I’m sharing an email exchange that I had with a colleague who had asked about the risk of L. pneumophila (the microbe that causes Legionnaire’s disease) in MWF.
Thank you for posting your query to BCA’s website.

You wrote:
“I wondered if you could help me answer a customer’s question. One of my customer’s machine tool operators is in the hospital being treated for Legionnaires’ disease. My customer asked me if the Kathon 886 MW or Kathon CC kills this strain of bacteria. I really appreciate your help and advice. I attend the annual STLE meeting every year and hear you speak on maintaining and monitoring metal working fluids, so I thought you would be the best source to ask. The Legionnaires’ disease was most likely contracted in Tennessee while this gentleman was on vacation. Other machine operators are now afraid they might contract the disease through the metal working fluids in the plant.
Thank you for your time and thoughts.”

The short answer is yes.

Not long after Legionella pneumophila was identified as the disease agent that caused Legionnaire’s disease, Rohm & Haas tested Kathon WT1.5 efficacy against the bacterium. WT1.5 is just Dow’s (formerly R & H) water treatment market label for the 1.5% active product we use as Kathon 886MW and 886MW 1.5 in the MW industry.

Keep in mind that L. pneumophila is ubiquitous. If you recall the incident at Ford’s Le Brea, OH plant some years ago, four machinists came down with Legionnaire’s disease. Attempts to detect L. pneumophila from MWF systems all failed. An immunological survey of all of the plant’s employees revealed that the majority has antibodies to L. pneumophila. Other immunological surveys (populations outside our industry) have demonstrated that the majority of the population has been exposed to the microbe (i.e.: has the antibodies). Most of the time, folks who contract the disease have other health problems that render them more susceptible than the general population. Back to Le Brea. That incident and a cluster of Pontiac Fever cases at a Pontiac Plant in Windsor Ontario in 1981 are the only two clusters of Legionnaire’s disease that have been reported in the MW industry. The 1981 outbreak was caused by L. feeleii growing in the facility’s cooling towers. The source of L. pneumophila at Le Brea was never confirmed.

From what we know, workers are much more likely to be at risk from improperly controlled heat exchange systems/cooling towers than from MWF.