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= Washington State Ambient Surface Water Monitoring Program For Pesticides in Salmon-Bearing Streams =

Introduction
The Washington State Department of Agriculture (WSDA) and Washington State Department of Ecology collaborate to monitor pesticides from surface water runoff that enter salmon rearing streams. Every three years the departments co-publish a report which provides information on pesticide exposure in several watershed basins throughout Washington State. Salmon rearing streams are a focus because the fish serve a substantial role in both the culture and economy of Washington State. Millions of dollars are spent yearly to restore the salmonid populations, therefore it is critical that these species are protected against environmental exposures to the various pesticides. Furthermore the Federal Insecticide, Fungicide, and Rodenticide Act allocates the regulatory authority for pesticide use and sale, to the Washington State Department of Agriculture. The Endangered Species Act, Washington State Pesticide Control Act, and Washington State Pesticide Application Act, demand the continual monitoring of pesticide within waterways that could adversely affect humans and/or ESA listed species. Funding for the program is provided by both the EPA and the Washington State Legislature. The findings from the Surface Water Monitoring program influence the regulation setting process as researchers try to minimize both salmonid exposure to pesticides and the economic loss from agricultural restrictions.

Along with providing information on the abundance of certain pesticides, the program provides insight into the fate and transport of the pesticides throughout water basins. Since the implementation of the Surface Water Monitoring program in 2003 various water sub-basins have been added and/or removed from the program. All the studied sub-basins are located in the Washington State and historically supported pacific salmon which are currently struggling to meet their recovery goals. The sub-basins are meant to be representative of a variety of land uses such as, urbanization, irrigation based agriculture, or residential landscapes. Since four of the five pacific salmon in Washington spend at least one year in freshwater streams, to best enhance their recovery the exposure to pesticides and their metabolites must not reach concentrations that may induce acute or chronic toxic effects. Additional research is done to check for effects in other aquatic organisms that may be directly affected by pesticides at exposure levels that have no observable effects on salmon, yet can result in changes to trophic structures or resource availability causing indirect effects on salmon.

Methods
The Ambient Surface Water Monitoring Program for Pesticides in Salmon-Bearing Streams is designed to track when and where pesticides are being exposed to salmon, as a result of residential and agricultural pesticide application. The information published in the program helps the EPA, and the U.S. Fish and Wildlife Service gain insight into how to best manage threatened and endangered aquatic species that are exposed to registered pesticides. Furthermore the WSDA use findings in the triennial reports to refine pesticide labels, and change regulations to uphold the water quality criteria outlined in FIFRA, and Washington Pesticide Control Act (Chap. 15.58 RCW).[3] The goal of the WSDA is to keep pesticide concentrations in surface water to at least half of the lowest reference value for acute or chronic toxicity to fish or invertebrates in freshwater. This is done to be protective of all the species living in salmon-rearing streams and uphold the water criteria outlined in the Washington State water quality standards and FIFRA. In order to monitor for possible adverse effects from to exposure to pesticides, the detected concentrations of each pesticide within a samples are compared to the reference values approved by the EPA and Washington State Pesticide Control Act to estimate whether a adverse effect is occurring to a organism as a result of current pesticide regulations and use. All the reports are readily available to the public to provide information on the present levels of pesticides in their waterways and application techniques that protect the water quality.

Assessment Criteria
For the purposes of this program, "Assessment Criteria" includes data taken from studies determining hazards to non- target organisms and refer to acute and chronic hazard levels for fish, invertebrates, and aquatic plants. Marine and freshwater toxicity guidelines are reviewed using Environmental Fate and Effects Division (EFED) risk assessments, which include Pesticide Effects Determinations, Reregistration Eligibility Decisions, and ecological risk assessments to determine the most comparable and up-to-date toxicity guidelines. If a laboratory study meets guidelines appropriate for inclusion in pesticide registration eligibility decision, the EPA can classify it as "core". A core designation may be made if the study is appropriately designed, monitored, and conditions controlled, and duration of exposure is consistent with other studies.

Field and Laboratory procedures
The data was compiled through weekly water grab samples at each of the designated sites throughout the typical pesticide application season (March-August). Field procedures follow "Ecology's Standard Operating Procedure for Sampling of Pesticides in Surface Water" for collection of one liter water samples, the program also uses a variety of field meters for conventional water parameters that are placed at one site for the entire sampling period. Following standardized data collection methods allows for other sources to use data and increases the consistency in sampling results. The one liter water samples measure conventional water quality parameters (pH, conductivity, Dissolved Oxygen, temperature, total suspended solids) along with active ingredients and metabolites which as of 2015 was up to 209. The list of chemicals monitored is constantly changing as new chemicals are found in data collection process each year. Laboratory analysis of water grab samples is conducted by the WSDA following EPA method SW 846. After performing Solid-Phase Extraction the samples undergo Gas-chromatography, Mass-spectroscopy and/or Liquid Chromatography in order to extract and separate all the chemicals within the samples. Throughout the years of processing grab water samples the department of agriculture has improved the detection methods for various pesticides in aquatic environments.

Assessment of Pesticide Mixtures
The program records when mixtures of pesticides are detected as this can influence the exposure and effect that a chemical has on a organism. When a mixture is detected, the sample has its Toxic Units (TU) calculated to analyze whether a mixture is likely to produce a additive, synergistic or antagonistic effect on a specific organism. If the Toxic Units exceed one (TU$$\geq$$1) expect to see sub-lethal or lethal effects occurring, and increasing likelihood as TU increases. The program has detected mixtures in many sub-basins around the state with TU ≥1 for both fish and invertebrate. In 2015 there was 21 sampling events where invertebrates were exposed to a mixture of pesticides that had a synergistic effect at concentrations higher than the No Observable Adverse Effect Concentration (NOEAC). However the current assessment criteria does not account for the effects that mixtures of chemicals may have on organisms and mixture data is not used in regulation setting by the WSDA. By continually monitoring mixture detections, the program provides information on the abundance of likely untested pesticide mixtures and whether the salmon species are being exposed to these potentially more toxic mixtures.

Assessing Possible Effect(s)
To determine whether a potential effect is occurring collected data is evaluated against pesticide toxicity criteria from registration of that pesticide under FIFRA or other sources. The sources of the references values must come from either, FIFRA, the Clean Water Act, Water Quality Standards for Surface Waters of the State of Washington or data from the Requirements for Pesticide Registration. therefore are can be relied upon for predicting risk and potential effects. WSDA attempts to be protective of all organisms living in the salmon-rearing streams for that reason the reference values endpoints are the lowest LC50 or EC50 for freshwater/marine/estuarine fish, or invertebrates and the No Observable Adverse Effect Concentration (NAOEC) from a early or full stage life cycle test for a freshwater invertebrate or fish. When field recorded surface water pesticide concentrations exceed the reference values for either acute or chronic toxicity to either the fish or invertebrates and can be directly linked to adversely affect ESA listed salmon, the WSDA is granted authority to restrict the use of a pesticide or require a change in labels. If a pesticide is measured in any sample at a concentration exceeding the reference value for safe surface water criteria it is classified as a Pesticide Of Concern (POC) and the WSDA will require new labeling and provide information risk associated with that pesticide contamination in surface or ground water. Chemicals classified as POC also face new regulations in application or sale of the pesticide.

Current Use Pesticides
The report listed the following pesticides as “current use pesticides” in the state of Washington: azoxystrobin, bifenthrin, captan, chlorpyrifos, malathion, metolachlor, pyridaben, and sulfometuron-methyl. All seven pesticides are currently classified as Pesticides of Concern (POC). A Pesticide of Concern is a pesticide of interest that shows potential to contaminate surface water or groundwater, or otherwise impact the environment. When a Pesticide of Concern is determined, additional analysis by the WSDA is triggered. Each of these pesticides have a Mode of Action that fall into the following categories.

Acetylcholinesterase Inhibitors and Nervous System Disruptors
Chlorpyrifos is an acetylcholinesterase neurotransmitter inhibitor and nerve agent that

Malathion’s mechanism of action is acetylcholinesterase inhibition

Bifenthrin blocks the voltage-gated sodium channels in the cell's plasma membrane and interferes with the nervous system

Azoxystrobin interferes with mitochondrial production in the Electron Transport Chain

Enzyme Inhibitors
Pyridaben is a mitochondrial NADH:ubiquinone reductase inhibitor.

Sulfometuron-Methyl is an acetolactate synthase enzyme inhibitor

Potential Carcinogens
Captan is a potential carcinogen that causes cytotoxicity and regenerative cell hyperplasia

Additional Chemical Information
The intended pest, method and time of application, solubility in water, log Kow, effects in salmon, and effects in humans are all summarized in the table below for the seven current-use pesticides.

Results
In 2015 alone, 80 different pesticides and pesticide analytes contributed to 1,663 detection events across 14 sampling sites. Comparatively, 2014 had only 1,151 detections of 61 individual pesticides across 15 sites. Pesticides were sorted by type and ordered by number of detections. Detection levels were then compared against preset assessment criteria to determine exceedances.

Below is a table of detected pesticides and their analytes from 2015 sorted by class and number of detections across all monitoring sites.

Herbicide Detections
For 2015, Herbicides were the most commonly detected pesticides making up 51% of the detections. 38 out of the 74 total herbicide detections were found in surface water with Diuron, 2,4-D, and Dichlobenil being the most prevalent. These three herbicides were also the top three detections for 2014. Only two herbicides, Metolachlor and sulfometuron methyl exceeded the assessment criteria.

Fungicide Detections
With 413 detections, fungicides were the second most detected pesticide at 25% of total detections. In 2014, fungicide only made up 8.3% of all detections, and was the third most detected pesticide. Only two fungicides exceeded the assessment criteria; Captan and azoxystrobin.

Insecticide Detections
Insecticides accounted for 16% of total detections in 2015. Out of the 79 insecticides analysed for, 19 were detected in surface water including the legacy pesticide, 4,4'- DDT.

Degradate Detections
6% of total detections were of degradates for a total of 95 detections. Notably, the degradates that exceeded the assessment criteria were 4,4'-DDE and 4,4'-DDD. Both of these are degradates of the legacy pesticide 4,4'-DDT.

Other Detections
WSDA also tested for glyphosate, glufosinate, and aminomethylphosphonic acid, a metabolite of glyphosate. In addition to this, the wood preservative pentachlorophenol, the insect repellent N,N-Diethyl-m-toluamide, and the pesticide synergist piperonyl butoxide were all included in detection numbers.

Exceedance Conclusions
In 2015, both detections and pesticides that exceeded assessment criteria levels increased. In 2014, only 48 exceedances were recorded in 1,151 detections. In 2015, the number of exceedances increased by 60% to 76 as the total number of detections increased by 40% to 1,663. These increases are attributed to the addition of more laboratory analytes, a strong trend of regional drought, and a reduction in the levels that constitute an exceedance by a factor of one and a half.

Azoxystrobin, bifenthrin, captan, chlorpyrifos, malathion, metolachlor, pyridaben, and sulfometuron-methyl accounted for a third of all exceedances with the other two thirds represented by DDT and its degradates. These seven pesticides are now considered Pesticides of Concern (POC). Pesticides are designated POCs when they exceed assessment criteria at least once within a three year time period. This designation helps to identify chemicals of importance and target reduction efforts. As well as being labelled POCs, chlorpyrifos and malathion are being considered under the Federal Endangered Species Act and are under evaluation by the EPA.

Conclusions and Future Insights
The Ambient Surface Water Monitoring Program for Pesticides in Salmon-Rearing Streams publishes a triennial report of the current levels of pesticide contamination in various salmon supporting sub-basins throughout Washington state. The program examines pesticides exposure to salmon from agricultural and residential practices. Many of the pesticides travel through the ground or surface water before reaching the salmon bearing streams. As of 2019 eleven major wild salmon populations in Washington are listed as endangered or threatened and face a serious risk of extinction. The recovery of diminished salmon stocks is critical due to the fact that in 2011 returning salmon provided jobs for over 28,000 people and resulted in a 2.4 billion dollar market for sport and commercial fishermen[4]. The First Nation s people of Washington State have legal rights to half of the annual salmon catch as a result of the Treaty of Point Elliot and depend on the salmon for income along with cultural traditions.[5] Due to having so many groups dependent on the recovery of ESA listed wild salmon stocks the WSDA must regulated the use of potentially harmful pesticides so that it can uphold the water quality criteria outlined by FIFRA and the Washington state water quality standards. The program provides the WSDA with a collection of data that describes the abundance and timing at which pesticides are entering the waterways, that is used to estimate the risk facing salmon. The WSDA will introduce new restrictions or the use or sale of pesticides in Washington if the estimated risk of current regulations is too potentially damaging to the salmon recovery goals. Although recommendations of each report change with every iteration, including the addition or removal of pesticides to their list of Pesticides of Concern, one common trend in their recommendations is the continuation and improvement of testing for future studies. As climate change continues to worsen in the coming years, increased temperature, droughts, floods, and other extreme weather events will impact the distribution of pesticides in new and unexpected ways, making the continued production of this program increasingly important.