SAN DIEGO (CN) — Scientists studying polluted waters which have fouled the Pacific Ocean and Southern California beaches after breaching crumbling wastewater infrastructure in Mexico said Thursday a new scientific prediction model can prevent beachgoers from getting sick.
Scientists with the Scripps Institution of Oceanography at the University of California, San Diego held a webinar Thursday with San Diego City Councilwoman Vivian Moreno attended by more than 120 people to discuss strides researchers have made in understanding the way polluted wastewater moves from the Tijuana River Valley to the Pacific Ocean.
Wastewater pollution at beaches bordering the U.S.-Mexico border in San Diego has been a decades-long issue, with the city of San Diego continuously declaring a state of emergency related to the issue since 1994. For the first time, San Diego County declared the sewage-tainted water a public health crisis earlier this month.
“This environmental disaster hits close to home for me as I live less than a mile away from the Tijuana River and I have the distinct honor of smelling the contamination when the flows run rampant,” Moreno, who represents Council District 8, said.
The decades-long pollution problem was exacerbated by crumbling wastewater treatment facilities in Mexico that were strained so much during the wet winter of 2017, there was a major break which released hundreds of millions of gallons of raw sewage.
The breach prompted lawsuits by local cities and state of California and a $300 million investment by the Environmental Protection Agency to address cross-border pollution as part of the United States-Mexico-Canada Agreement.
Since that breach, wastewater pollution “has gotten so much worse,” Falk Feddersen, a professor in the Integrative Oceanography Division at Scripps, said in an interview with Courthouse News Thursday.
“There’s no doubt a lot more wastewater and sewage has basically gone into the estuary and that is going to affect Imperial Beach and the regions up the coast as well as Playas de Tijuana,” Feddersen said.
“That metric has gotten worse and beach closures have gotten worse, but we don’t really know how many people are getting ill because there isn’t any way of backtracking the public health impacts of this and they have to be substantial,” he added.
Feddersen’s team of researchers is trying to predict those illnesses, however.
They have conducted several studies since 2015 where a pink dye mimicking a wastewater plume is released into the surf zone to watch how it spreads from two locations in Tijuana — the Tijuana River Estuary and San Antonio de los Buenos wastewater treatment plant.
Using the data from the dye studies, Feddersen was able to develop computer prediction models analogous to weather prediction models which can help scientists simulate and understand the probability beachgoers — swimmers and surfers — would get sick from pathogens in the water.
The top risk to swimmers is norovirus, Feddersen said, which causes gastrointestinal issues.
By estimating the dilution of wastewater in the ocean and comparing it to the number of swimmers who went to the beach, Feddersen said he and his team determined how many swimmers likely got sick from norovirus.
In a year where 864,000 swimmers were logged as having recreated at the beach, 34,000 or 4% were estimated as having become sickened by norovirus.
They also estimated how many days the beach should be closed based on Environmental Protection Agency guidelines advising beaches should be closed if more than 3.2 out of 100 swimmers get sick.
Based on the EPA guidelines, Playas de Tijuana would have to be closed 60% of the year while beaches on the U.S. side of the border, including Imperial Beach, Silver Strand Beach and Coronado Beach would need to be closed between 15% and 35% of the year, according to Feddersen’s model.
He said Scripps researchers hope to use the model to predict pollution forecasts where beachgoers could know three to five days in advance the likely risk of illness by going to the beach.
Kimberly Prather, director of the Center for Aerosol Impacts on Chemistry of the Environment at UC San Diego, said during the webinar Thursday her team’s research piggybacked off Feddersen’s research where they tested air quality samples in the region to see if the pink dye Feddersen released in the ocean had aerosolized and landed inland.
In two of the three studies, Prather found the dye in air samples taken inland, further confirming polluted wastewater and pathogens found in the ocean not only contaminate the water, but the air quality along the coast.
Her team is also studying the aerosolization of the Covid-19 virus from sewage in the estuary and ocean.