April 16, 2021, Tijuana, Mexico.Raquel Natalicchio / ZUMA

This story was originally published by the Guardian and is reproduced here as part of the Climate Desk collaboration.

Raw sewage and runoff in the Tijuana River is exposing communities at the US-Mexico border to an unusual and noxious brew of pathogens and toxic chemicals, according to a report released this week.

Billions of gallons of sewage flow through the river, which winds north from Mexico through California and empties into the Pacific Ocean, containing a mix of carcinogenic chemicals including arsenic, as well as viruses, bacteria and parasites, according to public health researchers at San Diego State University, who published the report.

The researchers have called the situation “a pressing public health crisis.”

Wastewater flowing into the ocean has resulted in more than 700 consecutive days of beach closures in San Diego county, but the contamination isn’t limited to the water. Pollutants and pathogens contained in sewage have also been detected in the local air and soil—exposing even those who live miles away from the water.

Communities on both sides of the border have been raising the alarm about this contamination for decades, complaining of the near-constant stench in the air, and pushing for........

© Mother Jones