The small town of Calexico, California, suffers disproportionately high air pollution because of its proximity to a major border crossing with Mexico, and the nearby industrial city of Mexicali, home to over 1 million, and highlights the difficulties in enforcing regulations applying to one country, at the border with another without the resources to legislate, or enforce legislation, to the same degree.
PM2.5 concentrations regularly exceed legislative limits, with the US EPA and California Air Resources Board noting that the county would have met PM2.5 standards were it not for emissions from, or relating to border crossings with, Mexico. To compound the problem, in addition to industrial and traffic emissions, the climate in the region is hot and dry, with resulting particle sources from both desert dust and resuspended particles from paved and unpaved roads, and agricultural (and other legal and illegal) burning also produces large quantities of smoke seasonally. Over 1 million vehicles make the crossing monthly, with 53% of PM2.5 emissions caused by traffic being delayed at the overburdened crossing points.
While the perception on the US side is sometimes that the problem is due to Mexican vehicles, a recent study pointed out that the average age of the US-registered vehicles was older, and that the differences in quality of fuel may be most to blame – Mexico’s gasoline sulphur fuel limit is 30 ppm, while the US will have a limit of 10 ppm from 2017. The US EPA is helping to improve the situation by providing funds for better air quality monitoring in Mexicali, and the Border 2020 Program, a bilateral program to improve the environment and public health on the US-Mexico border, although progress is slow.
Read the full story by Alejandro Davila Fragoso here