Air pollution is a little-discussed aspect of the state’s I-285/Ga. 400 interchange reconstruction and expansion projects, partly because planning studies said it essentially has a neutral effect by improving air quality in some ways and harming it in others. But the interchange area’s exhaust-related pollution is already among metro Atlanta’s highest, and the expanded highway lanes will have one new impact: dumping pollutants closer to homes, businesses and parks.

The state’s current “Transform 285/400” interchange rebuild, and its plan to add toll lanes over the next decade, present various pollution trade-offs, according to the Georgia Department of Transportation and air-quality experts. Faster traffic flow and possible Ga. 400 mass transit could reduce local air pollution; more traffic, ineffective transit and lanes closer to neighborhoods could increase pollution. GDOT’s environmental study for Transform 285/400 found it had no overall significant impact on air pollution and meets federal standards.

But, regardless of federal guidelines, motor vehicle exhaust contains dangerous, tiny particles of pollution that the World Health Organization says has no known safe level of exposure. An Atlanta Regional Commission map of how such pollution spreads off highways shows that the 285/400 interchange is rivaled only by Atlanta’s Downtown Connector for concentrations of the dangerous particles. Relatively high concentrations of the pollution blows onto some Sandy Springs city parks and the Medical Center’s hospitals, among other areas, according to the map — and that’s only one type of air pollution.

“Too much time spent in that area outdoors … is probably not healthy,” said Paul D’Onofrio, an ARC planner on air quality and climate change who worked on the map, about those higher-concentration spots.

An Atlanta Regional Commission map showing estimated levels of particulate matter pollution in the I-285/Ga. 400 interchange area in terms of average annual micrograms per cubic meter. High levels are red; low levels are green. All of the levels are within federal guidelines, but health officials say any level can cause illness.

Transform 285/400 is expected to wrap up in 2020. The additional toll, or “managed,” lanes — four on each highway — are in the planning stages.

According to GDOT’s website, environmental studies for the Ga. 400 toll lanes are underway with construction expected to start in 2021 and finish in 2024; the I-285 toll lanes have early studies underway and are expected to start construction in 2023 for a 2028 opening. GDOT has committed to design transit bus access on the Ga. 400 lanes, and local cities are studying the possibility of some sort of I-285 transit as well.

Brian Gist, an attorney in the Atlanta office of the Southern Environmental Law Center, said his advocacy organization has various air-quality concerns about the toll lanes. Those include whether transit will actually work on the lanes, whether they will use “clean” buses, and whether drivers who can’t afford tolls will boost pollution by sitting in congestion or using local streets instead.

“The question is, if we want these [toll lanes] to benefit regional transit … are we really incorporating transit into those lanes?” asks Gist. His group also believes GDOT could do a better job of “taking a hard look at the aggregate impact of all these projects,” he said.

Another new factor with toll lanes is the proposal for portions of them to run on elevated ramps 30 or more feet tall. That idea has drawn some local criticism about aesthetics and right of way, but it may have air quality effects, too. Gist said his group has yet to study the issue, but that elevated lanes could spread vehicle exhaust similar to a smokestack, dispersing pollution over a larger area, but at lower concentrations.

Pollution types and mapping

Exhaust-related air pollution is broadly trending downward due to tighter fuel-efficiency standards and other regulations, Gist and D’Onofrio said, but remains a significant problem, and new transportation technology hasn’t solved it. Electric vehicles, which eliminate local pollution, are still a small factor, and such new developments as ride-sharing services and autonomous vehicles may increase congestion and pollution, Gist said.

Fossil-fuel vehicles produce several types of air pollution, such as ozone, which can cause health problems, and greenhouse gases that contribute to climate change. They also produce “particulate matter” — tiny particles of pollutants that, when inhaled, can cause cancer and heart and lung disease, among other lethal ills.

Metro Atlanta’s highway pollution was a major issue and legal battle in the late 1990s and early 2000s, Gist said, when the region was ruled out of compliance with federal air-quality standards. Various regulations, along with tighter federal fuel-efficiency standards, now have the region in compliance, Gist said. Road projects like Transform 285/400 are required to be built in ways that do not increase air pollution above those federal rules.

But federal standards don’t tell the entire story about such dangerous pollutants as particulate matter. An example is a type known as “PM2.5,” meaning particles 2.5 micrometers in size — so tiny they can go directly into the bloodstream when inhaled. PM2.5 from vehicle exhaust usually falls out of the air within 300 to 500 feet of roads, Gist and D’Onofrio say.

The federal limit for PM2.5 exposure is an annual average of 12 micrograms per cubic meter, which the metro area at least meets, according to Gist and D’Onofrio.

But the World Health Organization recommends a practical standard of 10 micrograms per cubic meter, and also says that any amount of PM2.5 air pollution has demonstrated illness-causing effects. “There is no evidence of a safe level of exposure or a threshold below which no adverse health effects occur,” the WHO said in a 2013 report, which estimated 3.1 million deaths from the pollution worldwide in 2010.

To the ARC, even today’s lower levels of PM2.5 are a significant health concern. In 2016, the ARC produced the “Atlanta Roadside Emissions Exposure Study” to look at the local effects of PM2.5 pollution from vehicle exhaust. A major motive, D’Onofrio said, is informing governments that might build along roadways about pollution risks.

“People shouldn’t be building schools right next to freeways. Playgrounds shouldn’t be next to freeways,” he said.

The study includes a highly detailed map of how PM2.5 pollution is estimated to spread from metro Atlanta roadways, color-coded to show annual average concentrations of 1.2 to 7.1 micrograms per cubic meter. The map uses traffic, emissions, weather and physics modeling based on 2015 data that D’Onofrio said would not have changed significantly yet; an update is planned in about two years.

A closer look at the interchange’s particulate matter pollution in the Atlanta Regional Commission map.

On the map, the 285/400 interchange puts much of Perimeter Center into red and orange areas reflecting higher PM2.5 concentrations. The most intense estimated pollution is along I-285 in Sandy Springs between Long Island and Glenridge drives. Allen Road Park, featuring a playground and sports courts, is within that area; the city’s Hammond and Ridgeview parks are in higher-concentration areas as well. So are Dunwoody’s Georgetown Recreation Club and the publicly accessible green spaces in Perimeter Center’s Concourse and Ravinia skyscraper complexes.

All of the “Pill Hill” hospitals — Northside, Emory Saint Joseph’s and Children’s Healthcare of Atlanta at Scottish Rite — are also in higher-concentration zones. Northside and Emory Saint Joseph’s say they have no immediate concerns about the interchange’s air pollution and both hospitals use industry-standard air filtration and monitoring systems that would keep out pollutants.

Air patterns make some results surprising. Fulton County’s Heards Ferry Elementary and Riverwood high schools are directly next to I-285, but in lower-concentration areas for PM2.5 — though they still get some, between 2 and 3 micrograms per cubic meter.

D’Onofrio said that exhaust-related particulate matter is only about 30 to 50 percent of overall air pollution, so areas with higher PM2.5 concentration probably have other significant air pollutant levels as well.

“You should be worried about any kind of air pollution in general,” he said.

285/400 impacts

When GDOT’s 2015 environmental study for Transform 285/400 reported “no significant impact,” that meant it will meet federal pollution standards. What that means at the local level has some nuances.

The study broadly refers to what Gist calls the typically “give and take” concept of vehicle-caused pollution: If traffic moves through the area faster as intended by the project, vehicles will dump less pollution in any given spot; but the improved road might attract more drivers, which will boost overall pollution. The study does not quantify the assumptions and generally presented it as a canceling-out effect.

The study predicted that Transform 285/400 will slightly reduce carbon monoxide emissions in the entire area, but may slightly increase around certain interchanges. Particulate matter pollution would continue to meet federal standards, and GDOT avoided doing a “hotspot” analysis of the effects after a state and federal review.

Another type of pollution addressed by GDOT’s study was “mobile source air toxics,” referring to various particular pollutants, including cancer-causing substances. GDOT said there are no agreed-upon standards for measuring and controlling them yet and predicted the project would have “no appreciate impact” on their local levels. But that still meant a projected 9.4 percent increase in the interchange area by 2039. And, GDOT said, new lanes added as part of the interchange reconstruction would put such pollution closer to homes and businesses.

GDOT also addressed “environmental justice” issues, saying that minority and low-income households within the project area were clustered along the western section of I-285. GDOT reported no project impact on that area, but it’s the zone that the ARC maps show as having the highest local concentrations of PM2.5 highway pollution.

As GDOT begins planning the additional toll lanes, Gist said air quality should be a significant concern. The bus transit, which could reduce vehicle trips, will only work if the design doesn’t leave the buses “stuck in traffic like everybody else,” he says.

There is also the possibility the buses themselves will produce pollution. “We strongly support clean buses,” Gist said, saying his group prefers compressed natural gas fuel over diesel, and electric power above all.

Another concern is that drivers who cannot afford the toll lanes will be stuck in traffic and divert their trips onto local streets, increasing congestion and pollution there. Pollution on local streets has a bigger impact, Gist said.

“Where there are people walking and riding bikes and waiting for the bus,” he said, “they’re breathing that automobile exhaust.”

John Ruch is an Atlanta-based journalist. Previously, he was Managing Editor of Reporter Newspapers.