SAN DIEGO (AP) — The smell of rotten eggs permeates Steve Egger’s Southern California home, especially at night as the nearby Tijuana River foams up with sewage from Mexico before emptying into the Pacific Ocean.

Egger, 72, says he and his wife have frequent headaches and wake up congested and coughing up phlegm. Their home is outfitted with a hospital-grade filtration system that cycles the air every 15 minutes. Despite those measures, “most nights we breathe in a horrible stench,” he said. “It’s awful.”

Since 2018, more than 100 billion gallons (378 billion liters) of raw sewage laden with industrial chemicals and trash have poured into the Tijuana River. The river traverses land where three generations of the Egger family once raised dairy cows. The United States and Mexico signed an agreement last year to clean up the longstanding problem by upgrading wastewater plants to keep up with Tijuana’s population growth and industrial waste from factories, many owned by U.S. companies.

Steve Egger stands near contaminated Tijuana River.

In the meantime, tens of thousands of people are being exposed to the sewage. EPA Administrator Lee Zeldin mentioned it will take about two years to address one of the nation’s worst environmental crises, affecting a largely Latino population.

Raw sewage emits hydrogen sulfide, a toxic gas linked to serious health complications like headaches, nausea, and respiratory problems. Additionally, health experts noted that low levels of exposure can lead to chronic illnesses, with local doctors reporting rising caseloads of patients suffering from migraine and respiratory issues linked to the odor.