In This Issue
Microbiomes of the Built Environment
September 15, 2022 Volume 52 Issue 3
The covid-19 pandemic suddenly directed awareness to potential health impacts of the built environment of everyday living – schools, dwellings, offices, public buildings, and other spaces. This issue explores the “microbiome” of the built environment in the postpandemic reality in terms of ventilation performance, filtration, understanding and quantification of transmission risk, protection of “benign” microbes, and the important role of equity, among others.

Housing-based Inequities in Microbial Exposure and Respiratory Infection Risk

Tuesday, September 13, 2022

Author: Diane R. Gold, Tyra Bryant-Stephens, Elizabeth C. Matsui, and Lee Ann Kahlor

Community engagement, communication, and collaboration are needed to help address poor housing quality that contributes to disease.

Research in recent decades has helped disaggregate the components of the built environment that contribute to the increased risk of respiratory infections in poorer neighborhoods (Engineer et al. 2021). The covid-19 pandemic highlighted the role of these components as well as neighborhood-level housing inequities (Pitzalis and Spano 2021)—such as unstable access to housing (Nobari et al. 2022), crowding, and inadequate or faulty plumbing and ventilation—in increasing respiratory infection incidence, morbidity, and mortality (Rossen et al. 2021; Tieskens et al. 2021).

The realities of housing circumstances in many underresourced neighborhoods make it very challenging for individuals in households to implement recommended respiratory infection prevention practices such as distancing, quarantine, and effective ventilation. In this article we describe the contributing factors to housing inequities and then explain the critical role of respectful community engagement and risk communication to support collaborative efforts that can mitigate risks and facilitate control strategies.

Factors Associated with Inequity and Infection Risk

To devise housing and neighborhood infection control strategies that complement vaccination and the use of personal protective equipment (when available), it is necessary to understand how respiratory infections and their variants are spread. Infection risk—and hence potentially effective control strategies—vary by virulence (a quantitative measure of the likelihood of causing disease), transmissibility (ease of spread from one host to another), mode(s) of transmission, and whether transmission can occur in asymptomatic people. However, common risk factors for the spread of many respiratory infections (e.g., influenza and tuberculosis) also include urban density, poverty (Lobato-Cordero et al. 2019; Nardell 1989), and associated built environment conditions.

Housing circumstances in many underresourced neighborhoods make it very challenging to implement respiratory infection prevention practices.

Multiple features of poor-quality housing have been tied to poor health generally and to risk of chronic respiratory illness as well as acute respiratory infection specifically. Crowding (Gonzalez et al. 2021), lack of space for family members to isolate or quarantine, and poor ventilation and air filtration all directly affect transmission risk of infectious microbes, as clearly demonstrated during the covid-19 pandemic (Bazant and Bush 2021). Pest infestation, which is more common in housing that is in disrepair and located in disadvantaged neighborhoods, can be allergenic (increasing susceptibility to and exacerbation of asthma, often in the setting of acute respiratory infection; O’Connor et al. 2018), carry pathogens, and negatively influence indoor microbial ecosystems (Kakumanu et al. 2020).

Crowding and Proximity

Beyond crowding in family homes, congregate housing such as dormitories (Cedeno Laurent et al. 2020), homeless shelters, prisons, and nursing homes are the settings of high rates of spread of respiratory infections (Mphaphlele et al. 2015; Nardell 1989).

In homeless shelters, reports have noted between--resident reinfection with tuberculosis, potential TB transmission through ventilation systems, and, on the other hand, the safety and effectiveness of well--maintained upper-room germicidal ultraviolet (UV) air disinfection (Mphaphlele et al. 2015; Nardell et al. 2008) in reducing infection risk. For covid-19 and influenza, direct air transfer between humans is well documented; their potential viability and trans-missibility through ventilation systems is less certain than for tuberculosis.[1]

Poor Ventilation and Air Quality

Congregate and individual/family housing in under-resourced neighborhoods may lack adequate air exchange for dilution of airborne respiratory infection to reduce risk of spread. The workplaces of people from under-resourced neighborhoods may also have sub-optimal building ventilation conditions, compounding the risk of bringing home respiratory infections such as covid-19.

For overall respiratory health, along with introduction of outdoor air, there is also a need to prevent outdoor air pollution and allergens from penetrating indoors and to maintain a comfortable temperature and humidity level, while ensuring control of indoor sources of pollution and bioaerosols, including microbial exposures that are detrimental to health (ASM 2004). Building conditions such as temperature and humidity also influence the mode as well as the likelihood of spread of respiratory infections (Lobato-Cordero et al. 2019; Wang et al. 2022).

Guidance for hospitals and other communal spaces to reduce building-related covid-19 risk has included recommendations regarding air filtration of outdoor particle pollution while bringing in adequate fresh air, indoor room particle filtration, and consideration of upper-room germicidal UV to reduce viral particle burden (Klompas et al. 2021; Morawska et al. 2020). Research has demonstrated the risks of indoor air recirculation, which is more common with current--generation air conditioning, in potentially concentrating some infectious airborne microbial exposures (Nardell et al. 2020).

Increasing ventilation is certainly helpful, but it is not possible to provide precise recommendations on air exchange rates that keep pace with changes in covid-19 viral transmissibility (Ghoroghi et al. 2022)—since 2021, with the appearance of new variants, the transmissibility of covid-19 has not only evolved but also, with the Delta and Omicron variants, increased (Mohsin and Mahmud 2022).

Lack of Basic Resources

Adverse housing conditions make the provision of adequate air exchange, as well as isolation or quarantine to reduce respiratory infection risk, infeasible in many homes. Housing mobility programs (Pollack et al. 2019) can offer families a timely solution, and isolation outside the home has sometimes been available (e.g., in a hotel; Huggett et al. 2021). But leaving a loved one with strangers or on their own in temporary housing for isolation or quarantine can be culturally incompatible and emotionally distressing for family members and caregivers.

These challenges are not confined to families in urban areas. For example, while many Native American families in rural homes have benefited from the support of traditional healers and community health representatives[2] to help tend to family members suffering from covid-19 (Solomon et al. 2022), they have been constrained by contaminated water supply, lack of transportation, and inaccessible health communication (Yellow Horse et al. 2022).

Legacy of Discrimination in Housing

Multilayered discriminatory policies that were codified and implemented through racial covenants, red-lining, and other unfavorable lending practices more than a century ago created segregated neighborhoods and stripped residents of opportunities to build wealth needed to purchase, repair, and maintain healthy housing. Zoning allowed the siting of nearby pollution sources (Deshmukh et al. 2020; Lane et al. 2022), shown to increase covid-19 mortality risk (Chakraborty et al. 2022). These and other factors also contribute to the presence of urban heat islands (Jesdale et al. 2013) and vacant lots that promote the growth of ragweed, a common allergen (Katz and Batterman 2019). For all these reasons, ensuring a healthy indoor home environment in these neighborhoods can be particularly challenging.

Gold et al box 1.gifThe problems are illustrated in a composite scenario (box 1) drawn from the experiences of participants in the Community Asthma Prevention Program in Philadelphia.

Community Engagement and Risk Communication

The challenges described above are long-standing, complex, and interconnected. They must be addressed by long-term and systemic approaches involving stakeholders at multiple levels, policymakers, engineers, architects, community members, and others. As part of that process, in this article we consider the role of community-engaged research and effective risk communication in addressing health disparities related to the indoor environment.

Community Engagement around Indoor Environmental Health

Black, Hispanic, and Indigenous communities in the United States have endured a lengthy history of exploitative research and medical practices (Corbie-Smith et al. 2002; Nuriddin et al. 2020); thus, public health engagement in these communities can be fraught with mistrust and skepticism. But respectful research methods and communication can foster the development of relationships and trust between public health researchers, engineers, and clinical workers and the minoritized communities they seek to learn from and support (Holzer et al. 2014; Rhodes et al. 2018).

Exposure to misinformation can influence intentions to avoid or seek additional information.

Community-engaged research is (i) driven by needs defined by the community, (ii) conducted in service to helping the community meet its needs, and (iii) wholly collaborative, with scholars working alongside community members to collect data and put it to use for the benefit of the community (Ahmed and Palermo 2010). For example, as noted above in the composite scenario, the Community Asthma Prevention Program works closely with Philadelphia families in underresourced neighborhoods to jointly identify and implement housing repairs that can improve asthma control and that may also reduce covid-19 risk through better-ventilated living spaces (Bryant-Stephens et al. 2021).

Understanding Risk Communication

Risk communication scholars have identified a number of factors that can enhance community-engaged research as it works to build trust, share research findings, and help communities navigate complex health risks.

Risk communication research has evolved dramatically over the past 40 years. What started as a field dedicated to aligning “‘lay’ perspectives with those of ‘the experts’” has evolved to recognize that risk perceptions are subjective and socially constructed (Balog-Way et al. 2020, p. 2242). A more modern approach to risk communication begins with an acknowledgment of the complex (and often environmentally constrained) ways in which a community has already navigated a risk; from there, researchers and community stakeholders can craft an achievable plan for moving forward with mutual goals (Hampel 2006).

One important finding in the risk communication literature is that people are significantly motivated by others’ information behaviors and expectations (Ahn and Kahlor 2020; Wang et al. 2021). That is, they consider whether people in their family and community expect them to know something about the risk, or whether the topic is more or less avoided. The influence of extended families and social networks becomes even more important in crisis communication contexts, such as natural disasters and pandemics (Eisenman et al. 2007; Kahn et al. 2022).

Like risk itself, risk information behaviors (including seeking, sharing, and avoiding) are socially constructed, and individuals are more heavily influenced by information-related norms than by their own perceived risk, worry about the risk, or hope for its mitigation (Kahlor et al. 2020). Exposure to misinformation can further influence intentions to avoid or seek additional risk information (Kim et al. 2020), as can lack of trust in the government entities expected to mitigate the risk (Ahn et al. 2021).

In the context of covid-19, while public health communication kept pace with scientists’ evolving understanding of viral transmission and risk mitigation, the public’s tolerance for the pace of science waned as the pandemic dragged on, and purveyors of misinformation quickly “filled” perceived voids in the information landscape (Ayers et al. 2021; Vanderpool et al. 2020). The misinformation was rapidly amplified across social media channels, and a global crisis ensued in which individuals were just as likely to encounter misinformation as factual information (Singh et al. 2020).

However, research suggests that partnerships with community-based organizations and local and mainstream mass media channels have the potential and capacity to support public health efforts to combat misinformation (Korin et al. 2022; Lwin et al. 2021).

It is therefore vital that researchers work with community members, not just to study health risks in the built environment and how to mitigate them, but also to learn how to talk about these risks, who the trusted voices are, how to present each risk in a way that situates it in the larger risk profile for the family and the community,[3] and what resources are available to pursue reasonable changes.


We have highlighted the associations between poor housing quality and disease, as well as challenges to meaningful communication about the related risks. The lingering damage from long-standing discriminatory practices and policies that contribute to unhealthy living conditions must be addressed through extensive, systemic changes. Initiatives at the national, regional, state, city, and neighborhood levels are needed to engage with community stakeholders and families and build collaborative approaches that undo this enduring legacy over the longer term.

But there is also an urgent need for near-term approaches to improve housing quality in order to better protect individuals, families, and communities from respiratory infection transmission and exacerbation of chronic respiratory diseases like asthma. The success of these approaches depends on community engagement and evidence-based risk communication strategies. The covid-19 pandemic persists—and it will not be the last.


Diane Gold’s work is supported by a grant from the National Institute of Environmental Health Sciences (NIEHS; P30-ES000002). Elizabeth Matsui is funded by the National Institute of Allergy & Infectious Diseases (K24AI114769) and NIEHS (R01ES026170).


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[1]  For a more extensive discussion of pathogen transmission in the built environment, see Wilson et al. (2022) in this issue.

[2]  DHHS Indian Health Service Community Health Representative Program (

[3]  A community’s broader risk profile can include housing inequities, poverty, urban density, crime and physical safety, financial insecurity and job instability, lack of child care, addiction, food insecurity and limited access to food, and racism (Parker et al. 2018).

About the Author:Diane Gold is professor, Department of Environmental Health, Harvard T.H. Chan School of Public Health; and Channing Division of Network Medicine, Brigham and Women’s Hospital, Harvard Medical School. Tyra Bryant-Stephens is medical director, Community Asthma Prevention Program, and senior director, Center for Health Equity, Children’s Hospital of Philadelphia, Perelman School of Medicine, University of Pennsylvania. Elizabeth Matsui is professor, Departments of Population Health and Pediatrics, University of Texas at Austin (UTA) Dell Medical School. Lee Ann Kahlor is professor, UTA’s Moody College of Communication.