Just weeks after unveiling a new odor alert system, the San Diego County Air Pollution Control District on Monday issued an advisory warning that levels of sewer gases above state thresholds were detected near the Tijuana River Valley. The district’s air monitoring equipment in Nestor had recorded concentrations of hydrogen sulfide, a toxic gas that smells like rotten eggs, above the state standard of 30 parts per billion (ppb), which is intended to be protective against headaches and nausea. The limit is also designed to protect sensitive groups, such as children, older adults and people with certain health conditions. Communities including Nestor, Imperial Beach, San Ysidro and surrounding areas have reported feeling ill after smelling sewer gas odors due to untreated wastewater that spills over the border from Tijuana. According to readings from Berry Elementary School, located on Rimbey Avenue near Saturn Boulevard, levels of the gas peaked at 100 ppb around 10 p.m. and 39 ppb around 11 p.m. on Sunday. Several residents living and working near the Tijuana River Valley reported smelling strong odors of the past couple of days. Among them was Regina Gamboa, who said the stench had infiltrated her home. Her daughter has lung complications and Gamboa said exposure to the sewer gas has exacerbated her daughter’s condition. “The smell isn’t as strong as it was a few months ago but it’s still noticeable and worrisome,” she said. The advisory recommends that if odors persist, one should consider taking the following precautions to reduce exposure to the gas: Limit outdoor activities if odors are bothersome;Keep doors and windows closed until odors are no longer present. For indoor air quality, use air conditioning or air purifiers. If possible, businesses should run the HVAC system for 1-2 hours before opening. People with asthma, chronic obstructive pulmonary disease or other chronic lung conditions should have their rescue medications readily available. If symptoms from strong odor persists, are worrisome, or worsen, seek medical care. The alert comes after the district earlier this month launched an online dashboard to track sewer gas levels and an index to advise the public on what to do. The dashboard shows hourly levels of hydrogen sulfide tracked from Nestor and San Ysidro. Readings from Imperial Beach City Hall will also be available in the coming weeks. For more information about air monitoring, visit www.sdapcd.org/TJRiver.