The investigation of the New River found that the pollution — in the water, air, and all around the region — is linked to the rise of industry in Mexicali, where factories manufacture products that supply Mexico and the United States. The pollution is linked to high rates of respiratory illnesses and deaths, but the system of regulation in Mexicali does little to regulate factories or punish polluters.
https://www.usatoday.com/story/news/pr/2018/12/05/usa-today-networks-poisoned-cities-deadly-border-investigation-uncovers-pattern-unchecked-pollution/2212802002/