THE TOBIN BRIDGE, with its stretches of lead paint and continuously moving truck traffic, looms over Chelsea with vehicle emissions raining microparticles down on the people who live near there.  

Under the bridge and along Route 1, the city is home to the New England Produce Center, which sees tens of thousands of deliveries every year, and The Eastern Salt Company, which stores thousands of tons of road salt in piles next to residential neighborhoods. If there is a constant, it’s the hum of trucks going by, planes flying overhead from Logan Airport, or wafts of air pollution coming from the different industrial facilities. 

Chelsea – a low-income, majority Hispanic city – is overburdened with numerous sources of air pollution. Located just a few miles north of Boston, Chelsea also has one of the highest rates of asthma in Massachusetts and had the highest rate of COVID-19 in the state.  

But now, there are new fixtures – more than 80 air quality sensors – being added to its landscape. Every couple of blocks, sensors are mounted onto traffic poles or buildings with a QR code and a solar panel on top. The sensors measure air quality and give residents information about whether the air they breathe is safe for them through a recently launched digital dashboard.  

In collaboration with the city of Chelsea and the local non-profit GreenRoots, scientists and engineers at Northeastern University, which is funding the study, installed these sensors near homes, schools, workplaces, and outside of grocery stores during an 18-month period between the fall of 2023 to the spring of 2025. 

The city is taking part in a project called Intelligent Solutions to Urban Pollution for Equity and Resilience, or iSUPER, which is monitoring air quality in a hyperlocal way. Northeastern’s researchers will analyze the data and test how changes in an urban landscape impact air quality, neighborhood by neighborhood. Brookline is also participating in the study and has around 60 sensors around the town.  

“It was clear that Chelsea is a place where this would help,” said Amy Mueller, a civil and environmental engineering professor at Northeastern and one of the leads on the iSUPER project. “We’re directly taking the data from the sensors to understand things that happen [on the neighborhood level] – … the effect of traffic, the effect of buses, of trucks, of parks, of weather, and all of those things. Finding hotspots in the city that might be places that need a little bit more attention.” 

At a time when environmental justice communities are becoming more at risk because of federal rollbacks to clean air protections, the air quality sensors will allow the residents of Chelsea to take steps to protect themselves and the city government the data to know what mitigation projects would be the most effective. 

At the start of the Covid-19 pandemic, Chelsea had one of the highest rates of infection. By June 2020, the city had a positivity rate of 38 percent — 23 points higher than the state average at that time. In response, US Sen. Ed Markey and Rep. Ayanna Pressley pushed the Environmental Protection Agency to put an air monitor in the city.  

The EPA obliged, and an air monitor was placed in 2021 within the city in Highland Park near Chelsea Creek to measure air quality. The EPA’s air monitors are accurate and expensive. They take a snapshot of the air quality in their immediate area. 

However, because there are so many sources of pollution in Chelsea, the air quality varies widely from neighborhood to neighborhood.  

“We refer to these [sensors] as hyperlocal because they’re able to account for variations sometimes even within blocks,” said Barbara Espinosa Barrera, environmental justice and health equity organizer at GreenRoots. “There can be a wide variation in the air quality of a block that is next to a truck route versus a block that isn’t. There can be a lot of variation between an area that is next to a park versus an area that isn’t. … It is important information for people to think about because if you live in downtown Broadway, you are not breathing the air that the EPA monitor in Highland Park tells you that you are.” 

That’s where the more than 80 sensors come in. The air sensors use a cheaper technology that is somewhat less precise than the EPA-grade air monitors but still measures different types of particles in the air.  

Having hyperlocal air monitoring in a city can give residents data to make day-to-day decisions, allow the city to track areas with more pollution, and give advocates the data they need to ask local or state government for needed policy changes and more resources. 

Air pollution is directly linked to higher rates of asthma, and poor air quality can trigger asthma attacks. 

 “Chronic exposure to pollutants like PM2.5 [particles less than 2.5 micrometers in diameter] or ozone or other industrial emissions contributes to [high] rates of asthma, heart disease, and other health problems,” said Doug Brugge, the head of the public health sciences department at the University of Connecticut School of Medicine.  

The iSuper team made a dashboard – which has an English and Spanish version – that shows real-time air quality data on a map of Chelsea with color coding indicating the air quality on a spectrum from good to hazardous.  The dashboard, which launched last month, allows Chelsea residents to access hyperlocal data in their neighborhoods and make informed decisions about their health, like whether to go for a run in a local park or to avoid going to a certain part of the city.  

Espinosa Barrera said that people are excited and asking what these new devices in their neighborhoods can do. “Information is power and in getting people involved in air quality monitoring, we’re hoping that will get them more engaged in the conversation,” she added. 

The scientists working on the project are using the hyperlocal data to run analyses that ask questions like: Does replacing a parking lot with a park change air quality in a neighborhood? Are areas near schools particularly polluted? Should the city install heating, ventilation, and air conditioning systems to ensure better air quality indoors, where children are in classrooms?  

Hyperlocal monitoring can be useful to map measurable numbers onto people’s day-to-day experiences. 

 “Maybe you have somebody who has a child with asthma, and they say that whenever I take my son to grandma’s house, he always has more asthma exacerbations when he’s outside,” said Misti Zamora, a professor of public health sciences at the University of Connecticut School of Medicine. “Maybe that’s because they live near a landfill, or it’s near an industrial facility that’s producing something that’s aggravating these lungs. It’s just really nice to be able to work with communities to listen to their voice and then just say, ‘Okay, let’s see if we can put some data to your experiences’ and like see what’s really happening here in the world that they’re living in.” 

Data from hyperlocal monitoring can also help residents lobby for specific changes within their neighborhoods. For example, policymakers can have more insight into how a particular construction site impacts residents in a neighborhood and make decisions about where to put critical infrastructure. 

“We are trying to think of this as a helpful tool for policymakers, and for people who have power in Chelsea,” said Espinosa Barrera. 

And the sensors will help monitor changes that occur in air quality as the Trump administration rescinds key federal policies designed to combat climate change. The head of the Environmental Protection Agency has stated that the agency wants to roll back emissions regulations on power plants, cars, trucks, and the manufacturing sector.   

In Massachusetts, state officials recently pushed back implementation of a rule that would have required truck manufacturers to make more zero-emission vehicles after pressure from the trucking industry.  

A community like Chelsea is immediately affected by changes to these standards because it has so many trucks going over Tobin Bridge, on highways, and along its streets. Places with high traffic will face direct impact if the California rules – which impose standards on vehicle emissions that are stricter than federal standards – are removed by the Trump administration.  

But Chelsea has a layer of protection because it has data about its air and can make changes at the local level, said Mueller. For her, the air quality information is a tool that Chelsea residents will have in the face of any rollbacks.  

“Cities have a lot of power to make local decisions independent of what’s happening at the federal government,” said Mueller. “The federal government is not telling us whether or not we can put in a new park. They’re not telling us whether or not we can have a bus lane.  … Trying to find the pathways where we can actually have a positive impact is the way to look at it.”