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Sewage Treatment Removes Widely Used Home and Garden Insecticides From Wastewater

Released: 8/26/2013 7:00 AM EDT
Embargo expired: 9/12/2013 2:15 PM EDT
Source Newsroom: American Chemical Society (ACS)

Thursday, Sept. 12, 2013, 2:15 p.m. Eastern Time

Note to journalists: Please report that this research was presented at a meeting of the American Chemical Society.

A press conference on this topic will be held Wednesday, Sept. 11, at 9:30 a.m. in the ACS Press Center, Room 211, in the Indiana Convention Center. Reporters can attend in person or access live audio and video of the event and ask questions at

Sep. 13, 2013 - INDIANAPOLIS, Sept. 12, 2013 — Even though sewage treatment plants are not designed to remove tiny amounts of pesticides, they do an excellent job of dealing with the most widely used family of home and garden insecticides, scientists reported here today. Their study on pyrethroid insecticides — used in more than 3,500 products — was part of the 246th National Meeting & Exposition of the American Chemical Society (ACS), the world’s largest scientific society.

“We found that advanced sewage treatment reduced the levels of pyrethroids by more than 97 percent,” said Kurt N. Ohlinger, Ph.D., who presented the results of the study. “That’s a reduction to less than one part per trillion, and pretty impressive. Conventional treatment processes remove about 89 percent, something we knew from previous research. Based on these results, we do not expect the trace amounts of pyrethroids in sewage treatment plant effluent to be toxic to even the most sensitive aquatic life.”

Use of pyrethrins, derived from chrysanthemum flowers, and the related synthetic pyrethroids, has been on the increase during the last decade. They are replacing organophosphate pesticides, which are more acutely toxic to birds and mammals, with uses that include home insect control, insect-repellant clothing, dog and cat flea shampoos, mosquito control and agriculture.

The growing use led Ohlinger and colleagues to check on the effectiveness of advanced sewage treatment processes in removing pyrethroids from wastewater from a sewage treatment plant. They are with the Sacramento Regional County Sanitation District in California, which was implementing advanced sewage treatment. They knew that high levels of pyrethroids in treated water (which flows out of sewage facilities and into lakes and streams) could harm aquatic life.

“Although conventional wastewater treatment processes were not designed to remove trace pyrethroid residues, we found in an earlier study of our existing treatment processes that the treatment processes were quite effective at pyrethroid removal,” he explained. “We wanted to see if advanced treatment processes were even more effective. The results provide welcome reassurance.”

Ohlinger’s presentation was part of a symposium called “Assessing Potential Ecological and Human Health Effects from Fertilizer and Pesticide Use in Urban Environments.” Abstracts of other symposium presentations appear below. He acknowledged funding from the Pyrethroid Working Group.

The American Chemical Society is a nonprofit organization chartered by the U.S. Congress. With more than 163,000 members, ACS is the world’s largest scientific society and a global leader in providing access to chemistry-related research through its multiple databases, peer-reviewed journals and scientific conferences. Its main offices are in Washington, D.C., and Columbus, Ohio.

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Kurt N Ohlinger, Ph.D.
Sacramento Regional County Sanitation District
Sacramento, Calif. 95821
Phone: 916-278-4407


Potential influence of pyrethroids, metals, sediment characteristics, and water quality conditions on benthic communities in Cache Slough California in 2012
Lenwood Hall1,, William Killen1, Ronald Anderson1, Raymond Alden III2. (1) Wye Research and Education Center, University of Maryland, Queenstown, Maryland 21658, United States, (2) Northern Illinois University, DeKalb, Illinois 60115, United States

Tasks conducted at twelve sites in Cache Slough California during both spring and fall of 2012 were: (1) collect and identify benthic macroinvertebrates; (2) measure TOC, grain size, bulk metals, simultaneously extracted metals (SEM) and acid volatile sulfides (AVS), 8 pyrethroids and basic water quality parameters; and (3) use univariate and stepwise multiple regressions to determine the relationship between various benthic metrics and TOC, grain size, metals (bulk metals and SEM/AVS), and pyrethroids. A total of 54 different tolerant benthic taxa were collected from the twelve Cache Slough sites during the spring, and 43 different tolerant taxa were collected during the fall. The highest number of metals threshold effects levels (TEL) exceedances for the twelve sites with both seasons combined in descending order was: 24 for nickel; 21 for chromium; 19 for copper; 12 for arsenic; 6 for mercury; and 2 for cadmium. Sediment pyrethroid toxic units (TUs) for the sum of pyrethroids based on Hyalella were calculated. The sum of pyrethroid TUs was slightly greater than 1 (1.07 - 1.97) at four upstream sites sampled during the spring. However, for the fall sampling the sum of pyrethroid TUs was less than 0.5 at all twelve sites which suggests no toxicity due to pyrethroids. The benthic metrics % Collectors/Filterers & Collectors/Gatherers appeared to be directly related to arsenic in the sediments. The metric Abundance was also inversely related to TOC and % silt. Multivariate canonical correlation analysis showed that samples with sandier sediments tended to have benthic communities that were more diverse. No significant relationships were detected between the benthic principal components and the principal components associated with metals or pyrethroids. Results from this limited data set suggest that sediment characteristics are a more important factor than toxicant concentrations in the sediments for the benthic communities of Cache Slough.

Fate of pyrethroid pesticides through advanced wastewater treatment processes
Kurt N Ohlinger,, Sacramento Regional County Sanitation District, Sacramento, CA 95821, United States

Pyrethoid pesticides are known to enter wastewater collection systems and wastewater treatment plants through direct and indirect disposal. The fate of pyrethroids passing through conventional wastewater treatment processes is not well understood and has been the subject of a series of recent studies conducted at the Sacramento Regional Wastewater Treatment Plant (SRWTP). The SRWTP provides wastewater treatment services for the urbanized areas of Sacramento County, on average treating 145 mgd of wastewater. A study of pyrethroid treatability was conducted as part of a demonstration-scale study for selecting advanced treatment processes for the SRWTP. The studies provided a unique opportunity to evaluate the performance of several treatment process alternatives in removing pyrethroid pesticide residues. The advanced treatment processes studied included biological nutrient removal, membrane filtration, granular media filtration, ozonation followed by biologically-active media filtration, and three disinfection alternatives: chlorination, UV irradiation, and ozonation. Although conventional and advanced wastewater treatment processes were not designed to remove pyrethroid pesticide residues, the measured removals were significant. Treatment performance for all tested treatment processes and all pyrethroids will be presented.

Analysis of pyrethroid insecticides in complex environmental samples using stable isotope labeled standards as surrogates
Kevin Clark1,, Del A Koch2, Daniel M Tessier3, James C Markle4. (1) Morse Laboratories, Sacramento, California 95825, United States, (2) ABC Laboratories, Columbia, Missouri 65202, United States, (3) Stine-Haskell Research Center, DuPont Crop Protection, Newark, Delaware 19711, United States, (4) Coalition for Urban/Rural Environmental Stewardship, Davis, CA 95618, United States

Several synthetic pyrethroids have indoor, as well as lawn, garden, and external structural barrier uses. This broad range of use patterns may result in the presence of multiple pyrethroids in influent/effluent waters and biosolids from publicly-owned treatment works (POTWs). The presentation will describe an analytical approach to analyzing these complex matrices for eight representative pyrethroids, using the previously reported NCI-GC-MS instrumental analysis with D6 stable isotope analogues as internal standards. Due to significant variability in the composition of biosolids from different POTWs, adding known amounts of surrogate compounds to each sample prior to extraction and then measuring recoveries in order to demonstrate acceptable method performance is highly desirable. The presentation will further describe the use of two selected D6 analogues as surrogates that closely match the method behavior of the eight target analytes. Details of a recently-validated biosolids method now in routine use will be reported along with associated method performance and surrogate stable isotope analogue recovery data.

Pyrethroid pesticides in municipal wastewater: A baseline survey of publicly-owned treatment works facilities in California
James C Markle1,, Beverly H van Buuren2, Kelly Moran3, Aldos C Barefoot4. (1) Coalition for Urban/Rural Environmental Stewardship, Lincoln, California 95648, United States, (2) Van Buuren Consulting, LLC, Seattle, Washington 98107, United States, (3) TDC Environmental, San Mateo, CA 94403, United States, (4) Environmental Safety Assessment, DuPont Crop Protection, Newark, Delaware 19714, United States

In response to the 2006 California Department of Pesticide Regulation data re-evaluation, the Pyrethroid Working Group and Tri-TAC, representing publicly-owned treatment works (POTWs) developed a monitoring project for eight pyrethroid pesticides in influent, effluent, and biosolids. The project surveyed 32 POTWs between January and March 2013. At each location, samples of influent and effluent were collected as consecutive grab samples, and at sites that accommodated sampling of biosolids, this matrix was collected and composited. Two laboratories were used to analyze the biosolids samples as replicates and the effluent and influent samples as consecutive grabs (distinct samples). A pre-project intercomparison study was conducted to ensure sampling technique and comparability of the laboratories and methods. To maintain comparability with other pyrethroid pesticides data collected in the state of California, the project used the quality control criteria from the State of California's Surface Water Ambient Monitoring Program. Samples were analyzed using gas chromatography/mass spectrometry using a chemical ionization detector. Laboratory reporting limits ranged from 0.5 ng/L in the effluent to 80 ng/g in the biosolids. As predicted for a hydrophobic chemical, residues were greatest in the biosolids and lowest in the effluent. Of the eight pyrethroids monitored, permethrin was the dominant pyrethroid found followed by cypermethrin and bifenthrin.

Conducting ecological risk assessments for urban uses of pesticides
Mah T Shamim,, Jose Melendez, Keith Sappington, Mohammed Ruhman. Environmental Fate and Effects Division, US Environmental Protection Agency, Washington, DC 20460, United States

Recent studies have reported pesticides in toxicologically-significant concentrations in surface water, sediments, stormwater, and POTW influent/effluent wastewater from residential uses at several locations across the United States. The US EPA faces many challenges in assessing the ecological risks from indoor and outdoor residential pesticide uses. Pesticides released to domestic wastewater from indoor residential uses are being assessed with the Exposure and Fate Assessment Screening Tool (E-FAST). Bench-scale treatability studies and POTW monitoring data will be used to refine exposure estimates of pesticides in wastewater, surface water, and biosolids resulting from indoor uses. It remains difficult to assess ecological impact from outdoor residential uses because existing urban models are inadequate to estimate exposure. Quantifying residential pesticide use at the national level remains an obstacle. Data are lacking on the timing, frequency, and location of residential pesticide application at a national scale. However, data are being collected on estimated run-off from impervious surfaces, housing density, application timing, method, and frequency for constructing representative residential exposure scenarios. In the absence of these data and tools, the Agency has relied on urban monitoring data for conducting the ecological risk assessments. (The content of this presentation does not necessarily represent the official views of the US EPA.)

Application of a modeling approach for predicting pyrethroid residues is urban water bodies for use in environmental risk assessments
Michael Winchell1,, Scott Jackson2, Gary Mitchell3. (1) Stone Environmental, Inc., Montpelier, VT 05602, United States, (2) BASF Corporation, Research Triangle Park, NC 27709, United States, (3) FMC Agricultural Products, Ewing, NJ 08628, United States

Modeling pyrethroid environmental fate in an urban setting can help us to understand better the sources, transport pathways, and mitigation strategies for reducing their environmental concentrations. Recently, a modeling approach using the Storm Water Management Model (SWMM) has been developed and validated in a high density residential watershed in southern California. The approach incorporated pyrethroid wash-off characteristics from pervious and impervious surfaces, neighborhood characteristics, and pyrethroid application practices typical of the region. To extend this modeling approach to new geographic regions, a survey was conducted to gather regionally-specific, pyrethroid-use practices. These local use practices, along with local weather and neighborhood characteristics, have enabled the geographical extension of the California modeling approach to a diverse collection of locations. Application of the SWMM modeling approach to a broader population of residential neighborhood conditions has provided aquatic exposure estimates important for developing a comprehensive higher tier ecological risk assessment for pyrethroids at the national scale.

Semimechanistic modeling of pesticide washoff from concrete surfaces
Yuzhou Luo,, Frank Spurlock, Sheryl Gill, Kean S Goh. Department of Pesticide Regulation, California Environmental Protection Agency, Sacramento, CA 95812, United States

Pesticide uses over impervious surfaces like concrete significantly contribute to pesticide detection and aquatic toxicity in urban watersheds. California Department of Pesticide Regulation (CDPR) has been involved in multiple projects of lab/field experiments and surface water monitoring to evaluate urban pesticide use and their effects on the receiving water quality. In addition, regulations and mitigations have recently been proposed in California to restrict urban pesticide uses. A modeling approach is required for better characterization and prediction for off-site transport processes of urban pesticides. Presented here is a comprehensive study on pesticide washoff from concrete surfaces, including reviews of experiments and models, development of a new model, and its application. Analysis of experimental data indicated that pesticide washoff was generally associated with irreversible adsorption, dynamic dissipation rate constant, and dynamic effective diffusivity. The existing modeling approaches, mainly exponential function and power-law function, have limitations in explaining those processes. A mathematical and conceptual framework was developed to predict pesticide buildup and washoff processes on concrete surfaces, including the time-dependence of washoff potential after application and the dynamics in pesticide washoff during a runoff event. The model was applied to published data from controlled rainfall experiments. The model satisfactorily captured pesticide mass loads and their temporal variations for tested pesticides with a wide range of chemical properties (log Kow= 0.6 - 6.9) and set times (1 - 238 days after application) under both single and repeated rainfall events (1 - 7 times). Results suggested that, with appropriate parameterization and modeling scenarios, the model can be used to predict washoff potentials of pesticide products from concrete surfaces and to support pesticide risk assessments in urban environmental settings.

Determining critical factors controlling off-site transport of pyrethroids in the urban environment
Paul S Miller1Paul C Davidson1,, Christopher M Harbourt1, Xinyu Zhang1, Charles C Boast1, Russell L Jones2, Gregory E Goodwin1, Bradley A Sliz1. (1) Waterborne Environmental, Inc., Champaign, IL 61820, United States, (2) Bayer CropScience, Research Triangle Park, NC 27709, United States

Off-target pyrethroid transport from urban and suburban landscapes is not well understood, especially when compared to the off-target transport in agricultural production systems. Various combinations of pervious surfaces (lawns, flower beds, shrubbery) and impervious surfaces (concrete, asphalt, house siding) surfaces, lawn irrigation, and rainfall contribute to some of the variability. Different methods of product applications to those surfaces (general broadcast, target spraying, and applications to both horizontal and vertical surfaces) compound the complexity in these environments. In outdoor settings, additional variables control the washoff of pyrethroids, including the timing and number of applications, meteorological conditions (including rainfall, temperatures, and evapotranspiration), irrigation amounts and methods, product formulations, and mass remaining as a function of time. A full-scale experimental site was constructed in California and applications were conducted matching historic and newly-revised label recommendations for pyrethroids. Initial results indicate a time-based, three-phase process with washoff occurring, changing, and gradually slowing over time. Also, natural and simulated rainfall events accounted for the majority of mass loss from the study site when compared to mass loss under lawn irrigation and its associated urban drool. Additional results will be presented, including a multivariate analysis of pyrethroid washoff from various surfaces to determine critical factors influencing the process-based mass loss of pyrethroids under California suburban conditions.

Factors affecting residential runoff transport of pyrethroids
Russell L Jones1,, Paul C Davidson2, Christopher M Harbourt2, Paul Hendley3. (1) Bayer CropScience, Research Triangle Park, North Carolina 27709, United States, (2) Waterborne Environmental, Inc., Champaign, Illinois 61820, United States, (3) Phasera Ltd., Bracknell, Berkshire RG12 2JJ, United Kingdom

Replicated runoff studies investigating the transport of pyrethroids applied to suburban residences were conducted at a full scale test facility in central California over 18 months. The first 12 months of results showed losses from historic practices mainly from applications made to impervious surfaces (such as driveways or walls adjacent to driveways) as a result of runoff generated by simulated or natural rainfall. Revised application procedures according to new product labeling specifying spot applications to impervious surfaces reduced runoff losses of pyrethroids by a factor of 40 compared to historic practices. The last 6 months of testing examined the effect of formulation on washoff from driveways or walls adjacent to driveways. Variability in runoff loses between product formulations under field scale conditions were considerably less than in small scale laboratory experiments. Also the ranking of runoff losses by product in laboratory experiments were not always the same as in the field experiments. This indicates that using laboratory studies to assess the effect of formulation on runoff losses under field conditions may not always be predictive of behavior under actual use conditions, thus field studies remain important for understanding washoff losses from residential pesticide treatments.

Factors influencing pesticide concentrations in dusts on residential outdoor impervious surfaces
Weiying Jiang1,, Jay Gan2. (1) Department of Pesticide Regulation, California Environmental Protection Agency, Sacramento, CA 95814, United States, (2) Department of Environmental Sciences, University of California, Riverside, Riverside, CA 92521, United States

Impervious surfaces are an important source of pesticides in residential runoff, and association with solid materials is the primary route of pyrethroid transport with runoff water. Although monitoring studies have showed temporal variations of pesticide runoff concentrations, their levels on residential outdoor surfaces are seldom measured directly, and the changes of their concentrations over time is unknown. We collected 360 dust samples in May, July, and September of 2011 from impervious surfaces around residential homes and used a linear mixed model to assess factors that may influence pesticide levels. Pesticides were detected in almost all samples, and in more than 75% of the dust samples, at least 5 pesticides were detected. Bifenthrin, permethrin, cypermethrin and cyfluthrin were found at highest levels, and bifenthrin also contributed >40% of total toxicity potential to aquatic invertebrates. Dust collected in July and September contained higher pesticide amounts than in May, and the curbside gutter samples showed higher contamination than sidewalk and street samples.

Pyrethroid monitoring of the Lower American River in California (USA)
Christopher M. Harbourt1,, Stephen A. Clark2, Gregory E. Goodwin1, Todd Albertson3, Michael Dobbs4, Kevin Henry5, Gary Mitchell6. (1) Waterborne Environmental, Inc., Champaign, IL 61820, United States, (2) Pacific EcoRisk, Inc., Fairfield, CA 94534, United States, (3) Caltest Analytical Laboratory, Napa, CA 94558, United States, (4) Bayer CropScience LP, Research Triangle Park, NC 27709, United States, (5) Syngenta, Greensboro, NC 27409, United States, (6) FMC Agricultural Products, Ewing, NJ 08628, United States

The Lower American River starts below Folsom Dam (Folsom Lake) and runs 49.2 km to the river's confluence with the Sacramento River. This portion of the river is very wide and shallow and moves swiftly as it passes through an urbanized area; it is buffered by riparian parks, cycle paths, and is used extensively for recreation. The majority of the flow in this section of the river throughout the year is a controlled discharge from the Folsom Dam. Local storm drains, small ephemeral channels and an extensive network of organized storm drain collection and pump stations discharge excess rainfall from surrounding urban and suburban environments into the Lower American River channel. The current study was designed to systematically investigate the nature, timing, likelihood, and scale of potential pyrethroid detections. This objective was accomplished through (1) various rainfall event-driven sampling studies during the 2011-2012 and 2012-2013 rainy seasons and (2) a robust, multi-site, spatio-temporal transect study, appropriate for investigating a river system of this size and scale. Results demonstrate that pyrethroid residues have generally been low and infrequent.


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