Astrophysicists fall into either the fire or ice camp when it comes to deciding the fate of the universe. Will expansion continue until everything flies apart into a state of absolute zero, or will the Big Bang reverse itself into an unimaginably fiery Big Crunch? In the social sciences, the big debate is whether nature or nurture reigns supreme in shaping human behavior.

In our industry's little corner of the world, a similar dialectic lurks in the background over the cause of Legionnaire's Disease (LD). My guess is that upwards of 90% of plumbing engineers accept the conventional scientific wisdom that the culprit is the Legionella pneumophilia bacterium. However, it's hard to completely shake a 25-year-old theory that the disease is caused by phosgene gas resulting from the breakdown of refrigerant gases at elevated temperature. It's bugs versus gas, plumbing vs. air conditioning, nature vs. man-made in the quest to identify the villain.

Both points of view were featured in seminars at last fall's ASPE Convention in Nashville, and they offered this observer a fascinating look at one of the murkier issues impacting our industry. Richard H. Toder, P.E., chairman of the ASSE Legionnaire's Disease Task Force Committee, is the main proponent of the phosgene theory. He attacks with missionary zeal the job of drumming up funds to continue research in this area, which was begun by the late Dr. Harold Runsdorf a quarter-century ago after the first identifiable outbreak that gave the disease its name following the 1976 American Legion Convention in Philadelphia.

Toder's case rests on the following key points:

  • Phosgene inhalation produces symptoms, and sometimes fatalities, similar to that of Legionnaire's Disease, which also seems to be acquired solely through inhalation. Phosgene was among the chemical agents unleashed as a military weapon by the Germans in World War I, so there is a considerable body of medical study behind it. Nobody disputes that phosgene gas is produced by pyrolyzing fluorocarbons, such as refrigerants R-11 and R-12.

  • The initial Philadelphia outbreak and many subsequent flare-ups have been associated with aerosols from cooling towers, supermarket mist sprays and other equipment containing refrigerants. Toder also puts much stock in the fact that LD occurs mainly during the summer months.

  • There are scores of Legionella species, and they are ubiquitous in water supplies but difficult to grow in lab cultures. They don't become pathogenic until exposed to a rise in acidity (pH between 6.6 and 6.9) and temperatures between 100 degrees F and 140 degrees F. These are the same conditions associated with the transformation of refrigerants into phosgene. Toder also claims that Legionella has not been found in every diagnosed case of LD.

  • "Each outbreak is generally limited to a single building or surrounding," says Toder, "even when all adjacent buildings are connected to the same water supply. If you change the air conditioning system, it doesn't reappear."

  • The Centers for Disease Control in Atlanta, the focal point for LD identification and research, is institutionally biased toward finding a medical cause to the problem, says Toder.

The Bug Perspective

Among the 75 or so people in the audience at Toder's presentation was Matt Freije, P.E., author of Legionellae Control in Health Care Facilities and numerous articles on LD, including a couple that have appeared in PME. He is one of our industry's most prominent LD authorities, and was also a presenter at the Nashville ASPE Convention with an update on his Legionella findings.

Freije prefaced his remarks with a brief summary of Toder's presentation the previous day. He paid respect to Toder and his chemical theory, saying it deserved more research, but made clear that his own extensive work on the subject is hinged to the belief that LD is bug-based. "Water sources of Legionnaire's Disease are scientifically proven," insists Freije, noting that many outbreaks have occurred without proximity to refrigerants. Specifically, he discussed a March 1999 eruption at a Netherlands trade show that killed 29 people and sickened 244 others. It was traced to steam coming from a hot tub display at the show, in which the same strain of Legionella was found that was present in the victims.

Toder would likely argue that one cannot rule out the presence of phosgene in such cases. The Philadelphia LD epidemic was traced to aerosol mist wafting down the sides of the Bellevue Stratford Hotel from a rooftop cooling tower. Some of the LD victims never set foot inside the building, and no hotel employees were stricken. "You can find Legionella bugs everywhere, but why aren't more people getting sick? Nobody can explain what causes them to turn pathogenic," says Toder. "We believe it's because Legionnaire's Disease is man-made."

Freije's explanation is, "Most Legionnaire's cases occur one or two at a time. It's not that rare of a disease, but unless it occurs as part of a major outbreak, it doesn't get publicized." Also, he contends that many cases are apt to get diagnosed as pneumonia or some other respiratory ailment.

Who to Believe?

Freije is a soft-spoken individual and consummate gentleman. He reacts almost too deferentially towards his counterpart, considering that if Toder is right, then everything Freije knows is wrong. And vice versa.

If the debate were to be settled by fervor, Freije wouldn't stand a chance. Toder rails like a preacher against sin in blaming vested economic interests for pushing the phosgene theory into the background. He told the ASPE audience, and later reiterated to me in a phone conversation, that he received a death threat for pursuing his line of inquiry. He says it occurred years ago in the days leading up to a "60 Minutes" broadcast on the phosgene theory. Toder sells a video containing that program and another documentary on the Philadelphia LD investigation as a means of raising money to fund ASSE's research.

This reporter's skepticism neurons turn into a fireworks display in the presence of impassioned conspiracy theories. I spoke with a handful of ASPE members who attended Toder's presentation, and they seemed to feel the same way, although everyone I spoke with acknowledged the unresolved mysteries in his message.

Putting aside Toder's accusations about evil intent, we are left with a scientific jigsaw puzzle that is nowhere near complete, and many of the phosgene pieces are of the right shape and color. Moreover, the reasoning mind is haunted by the legacy of Galileo, Pasteur and so many other scientists throughout history who have made colleagues look foolish for scoffing at disruptive ideas.

Of course, let's not forget that for every Galileo and Pasteur, there have been thousands of spurious insurrections against conventional wisdom. Toder makes much of the fact that 25 years of bug-based LD research has failed to rule out the phosgene theory, seemingly unaware of the logical fallacy inherent in expecting to prove a negative. One also has to be wary of investigator bias coloring any research in which a party has invested so much emotional energy in a particular outcome.

Yet, Toder poses some questions that cry out for definitive answers. How certain are we of LD's genesis? Why does the pathogen behave so mysteriously? Does the bug theory account for all the loose ends? Should the ASSE Legionnaire?' Disease Task Force Committee continue its work, and if so, where should the funding come from?

I'd love to hear your opinions.