Sub-sewershed Monitoring to Elucidate Down-the-Drain Pesticide Sources.

Pesticides have been reported in treated wastewater effluent at concentrations that exceed aquatic toxicity thresholds, indicating that treatment may be insufficient to adequately address potential pesticide impacts on aquatic life. Gaining a better understanding of the relative contribution from specific use patterns, transport pathways, and flow characteristics is an essential first step to informing source control measures. The results of this study are the first of their kind, reporting pesticide concentrations at sub-sewershed sites within a single sewer catchment to provide information on the relative contribution from various urban sources. Seven monitoring events were collected from influent, effluent, and seven sub-sewershed sites to capture seasonal variability. In addition, samples were collected from sites with the potential for relatively large mass fluxes of pesticides (pet grooming operations, pest control operators, and laundromats). Fipronil and imidacloprid were detected in most samples (>70%). Pyrethroids were detected in >50% of all influent and lateral samples. There were significant removals of pyrethroids from the aqueous process stream within the facility to below reporting limits. Imidacloprid and fiproles were the only pesticides that were detected above reporting limits in effluent, highlighting the importance of source identification and control for the more hydrophilic compounds. Single source monitoring revealed large contributions of fipronil, imidacloprid, and permethrin originating from a pet groomer, with elevated levels of cypermethrin at a commercial laundry location. The results provide important information needed to prioritize future monitoring efforts, calibrate down-the-drain models, and identify potential mitigation strategies at the site of pesticide use to prevent introduction to sewersheds.

Wash-off potential of pyrethroids after use of total release fogger products.

Pyrethroids are frequently detected in urban wastewater. Even though treatment facilities remove most pyrethroids (> 90 %) in wastewater, residual concentrations can exceed thresholds that are acutely toxic to sensitive aquatic species. Total release foggers (also known as "bug bombs") are widely used by the general public for insect control. It was hypothesized that these products serve as a source of pyrethroids entering the urban wastewater through the deposition of the active ingredients on various surfaces and subsequent transfer from the contaminated surfaces to the waste stream through cleaning activities. Based on experiments conducted in an enclosure, we found that substantial amounts of a pyrethroid (i.e., cypermethrin) were deposited on various surfaces after a total release fogger use. A series of experiments simulating scenarios that would be representative of common residential cleaning activities indicated that the pyrethroid could be transferred from the contaminated surfaces to other adsorptive materials via physical contact (with or without water as a solvent). The pyrethroid was readily extracted from the adsorptive materials (cotton fabric and filter paper) when water was used as a solvent. Adding a small amount of detergent to the water significantly increased the extraction efficiency compared to water alone. These results indicate that insecticides used in total release foggers can contribute to insecticide loading into the wastewater treatment system via several possible routes, such as contact with or cleaning of exposed surfaces and washing contaminated clothing after their use within a structure.

Assessing pesticide uses with potentials for down-the-drain transport to wastewater in California.

Pesticides and degradates are ubiquitously detected in municipal wastewater influent in the United States. However, little detailed information exists on their sources. The aim of this study is to investigate California Pesticide Use Report (PUR) and sales data to identify pesticide uses with a high potential for indoor down-the-drain (DtD) transport. The DtD transport of pesticides could result from direct applications to drains and sewers or through indirect activities such as washing pets, treated textiles, laundries, and cleaning surfaces treated with pesticides. An initial screening on pesticide products registered in California with DtD potentials showed that fipronil, imidacloprid, and seven pyrethroids were pesticides of concern due to the relatively high sales in DtD use patterns and high toxicity to aquatic organisms; and thus prioritized for additional evaluation. Uses and sales data of products containing the selected pesticides were analyzed for mass of active ingredient applied with specific DtD pathways and by different user groups. Professional uses were retrieved from the PUR and consumer uses were estimated by comparing PUR data to sales data. Overall, approximately 38,615 kg fipronil, 44,561 kg imidacloprid, and 240,550 kg pyrethroids were used annually in California from 2011 to 2015 with some likelihoods of DtD transport. The shares of professional use ranged from 56% (cypermethrin) to 98% (cyfluthrin), depending on the pesticide, with the majority of the mass applied in and around structures and for some pesticides (imidacloprid and permethrin) on landscapes as well. The remaining mass was applied by consumers on various DtD sources, including pet treatments (fipronil, imidacloprid, and permethrin), treated textiles (permethrin), indoor-only uses (cypermethrin), and mixed indoor/outdoor or outdoor-only applications (other pyrethroids). Results from this study help elucidate the relative significance of specific DtD pathways and pesticide occurrence in California waste streams.

An evaluation of temporal and spatial trends of pyrethroid concentrations in California surface waters.

Pyrethroid insecticides are frequently detected in urban surface waters at levels that are deleterious to sensitive aquatic species. The California Department of Pesticide Regulation (CDPR) Surface Water Protection Program collected 717 water and 191 sediment samples from 2009 to 2018 throughout California, providing a large dataset to conduct spatial and temporal trend analysis of pyrethroid concentrations. The pyrethroid bifenthrin accounted for 72% of average sample concentrations, and a strong relationship between whole water bifenthrin concentrations and the observed toxicity to the test species Hyallela azteca was established. To help mitigate runoff concentrations, CDPR adopted regulations in 2012 intended to limit the mass of pyrethroids applied to structures by professional pest control operators. A statistical analysis of CDPR statewide monitoring data collected at storm drain outfall and receiving water sites was conducted to determine if any significant trends in pyrethroid concentrations exist. Nonparametric statistical analysis of monitoring data revealed significant regional differences. In Northern California, decreasing trends in bifenthrin and cypermethrin concentrations may be counterbalanced by a potential switch to deltamethrin-containing products. Conversely, the few observed trends in concentrations at Southern California monitoring stations could be a result of regional hydrological and pest pressure differences. To evaluate the effects of structural applications on pyrethroid concentrations in urban runoff, CDPR conducted field trials using a tracer pyrethroid that was applied in accordance with the regulations. Detectable levels in runoff were observed, with an estimated 0.004-0.005% mass transport offsite per storm. Using field-derived sediment, the observed half-lives (514 days+) highlight the potential for contaminant laden sediment to serve as a long-term source of pyrethroids within waterways. Both chemistry and observed toxicity data identify storm water runoff as a primary transport mechanism. However, the presence of pyrethroids in dry-weather runoff suggests that significant loading can occur under various hydrologic conditions.

Fipronil washoff to municipal wastewater from dogs treated with spot-on products.

Fipronil and fipronil degradates have been reported in treated wastewater effluent at concentrations that exceed USEPA Aquatic Life Benchmarks, posing a potential risk to the surface waters to which they discharge. Fipronil is a common insecticide found in spot-on flea and tick treatment products that have the potential for down-the-drain transport and direct washoff into surface water. Volunteers currently treating their dogs with a fipronil-containing spot-on product were recruited. Dogs were washed either 2, 7, or 28days after product application, and rinsate from 34 discrete bathing events were analyzed by LC-MS/MS for fipronil and fipronil degradates (collectively known as fiproles). Total fipronil application dosage ranged from 67.1-410.0mg per dog following manufacturers' recommendation based on dog body weight. Total mass of fiproles measured in rinsate ranged from 3.6-230.6mg per dog (0.2 ̶ 86.0% of mass applied). Average percentage of fiproles detected in rinsate generally decreased with increasing time from initial application: 21±22, 16±13, and 4±5% respectively for 2, 7, and 28days post application. Fipronil was the dominant fiprole, >63% of total fiproles for all samples and >92% of total fiproles in 2 and 7day samples. Results confirm a direct pathway of pesticides to municipal wastewater through the use of spot-on products on dogs and subsequent bathing by either professional groomers or by pet owners in the home. Comparisons of mass loading calculated using California sales data and recent wastewater monitoring results suggest fipronil-containing spot-on products are a potentially important source of fipronil to wastewater treatment systems in California. This study highlights the potential for other active ingredients (i.e., bifenthrin, permethrin, etofenprox, imidacloprid) contained in spot-on and other pet products (i.e., shampoos, sprays) to enter wastewater catchments through bathing activities, posing a potential risk to the aquatic organisms downstream of wastewater discharge.

An integrated vegetated ditch system reduces chlorpyrifos loading in agricultural runoff.

Agricultural runoff containing toxic concentrations of the organophosphate pesticide chlorpyrifos has led to impaired water body listings and total maximum daily load restrictions in California's central coast watersheds. Chlorpyrifos use is now tightly regulated by the Central Coast Regional Water Quality Control Board. This study evaluated treatments designed to reduce chlorpyrifos in agricultural runoff. Initial trials evaluated the efficacy of 3 different drainage ditch installations individually: compost filters, granulated activated carbon (GAC) filters, and native grasses in a vegetated ditch. Treatments were compared to bare ditch controls, and experiments were conducted with simulated runoff spiked with chlorpyrifos at a 1.9 L/s flow rate. Chlorpyrifos concentrations and toxicity to Ceriodaphnia dubia were measured at the input and output of the system. Input concentrations of chlorpyrifos ranged from 858 ng/L to 2840 ng/L. Carbon filters and vegetation provided the greatest load reduction of chlorpyrifos (99% and 90%, respectively). Toxicity was completely removed in only one of the carbon filter trials. A second set of trials evaluated an integrated approach combining all 3 treatments. Three trials were conducted each at 3.2 L/s and 6.3 L/s flow rates at input concentrations ranging from 282 ng/L to 973 ng/L. Chlorpyrifos loadings were reduced by an average of 98% at the low flow rate and 94% at the high flow rate. Final chlorpyrifos concentrations ranged from nondetect (<50 ng/L) to 82 ng/L. Toxicity to C. dubia was eliminated in 3 of 6 integrated trials. Modeling of the ditch and its components informed design alterations that are intended to eventually remove up to 100% of pesticides and sediment. Future work includes investigating the adsorption capacity of GAC, costs associated with GAC disposal, and real-world field trials to further reduce model uncertainties and confirm design optimization. Trials with more water-soluble pesticides such as neonicotinoids are also recommended. Integr Environ Assess Manag 2017;13:423-430. © 2016 SETAC.

The Effects of the Landguard™ A900 Enzyme on the Macroinvertebrate Community in the Salinas River, California, United States of America.

Agricultural use of organophosphate pesticides are responsible for surface water toxicity in California and has led to a number of impaired water body listings under section 303(d) of the Clean Water Act. Integrated passive-treatment systems can reduce pesticide loading in row crop runoff, but they are only partially effective for the more soluble organophosphates. The Landguard™ enzyme has been effectively proven as an on-farm management practice for the removal of chlorpyrifos and diazinon in furrow runoff, but it has not been used in larger-scale treatment because of concerns regarding the potential impact on in-stream macroinvertebrates after chronic use. A first-order agricultural creek was treated with the Landguard enzyme for 30 days approximately 450 m upstream of its intersection with the Salinas River. Toxicity and pesticide chemistry were measured in the creek during treatment as well as in the river both upstream and downstream of the creek input before and after treatment. Benthic macroinvertebrates were also surveyed in the river before and after enzyme treatment. Low concentrations of organophosphate pesticides were detected in the creek, but Landguard removed detected concentrations of chlorpyrifos. Toxicity detected in the creek was likely caused by pyrethroid pesticides, and no toxicity was detected in river samples. There were no differences in habitat or macroinvertebrate assemblages between upstream and downstream samples or between pre- and post-treatment samples. These results indicate that chronic treatment of the creek with Landguard enzyme had no impact on macroinvertebrate community structure in the river.

Monitoring Fipronil and Degradates in California Surface Waters, 2008-2013.

The phenylpyrazole insecticide fipronil has become a popular replacement pest management tool as organophosphorus insecticides have been phased out for residential use and pyrethroids have come under scrutiny as a surface water contaminant. There has been an increasing concern of offsite transport of fipronil to surrounding surface waters and a corresponding increase in potential toxicity to aquatic organisms. The California Department of Pesticide Regulation Environmental Monitoring Program has collected over 500 urban surface water samples throughout California since 2008 to determine the presence and concentrations of fipronil and five degradate products. Statewide, fipronil was detected at high frequency (49%), as were the sulfone (43%) and desulfinyl (33%) degradates. Data collected at long-term monitoring stations indicate higher concentrations in southern California, corresponding to a higher use pattern in the region. There is a clear pattern of increased transport of fipronil with higher flow associated with rain events. However, the lack of seasonality effects on degradates' concentrations suggest a constant source of fipronil with a corresponding lag time of transport to surface waters during the dry season. Receiving waters had a diluting effect on concentrations; however, a significant proportion (46%) of receiving water samples had associated fipronil concentrations above USEPA aquatic life chronic benchmark values. Total mass loading estimates from a long-term monitoring site suggest that the annual fipronil loading is greater in the dry season than during storm events. This could have implications for future mitigation efforts because most runoff during this period was generated from irrigation and outdoor residential use.

Pesticide occurrence and aquatic benchmark exceedances in urban surface waters and sediments in three urban areas of California, USA, 2008-2011.

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.

Removal mechanisms and fate of insecticides in constructed wetlands.

Constructed wetlands (CWs), along with other vegetative systems, are increasingly being promoted as a mitigation practice to treat non-point source runoff to reduce contaminants such as pesticides. However, studies so far have mostly focused on demonstrating contaminant removal efficiency. In this study, using two operational CWs located in the Central Valley of California, we explored the mechanisms underlying the removal of pyrethroids and chlorpyrifos from agricultural runoff water, and further evaluated the likelihood for the retained pesticides to accumulate within the CWs over time. In the runoff water passing through the CWs, pyrethroids were associated overwhelmingly with suspended solids >0.7 µm, and the sorbed fraction accounted for 38-100% of the total concentrations. The derived K(d) values for the suspended solids were in the order of 10(4)-10(5), substantially greater than those reported for bulk soils and sediments. Distribution of pyrethroids in the wetland sediments was found to mimic organic carbon distribution, and was enriched in large particles that were partially decomposed plant materials, and clay-size particles (<2 µm). Retention of suspended particles, especially the very large particles (>250 µm) and the very fine particles, is thus essential in removing pyrethroids and chlorpyrifos in CWs. Under flooded and anaerobic conditions, most pyrethroids and chlorpyrifos showed moderate persistence, with DT(50) values between 106-353 d. However, the retained pyrethroids were very stable in dry and aerobic sediments between irrigation seasons, suggesting a possibility for accumulation over time. Therefore, the long-term ecological risks of CWs should be further understood before their wide adoption.

Zaleplon (Sonata) analysis in postmortem specimens by gas chromatography-electron capture detection.

Zaleplon (Sonata) is a sedative hypnotic prescription medication used for the short-term treatment of insomnia. Although Zaleplon was approved by the FDA in 1999, there has been limited postmortem information about the drug cited in the toxicology literature. Zaleplon was separated from postmortem biological specimens utilizing liquid-liquid extraction coupled with a solid-phase extraction technique, and detection was accomplished by a gas chromatography-electron capture detector. The method was linear from 5.0 to 150 ng/mL with the limit of quantitation and detection determined to be 3.0 and 0.50 ng/mL, respectively. The postmortem tissue distribution of zaleplon in seven cases was as follows: 6.1-1490 ng/mL central blood (seven cases), < 3.0-503 ng/mL femoral blood (five cases), 108 ng/mL harvest blood (one case), 343-679 ng/g liver (four cases), 950 ng/g spleen (one case), < 3.0-85 ng/mL bile (three cases), 3.8-106 ng/mL urine (four cases), < 3.0-486 ng/mL vitreous humor (five cases), and 0.005-3.4 mg total gastric contents (four cases). A validated method for the analysis of zaleplon and postmortem concentrations of autopsy specimens are reported to aid the forensic toxicologist with interpretation of future casework.

Efficacy of constructed wetlands in pesticide removal from tailwaters in the Central Valley, California.

Pollutants in agricultural irrigation return flow (tailwater) constitute a significant nonpoint source of pollution in intensive agricultural regions such as the Central Valley of California. Constructed wetlands (CWs) represent a feasible mitigation option to remove pollutants including pesticides in the tailwater. In this study, we evaluated two CWs in the Central Valley for their performance in removing pyrethroid and organophosphate insecticides under field-scale production conditions. Both CWs were found to be highly effective in reducing pyrethroid concentrations in the tailwater, with season-average concentration reductions ranging from 52 to 94%. The wetlands also reduced the flow volume by 68-87%, through percolation and evapotranspiration. When both concentration and volume reductions were considered, the season-average removal of pyrethroids ranged from 95 to 100%. The primary mechanism for pyrethroid removal was through sedimentation of pesticide-laden particles, which was influenced by hydraulic residence time and vegetation density. Temporal analysis indicates a potential efficiency threshold during high flow periods. The season-average removal of chlorpyrifos ranged 52-61%. The wetlands, however, were less effective at removing diazinon, likely due to its limited sorption to sediment particles. Analysis of pesticide partitioning showed that pyrethroids were enriched on suspended particles in the tailwater. Monitoring of pesticide association with suspended solids and bed sediments suggested an increased affinity of pyrethroids for lighter particles with the potential to move further downstream before subject to sedimentation. Results from this study show that flow-through CWs, when properly designed, are an effective practice for mitigating hydrophobic pesticides in the irrigation tailwater.

Enantioselective degradation and chiral stability of pyrethroids in soil and sediment.

Synthetic pyrethroids contain two or three chiral centers, making them a family of chiral pesticides with a large number of stereoisomers. Recent studies showed significant differences in aquatic toxicity between enantiomers from the same diastereomers of pyrethroids. To better understand the ecotoxicological effect and fate of pyrethroid insecticides, chirality in biodegradation must also be considered. In this study, we examined enantiomer compositions of selected pyrethroids in field sediment samples taken from various locations in southern California. Enantioselective degradation was frequently observed for cis-bifenthrin, permethrin, and cyfluthrin under field conditions. We further conducted long incubation experiments under laboratory-controlled conditions using single enantiomers of cis-bifenthrin, cis-permethrin, and cypermethrin. The half-lives for individual enantiomers were calculated to be 277-770 days for cis-bifenthrin enantiomers, 99-141 days for cis-permethrin enantiomers, and 52-135 days for cypermethrin enantiomers, respectively. The direction and degree of enantioselectivity in degradation were found to closely depend on the specific compound as well as experimental conditions. Because no significant difference in degradation was observed after samples were sterilized, the observed enantioselectivity may be attributed to preferential biological transformations.