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Seventy-five surface water samples were collected from three agricultural regions of California and analyzed for the neonicotinoid insecticide imidacloprid. Samples were collected during California's relatively dry-weather irrigation seasons in 2010 and 2011. Imidacloprid was detected in 67 samples (89%); concentrations exceeded the United States Environmental Protection Agency's chronic invertebrate Aquatic Life Benchmark of 1.05 μg/L in 14 samples (19%). Concentrations were also frequently greater than similar toxicity guidelines developed for use in Europe and Canada. The results indicate that imidacloprid commonly moves offsite and contaminates surface waters at concentrations that could harm aquatic organisms following use under irrigated agriculture conditions in California.

Urban pesticide use has a direct impact on surface water quality. To determine the extent of pesticide contamination, the California Department of Pesticide Regulation initiated a multi-area urban monitoring program in 2008. Water and sediment samples were collected at sites unaffected by agricultural inputs in three areas: Sacramento (SAC), San Francisco Bay (SFB), and Orange County (OC). Samples were analyzed for up to 64 pesticides or degradates. Multiple detections were common; 50 % of the water samples contained five or more pesticides. Statewide, the most frequently detected insecticides in water were bifenthrin, imidacloprid, fipronil, fipronil sulfone, fipronil desulfinyl, carbaryl, and malathion. Bifenthrin was the most common contaminant in sediment samples. Key differences by area: OC had more pesticides detected than SAC or SFB with higher concentrations of fipronil, whereas SAC had higher concentrations of bifenthrin. The most frequently detected herbicides were 2,4-D, triclopyr, dicamba, diuron, and pendimethalin. Key differences by area: OC and SFB had higher concentrations of triclopyr, whereas SAC had higher concentrations of 2,4-D and dicamba. Detection frequency, number of pesticides per sample, and pesticide concentration increased during rainstorm events. In water samples, all of the bifenthrin, malathion, fipronil, permethrin, and λ-cyhalothrin detections, and most of the fipronil sulfone and cyfluthrin detections were above their lowest US EPA aquatic benchmark. Diuron was the only herbicide that was detected above its lowest benchmark. Based on the number of pesticides and exceedances of aquatic benchmarks or the high number of sediment toxicity units, pesticides are abundant in California surface waters.

Pyriproxyfen is a broad-spectrum insect growth regulator (IGR) with insecticidal activity against public health insect pests such as houseflies, mosquitoes and cockroaches. In agriculture and horticulture, pyriproxyfen has registered uses for the control of scale, whitefly, aphids and fire ants. It is used extensively worldwide, particularly in developing countries, although it has no significant uses in California. Pyriproxyfen acts on the endocrine system of insects by mimicking the juvenile hormone, thereby hindering molting and subsequently inhibiting reproduction. IGRs are unique in that they are specific for insects and have very low mammalian toxicity. As such, pyriproxyfen has received U.S. EPA status as a Reduced Risk insecticide and an organophosphate alternative and is the only pesticide approved by the World Health Organization (WHO) for treatment of potable water against mosquito. However, concerns about its environmental persistence and latent toxicity to nontarget organisms have been recently raised and discussed. In this context, a detailed review of the environmental fate and physicochemical properties of pyriproxyfen from the available scientific literature and from data gathered in its development and testing is needed. This paper gathers, combines, and abridges important environmental fate and property data on pyriproxyfen for academics, environmental scientists and agricultural professionals needing ready access to this information.