Professional Insecticide Applicators Key to Urban Stream Pollution
Surface water pollution from urban pesticide use is a known, widespread problem in the U.S. This has been documented not only by USGS, but also by numerous scientific studies by academic researchers, data from municipal urban runoff programs, and surface water impairment designations under section 303(d) of the Clean Water Act (often these listings are for "toxicity" rather than a specific pesticide). U.S. EPA's pesticides office is keenly aware of this problem.
In California, pesticide-related toxicity in surface waters receiving urban runoff is has been severe and widespread since the mid-1990s. Addressing this toxicity is a priority for Calfornia's water and pesticide regulators. With the phase-out of most urban uses of diazinon and chlorpyrifos, the toxicity has shifted--it is now occurring in both the water column (during storm events) and sediments (all the time) in urban creeks across California.
The current toxicity is associated with the use of the currently most common class of urban insecticides--the pyrethroids (i.e. bifenthrin, cypermethrin, cyfluthrin, etc.). Similar toxicity has also been documented in Texas urban areas.Substituting Pesticides Also Causes Biodiversity Problems
Since some in this thread mentioned pesticide phase outs, it is important to recognize that the likely substitute for pyrethroids is fipronil, which is already seeing growing use in California--and is beginning to appear in surface water at levels close to those known to be toxic to sensitive aquatic organisms. It is becoming clear that simply changing pesticides isn't going to solve these water quality problems.
Professional Insecticide Applicators Are the Link
Substantial effort is underway in California to identify the sources of pesticide-related urban surface water toxicity. Available data show a direct link to outdoor, above-ground insecticide applications by professional applicators.
Ants Are the Most Common Insect Problem in California
In California, ants are the most common insect problem and it is a common practice (particularly among commercial property owners and multi-family residential property managers) to retain a professional applicator to spray a band of insecticides around structures every 1-2 months. Much of the treated area around structures is impervious surface, some of which is directly connected to storm drains (DCIA).
Pre-construction termiticide and Post-construction Pyrethroids
Other possible sources include pre-construction termiticide ground surface treatments (if a rain event occurs before building foundations are poured), and both professional and non-professional applications in other outdoor locations (applications to lawns/landscaping have not been ruled out as potentially meaningful contributors to toxicity).
Underground injection of pyrethroids (i.e., for post-construction termite control) is unlikely to contribute to surface water toxicity. Most California municipalities are served by separate storm drain systems comprised completely of hard surfaces (i.e., no vegetated channels)--thus pesticides in runoff are efficiently delivered to urban creeks.
Greatest Water Pollution Problem: Insecticides vs Herbicides
There is a long-time myth that homeowner lawn/garden applications of pesticides (particularly herbicides) are a big problem. Maybe they are in some locations, but available scientific data strongly suggest that insecticides--not herbicides--are of greatest concern in urban areas and that (at least in California) professional pesticide applications--and intentional applications of pesticides to impervious surfaces--should be the priorities for stormwater quality management.
Urban Pesticides Pollution Prevention Project (UP3 Project)
With grant funding from the California State Water Resources Control Board, the Urban Pesticides Pollution Prevention Project (UP3 Project) is working with U.S. EPA, California EPA, municipalities, and other stakeholders to understand and prevent pesticide-related surface water pollution. Pesticide regulators and pesticide manufacturers are aware of these problems and are working to change their systems to address them. For more information (and reports that document the statements above), please see www.up3project.org.
Kelly Moran, Ph.D.
P.S. Wastewater treatment plants are not immune to pesticide-related problems. Discharges of certain pesticides (including biocides) to municipal wastewater treatment plants have been problematic, in some instances, for compliance with NPDES permit effluent limitations and operation of biological treatment processes.