Due to both discharges from storm drains and natural run-off to rivers and streams, a number of cities within and up stream of the Delta release hundreds of thousands of gallons of water containing contaminants and toxic chemicals each day.

According to the Center for Biological Diversity, both delta smelt and the plankton on which it feeds are suffering direct mortality or impairment from the presence of toxic substances in the water.

Pyrethroids, among the most widely used home pesticides, are winding up in the Delta at toxic levels, and endangering the food supply of fish and other aquatic animals, according to a new study by researchers at the University of California, Berkeley. Pyrethroids have been around for decades, but their use skyrocketed after 2004, when other home-use pesticides were banned.

Pyrethroid insecticides have been widely found in residential run-off and in the outflow from sewage treatment plants in the Sacramento area. The insecticide is being increasingly found in the San Joaquin River and a 20-mile stretch of the American River – traditionally considered to be one of the most pristine rivers in the region.

Additionally, salinity, herbicides, pesticides, and other toxic chemicals and pollutants from upstream and in-delta farming operation directly impact delta smelt, salmon and other endangered fish and their ecosystem.

According to the Center for Biological Diversity (CBD):

“…all life stages of delta smelt are at least periodically exposed to lethal or sub-lethal concentrations of herbicides and pesticides…”

According to CBD, both the smelt and the plankton on which the endangered fish feeds are suffering direct mortality or impairment from the presence of toxic substances in the water.

The Sacramento region is a large polluter and each day discharges millions of gallons of partially treated sewage into the Delta. Contained in this wastewater are significant concentrations of ammonia. On a monthly basis, Sacramento adds high levels of ammonia to the Delta – far more than any other source. These discharges are believed to have a significant impact  on Delta Smelt and other threatened and endangered species.

Visit our Violating the Delta page for more detailed information on major polluters around the Delta.