Tech: Roadside Dust Analysis to Identify Potential Health Problems – (Report)

However, a new study conducted by Reto Gieré of the University of Pennsylvania, in collaboration with collaborators around the world, is helping to shed light on another important cause of traffic-related air pollution: tiny pieces of suspended air when the vehicles pass.

"Increasingly, I've noticed that we do not know enough about what's happening on our roads," says Gieré, professor and president of Penn's Department of Earth and Environmental Sciences at School. arts and sciences. "If you have a lot of traffic, passing cars and trucks, they put the dust back on the roads in the atmosphere, and then they become respirable. To understand the potential health consequences of these dust particles, it is very important to understand what is happening on the road. "

Although regulatory efforts have contributed to making cars cleaner and more efficient, these restrictions do not take into account pollution from wear and tear on tires and brakes. The increase in urban congestion may aggravate them as sources of pollution and possibly adverse health effects.

"About 4 million people die prematurely from air pollution every year," says Gieré. "Unsafe water, the number is 2 million. Yet, we have a UN Sustainable Development Goal on water pollution, but not on air pollution. "

In order to highlight the content of traffic-related dust and the conditions that accentuate it, Gieré has teamed up with German colleagues from the Federal Highway Research Institute, the German Meteorological Service and the University of Zurich. Friborg to sample and analyze air along the roads. In 2017, they released the results of a year-long sampling effort on two busy highways in Germany, one subject to more stop-and-go traffic and the following year. Another in a more rural area lined with agricultural fields.

To passively collect dust along the roads, they used custom cylindrical samplers with a clear adhesive sheet at the bottom to trap incoming particles. The researchers checked the collection points and turned off the sticky trap each week.

Using optical microscopy to analyze airborne particles, the team found that the site, which had a more dense circulation, overall had 30% more particles, with a larger proportion coming from the airborne particles. tire wear. The weather has taken into account the observed patterns significantly; dry and hot conditions have been associated with greater particle accumulation.

"At higher temperatures, we saw more tire abrasion, more pollution than intermediate temperatures," says Gieré. "It was exactly like what two lab studies found."

With the higher temperatures and the drier periods predicted by climate change, Gieré notes that this problem of tire abrasion can only worsen, "which is significant", because nearly 30% of microplastics rejected in oceans. "

In a more recent study, published last month Aerosol research and air quality, Gieré and colleagues used a powerful scanning electron microscope to more accurately identify the composition of particles collected on the two highways studied in the 2017 report, as well as a third collection site, on a circulating expressway slower.

"The optical microscope gives us a first approximation," explains Mr. Gieré, "while the scanning electron microscope allows us to distinguish tire abrasion, brake abrasion, carbon or the presence of minerals."

In another step, the team also performed analyzes through an analysis that provides information on the elements that make up each specimen, called energy dispersive X-ray spectroscopy.

This study focused on "super-coarse" particles collected, larger than 10 micrometers. (For comparison, a hair is about 75 micrometers in diameter.) Though still tiny, these particles pose fewer health problems than those that are even smaller and are more easily inhaled. However, these larger particles can be found in water courses and soil, affecting wildlife or even agricultural crops.

Ninety percent of the dust particles collected at the three sites were traffic-related and the researchers still found differences between the sites. Slower traffic on the urban road generated fewer particles from brake wear, but more tires; they noted that the rubber tires were covered with minerals and other materials from the roads. The highway with more continuous traffic generated more brake particles.

Manufacturers of tires and brake pads do not disclose the full content of their products, but zinc, lead, antimony, silicates, cadmium and asbestos are known to be used by some. These are chemicals that can pose a health risk if they enter the environment or, if the tires are burned, as is sometimes the case with coal-fired plants, in the atmosphere.

"These coarse particles will not be transported very far, so pollution will be limited around these roads, especially during traffic jams," says Gieré. "But they also gather on the road and wash themselves in the rivers. Our team believes that the microplastics pathway in streams is essential. "

One way to reduce this possibility of pollution would be to take traffic calming measures, such as coordinated traffic lights, which reduce the number of starts and stops that drivers must make. Gieré and his colleagues, including Ph.D. student Michael O'Shea, are also doing similar experiments on the streets of Philadelphia and comparing pollution levels across neighborhoods to see what's happening a little closer to home.

The work was funded in part by the Federal Highway Research Institute in cooperation with the German Meteorological Service.