The amounts of tiny -- but potentially harmful -- air particles from diesel emissions tend to double at the Bridge of Americas during peak traffic hours, according to a study by experts at the University of Texas at El Paso.
The nationally known Journal of Exposure Science and Environmental Epidemiology in January published the UTEP study, titled "Ultrafine particle levels at an international port of entry between the US and Mexico: Exposure implications for users, workers, and neighbors."
"Normally, our lungs act as filters for airborne particles, but these smaller particles travel deeper within our lungs," said Hector Olvera, a research assistant professor at UTEP who conducted the study. "Nanoparticles like UFPs are so
small they can reach our bloodstream. Other studies have shown that after entering the bloodstream, they end up in our brain, liver, bone marrow and kidneys."
The emissions may be most harmful to border agents working near and around the port, to workers on both sides of the bridge, to people who live near it and to students who attend schools nearby. Olvera said that above-normal levels of emissions may be found at the Chamizal National Memorial and Bowie High School.
Every day people can be seen jogging or walking through the Chamizal park next to Bowie High.
Chamizal National Memorial's acting superintendent, Jerome Flood, said he could not comment now because his office is not familiar with the study.
U.S. Customs and Border Protection spokesman Roger Maier said the health and safety of the agency's agents is "of utmost importance. An El Paso-based CBP safety officer read the abstract and points out that the study was based on outdoor ambient air monitoring, not personal monitoring specific to sampling strategies dictated by OSHA standards to determine actual employee exposure to specific contaminants."
Maier added that "none of the studies that have been conducted at area ports over the
years concerning exposure to carbon monoxide have documented over-exposures to (carbon monoxide) 50 ppm (parts per million) based on a time-weighted average of eight hours for those employees wearing personal air monitors. In order to obtain exposure data, similar personal testing would need to be conducted for the contaminant discussed in the abstract."
Maier said the CBP does not have control over other agencies on either side of the border that, with their inspection procedures, may contribute to worsening traffic congestion at the bridge.
Renee de Santos, spokeswoman for the El Paso Independent School District, said no one at UTEP notified the district about the air pollution study results. Consequently, the district has not had a chance to review the data.
"We are obviously very concerned about the implications Dr. Olvera's study raises," De Santos said. "The safety and well-being of our students and staff is a priority. The district relies heavily on the city's Department of Public Health and the Texas Commission on Environmental Quality for information on air quality issues that may affect our campuses."
Last year, the World Health Organization established that diesel emissions are cancer-causing pollutants. Currently, the U.S. Environmental Protection Agency characterizes diesel emissions as "likely" cancer-causing pollutants.
The EPA has set standards for safe levels of particulates PM-10 and PM-2.5, which are larger than ultrafine particles. For example, PMs are measured in micrometers, so a PM-10 is the size of 10 micrometers (1 micrometer equals 1 millionth of a meter).
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 email@example.com; 546-6140.
Distributed by MCT Information Services
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