Y’all know I have lived in the DC Metropolitan area for almost 3 decades. Over that time, the Potomac River has been cleaned up. (No, it’s not clean. But, coming from where it was in the 70’s and 80’s, there has been an amazing improvement.) And, over the past 3 decades, those EPA regulations that a certain party bitches about have made an amazing difference in local air quality.  (That’s true even though DC has a slew of bus traffic- more tourist buses than almost every other place in the US.)

And, that has led to a set of unintended circumstances. Our gorgeous federal monuments are suffering from ‘creeping crud’ disease. Blackish collections of algae, bacteria, and fungi form biofilms that become attached to the structures.

Given that the monuments are basically calcium carbonate (both limestone and marble are forms of this mineral), its tough to clean the structures. Because most cleaners would remove part of the structure at the same time.

One of the worst affected structures is one of my favorites- the Jefferson Memorial (comprised of marble and pictured above)- which is reminiscent of Jefferson’s home in Charlottesville [Monticello] and his university [UVa]. But, this monument is not alone in succumbing to the malady. The Washington Monument, the Lincoln Memorial, and the amphitheatre at Arlington National Cemetery have succumbed to the creeping crud.

So far, the National Park Service has found no “wonder chemical’. And, they can’t use scrub brushes- because they would clearly damage the underlying structure. To top off the problem, we don’t know if the biofilm is harming the stone- or protecting it from destruction!

It is thought that the biofilm microbes are exuding the black pigment to protect themselves from the UV rays the sun emits. It seems that the Park Service has been working with the Center for Biofilm Engineering, which Dr. Bill Charaklis (a brilliant engineer, who died way too early) instituted at Montana State University. And, they have few, if any, ideas about what to do.

Interestingly, the culprit- not the microbes- but the underlying cause- may be the reduction in air pollution. Because those polluting compounds would make it much harder for the microbes to survive on the structure. But, now that they are gone, there is no impediment to the microbial biofilm formation.

This hypothesis exists because photographs from 5 or 6 years ago shows no biofilm- but over the past few years, there has been the accumulation that is now plaguing the monuments. In 2009, red days (dangerous air pollution presence) were prevalent in DC. By 2013, there was not a single such red-letter (actually black letter would be the more appropriate concept) day.

And, the humidity near the structures (they are all contiguous to the Potomac River) may improve the ability of biofilms to survive. (We’ve known for decades that Serratia marcescens (a virulent pathogen that causes hospital acquired infections) can survive on hospital walls for at least 36 hours if the humidity exceeds 45% or so).

One idea would be to employ a small ozone generator, in conjunction with a small liquid flow- or to use the gas by itself (in air) directed at the creeping crud on the structure.  Because ozone doesn’t react with calcium carbonate, the ozone would still would inhibit the biofilm growth- and the microbial adherence to the structures.

Of course, this treatment would be done at night, when the tourists would not be present. And,  the small amount of water would not mist the tourists- or the ozonated air flow would dissipate before the tourists arrived.

I think an experiment in Arlington Cemetery would prove the concept. But, the Park Service hasn’t asked me.

In case you didn’t understand the title choice:  Jonathan B. Jarvis is the Director of the National Park Service.

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