Mexicali pollution skews Imperial County’s air quality rating into the red

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An CE8KBT aerial photo map of the Mexican-American border at the junction of Calexico and Mexicali.

EL CENTRO – The Imperial County Air Pollution Control District (ICAPCD) conducted a public workshop Thursday to discuss the newly proposed Draft 2017 State Implementation Plan for the 2008 8-hour Ozone Standard. In data, the report showed Imperial County would be in compliance with federal air standards, “but for” Mexicali’s pollution drifting into the Valley.

The Imperial County was reclassified as moderate non-attainment on May 4, 2016 for once again failing the United States Environmental Protection Agency’s (EPA) clean air standards, specifically, the 2008 ozone National Ambient Air Quality Standard (NAAQS), by the July 20, 2015 deadline.

Imperial County was identified as “out of compliance” since one or more of the four air quality monitors located in Calexico, El Centro, Westmorland, and Niland registered greater than 0.075 ppm for the 2012-2014 monitoring period.

The Clean Air Act established planning requirements for those areas that routinely exceeded national air quality standards. As per requirements, these non-attainment areas must adopt and implement a State Implementation Plan (SIP) demonstrating how they will comply by specified dates.

Because of the County’s non-attainment classification, the state of California must submit a revised SIP stating why the County was noncompliant, the underlying causes, and the steps necessary to reduce pollutant emissions and bring the Valley back into attainment. Additionally, the Valley must show attainment no later than July 20, 2018.

According to the EPA website, the major sources of pollutants are oxides of nitrogen (NOX) and Volatile Organic Compounds (VOC) which mix together to create the “bad” ozone. Ozone exists in two layers of the atmosphere. Ozone in the troposphere, the atmospheric layer closest to Earth’s surface, is known as ground-level ozone. Ground-level or “bad” ozone is not emitted directly into the air, but rather is formed by a complex series of chemical reactions involving oxides of nitrogen (NOX), the result of combustion processes, and Volatile Organic Compounds (VOC), including many industrial solvents, toluene, xylene, and hexane, as well as the various hydrocarbons that are evaporated from gasoline used by vehicles or emitted through the tailpipe. Emissions from factories and our electric utilities, car and truck exhaust, gasoline fumes, and chemical solvents are some of the major sources of NOX and VOCs, according to the website.

“At ground level, ozone is of greatest concern during the summer months because strong sunlight and hot weather result in harmful ozone concentrations,” explained Monica Bugarin Soucier, APC Division Manager. “This is because ozone’s formation is promoted by strong sunlight, warm temperatures, and winds. High concentrations of ground-level ozone tend to be a problem in Imperial County only during the hot summer months, when these conditions frequently occur.”

The Imperial County’s greatest challenge to improving air quality is sharing a border with Mexicali, whose metropolitan area has more than five times the population of the entire County. The reason why Imperial County has elevated ozone concentrations is because of emissions from Mexico blowing into the Valley. Therefore, the County’s 2016 Ozone SIP demonstrates Imperial County is in attainment of the ozone standard “but for” emissions emanating across the international border. A weight-of-evidence analysis has been included to show that Imperial County will maintain this status of attainment through the July 2018 attainment date, explained Soucier.

“If we shut down the Imperial County completely, we basically would not move the needle,” said Reyes Romero, the County’s assistant air pollution control officer, speaking about the pollution levels. “Mexicali has five times the residents of the Valley, all are located right on the border, they have more vehicles, factories, and a backed-up border crossing.”

Since the North America Free Trade Agreement (NAFTA) was implemented in 1994, Mexicali has grown from a primarily agricultural region to an economic center that includes a wide range of agricultural activities, manufacturing plants, and food processing. Over the same period, the population has grown from around 600,000 in the early 1990s to nearly one million in 2015. Mexicali’s growth has led to an increase in factory and vehicle emissions, according to the 2017 SIP.

The County’s 2017 Ozone SIP hopes to demonstrate attainment of the federal 2008 Ozone Standard “but for” emissions from Mexico. Yet, within the report are extra measures for the Valley to work on its own pollutants. One example includes ensuring all new or modified factories do not significantly add to the pollution by applying best available control technology and emission offsets.

Reducing ozone-creating emissions from idling vehicles at ports of entry is one of the most important air quality challenges facing the Imperial County and Mexicali region. Even with standards taking effect over the next decade for idling vehicles, millions of vehicles will continue to emit large amounts of air toxins, contributing to serious public health problems.

Border delay accounts for about 63 percent of the VOC emissions and 46 percent of the NOx emissions from northbound vehicles crossing into the United States, according to ICAPCD.

The County is coordinating with counterparts in Mexico to clean up emissions to improve border air quality. As such, in August 2012, the U.S. and Mexico signed the U.S.-Mexico Environmental Program Border 2020.

Border 2020 is a cooperative effort between the EPA, Mexico’s SEMARNAT (federal environmental agency), the four U.S. border states (Texas, New Mexico, Arizona, and California) and the six Mexican border states (Tamaulipas, Nuevo León, Coahuila, Chihuahua, Sonora, and Baja California), plus U.S. border tribes.

The 2017 State Implementation Plan can be viewed on the Imperial County’s website.