UC Berkeley

Water intrusion can result from hurricanes and flood damage, condensation, and elevated humidity indoors. Increased water availability and moisture indoors allows for the proliferation of fungi and other microorganisms that are able to grow on most building materials. Damp, moldy housing has been associated with a number of negative health outcomes, principally respiratory disease, allergy, asthma, anxiety and depression. For the promotion of public health, there has been a long history of studying the microorganisms that inhabit the built environment. Nonetheless, there are currently no federal standards set by the Environmental Protection Agency distinguishing what is ‘safe’ or ‘abnormal’ microbial exposure indoors. In part this is because until very recently, the main tools used to identify microbes have relied on culture-based methods, microscopy, and immunochemical techniques. We now know that the vast majority of microorganisms cannot be cultured in the laboratory, and we have made epic strides in fungal and bacterial taxonomy by using molecular tools for phylogenetic identification.

My dissertation research used high-throughput DNA sequencing technologies to characterize the microbiomes of water-damaged public and private housing in Richmond, CA, and New York City, NY. We collected house dust from over 90 homes and profiled bacterial and fungal communities using multiple sampling methods. We surveyed one public housing project in Richmond that was condemned by the local Housing Authority, yet remained occupied by seniors, disabled persons, and low-income residents for years after being deemed uninhabitable. We also surveyed over 40 buildings in Brooklyn and Manhattan, NYC, in the notoriously underserved New York City Housing Authority (NYCHA) buildings and privately-owned apartments in the same neighborhoods. The NYC buildings endured Hurricane Sandy in 2012 and the public housing projects were woefully neglected in the storm’s wake. A year later, NYCHA had yet to address major structural damage caused by the flooding and many residents fell ill. A class action lawsuit was successfully filed against the Housing Authority for violating the Americans with Disabilities Act (which provides protections to persons with asthma and breathing disorders) for failing to abate spreading mold contamination in NYCHA buildings and exacerbating the deterioration of residents’ health.

By working collaboratively with building scientists, non-profit organizations, resident activists, and attorneys, we were able to deduce a microbiological signature of building negligence and the impact of long-term water-damage on residential buildings. We conducted amplicon sequencing and quantitative-PCR on dust collected from the outdoors, in kitchens, bathrooms, bedrooms, and living rooms. We found that there are distinct microbial communities in water-damaged homes compared to homes with no damage, and different microbial communities in public housing units compared to private housing.

In Richmond, we evaluated fungal communities in units with visible mold and compared these to fungi in units with no visible mold and the outdoors. We learned that fungal communities in units with visible mold are less diverse than communities in units with no visible mold and outdoors. Fungal communities in units with visible mold have increased abundance of Eurotiomycetes, Saccharomycetes, and Wallemiomycetes. Samples collected from actively growing mold on walls and surfaces were dominated by two Cladosporium species. We also saw that fungi growing on walls became airborne and could be detected in our passive samplers that collected settled dust over the course of four weeks.

In NYC, we similarly saw that units with water-damage were characterized by lower bacterial and fungal diversity, lower fungal biomass, and compositionally distinct microbial communities. Microbial communities in water-damaged units had a significant reduction in outdoor microbes and increased abundance of Clostridia, Coriobacteriia, Agaricomycetes, and Pezizomycetes fungi. These classes include taxa that are known opportunistic pathogens and could trigger an allergic response. In addition, we observed evidence of microbial dysbiosis in public housing units. Compared to private housing, microbial communities in public housing had reduced alpha- and beta-diversity, and increased abundance of Bacteroida, Erysiphelotrichia, Negativicutes, and Saccharomycetes; budding yeasts and taxa found in association with the human gut. Beyond this, we evaluated the utility of various sampling methods, including swabbing surfaces and door trims, vacuuming floors, collecting passively settled dust, and using electrostatically charged wipes, to collect biological material. We provide recommendations to the field of indoor air microbiology for sampling methodology, and advocate for the use of simple, empty, sterile petri dishes to collect settled dust. This allows for accumulation of airborne taxa over the course of one month, both indoors and outdoors, accounting for fluctuations in season, diurnal dynamics, and resident behaviors.

Housing has long been deemed a major social determinant of health. Living in substandard housing increases risk of injury, exposure to environmental toxins like lead, asbestos, outdoor pollution, mold, and allergens. Public housing residents have the worst documented health outcomes of any population in the United States. Nearly half of all public housing in this country is occupied by African Americans, yet this population only accounts for 12% the national census. The concentration of People of Color in substandard and unhealthy housing today is the result of a long history of housing segregation and racial exclusion from the federal subsidies that led white Americans to become home-owners and build wealth. Afterwards, neoliberal policies focused on diminishing social welfare dramatically defunded New Deal-style public housing and began demolishing thousands of public housing complexes. This ultimately led to the current sociopolitical catastrophe and chronic disrepair of North American public housing stock. A consequence of this malignant building management is an asthma epidemic, to which low-income Children of Color living in urban public housing suffer disproportionately.

Characterizing the microbiota of low-income housing is a critical step towards addressing disparate exposure to indoor air pollution caused by microorganisms. Elevated moisture indoors, which leads to the growth of toxic mold, is preventable and can be remediated. But to fix a problem we must first know it exists. In the case of a microbiological problem, the culprits are invisible to the naked eye due to their microscopic size, so it is imperative to use tools that are rapid, efficient, and informative for adequate detection. Here is where environmental justice and activism meets basic microbiology and microbial ecology. Here is where a DNA sequence is fuel for proletariat resistance. Here is where science becomes a tool of empowerment, self-advocacy, and for healthy affordable housing. For years the residents of low-income housing have complained they can’t breathe in their homes. By finally putting names on the fungi and bacteria that comprise the mold on their walls and circulate in the air, we now have a cleared picture of why.