Recently, the Joint Center has been researching what makes a healthy home.  As Mariel Wolfson pointed out in her recent blog, indoor air quality has been a major component of modern healthy home research dating back to the 1970s.  Radon, formaldehyde, and combustion pollution from cooking and heating are traditionally identified as key risks.  One emerging topic that has yet to be understood is how microbial communities living among us affect household health.  As it turns out, these microbiomes (diverse communities of bacteria and other microorganisms sharing space with humans) are not well understood, but have great potential to impact human health indoors.

Earlier this year, I had the opportunity to attend a symposium on Microbiomes of the Built Environment at the American Association for the Advancement of Science (AAAS).  With some astonishment, I discovered there are millions of microbial species on earth, and while some are pathogens that are linked to illness and diseases, the majority are beneficial for humans.  For example, microbes have the potential to educate our immune systems, produce vitamins, energy, anti-inflammatories, and even neurotransmitters.

The squeamish may wince, but the fact remains: humans live in a sea of indoor bacteria—at home, work and in other public spaces—many of which promote human health.  Indeed, a central theme of the conference was that people not only need to be protected from pathogens, but they also need to be exposed to diverse microbes, especially at a young age.

Further research is needed on this front.  The vast majority of these microbes have yet to be classified.  And scientists don’t yet understand what constitutes a ‘healthy’ microbiome in the built environment.  More research is also needed on how to design, properly maintain, and fix buildings to prevent or eliminate problematic microbial indoor communities.  Currently, the Alfred P. Sloan Foundation is investing millions of dollars into a Microbiology of the Built Environment Program to study these and many other questions.  While answers remain far off, I came away from the conference with several takeaways relevant to the residential housing sector:

1. Building design and management both play a role in the transmission of microbial communities.  In any built environment, the rate and efficiency of air circulation and filtration, as well as disinfection by UV light, all impact transmission of microbiomes. Rooms in same air handling units have similar microbiomes.  Even the type of ventilation—mechanical versus natural—impacts the diversity and composition of microbial communities indoors.  All of this suggests a distant, future role for ‘bioinformed’ design and management of homes and other residential communities.
2. Building materials, and even appliances and fixtures, impact growth of microbial communities.  Bamboo, for example, widely heralded as a cheap and rapidly renewable building product, also exhibits rapid oxidative aging, enabling mold to grow more rapidly once the wood has been aged for long periods.  Even showerhead design can impact the spread waterborne microbial communities.  Some high efficiency showerheads can put out a fine mist that enters deep into human lungs, the effects of which need to be examined further.  Additional research and understanding is undoubtedly needed on how a variety of materials, fixtures, and appliances impact indoor microbial communities.
3. Water quality will remain a challenge.  Scientists know surprisingly little about our drinking water’s microbial composition. Additionally, while the quality of U.S. drinking water is exceptionally high by world standards, our water infrastructure is aging and “nearing the end of its useful life,” according to the American Society of Civil Engineers.  The cost for replacement may be as much as $1 trillion over the next several decades.  As concern for water sustainability increases, water may be sitting in pipes longer, which may promote the growth of bacteria.  A prominent example can be seen in the case of hands-free faucets that can pose risks in a hospital setting.
4. While scientists still don’t understand what a ‘healthy’ indoor microbiome may be, some preliminary findings and suggestions were offered to promote indoor health.  Most prominently, dampness and mold are widely identified as known factors associated with asthma, eczema, and other related health problems under the umbrella of ‘sick building syndrome.’  As Dr. Mark Mendell explained at the conference, films of fungi or bacteria on air conditioning coils are likely responsible for many of these cases.  Identifying and removing extra building moisture, removing settled dust, and properly operating and maintaining HVAC systems were are all recommended for preventing and remediating sick building syndrome.  A helpful 2012 alertfrom the National Institute for Occupational Safety and Health (NIOSH) contains further guidelines.  In addition to protecting against pathogens, some epidemiological evidence suggests that having dogs at home may actually protect against asthma early in life by facilitating exposure to diverse microbes.

If and when scientists do eventually unravel the complex riddle of what constitutes a healthy indoor microbiome, further questions and challenges will remain.  How can healthy, bioinformed buildings be designed and maintained?   Perhaps an even greater challenge will be what to do from a policy perspective. Should architects, building scientists, and policy makers take steps to promote certain bacterial communities in buildings?   As Dr. Jeffery Seigel pointed out at the conference, public perception could be tricky—for instance, if people get sick inside a building designed to promote certain bacteria, they could assume it’s because of the particular microbiome in the building.

Study of microbiomes in the built environment is a challenging and wild frontier in the realm of healthy housing research, but findings relevant to residential health likely will inform consumers’ future home improvement behaviors and spending.  Indeed, according to a recent Joint Center survey, one out of every four homeowners expressed concern about some aspect of their home negatively impacting their household’s health. And among owners specifically concerned about ‘invisible’ risks, such as indoor air or water quality, more than half took at least one specific action to remediate their concern, including installation of water filters, mold removal, and choice of paints with low- or no airborne toxins.  In other words, U.S. consumers’ perception of invisible health risks and problems, and their growing knowledge of best practices in healthy housing, impacts their home improvement behavior.  Further developments in healthy housing research likely will impact their choices of remodeling projects and materials, and may even influence how they go about choosing remodeling contractors who they feel will best protect and even promote their households’ health.