Air quality officials detected a spike in a toxic gas in the South Bay Monday evening stemming from sewage pollution from Tijuana. The San Diego County Air Pollution Control District issued an odor advisory after high levels of Hydrogen Sulfide were detected from their monitor near Berry Elementary School in Nestor. The agency said the readings at 51.3 parts per billion exceeded the 30 ppB level set by the state. Readings began to rise around 6 p.m. and peaked around 10 to 11 p.m., data shows. No readings have been reported since, and data is refreshed once every 24 hours, according to the agency. WATCH NBC 7’s special ‘Toxic Tide: The sewage crisis at the border’ NBC 7 investigates the millions of gallons of raw sewage crossing from Tijuana into the United States every day, including how the crisis affects our health — and what must be done to end it. Following the border sewage crisis Nov 18 Lawsuit filed against operators of South Bay International Water Treatment Plant South Bay Nov 19 Biden includes $310M for South Bay plant at center of border sewage crisis in relief package Feb 13 Toxic Tide: Study finds sewage, pollution from Mexico pose health risk to kids, elderly, pregnant The odors stem from the release of millions of gallons of sewage daily from Mexico into the U.S. of which the South Bay International Wastewater Treatment Plant has failed to keep up — an issue that has dated back decades. The SDAPCD began monitoring toxic gas levels in 2023 after receiving an increase in complaints over odors in the South Bay. The data is collected in an online dashboard and alerts are issued when spikes occur, as they did Monday. Testing led the SDAPCD to send a violation notice to the U.S. International Boundary Water Commission and its contractor, Veolia, who operate the treatment plant. The launch of a recent rehabilitation project aims to reduce the amount of transborder flows reaching the coast by about 90%, according to the U.S. International Boundary Water Comission. But residents in the South Bay believe progress to address the issue — which dates back decades — is moving at a glacial pace and lawsuits have been filed by some who complain of chronic health issues associated with bacteria and odors coming from the river. The crisis has also closed their beaches for more than 1,000 days. In May 2024, the elected officials called on the U.S. Centers for Disease Control and Prevention to look into the contaminants in the water, soil and air from the sewage and the connection to reported increases in illnesses and other symptoms.  The survey wrapped up this week with thousands of households participating. Results won’t be available until early next year. In the “yellow tier” that was reached Monday, the SDAPCD said levels of toxic gas in the air could affect sensitive groups — children, older adults and those with health conditions. Some could experience headaches or nausea. Residents who smell the “rotten egg” smell should limit outdoor activities, keep doors and windows closed, the agency advises. Air conditioning and ventilation can help eliminate the smell, so residents should air out their homes once the odor is gone. The SDAPCD said readings can spike due to weather conditions and “equipment sensitivity.”