Ultrafine particles are smaller than 100 nanometers -- 1 nanometer being equal to 1 billionth of a meter. U.S. standards for unhealthful levels of ultrafine particles do not exist.
"Diesel emissions contain UFPs (ultrafine particles), and that's part of why the scientific community considers them to be harmful," Olvera said. "Neither the EPA or TCEQ (Texas Commission on Environmental Quality) have set thresholds for what constitutes safe levels of ultrafine particles. Countries in Europe and Australia are moving ahead of us to establish healthful level standards of UFPs.
"Even without knowing what the unhealthful levels are, because they haven't been set yet," Olvera said, "we know that the most affected populations are the customs officers who work on both sides of the international bridge, daily commuters, street vendors, neighbors and students near the source of the pollution."
In response to the study results, U.S. Rep. Robert "Beto" O'Rourke, D-El Paso, said, "When we keep bridge-crossers in line for hours at a time, it's bad for our economy, it's harmful to our regional competitiveness and it's inhumane to those affected -- including those crossing the bridges, the officers who process them and the people living in the surrounding neighborhoods.
"These findings demonstrate that there is a clear public health danger associated with the current bridge wait times at our ports of entry. I will use my position in Congress and on the Committee for Homeland Security to press for the resources to securely and quickly cross pedestrians, cars and cargo at our bridges," O'Rourke said.
A 2012 article by the EPA, "An Overview of Ultrafine Particles in Ambient Air" by Paul A. Solomon, states, "The strong association between ultrafine particles (UFPs) and adverse health effects -- cardiovascular and pulmonary -- are becoming widely recognized yet considerable uncertainty remains as to the metric(s) and the mechanisms that result in the adverse effects."
The EPA has also commissioned research into ultrafine particles and their potential effects on human health.
Experts said that UFPs come from numerous man-made and naturally occurring sources, including printer cartridges, the friction of ocean waves, vacuum cleaners, volcanoes, and vehicle emissions. In urban settings, vehicle emissions are the most common source of UFPs.
Olvera, 37, a research assistant professor at UTEP's Center for Environmental Resource Management and the Hispanic Health Disparities Research Center, and a native of Juarez, said he had wondered about pollution at the border crossing
"When I was a student at UTEP, I crossed the bridge on a daily basis," Olvera said. "For me, an environmental engineer, the concern was obvious. I wanted to know how harmful the pollution at the international bridge could be."
Olvera and a team of researchers conducted the study at the Bridge of Americas for an entire year in 2009. The team set up a TSI Scanning Mobility Particle Sizer (SMPS), at the El Paso Water Utilities stormwater-pumping station, between the Chamizal Memorial and the bridge, to record continuous daily readings. This was done for two-week periods during each of the year's four seasons.
In 2009, the study said, 4.7 million vehicles crossed to El Paso on the Bridge of the Americas, of which 7.3 percent were commercial vehicles. In 1999, a total of 8.5 million northbound vehicles crossed the bridge, of which 4.2 percent were commercial vehicles. The study speculates that stricter rules for crossings after Sept. 11, 2001, contributed to the decrease in vehicles.
The UTEP study team spent the rest of the time analyzing the data that it collected from the readings. New technologies like the SMPS instruments are making it easier to study and measure ultrafine particles, Olvera said.
The results showed that particle concentrations doubled from estimated normal amounts during peak hours of traffic and remained at least above local background levels at all other times, Olvera said.
Peak exposure levels in the area were comparable to the severest occupational exposure settings, such as where soldering and welding occur, he said.
Background levels stand for the lowest levels that occur normally around the bridge in the middle of the night.
"The study suggests that the above-normal UFP levels are expected within distances of 400 meters from the border crossing, which include the Chamizal National (Memorial) and Bowie High School," Olvera said. "The measurements were performed on the U.S. side of the bridge. But the results are relevant for any area near the bridge independent of the side."
For now, until safe levels are established, Olvera recommends several actions to reduce exposure to ultrafine particles.
"You want to avoid exposure," Olvera said. "I would avoid peak hours of traffic and cross very early in the morning or late in the evening if you need to."
Other helpful measures include crossing the border bridge with vehicle windows closed, keeping the air conditioner running, and crossing on Sundays when commercial traffic does not take place and when UFP concentrations are at their lowest.
Customs and Border Protection regularly recommends that commuters try to avoid crossing the bridge at peak periods, and for border businesses to enroll in U.S. trusted trader programs that result in faster crossing times.
"These include Free and Secure Trade (FAST) and the Customs Trade Partnership Against Terrorism (C-TPAT)," Maier said. "CBP also encourages area shippers to better utilize all hours our cargo facilities are open to reduce congestion during peak periods. There are periods when our facilities are underutilized and crossing times are virtually nonexistent. We would also urge commercial shippers to utilize facilities located away from the city center that are better designed to process large quantities of trade. These include the (Zaragoza), Santa Teresa and soon to be completed Tornillo, cargo lots."
Besides Olvera, the research team for the recent study included former UTEP students Veronica Guerrero and Mario Lopez, UTEP professor of civil engineering Wen-Whai Li, and Humberto Garcia, professor of environmental engineering at the Instituto Technologico de Monterrey. UTEP's Center for Environmental Resource Management and the Hispanic Health Disparities Research Center collaborated on the study.
Olvera is continuing his research on ultrafine particles by studying UFP concentrations at U.S. 54 and Interstate 10, the Spaghetti Bowl interchange.
"UTEP is very interested in this, and we're hoping that the research that we are doing will lead to policies, standards and answers to the questions we all have about UFPs."
Diana Washington Valdez may be reached at firstname.lastname@example.org; 546-6140.
Distributed by MCT Information Services
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