If you're like most people, you're inside right now. And you've probably been inside for roughly 21 of the last 24 hours, cordoned off from the great outdoors by windows, walls, and doors. Given the fact that the majority of our existence is spent in the artificial and highly engineered interior environment, we know very little about our microbial co-inhabitants, the microscopic creatures that coat the surfaces and float in the air of the rooms we live in.
A recent study from Steven Kembel and his colleagues at the University of Oregon seeks to change that. By comparing the microbial communities from rooms with different air ventilation systems – and thus different temperature, humidity, and light regimes – the scientists make the case that architecture determines microbial community, to potentially dangerous effect.
Kembel sampled rooms at the misleadingly named Providence Milwaukie Hospital, which is in neither Rhode Island nor Wisconsin, but a suburb of Portland, Oregon. It was a strategic choice to test the theories of selection through architecture, as medical facilities work to tackle home-grown superbugs and understand the forces that create them. The subject matter also has heritage: Florence Nightingale wrote in 1859 that open windows made for a healthy hospital. (Bonus points for any study citing a pre-1900s paper.)
The team collected 1,500 liters of air from three sites: a mechanically ventilated room, a naturally ventilated (via open window) room, and the outside air. Microbial concentrations ranged from about 500,000 to 2.5 million cells per cubic meter, and the naturally ventilated room harbored a community intermediate between the mechanically ventilated and building exterior samples. Perhaps most alarming was Kembel's finding that “indoor air contained communities that were dominated by a few closely related bacteria that were related to known human pathogens and human-associated bacteria.” This conclusion suggests that, rather than keeping dangerous microbes out, mechanically ventilated hospital rooms are actually keeping potentially harmful species in. On the plus side: Filtration mechanisms did keep pollen and other allergens out.
It's an important – if not completely unexpected – result, but one gets the sense that Kembel is onto something big. The field of microbial ecology has traditionally looked outward to the “natural” world for study sites, places like lakes, desert soil, or deep-sea sediments. But in recent years, things have become more human-centric, as we've realized that microbes permeate everything. (Indeed, the human body itself is mostly microbe.) The human body and its surroundings are no less of a microbial environment than the ocean water we swim in on a hot summer day.
We are intimately connected with the microbes around us, and the community composition can have important implications for our health. The good news is that we have the power to shape the selection pressures that determine which microorganisms survive, and which don't. Of course, the same selection pressures would impinge upon human inhabitants, and there's only a relatively narrow envelope of temperature and humidity that we're willing to tolerate. But within this range, specific strategies can be employed: Different levels of natural light at given wavelengths can be permitted, surfaces could be kept sterile or seeded with a particular nutrient cocktail, and air ducts can selectively filter out specific microbes or biologically active macromolecules.
In the Providence Milwaukie Hospital, the architectural selection parameters enriched for potentially harmful organisms, but that need not be the case. Through the fledgling field of architectural ecology, it should be possible to promote better health through better design.
