Human-associated viral pathogens in water and air and evaluation of PMMoV as an indicator of airborne viruses near the Tijuana River, CA.

Coastal waters impacted by fecal contamination pose health risks to recreational users through direct water contact; however, risk to users, workers and surrounding communities from potential airborne exposure remain poorly understood. This study quantified two human-associated sewage markers (HF183 and pepper mild mottle virus (PMMoV)) and two enteric viruses (norovirus GII (NoVGII) and human adenovirus (HAdV)) in paired water and air samples collected in San Diego County, USA, from the Tijuana River, a binational river flowing into the US from Mexico that is polluted with untreated and treated wastewater, a community site on the beach (Imperial Beach), and a northern reference site (La Jolla Shores). A total of 23 paired water and air samples were collected during the dry season, with 10 water samples collected during the wet season. All microbial targets were consistently detected at high concentrations in the Tijuana River water, while concentrations in Imperial Beach water were significantly lower. In contrast, airborne concentrations were comparable between the two sites, with PMMoV detected in all air samples. Log-transformed ratios of the concentrations in air and water samples indicate enrichment in the air samples from Imperial Beach compared to the Tijuana River. PMMoV showed the most consistent detection and the strongest relationship with airborne HAdV and NoV levels, suggesting PMMoV as a conservative indicator of aerosolized viruses of human fecal origin in such settings. These findings indicate that coastal surf zones may serve as important interfaces for aerosolization of wastewater-associated microorganisms and suggest that inhalation could represent a previously underrecognized exposure pathway in contaminated coastal environments.