DDX Concentrations in Fish Tissue and Sediment from the Southern California Bight

Dichlorodiphenyltrichloroethane (DDT) is an insecticide that is resistant to degradation and can cause increased risks of cancer, premature births, developmental abnormalities, and neurological diseases in humans and animals. Although banned in 1972, DDT was dumped into the ocean off the coast of southern California for decades. Recent documentation of the extent of this contamination has captured the attention of the public and raised concerns regarding the consumption of contaminated seafood. The state of California currently issues consumption advisories for coastal communities, but these advisories do not address DDT. To fill this gap and improve advisory accessibility, SaferSeafood has partnered with Scripps Institution of Oceanography and the California Cooperative Oceanic Fisheries Investigations, who collected data on the incidence of DDT in sediments and fish in nearshore southern California waters. Using this data, we updated and validated their spatiotemporal statistical model to predict DDT concentrations in fish based on species and location. We then integrated this model into an interactive web application that allows anglers to receive predicted DDT concentrations in the fish they have just caught, along with serving size recommendations and other relevant advisories. The results of this project will allow individuals to make well-informed decisions about their seafood choices in the face of environmental challenges and health risks associated with DDT contamination.

Methods
The data was compiled from researchers at the Scripps Institution of Oceanography from previously collected fish and sediment contaminant monitoring data from 1998 through 2021. The data came from the following sources: Southern California Bight Regional Monitoring Program, SWAMP Statewide Coastal Screening Survey, SWAMP Coastal Fish Contamination Program, Jarvis et al. 2007, McLaughlin et al. 2021, Southern California Coastal Marine Fish Contaminants Survey, LA County Sanitation District Local Trends Assessment, LA County Sanitation District Seafood Safety Assessment, and City of San Diego POTW Monitoring. This data focuses on the Southern California Bight. The sediment samples were collected via grab samples of top 5 cm at embayment sites and top 2 cm at offshore sites in 2003, 2008, 2013, and 2018. Fish tissue samples were collected off piers and boats, and composites consisted of 5-10 specimens and included only single species per composite. The data was subset to include only sediment and fish samples that explicitly measured DDX (2,4′-DDE, 4,4′-DDE, 2,4′-DDD, 4,4′-DDD, 2,4′-DDT, and 4,4′-DDT). Each species was assigned diet and habitat, and composites were assigned to fishing zones. The DDT concentrations, both lipid-normalized and non lipid-normalized was normalized, and the sediment DDT concentrations were also normalized.