Questions and answers about schools and traffic pollution

Why nearness is a problem, what schools can do and how parents have led the way

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Montgomery Blair High School in Silver Spring, Maryland — hemmed in by three roads, including Washington's Beltway — is one of thousands of public schools near significant traffic.

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How close is too close, and how much traffic is too much traffic?

Traffic pollutants travel, but they’re higher on and close to roads. In general, studies suggest that the biggest daytime exposures are within 500 feet of the road, though some studies have found elevated levels farther out, such as roughly 900 to 1,000 feet. California’s school-siting law, which aims to keep new schools away from freeways and other major routes, uses 500 feet as the area of concern.

California’s law focuses on very heavily traveled roads, but there’s no true dividing line between bad and OK. Some studies have found health effects among people near roads with at least 10,000 vehicles a day, which includes routes with a tiny fraction of the traffic on an L.A. freeway. In fact, because steady speeds produce less pollution than acceleration, vehicles on highways that aren’t plagued by stop-by-go congestion are cleaner than they are on lower-speed roads with traffic lights and stop signs. And a road that draws diesel trucks, particularly old ones, could be worse than a higher-traffic route with only cars.

“As people are looking more and more at traffic pollution, they’re finding effects with less vehicles and they’re finding effects farther away as well,” said Barbara Weller, a toxicology expert who works at California’s Air Resources Board as supervisor for the population studies section of the health and exposure assessment branch.

To try to account for some of these complexities, the Center for Public Integrity and Reveal from The Center for Investigative Reporting focused on roads with average traffic of at least 30,000 vehicles a day, as well as roads with at least 500 trucks and 10,000 total vehicles a day.

What are the health implications of putting a school near a busy road?

“The closer anybody is to a major road – school, home, business, whatever – the more they’re going to be exposed to air pollution from vehicles that are traveling on that road,” said Dr. Jerome Paulson, professor emeritus in pediatrics and environmental and occupational health at the George Washington University.

It's not just about the time spent outdoors.

“There’s sort of this myth that when we close our windows and shut our doors, we’re completely protected, but that is not true,” said Frederica Perera, director of the Columbia Center for Children's Environmental Health at Columbia University. “Fine particles, ultrafine particles and gases, vapors, are able to come into the indoor environment. They penetrate very readily.”

That matters, because traffic pollution can stunt lung growth in children. The difference isn’t enough for immediate symptoms — though traffic exposure can also cause wheezing and worsen asthma symptoms, not everyone will feel those effects — but lung size could have implications later in life. Adults lose a bit of their lung function each year. Researchers worry that starting adulthood with smaller lungs could increase the odds of future health problems.

Newer research has also linked traffic pollution to the development (not just the worsening) of asthma, chronic obstructive pulmonary disease, cognitive and learning problems, heart disease and dementia. Some research has also linked traffic pollution to cancer; diesel exhaust from older trucks and certain chemicals emitted by gasoline-powered vehicles are known carcinogens. So the health concerns aren’t limited to children.

In Detroit, where the asthma hospitalization rate for kids is nearly three times the statewide rate, the head of the city’s health department is concerned about the long-term effects of traffic proximity.

“We built highways well into the heart of Detroit,” said Dr. Abdul El-Sayed, executive director of the Detroit Health Department. The city has lots of schools near significant traffic, and “we’re only now starting to appreciate that maybe these aren’t the best places to put our kids,” he said.

What factors affect exposure near roads?

Wind direction, for one. If the wind tends to blow from the road to your nearby location, you’ll get more exposure overall than someone on the other side of the pavement.

Elevated highways tend to be worse for people near them. Cut-section highways — roads lower than the land around them — are somewhat better. Sound barriers can help reduce exposure for people very close to the highway, though they might increase it for people a bit farther away (and can definitely do so for the drivers on the road, because more of it sticks around). An EPA paper you can download here sums up some of these issues.

The EPA thinks vegetation can help trap pollution as well, so a school separated from a road by a thick buffer of trees is likely better off — but this research is still developing. And location could matter. Some scientists have found that trees don’t help in urban areas because their ability to remove pollutants isn’t as strong as their ability to block airflow, keeping pollutants from escaping and getting diluted.

So what can schools near roads do about their air quality?

Closing a school’s doors and windows won’t keep traffic pollutants out (though that helps). Heavy-duty air filters — higher quality than the typical filters in schools — can substantially reduce what gets into the air the kids and teachers are breathing inside.

Filters rated MERV 16, characterized as surgery-grade, have been installed in dozens of Southern California schools. In the Los Angeles Unified School District alone, more than 40 schools have high-grade filters to improve air in areas near highways, ports and other pollution sources.

Measurements by the South Coast Air Quality Management District — a local air-pollution control agency — found that MERV 16 filters in schools catch approximately 90 percent of fine and ultrafine particles, pollutants that are a key part of what makes traffic pollution a health risk. A much lower 20 to 50 percent of the particles were caught by the measured schools’ earlier efforts, which at best had involved air filters with a rating of MERV 7.

MERV 16 filters aren’t high price. You can buy them for less than $100 apiece. Schools with central air conditioning and heating — an HVAC system — should be able to use them, but it might take some retrofitting. IQAir, a company that’s installed high-grade filtration in hundreds of schools, most in California, says schools with a central system usually don’t need to spend much on alterations.

The big cost is for schools without HVAC. They’re left with two expensive options: pony up for HVAC, or pay for stand-alone air purification systems that are much pricier than air filters.

The South Coast air district offered a rough estimate of around $2,500 per classroom to install high-quality filters — averaging between schools that don’t need to do much and those staring down big-ticket HVAC costs.

At El Marino Language School in Culver City, California, officials retrofitted the heating system to get the filters in — that work cost about $500,000 — and plan to spend an additional $2 million installing air conditioning this summer so teachers can keep the doors and windows closed, allowing the filters to do their work.

How have schools paid for indoor-air fixes?

Dozens of schools in Southern California have received high-grade air filters paid for by the South Coast air district, which has funded the work with a pool of money that includes penalties assessed on polluting companies.

Not all schools near major roads in that region qualify, though. So the freeway-adjacent El Marino Language School got funding after the Culver City Unified School District in California proposed an ultimately successful bond measure, some of which was earmarked for work there. The lack of air conditioning at El Marino meant a higher price tag for effective filtration. The school could (and ultimately did) install filters by retrofitting the heating system, but it really needed to add AC, too, so unfiltered air wouldn’t flow in through doors open directly to the outdoors.

In Utah, meanwhile, the state Department of Transportation is paying for higher-quality air filters at five schools within about 1,600 feet of a highway under construction. That’s part of a deal struck after parents, environmentalists and doctors mobilized during the planning stages nearly a decade ago, modeled after a settlement over a highway-widening project in Las Vegas. Funding allotted for the Utah school upgrades and 30 years of future maintenance: $1.1 million, the equivalent of about $7,300 per school per year.

My school has air filters. That’s good enough, right?

School filtration and ventilation is often subpar, according to researchers who have documented conditions in the West and Midwest. Years ago, when he was at the California Air Resources Board, Thomas J. Phillips was part of a study of school classrooms and found air filters that “hadn’t been changed in quite a while — maybe the life of the school.”

Phillips, now principal scientist at Healthy Building Research in California, points out that school budgets are usually crunched.

“Things like air sealing and better air filtration will help,” he said. “But the devil’s in the details. How do you make sure it’s done right? How do you fund it? How do you maintain it?”

Being vigilant about maintenance is a good start. But the EPA also recommends that schools with traffic-pollution challenges install the highest-grade air filters they can. (For more details on that, see the answer above to “So what can schools near roads do about their air quality?”)

What can I do if my district is building a school near a highway or other significant road?

You could start a conversation if it’s not a done deal: Does your school district realize the health implications of nearby traffic? (Many don’t.) Are there other viable sites farther from busy roads?

Traffic isn’t the only environmental-health hazard, and the EPA cautions that building schools in far-off locations to avoid traffic just forces kids and staff to spend more time on roads to get there, breathing those pollutants while sitting in buses and cars. If a school must be built near significant traffic, experts recommend designing the site to improve air quality.

An effective HVAC system with high-grade air filters will substantially reduce the traffic particles getting to the classrooms, as schools in freeway-heavy Southern California have found. It’s also a good idea to put outdoor-activity areas, such as playgrounds and athletic fields, farther from the road while earmarking the closest spots for uses such as parking and storage, the EPA says. Other measures, such as placing the air intake away from the fumes of the road and the school loading dock, can also help.

The state plans to build a big road near my child’s school. Now what?

That’s happening in Utah. After parents, environmentalists and doctors joined forces to object, the state Department of Transportation agreed to pay for air monitoring and higher-quality air filters at five schools near the incoming Mountain View Corridor highway project.

“We’ve come a long way just to understand there is a problem out there,” said Linda Hansen, a member of the Utah State Board of Education and a former PTA leader in the affected school district. “We’re hoping once we get the data … from this project, we’ll be able to use it in other projects and get districts to see they really need to put some mitigation into those schools they have near roadways, because it’s hard on kids.”

This is why she thinks the advocacy effort paid off: “Groups that usually don’t work together on issues all came together.”

Reed Soper, environmental manager on the Mountain View Corridor project for a Department of Transportation contractor, sees the outcome as a win, too. “Everyone was willing to roll up their sleeves and come up with a solution that didn’t involve a lawsuit,” he said.

A big increase in truck traffic is coming near my child’s school. What can I do?

If it’s temporary, see if the traffic can be timed to avoid school days. Residents in Mars, Pennsylvania, convinced an energy company to wait until summer to hydraulically fracture gas wells there so schools wouldn’t be in session during the ensuing spike in truck volumes on the road passing by them, said Patrice Tomcik, the western Pennsylvania field organizer for Moms Clean Air Force. State environmental protection officials acted as mediators between residents and the company.

“I just want other communities to realize they have options,” she said.

If it’s not temporary, talk to transportation officials. Could other roads handle the traffic instead? What would be the implications of rerouting it? Or talk to the company behind the increase, if there’s a single employer involved.

In Chicago, the Little Village Environmental Justice Organization has pressed a manufacturer to use newer, less-polluting trucks as it prepares for hundreds more trips a day on a site next to an elementary school. The group's leaders say they're encouraged by the ongoing conversation.

“That’s not to say we don’t want the jobs, or that this growth isn’t important. It is,” said Kim Wasserman, executive director of the group. “But not at the cost of the truck drivers” — who breathe air tainted with their exhaust — “or the communities where these trucks are going.”

My kid’s school isn’t near any major roads, but what about the diesel school buses that idle outside? Isn’t that a problem?

Yes. Getting bus drivers (and parents) to turn off their engines while waiting to pick up kids really can make a difference. Pat Ryan, an associate professor of pediatrics at Cincinnati Children’s Hospital Medical Center, led a study that found significant drops in air pollutants following an anti-idling campaign at a Cincinnati school with a lot of buses.

Just putting up a no-idling sign isn’t enough, Ryan said: “You have to be a little more active, at least until — hopefully — it becomes a habit.” There’s an assumption among some drivers that they’ll burn up more fuel turning their engine off and back on again than if they idle, but that’s not true, he said.

The EPA has also helped school districts replace old diesel buses with grants from its Diesel Emissions Reduction Act program. But the future of that funding is unclear.

I’m not in a big city. This stuff doesn’t apply to my area, right?

Schools near busy roads are a particular problem in big cities, but thousands of these cases are in suburbs, smaller cities and rural communities.

School districts in areas with more undeveloped land do have options a heavily urbanized district doesn’t, as long as the issue is on their radar. Consider the suburban Blue Valley district in Overland Park, Kansas. Officials there try to get new schools into the plans for future subdivisions while there’s still time for that — and to build their campuses as far from major roads as they can.

“Safety is one [reason], but the impact of pollutants on those major roads is another one,” said Dave Hill, executive director of facilities and operations for Blue Valley, which helps mentor other school districts on indoor-air quality.

How many vehicles are on the road near my child’s school? How can I find out exactly what’s in the air there?

To see if a school falls within 500 feet of a busy road, check out our interactive data tool above. You can enter any address, school or not, and see if it’s by a road that meets our traffic threshold.

Determining what’s in the air isn’t so easy. The odds are low that a government air-pollution monitor is located in your exact area of interest. But that’s not your only option these days.

“There are a lot of emerging technologies — low-cost sensors — out there that communities can use themselves to measure some air pollutants,” said Sacoby Wilson, an assistant professor with the Maryland Institute for Applied Environmental Health at the University of Maryland.

That’s particularly true of fine particles (particulate matter that’s 2.5 micrometers or less in diameter, or PM2.5 — far, far smaller than a grain of sand). The South Coast air district reviews those sensors here and here. Such sensors aren’t as accurate as high-cost government equipment yet, so use with caution, but you can get an idea of how the pollutants range in different locations and at different times of day. The EPA has a guide for how to do this type of “citizen science” air monitoring.

Unfortunately, sensors priced at a couple hundred dollars won’t help you track some key road pollutants, such as ultrafine particles — the even smaller specks that spike near roads — and diesel-emitted black carbon. That type of equipment is much more expensive, though it is possible to rent a black-carbon monitor rather than shell out thousands of dollars to buy it.

One strategy: Ask for help. A parent at the El Marino Language School in California borrowed air-monitoring equipment from a university to measure ultrafine particles at the near-highway site. She documented that ocean breezes weren’t ameliorating the problem, as some had hoped, and parents convinced the school district to install air filtration.

You could also encourage your community to conduct more air monitoring. The Array of Things project is installing all sorts of sensors, some measuring air pollution, across Chicago.

Does it make sense to pay for better air filters in thousands of schools, let alone other buildings near big roads? Isn’t it more efficient to just do something about the pollution?

High-grade air filters are a stop-gap measure. No-emission roads are likely a long ways off, and kids — as well as adults — have to keep breathing in the meantime.

But plenty of public-health advocates think that less traffic pollution should be the priority, because that would help air quality overall.

The good news: The trend’s heading in the right direction. New vehicles are much cleaner than old ones. The bad news: Diesel engines last a long time, so there are still a lot of old trucks in use. Besides California, no states have requirements to phase out old truck engines over time.

The Diesel Emissions Reduction Act has helped replace or retrofit tens of thousands of old diesel engines to speed up slow turnover, but this could be the last year of that funding. (The program technically lapsed already but received some money this year because the continuing-resolution budget measure extended prior-year levels of funding through April.)

Where can I go for more information?

The EPA put out a guide in 2015 to help schools deal with traffic pollution. It also has a broader 2011 guide about schools and environmental health, including traffic-pollution issues.

The Healthy Schools Network focuses on environmental health in schools. Here’s the group’s Towards Healthy Schools 2015 report.

The Reducing Outdoor Contaminants in Indoor Spaces site has resources about indoor-air quality.

The South Coast air district has studied better air filtration in schools as well as the effectiveness of low-cost air pollution sensors.

And don’t forget our interactive data tool, which lets you type in an address and see if it falls within 500 feet of a busy road.

Hopkins reported this story with the support of the Dennis A. Hunt Fund for Health Journalism and the National Fellowship, programs of the University of Southern California Center for Health Journalism.

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