Monitoring the Effects of Transboundary Water Pollution in Imperial Beach, California

Transboundary water pollution is a major global challenge as its movement and impacts remain unsurveyed. Monitoring pollution along international borders can reveal some of the pathways by which sewage and chemicals enter water bodies, and can hence advance the implementation of measures to prevent leakages and discharges into international waters. In this paper, we surveyed the impacts of sewage pollution and chemicals along the U.S.–Mexico international border, using Imperial Beach (California) as a main case study. Pollution was primarily attributed to the inflow of contaminated waters from the neighboring city of Tijuana (Mexico), where a malfunctioning wastewater treatment plant and a lack of sewage pipes being upgraded have caused direct leakage and toxic discharges into the Tijuana River. Reported effects from water pollution at the Tijuana River estuary in Imperial Beach include frequent beach closure, damages to coastal ecosystems, negative impacts on the fishery industry, and several effects on the health of beach users and surfers. Hence, the situation requires urgent measures oriented at coastal management at the mouth of the Tijuana River as well as the consistent monitoring and reporting of human health effects linked to beach uses.