6PPD-quinone in water from the San Francisco-San Joaquin Delta, California, 2018-2024.

The Sacramento-San Joaquin Delta (Delta) is an expansive river delta supplying a large portion of California's fresh water for agriculture and residential use, and it is also an area of critical habitat for numerous state and federally listed species of concern. In many locations, urban stormwater flows directly into the Delta. 6PPD-quinone (6PPD-Q), an ozonation byproduct of a tire antiozonant 6PPD, has been shown to enter surface water via these pathways and can cause various toxicological effects, including acute urban mortality syndrome to coho salmon (Oncorhynchus kisutch) at low levels (LC = 41 and 95 ng/L for juveniles and adults, respectively).

Increasing neonicotinoid use and the declining butterfly fauna of lowland California.

The butterfly fauna of lowland Northern California has exhibited a marked decline in recent years that previous studies have attributed in part to altered climatic conditions and changes in land use. Here, we ask if a shift in insecticide use towards neonicotinoids is associated with butterfly declines at four sites in the region that have been monitored for four decades. A negative association between butterfly populations and increasing neonicotinoid application is detectable while controlling for land use and other factors, and appears to be more severe for smaller-bodied species.