Asthma & Housing in Marginalized Communities: A Conversation with Adam Haber

Interview by Iris Yan

HHPR Editor Iris Yan interviewed Adam Haber, Assistant Professor of Computational Biology & Environmental Health at the Harvard T.H. Chan School of Public Health. Professor Haber's work uses statistical analysis and machine learning approaches to understand asthma at both mechanistic and population health levels.

IY: I would love to hear more about your research studying the impacts of housing and demographic factors on the occurrence of asthma. How did you get into this area of research?

AH: My postgraduate training was in computer science and artificial intelligence. During my postdoc at the Broad Institute, I worked on computational biology, applying machine learning methods to study the immunology of barrier tissues – the body’s defense systems which directly interact with the environment – initially focusing on the intestine, and later the airways of the lung. In learning about the lung, asthma loomed large: it is the most common chronic lung disease, and the most common chronic disease of any kind in children.

As in many diseases, our understanding of the biological mechanisms that cause asthma have been informed by evidence from genome-wide association studies (GWAS), which compare genome sequences from patients with healthy controls to identify genetic risk factors in particular biological pathways that help understand how the disease starts or worsens. However unlike, for example, the disease Cystic Fibrosis which is caused by mutations in a single gene (called CFTR), asthma GWAS revealed no smoking genetic gun, rather a collection of around 30 genetic loci which collectively explain around 2.5% of variation in disease liability¹. These findings highlight the importance of environmental factors, and of course their interaction with genetic architecture, in understanding and preventing asthma. Both outdoor exposures, most notably to air pollutants such as particulate matter, and indoor exposures, most importantly in the home, have been shown to be strong risk factors for asthma.

IY: In addition to studying asthma from a biological perspective, why do you feel that exploring the environmental and socioeconomic factors that influence risk for disease is also so important?

AH: To work towards a healthier and more equitable world, we have to understand how the current social and economic arrangement dictates who gets sick and when. This line of thinking in public health research goes back at least to 1845, when Friedrich Engels showed that emerging British capitalism, the socioeconomic system of the day, was compelling workers to live and work under circumstances that inevitably made them sick². In particular, he linked the poorly ventilated housing in working-class districts to dramatically increased transmission and subsequent death rates from infectious diseases like smallpox, measles and whooping cough.

In our time, asthma is among the diseases that are most strongly determined by the structural contours of racial capitalism in the US. Just as COVID-19 infection and mortality rates are much higher among communities of color largely because (among other socially determined factors) they are less able to avoid exposure by working from home, the current economic system and history of ‘redlining’ in US cities ensures that working-class people of color are far more likely to live in dilapidated housing or in areas with poor air quality. Thus, communities of color suffer not only a higher incidence of asthma, but also more severe illness and complications. While deaths from asthma are rare, they are far more common for Black children; in 2015, the CDC reported a 10.0-fold increased death rate for Black children compared to relative to White³. Racial disparities in asthma increased over the 2000-2010 period and are now steady at markedly unequal rates⁴. Aside from increased hospitalization and death rates, asthma contributes to decreased quality of life, poor health, stress and missed days of school and work for children and parents.

IY: What are some of the biggest indicators that you have discovered to be associated with higher risk for respiratory illness, and why do you feel these are such large contributing factors to this risk for disease?

AH: There is an extensive literature of observational and interventional studies which have shown that exposure to mold, pests and dust mites are among the strongest risk factors for asthma, and that the main route of exposure is through poor-quality housing. Crucially, interventional studies also find that repairing the bad conditions improves asthma outcomes.

The same literature has also demonstrated repeatedly that the tremendous inequality of housing quality provided to working class communities of color in U.S. cities is a primary driver of disparities in asthma burden. As we discussed above, the history of structural racism in the U.S. ensures that people of color, particularly those with lower incomes, disproportionately only have access to dilapidated and deteriorating housing. This increases risk of exposure to the associated asthma triggers: dampness and mold, cockroach and mouse allergens. Such allergens trigger immunological responses in the lungs, which can cause asthma exacerbations (‘attacks’), which often require visits to the emergency department.

IY: Could you provide some explanation or context as to why housing specifically has been so problematic for the occurrence of asthma and why you chose to focus on that specific factor?

AH: As I mentioned above, a number of environmental risk factors for asthma have been identified. Much research has focused on the role of outdoor air pollution, particularly ozone, sulfur dioxide (SO2) and particulate matter smaller than 2.5μm (PM2.5). Road traffic and industrial facilities are important sources of these noxious substances⁵. In addition to the outdoor environment, indoor air quality that we breathe in our homes is consistently a primary factor, and it is clear, of course, that not all indoor environments are equal. A large meta-analysis of 227 studies of risk factors for childhood asthma⁶ showed that indoor triggers, particularly mold, are the strongest risk factor (with the exception of respiratory viral infections, which can itself be strongly influenced by housing if residents are crowded). Importantly, in addition to associative evidence, there is also a body of literature showing that interventions that reduce indoor exposures result in substantial improvements in asthma symptoms. For example, a 2015 study in Boston⁷ showed that children who moved from conventional to ‘green’ public housing units with improved ventilation, less pests, and less mold, experienced 3-fold fewer asthma attacks, 4-fold fewer hospitalizations, and almost 5-fold fewer missed school days. So, housing is clearly a critical factor - and importantly, one which is easily fixable – which is driving high asthma rates and disparities in asthma burden.

IY: Would you like to share any information about what you are hoping to investigate with your current or upcoming projects?

AH: In large cities, which contains thousands of housing units, the sites of the worst exposures that should most urgently be targeted for repair frequently go undetected by healthcare and code enforcement systems. Recently however, municipal governments and healthcare systems have prioritized the construction of comprehensive datasets that integrate, for example, multiple measures of neighborhood characteristics, housing age and quality, and other factors that influence the geography of exposures contributing to asthma. This presents an exciting opportunity to develop statistical models that can identify housing complexes where there are strikingly high rates of asthma and intervene early to reduce the exposures.

Research projects in my group are focused on this possibility to identify dangerous housing by modeling, using geospatial analysis, where and when people suffer exacerbations of asthma while controlling for patient and neighborhood characteristics. Preliminary results from New Haven, Connecticut show our approach can accurately identify dangerous conditions in an unbiased manner far in advance of when they are found by housing code inspection teams. These findings lay the foundation for programs to proactively inspect and repair housing that is increasing asthma risk, and improved use of epidemiological evidence to support marginalized tenants as they hold their landlords accountable to improve housing conditions.

IY: What are some possible policies or other courses of action that you think could be helpful in combating this housing disparity?

AH: In US jurisdictions such as Boston where local governments are empowered to enforce safe housing conditions, they rely on sanitary code regulations and complaint-based inspection systems to sanction landlords who do not comply. However, a number of studies have shown that these regulatory systems fail to address the needs of marginalized tenants, who are less likely to complain for fear of incurring retaliation from their landlord, unwelcome interactions with law enforcement, or because housing rights and procedures to file a complaint are insufficiently disseminated. As we discussed above, these are the people most likely to be at high risk of asthma. There is therefore a pressing need to proactively identify housing that is contributing to dangerous indoor exposures that can be targeted for remediation, since there is abundant evidence that repairing such conditions substantially improves asthma outcomes.

In my group’s research we are finding that it is possible to use machine learning and geospatial analysis to identify which individual housing complexes are contributing the most to increased risk of asthma. I am hopeful that as we publish these findings and replicate them in other cities, we can eventually enable this approach to produce quantitative epidemiological evidence which can help address the root cause of racial and class differences in asthma rates in two ways. First, these data can potentially support the claims of marginalized tenants who struggle to have their requests for repairs addressed by landlords and housing courts by providing evidence of on elevated disease burden at specific buildings, which community groups can use to target and bolster their advocacy.

Second, there is potential for inspection programs to use high-resolution asthma risk estimates to cite and compel landlords to repair properties that are damaging the health of their tenants. This would help inspection programs work to avoid and eventually eradicate situations where marginalized tenants are exposed to dangerous conditions created by years of neglect, which is in many cases linked to a history of disinvestment and so-called ‘red-lining’ of neighborhoods with large Black populations and other communities of color.

Ultimately, people – particularly renters from socially marginalized communities – are subjected to dangerous exposures in their homes because they do not have control of their housing. The less control they have, the worse the exposure. To indicate how far we have to go on this, only 22 of 50 U.S. states currently require landlords to make repairs to maintain habitable conditions and comply with housing codes⁸, and as I’ve described above, even these laws are demonstrably failing to protect vulnerable communities from dangerous conditions. Thus, long-term policies which make the interests of residents the dominant concern can help push towards the provision of healthy and safe housing to all. In the meantime, policies that enable tenants to exert more control over their own housing can begin this push. For example, increasing accountability for landlords that do not make necessary repairs, and protecting the right to organize tenants’ unions to uphold the ability of renters to insist that dangerous conditions be repaired, even if it is expensive for the landlord, can begin to improve disparities in respiratory health.

IY: Definitely. Thank you so much for your insights and for your time today!

References

1. Vicente et al., Clinical & Translational Immunology (2017) 6, e165
2. Engels F. The Condition of the Working Class in England. Oxford University Press, USA; 1993.
3. U.S. Department of Health and Human Services. 2017. "Asthma and African Americans." U.S. Department of Health and Human Services, Office of Minority Health.
4. Akinbami, LJ, AE Simon, and LM Rossen. 2016. "Changing Trends in Asthma Prevalence Among Children." Pediatrics 137(1):e20152354-20152359.
5. Guarnieri, M, and JR Balmes. 2014. "Outdoor Air Pollution and Asthma." The Lancet 383(9928):1581-1592.
6. Castro-Rodriguez, JA, et al, 2016. "Risk and Protective Factors for Childhood Asthma: What Is the Evidence?" The Journal of Allergy and Clinical Immunology in Practice 4(6):1111-1122.
7. Colton, MD et al, 2015. "Health Benefits of Green Public Housing: Associations with Asthma Morbidity and Building-Related Symptoms." American Journal of Public Health 105(12):2482-2489.
8. Moran-McCabe, K, J Waimberg, and A Ghorashi. 2020. "Mapping Housing Laws in the United States." Journal of Public Health Management and Practice 26:S29-S36.