Officials are monitoring reports from the San Diego County Air Pollution Control District of an overnight uptick in hydrogen sulfide readings in the Tijuana River Valley, creating odor issues in South County. The increase in odors in the last 24 hours “appears to be associated with reports from the (International Boundary and Water Commission) that sewage infrastructure work in Mexico has resulted in the release of up to 5 million gallons per night of sewage into the Tijuana River Valley,” according to the county. This flow comes in addition to “rogue sewage flows” being investigated by the IBWC with its partners in Mexico. The IBWC operates the South Bay International Wastewater Treatment Plant and is tasked with collaborating with Mexico on border water issues. As a result of the odors, county public health officials urged nearby residents to limit outdoor activities, keep doors closed and use indoor fans and air purifiers to increase circulation and the quality of air. Free air purifiers from the APCD are still available to residents in the three primarily affected ZIP codes — 91932, 92154 and 92173 — which include Imperial Beach, San Ysidro, Nestor and other South Bay neighborhoods. To apply, go to sdapcd.org. “Our friends, co-workers and families who live or work near the Tijuana River Valley deserve access to clean air and beaches,” said Dr. Ankita Kadakia, the county’s interim public health officer. “While the county continues to advocate to the federal government for a solution that stops the flow of untreated wastewater, we also want people to be aware of the steps they can take when confronted by offensive hydrogen sulfide odors.” People with asthma, chronic obstructive pulmonary disease or other chronic lung conditions should have emergency medications such as rescue inhalers readily available, a statement from the county reads. If symptoms from strong odor persists, are worrisome or worsen, seek medical care. Mexico began releasing between 3-5 million gallons of wastewater daily last week into the Tijuana River as the country works on a major infrastructure project in Tijuana to replace a sewer pipeline. “The county of San Diego urges federal officials to continue working with their counterparts in Mexico on stopping the flow of raw sewage and bringing an ultimate resolution to this longtime source of water and air pollution,” the county said in a statement. City News Service contributed to this article.