected anthrax-toxin-producing Bacillus in 28 of 254 spot samples. Other probes into welder’s anthrax incidents have yielded similar findings.
To date, all nine cases have been identified in Louisiana or Texas. However, experts caution that cases are probably undercounted, and models indicate these pathogens could be present across many Southern U.S. states.
Investigators have also suggested iron exposure may be a factor. Bacillus bacteria require iron to grow, and metalworkers can accumulate excess iron in their airways during work. Such iron overload might create favorable conditions for infection. The teen had been working with carbon steel and low-hydrogen carbon steel electrodes.
At present, the exact risk factors and why this otherwise healthy teen — and not others at his workplace — became ill remain unanswered. CDC and state authorities recommended workplace changes to protect metalworkers, including improved respirator use, better ventilation, and enhanced dust control.
An anthrax vaccine exists and is advised for groups considered high risk, such as certain military personnel, laboratory staff, and livestock handlers. Whether metalworkers will be added to that high-risk category in the future is still uncertain.
