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Gwynne Mhuireach

Student in Landscape Architecture, University of Oregon

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Does urban “green” harbor healthier microbes?

We evolved in natural environments, characterized mainly by soil, water, vegetation, and the innumerable microorganisms associated with each. Many researchers have observed linkages between human well-being and exposure to green space, including mental restoration, reductions in disease and mortality, better birth outcomes, and decreased crime and violence. Explanations for why these benefits are observed are often based on the idea that humans are evolutionarily predisposed to prefer environmental settings that confer survival advantages, namely landscapes that are similar to the savannas and woodlands that humans are thought to have inhabited for thousands of years. Is it possible that vegetation is a source of the microbes we have co-evolved with over the millennium and whose presence we may require for physical and psychological health?

Westernized societies are plagued with increasing rates of auto-immune disorders. A recent study in New York City has shown that kids in neighborhoods with more street trees are less likely to have asthma, after controlling for socioeconomic factors. Several other research studies have found that children exposed to higher environmental diversity (i.e. living on a farm or forested rural setting versus living in a city) were exposed to higher microbial diversity and had lower rates of asthma and allergic disposition.

If we could quantify the relationships among human health, microbial diversity and urban green space, would it change the way we design cities? Should we put a higher priority on providing adequate green space for all urban residents? Majora Carter says, “Race and class are extremely reliable indicators as to where one might find the good stuff, like parks and trees, and where one might find the bad stuff, like power plants and waste facilities.” How can planners and designers ensure that all city residents will have a positive and equitable microbial experience as they interact with the invisible urban microbiome?

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    May 22 2013: I just met with someone from Kaiser who told me about the Community Health Needs Assessment http://assessment.communitycommons.org/CHNA/. Right now it sounds like Kaiser is linking physicians up with data from the communities where patients live, for example on airborne particular matter. I am thinking that it would be amazing one day to incorporate data on the urban microbiome with this database, as well as clinical data, to explore the potential links between health and the urban microbiome.
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      May 22 2013: This sounds like a great idea to me. It seems challenging to do research that links spatially explicit health data with environmental and microbial data in the U.S. because of the need to protect people's privacy.
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        May 22 2013: I haven't really been able to find many longitudinal studies on the link between microbial diversity and human health but that might give us great incite into what microbes are important and how they influence human health.
        • May 24 2013: I think that if you look for particular ways microbes may be important and therein by influence human health, e.g. environment and asthma you are more likely to find longitudinal studies. Take for example the study by Arrandale et al. 2011 (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3094407/) who take a look at exposure assessment studies of childhood asthma and look at ways to improve future exposure assessment studies. One reason for carrying about the quality of such assessments is that longitudinal studies are quite costly and time intensive. The Urban Environment and Childhood Asthma (UREA) is a study by Gern et al. (2011) http://www.biomedcentral.com/1471-2466/9/17 specifically studies what immune responses trigger asthma in inner-city children. They looked at children from birth until age 7 for the following cities: Baltimore, Boston, New York City, and St. Louis. That study was collecting data for 7 years before being able to fully analyze the data. Longitudinal data once is created is great and can be very insightful, however it takes time to compile and thus can kind of be like a "hail mary" for researchers to invest in such a gamble of a research project.
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      May 22 2013: This could be a good way to get more information about the the negative effects of pollution. Maybe a(nother) problem with air pollution is that it decreases the diversity of airborne microbes or the abundance of 'good' microbes.
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        May 24 2013: I have been trying to find a paper on the effects of air pollution on microbial diversity but haven't found anything yet. I did find this paper that talk about the effect of indoor air pollution on health http://www.jmsmd.net/images/Indoor_Air_Pollution_Health_Effects.pdf. It only mentions microbes very briefly but does say that some of these pollutants can kill microbes. With a population that is increasing its time spent indoor it will be important to improve air quality both indoors and outdoors.
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          May 24 2013: Your point about time spent indoors is important. In the U.S., we spend over 90% of our lives inside buildings [http://energy.lbl.gov/ied/pdf/LBNL-47713.pdf], so researchers have been looking at indoor air quality a lot. I think something that has been less studied is the strength of the link between indoors and outdoors, and how the quality of the immediate outdoor context might influence indoor air generally and airborne microbes specifically. Studies have shown that indoor airborne microbial communities tend to be similar to outdoor airborne microbial communities in buildings that ventilate with outdoor air, like buildings designed to use natural ventilation and many residences that lack a/c [for example, http://onlinelibrary.wiley.com/doi/10.1111/ina.12047/abstract]. It is less clear how the dominant airborne microbial communities in the immediate vicinity vary by neighborhood characteristics and over time.

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