STATE OF THE ESTUARY: An overview of Department of Pesticide Regulation’s Surface Water Protection Program

Department of Pesticide Regulation staff sample an urban waterway for pesticides.
Dr. Jennifer Teerlink discusses pesticide regulation, monitoring, assessments, and outreach efforts

The mission of the California Department of Pesticide Regulation’s Surface Water Protection Program is to protect surface water from pesticide contamination caused by the use of pesticides in agricultural and urban environments.  To achieve its mission, the program evaluates pesticide products, monitors surface water and sediment for pesticides, evaluates the effectiveness of best management practices to mitigate the offsite movement of pesticides, performs outreach to pesticide users to implement best management practices, and implements regulatory measures.

Dr. Jennifer Teerlink is a supervisor in the Surface Water Protection Program at the Department of Pesticide Regulation, and in this presentation from the 2019 State of the Estuary conference, she discussed the main components of the Surface Water Protection Program.

The Department of Pesticide Regulation has 15 full-time scientists and five scientific aides.  The scientists have a wide range of expertise, including ecotoxicologists, modelers, local chemists, statisticians, and ecologists which helps them take a broad approach to the regulation of pesticides to protect surface water.

Since aquatic organisms are constantly in the water, the thresholds are frequently much, much lower for aquatic organisms versus humans, so aquatic organisms have been the Department’s main focus to date.  They also keep a broad view and consider the exposure of humans to pesticides through drinking water.

The flower-like graphic shows the different areas the Surface Water Protection Program works in; she would only be focusing on prevention, monitoring, and a few others.

One of the keys is the idea of coordination and collaboration,” said Dr. Teerlink.  “We can’t work in a vacuum, so it’s really important to know who is doing science in what area and make sure that the data gets to the right people.  We conduct a lot of our own research, but it’s also important that we understand other pesticide data that folks are collecting so it can inform management decisions when necessary.”

The State Water Resources Control Board and the regional boards operate under the Clean Water Act at the federal level and the Porter-Cologne Act at the state level.  At the Department of Pesticide Regulation, they operate under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) at the federal level and the Food and Ag code at the state level.

The difference here is that we regulate the sales and use of pesticides, so we aren’t going to tell a water discharger what level of a pesticide needs to be in their effluent; that is our partners at the state and regional water quality control boards,” said Dr. Teerlink.  “Our legal mandates are distinct but they are complementary and we continue to try and work closely with these partners to make sure that science dollars at the state are going as far as they possibly can.”

On the list of contaminants of concern in the San Francisco Bay, the pesticides fipronil and imidacloprid are of moderate concern.  The pyrethroid pesticides are of low concern in the San Francisco Bay but are a higher concern in urban creeks.

Pesticides in general are noted as being of possible concern.  Through regulation and other steps, they hope to keep pesticides in the possible concern category and that nothing launches into a higher tier of concern.  Dr. Teerlink also pointed out that while they are a state agency that regulates pesticides throughout the state, it is really important to understand regional concerns, so collaboration is important.


New pesticide products must first be registered with the federal government.  In order to be sold within the state of California, it must next be evaluated by the Department of Pesticide Regulation.  The Surface Water Protection Program evaluates the products that are of higher risk to surface water.

Many different products are considered pesticides, including bleach and fungicides.  The burden of proof during the registration process lies with the registrant, so it’s important that they ask the right questions, Dr. Teerlink said.

During the registration process, we can ask for additional studies or additional information to ensure that we’re comfortable that that product will not cause harm to aquatic organisms in our waters,” she said.  “We’ve gotten better and better at that over the years and we’re always looking for ways to improve, so hopefully we’ll keep those pesticides that may be of concern and we’ll just deal with things that are already registered.”

The registration process includes scientific analysis using modeling tools when possible, by oftentimes due to the uniqueness of each product, they have to resort to scenarios and rely on expert judgement.

We look at the physical properties of those pesticides and try and predict the highest use possible, where they may end up in the environment and then condition their registration accordingly,” she said.  “We are constantly looking at this to make sure we’re asking the right questions to improve the process.”


There are four components to their monitoring program: Agricultural streams impacted by pesticide use, urban streams, wastewater, and copper in marinas.  In this presentation, Dr. Teerlink focused on urban streams and wastewater monitoring.

For monitoring, an analytical method needs to be in place in order to develop results.  They use a modeling tools to look at the use of pesticides and their relative toxicity to determine what they should monitor for.

We are really fortunate in this state to have really high resolution pesticide use data, so any pesticide that’s applied by a professional, we have records of when and where that’s applied, so we can predict where we think pesticide concentrations will be highest and what pesticides will be the largest concern,” she said.  “We also can be limited by our analytical tools, but we’re constantly working to improve those.  We’re a little bit more fortunate than some of the other contaminants of emerging concern, the pesticide manufacturers as part of developing those pesticides are already working on analytical methods.  That’s one of the things we review during registration to ensure that anything that’s used, we have a method to look for it in the environment.”

For urban monitoring, they have eleven monitoring sites in Northern California and fifteen in Southern California that they have been monitoring since about 2008.  Dr. Teerlink acknowledged it is by no means comprehensive.

Like any program, we have budgetary constraints, and so what we choose to do with those monitoring dollars is to select long-term sites that we think represent close to the worst case scenarios,” she said.  “So we look for really high use with the idea that if we have data that shows what’s happening in high use areas, we’re catching the worst case scenario.”

Once a regulation is put into place, it’s important to show that it’s being effective, so through consistent monitoring, they can show reduction over time.  They use modeling and pesticide use data to support what is monitored at each of the sites.

Urban monitoring

We look at storm drains or what’s directly coming off of neighborhoods, as well as the creeks and rivers that they flow into,” Dr. Teerlink said.  “We monitor everything in LA from concrete channels to more natural looking streams.”

They monitor in the summer and dry seasons when the runoff is mainly ‘urban drool’ – runoff from over irrigation, washing cars, etc.  They also look at storm events, trying to capture the ‘first flush’ or the large first runoff event which occurs in the fall.

She presented a chart showing data on fipronil and its many degradates from the Department’s urban monitoring sites, noting that many of the degredates have comparable toxicity to the parent.

The US EPA aquatic benchmark that we’ve used in this case is really low – 11 nanograms per liter, so essentially the take home message from this slide is that we’re seeing really high in both detection frequency and the exceedance of that benchmark of the parent as well as fipronil sulfone,” she said.  “This sort of story is important and helps prioritize what we do when we move out of monitoring and into assessment and mitigation.”

Wastewater monitoring

The Department of Pesticide Regulation partners with the Regional Monitoring Program, the San Francisco Estuary Institute, and others for wastewater monitoring.  One of their challenges is data; consistent data is needed to prioritize regulatory actions.  However, when it comes to pesticides in wastewater, there is inconsistent data, Dr. Teerlink said.

One issue is that there are limited spatial and temporal samples as most wastewater studies are focusing on one chemical and many plants or one plant and a number of chemicals.  The Department looked through data available from other wastewater treatment plants in the country, but there was not data with consistent locations or treatment type.  Sometimes there’s only effluent data, rather than both influent and effluent data.

There are variable detection limits, everything from 100 nannograms per liter down to subnanograms per liter. The issue also happens with the same chemical, so if a study is saying non-detectable but the detection limit is too high, that doesn’t really give good information, she said.  There is also limited data on degradates.  To address these issues, the Department of Pesticide Regulation has launched a permanent wastewater monitoring project with wastewater treatment plants across the state.

This is important because wastewater treatment plants are discharging 24 hours a day, 7 days a week, 365 days a year and a consistent source into water, so if there are chemicals of concern that are making the way into water that the treatment plant, it really has no ability to treat their way out of; that is the responsibility and role of regulators to work on source control to ensure that the aquatic organisms are not at risk,” said Dr. Teerlink.

The initial effort began this year with about 25 wastewater treatment plants participating; they are working on growing that number.  They have already completed two rounds of sampling for influent and effluent, with two remaining sampling events and a single biosolids event this fiscal year.

Our initial effort is to get an idea of consistent analytical techniques with what the concentrations are statewide instead of having these focus studies at specific plants,” she said.  “This data will help us prioritize what we need to do for products that make their way down the drain.”


The Department of Pesticide has a database called SURF that has pesticide data for both water and sediment.  The green dots on the map are the monitoring sites that are contained in the SURF database.  The SURF database includes pesticide monitoring data from other state agencies, federal agencies, and regional groups.  They’re approaching a million records for water and a hundred thousand records for sediment.

Dr. Teerlink acknowledged that the interchangeability of data between the Department’s SURF database and California Environmental Data Exchange Network (CEDEN) has been an issue but there’s now an effort at the State Water Board to populate CEDEN with DPR’s SURF database so it should be in both places with a bit of timelag.


Lastly, Dr. Teerlink turned to regulation and mitigation, noting that the reason they go together is that over the past few years, they’ve found that regulation isn’t necessarily the best approach.

She used fipronil to illustrate the point.  The old fipronil labels for residential applications by professionals or homeowners stated that the application could be a foot up and a foot out from the home and applied to the driveway and the garage.  It could be applied twice a year with no restrictions on what time of year it could be applied.  Monitoring was consistently finding concentrations that were of concern to aquatic organisms.

The Department could have gone straight to regulation; once a product is registered, it’s their responsibility to show that it is a specific threat.  However, in this case, did some research, including runoff trials and efficacy trials.  They tried a number of application scenarios and looked at the ant populations to determine if those applications were in fact efficacious.  They also looked at the percent of fipronil that was coming off of those homes.

We found that all of the treatments that we tried were efficacious for ant control,” she said.  “There was some variability but we basically used the runoff trials to propose what we wanted the label to look like.  We reached out to our partners, the professional pest control operators, so they would try this new application to make sure it was efficacious for their needs, and that basically means they don’t get callbacks.  They aren’t going to make money if they are constantly having to go back to a home.  And they had no change in the number of callbacks which was great.

With this information, they met with the registrants and presented a compelling case.  The manufacturers voluntarily worked to change the labels.  The new application instructions only allowed application 6” up and 6” out from the house, a lower concentration of pesticide, no application to the driveway, and no applications during rainy season.

They used modeling to predict that this would result in a 89% reduction in estimated concentrations.  “This has been in effect for a couple of years, but this month is the first month that the old labels can’t be sold and so we will need some more time to be sure that this has been efficacious and we’ll do that through our monitoring program,” she said.


The Department of Pesticide Regulation conducts a number of education and outreach programs, including in-person training that focuses on pesticide application.  They also coordinate with other agencies such as the state and regional water boards to ensure that the data that is collected as a part of permits is data that is useful to us and to also make sure that that data gets to them quickly.


Our goal is prevention so a lot of our efforts are focused there,” Dr. Teerlink said.  “We also strive for collaboration so we look to places where we can partner with other stakeholders, as well as have a transparent process so people know where our priorities are and can help us do our work wherever they see an opportunity for collaboration.”


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