Mobility Data and Public Health
On its newly central role
Written by Prachi Goel with technical support from Justin Bandoro
Like us, you might have breathed a sigh of relief when you saw the news that the Bay Area’s preemptive Shelter-in-Place policy is showing early signs of successfully flattening the COVID-19 curve. That breath you just took likely has cleaner air than before.
The strategies to fight COVID-19 are making all of us re-design our daily operations to limit its spread in our communities, and while social distancing as a strategy is not new, the mobility data that shows us how we move is giving us new insights into how the pandemic is affecting us.
The same data that helps us plan our commute, identify the nearest happy hour and find our friends is now playing an unprecedented central role in public health policy. In South Korea, mobility data helped track movement of COVID-19 positive people early on, informing targeted containment strategies that limited virus spread. In the US, we can see which counties are complying with social distancing policies through aggregated cellphone data. At Shair, we use real-time traffic data to model street-level air quality. The last few weeks have provided insight into the magnitude of pollution reduction from reduced traffic that we want to share.
Our Motivations
Before we get into that, though, we’d like to explain our motivations.
Like everyone else, we are affected by the numerous human and economic impacts of COVID-19 across the globe, and wish the analysis was a theoretical assessment. However, we want to be part of a constructive dialogue from this situation — our way of approaching that is by demonstrating the role of air quality models in assessing pollution-reduction initiatives, and the potential of work from home as a broader public health tool outside of the current emergency. We hope you find this approach useful in visualizing the post-pandemic world that we’ll get to together.
Modeling Analysis
In the image below, we have distilled the real-time traffic emissions layer of our model from the rest of the Shair model, and reduced traffic by 59% as per HERE API’s assessment. We selected NOx because it is directly related to traffic, and because long-term exposure increases susceptibility to respiratory illnesses like COVID-19 (one study established a direct link between air pollution related respiratory illness and the mortality rate of SARS).
On the left, you can see a visual of NOx emissions during rush hour at 8AM on a normal day — on the right, the visual of emissions one day after shelter-in-place pushed the majority of people to work from home.
You’ll observe clear reductions in emissions on the bridges and major highways (280, 101, 880), as well as office hubs (San Francisco, San Jose). What this visual shows us is how deeply the shift in mobility affects the air quality across streets in the Bay Area. It is a key input, but one of many, that shape air quality. Air quality modelers use tools like these to run scenarios of policy impacts of all types, to reach a desired reduction in pollutant concentrations that informs what actions to take to clear the air. Measurements from monitoring tools, like reference monitors, satellite imagery, and real-time sensors, help track whether these policies are working. If shelter-in-place was a pollution-reduction initiative, it would be showing a measurable impact on the air.
Takeaways
We will eventually win the fight against COVID-19, and normal life, including traffic, will resume — but we’ll carry a new understanding of the importance of protecting public health. Air quality affects key public health outcomes, and actions like working from home could make significant impacts if included in the arsenal of mitigation strategies. We recognize that the current shelter-in-place system is not sustainable without an immediate, pressing emergency, but incremental changes at the societal level can make an impact. As an example, the pandemic has highlighted the ability of many companies to run operations remotely — the workforce working from home more often could be an incremental economic, health, and sustainability win rolled into one.
Thanks to our first responders, health care workers, community leaders and all those working to minimize the impact of the pandemic and keep essential services running. Let’s work to support each other during this difficult time by respecting shelter-in-place, limiting supply purchases, and staying patient!
