DOWNTOWN — Air pollutants generated by those traveling on Interstate 10 in Santa Monica extend more than 1.5 miles from the source in the hours before sunrise, exposing more residents to traffic-related pollution than previously thought, increasing the risk for developing asthma and other respiratory illnesses, cardiovascular disease and even premature death.
That’s according to a new study by environmental health researchers from UCLA, USC and the California Air Resources Board, who studied pollutants by traveling along Stewart Street near the I-10 Freeway in an electric car, measuring gaseous and particulate air pollutants from 4 a.m. to 7 a.m. during the winter and summer months.
The distance the pollutants travel before the sun rises is 10 times what was previously measured during daytime hours, which has significant exposure implications, researchers said, because most people are in their homes asleep or just waking up, or perhaps exercising. Outdoor pollutants infiltrate indoor environments.
“The important message is that people need to rethink how close is too close, and at what time of day,” said researcher Dr. Scott Fruin of the USC Keck School of Medicine, who specializes in high exposure environments such as freeways and ports.
“This study is the first to [explore] the impact as far as it is,” Fruin added. “We still have some work to do figuring out what the long-term effects are. It’s a fairly new research topic. … But because of this study there is new cause for concern for people living downwind of a freeway within 2,000 meters.”
Fruin said the study does not just apply to Santa Monica, but to all freeways in Los Angeles County.
A second striking finding of the study was that although traffic volumes are lower in the pre-sunrise hours, the air pollution concentrations measured by the researchers were higher than even those during rush hour.
Concentrations are higher before sunrise even though emissions are lower because of the unique weather conditions. In the pre-sunrise hours, wind speeds are generally very low, and while the wind direction is somewhat variable, the predominant direction is from the northeast in the winter months and the northwest in the summer months.
This means that areas south of the I-10 Freeway are generally downwind in the pre-sunrise hours and areas north of the freeway are generally upwind; this is consistent with the observation that vehicle-related pollutants are found much further from the freeway on the south side in the pre-sunrise hours, compared with the north side.
“Our research shows that under the low wind speeds and shallow temperature inversions during the early morning, before sunrise, air pollution from freeways is trapped near the surface, limiting dilution and creating a zone of influence many times greater than during the day,” said Dr. Suzanne Paulson, a professor in the UCLA Department of Atmospheric and Oceanic Sciences and a co-principal investigator of the study. “These meteorological conditions are very common in the hours before sunrise.”
In comparing the winter and summer early mornings, researchers found much higher levels of air pollution in the winter.
“This is because the sun rises later in the winter, so the early morning period captures more of the early morning rush hour,” Paulson said.
In the study, other pollutants, including nitric oxide and particle-bound polycyclic aromatic hydrocarbons, also extended far from the freeway during the pre-sunrise hours.
Maria Loya, co-chair of the Pico Neighborhood Association, welcomed the study, saying more work needs to be done to identify exactly what residents living near the freeway are being exposed to and at what levels. Loya believes a health survey of Pico Neighborhood residents needs to be done and it should be conducted in conjunction with the update to the Land Use and Circulation Element, a planning document that will dictate development in the city for 20 years or more.
“It’s just anecdotal, but many families we have talked to who live along the freeway are suffering from asthma, but because there really isn’t a study that links it, at this point it’s just anecdotal,” Loya said. “[Pollution from the freeway] is a concern and has always been a concern, especially in the Pico Neighborhood, which has the largest concentration of young people in the city.”
What is especially troubling, Loya said, is that many families walk their children to school in the mornings, a time when the study found a higher concentration of pollutants. She said neighbors are referring to a part of Pico where the study was conducted — Stewart Street just south of Olympic Boulevard — as the “toxic triangle” because it is surrounded by the freeway, City Hall’s waste transfer station and recycling center, a private waste transfer station as well as a possible light rail maintenance yard for the Exposition Light Rail Line (a decision on the maintenance yard has not yet been made).
“What we are seeing is clearly environmental injustice,” Loya said.
The researchers recommend that residents living near freeways should consider keeping their windows closed at night and minimize outdoor exercise near major roadways in the hours before sunrise.
