The Arizona-Mexico border air pollution program is a bi-national study focusing on the air quality of the three largest border communities in Arizona.

• Ambos Nogales
• Douglas/Agua Prieta
• Yuma/San Luis

Ambos Nogales

The Nogales study was the first intensive air quality border study conducted by ADEQ. The first phase of the study, on hazardous air pollution (HAP) and particulate matter (PM) in the Ambos Nogales area was completed in November 1995. The study included collecting ambient air concentrations for 60 pollutants for one year. Samples were taken every sixth day, according to the standard EPA protocol, and every third day during an intensive study period in the winter season. The sampling was conducted at the Nogales Post Office and at Carrillo Place, a residential neighborhood near the border, which has experienced a number of cancer cases; and at two sites across the border.

The emissions inventory study for Ambos Nogales was completed July 1997 by a sub-contractor, Radian International (ENSR Consulting and Engineering was the prime contractor). The information from the emissions inventory was loaded by ENSR, along with meteorological data, into a three-dimensional computer model that computed pollutant concentrations throughout the area. The model's results were adjusted to align with the measured concentrations obtained during the sampling program. The modeling for spatial and temporal variations of HAP ambient concentrations were then used in the risk assessment study prepared by ENSR.

The risk assessment examined the pollutants, and the sources of the hazardous air pollutants and particulates. It concluded that the primary source of the PM10 concentrations in Ambos Nogales were a result of unpaved roads and that the dominant cause of hazardous air pollutants on both side of the border were organic compounds resulting from the operation of motor vehicles.

Plan of Action for Improving Air Quality in Ambos Nogales
Plan de Acción para Mejorar la Calidad del Aire en Ambos Nogales

Douglas/Agua Prieta

An intensive air quality monitoring study was conducted in the Douglas/Agua Prieta area from January 1999 to February 2002. Its purpose is to determine the temporal and spatial distribution of ambient air concentrations of toxic air pollutants and particulate matter in the region. For the study time period, meteorological data were collected, including upper air data using a wind profiler. An emissions inventory is being developed for the Douglas/Agua Prieta area by a contractor, with guidance from ADEQ staff. As part of the emissions inventory development, ADEQ staff are using a new approach - coupling Geographic Information System software with satellite image processing software to analyze digital high-resolution satellite images (resolution of one meter). This method allows staff to more accurately identify and locate land uses that contribute to air pollution, such as land with disturbed topsoil, vacant lots, agricultural land, and unpaved and paved roads.

The emissions inventory will be used to identify and quantify sources of air pollution in the Douglas/Agua Prieta area. Sources include vehicle traffic, maquiladoras, and disturbed land. The next step is to simulate air quality concentrations with numerical modeling. This modeling provides a means to perform human risk assessment and to evaluate the potential benefits of proposed control measures to reduce air emissions. The modeling began in July 2001 and will use the emissions inventory data, meteorological data, and air quality monitoring data collected from these studies.

Yuma/San Luis

With funding provided by US EPA Region 9 , ADEQ is conducting a Binational Air Quality Study for the Western Arizona-Sonora Border Region. This study is anticipated to determine the type and sources of harmful compounds in the air, and relate the emissions of these compounds to their concentrations in the air through computer modeling. Data collection for this study will occur over the next two years (2003 - 2004) and includes meteorological measurements and air quality measurements from various locations within the study area. Once all the data is collected, a complete emissions inventory will be built and meteorological and air quality modeling will be performed to evaluate the spatial and temporal distribution of the air pollution (2004 - 2005). Additionally, a health risk assessment will evaluate population exposure and the potential risk of such exposure (2005 - 2006). Final study results, expected 2006, will include an evaluation of the contribution of the various emissions sources and analyze various potential emissions reductions techniques.