AGROCHEMICAL IMPACTS ON HUMAN AND ENVIRONMENTAL HEALTH: MECHANISMS AND MITIGATION

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 0209599
• Multistate No.: W-2045
• Project Start Date: Oct 1, 2010
• Project End Date: Sep 30, 2015
• Program Code: [(N/A)]- (N/A)

Recipient Organization
UNIVERSITY OF CALIFORNIA, RIVERSIDE
(N/A)
RIVERSIDE,CA 92521

Performing Department
Environmental Sciences

Non Technical Summary
The growing demand for food and fiber places greater strain on agricultural production and environmental stewardship. Agrochemicals will remain fundamental as integrated pest management tools to assure an abundant food supply. Inevitably, a significant portion of the applied agrochemicals will be lost to the surrounding environment, where they can adversely affect human and environmental health. The use of conventional and emerging crop protection chemistries in agricultural and urban pest management will require understanding of the fate and effects of agrochemicals, along with mitigation strategies, to minimize their risks to humans and the environment. Renewal of the W-1045 multistate research project will enable multistate collaborations to more effectively advance and transfer science to agricultural and regulatory stakeholders, who require solutions to complex human and environmental health concerns that are beyond the scope for any individual state AES or USDA-ARS unit.

Animal Health Component

(N/A)

Research Effort Categories

Basic

(N/A)

Applied

(N/A)

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
102	0110	2000	50%
112	0320	1150	40%
133	0330	2050	10%

Knowledge Area
133 - Pollution Prevention and Mitigation; 102 - Soil, Plant, Water, Nutrient Relationships; 112 - Watershed Protection and Management;

Subject Of Investigation
0320 - Watersheds; 0110 - Soil; 0330 - Wetland and riparian systems;

Field Of Science
2050 - Hydrology; 2000 - Chemistry; 1150 - Toxicology;

Keywords

pesticides

soil

toxicity

biotransformation

bioavailability

agrochemicals

Goals / Objectives
Objectives: 1. Identify, develop, and/or validate trace residue analytical methods, immunological procedures, and biomarkers of chemical exposure and effects. 2. Characterize abiotic and biotic reaction mechanisms, transformation rates, and fate of chemicals in agricultural and natural ecosystems. Outputs: 1. The results of our research will be disseminated to the scientific community through publications in refereed journals, presentations at national and international meetings, and departmental seminars. Results will be presented to various lay stakeholders as described in Outreach Plan below. 2. Rapid and sensitive analytical methods for pesticides and other environmental pollutants including pyrethroids, neonicotinoid insecticides, adrenergic agonists, will be developed. These methods will allow for high-throughput screening of water and other environmental samples, and will increase our capability for screening environmental matrices contaminated with pesticides. Similar methods will be used in the analysis of urine in residential and occupational exposure assessments. A standard assay for cholinesterase levels as an indication of exposure to cholinesterase inhibitors (including nerve agents, pesticides, etc.) will be recommended, which will be valuable in protecting armed forces, agricultural workers, and others exposed to these chemicals from debilitating effects.

Project Methods
Reseachers at UC Riverside will continue to develop and evaluate analytical methods for measuring bioavailable concentrations of pesticides in sediment-water and soil-water systems. Many current-use pesticides are highly hydrophobic and they are preferentially sorbed to sediment or soil particles as well as dissolved organic matter. Most methods measure the total chemical concentration, which may have a poor relationship with the effective concentration causing the toxic effect. UC Riverside researchers will develop and evaluate biomimetic methods such as SPME, and use these methods to understand processes and factors governing the bioavailability of hydrophobic pesticides in sediments or soils. Nonpoint source pollution due to surface runoff is the main course for water quality impairment of surface streams in the U.S. The impairment may be caused by contamination by pesticides or nutrients. Irrigation and rain induced runoff of insecticides can lead to toxicity to sensitive aquatic invertebrates in both agricultural and urban watersheds. Researchers at UC Riverside will continue to work with stakeholders including regulators, growers, extension advisors, the agrochemical industry, and pesticide applicators to develop, evaluate and promote the use of mitigation practices such as constructed wetlands, vegetative buffers, and improved application techniques. Field studies will be carried out to test these mitigation practices, and results from these and other studies will be extended to the various stakeholders through outreach seminars, newsletters and websites.

Progress 10/01/10 to 09/30/15

Outputs
Target Audience:Environmental scientists, soil scientists, state agencies, chemical industry Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?One Ph.D. student (Echo Jia) was involved in this research and she received her Ph.D. in June 2014. She is now working as a chemist at Bayer Crop Sciences. A postdoctoral scientist (Chunyang Liao) also worked part-time on this topic. Another Ph.D. student (Jaben Richards) is currently working on this project. How have the results been disseminated to communities of interest?We have published over 15 articles on this topic during the project period We have made presentations at American Chemical Society meetings, Society of Environmental Toxicology & Chemistry meetings, and other national or international meetings or workshops. We have participated in stakeholder-oriented workshops on pesticide use and runoff in urban environments. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? During the project reporting period, we have carried out research to develop sampling and analytical methods to quantify the bioavailability of pesticides and other strongly hydrophobic compounds in water and sediment, and we have also conducted investigation on fate and transport of pesticides in urban environments in relation to use of pesticides for structural and landscape pest control. The primary funding is through California Department of Pesticide Regulation (CDPR) and NIEHS's Superfund Research Program. We have published over 15 original research articles from this research, and have also actively participated in regional, national and international meetings to present our research findings.

Publications

• Type: Journal Articles Status: Published Year Published: 2015 Citation: Lu, Z.J., R. Reif-Lopez, and J. Gan. 2015. Isomeric-specific biodegradation of nonylphenol in the activated sludge bioreactor. Water Research 282-290.
• Type: Journal Articles Status: Published Year Published: 2015 Citation: Delgado-Moreno, L., L.S. Wu, and J. Gan. 2015. Application of isotope dilution method for measuring bioavailability of organic contaminants sorbed to dissolved organic matter (DOM). Aquatic Toxicology 165: 129-135.
• Type: Journal Articles Status: Accepted Year Published: 2015 Citation: Jiang, W.Y., Y.Z. Luo, J. Conkle, J.Y. Li, and J. Gan. Pesticides on residential outdoor surfaces: Environmental impacts and aquatic toxicity. Pest Management Science (in press)
• Type: Journal Articles Status: Accepted Year Published: 2015 Citation: Fu, Q.G., E. Sanganyado, Q.F. Ye, and J. Gan. Biosolid amendment increases persistence of triclosan and triclocarban in soil. Environmental Pollution (in press)
• Type: Journal Articles Status: Accepted Year Published: 2016 Citation: Jiang, W.Y., and J. Gan. Conversion of pesticides to biologically active products on urban hard surfaces. Science of the Total Environment (in press)

Progress 10/01/13 to 09/30/14

Outputs
Target Audience: The scientific community, regulators, pesticide industry, farm advisors, and water quality managers Changes/Problems: No change. What opportunities for training and professional development has the project provided? One Ph.D. student (Echo Jia) has been involved in this research and she received her Ph.D. in June 2014. She is working as a chemist at Bayer Crop Sciences. A postdoctoral scientist has also worked part-time on this topic. An undergraduate student has participated in this research as a laboratory research assistant. How have the results been disseminated to communities of interest? We have published three articles on this topic in the last year. We have made presentations at American Chemical Society meetings, Society of Environmental Toxicology & Chemistry meetings, and other national or international meetings or workshops. We have participated in stakeholder-oriented workshops on pesticide use and runoff in urban environments. What do you plan to do during the next reporting period to accomplish the goals? We will continue our research in this direction by carrying out studies to develop passive samplers for pyrethroids and fipronil to be used for in situ monitoring in surface water, and evaluate the effect of aging on the bioavailability of hydrophobic contaminants such as DDT and PCBs in sediment.

Impacts
What was accomplished under these goals? We have carried out research to develop sampling and analytical methods to quantify the bioavailability of pesticides and other strongly hydrophobic compounds in water and sediment, and we have also conducted investigation on fate and transport of pesticides in urban environments in relation to use of pesticides for structural and landscape pest control. The primary funding is through California Department of Pesticide Regulation (CDPR) and NIEHS's Superfund Research Program.

Publications

• Type: Journal Articles Status: Published Year Published: 2014 Citation: Jia, F., and J. Gan. 2014. Comparing black carbon types in sequestering polybrominated diphenyl ethers (PBDEs) in sediments. Environmental Pollution 184: 131-137.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Jia, F., L.J. Bao, J. Crago, D. Schlenk, and J. Gan. 2014. Use of isotope dilution method (IDM) to predict bioavailability of organic pollutants in historically contaminated sediments. Environmental Science & Technology 48: 7966-7973.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Greenberg, L., M.K. Rust, J. Richards, X.Q. Wu, J. Kabashima, C. Wilen, J. Gan, and D.H. Choe. 2014. Practical pest management strategies to reduce pesticide runoff for Argentine ant (Hymenoptera: Formicidae) control. Journal of Economic Entomology 107: 2147-2153.

Progress 01/01/13 to 09/30/13

Outputs
Target Audience: The scientific communities, regulatory agencies such as California Pesticide Regulation and Water Quality Control Boards, and the provide industry such as the sanitation distrcts and chemical companies. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? We have provided research training and development to graduate students, undergraduate students (under-represented minority students) and postdoctoral scientists. How have the results been disseminated to communities of interest? We have reported our findings in a timely manner to a wide of audience including the scientific communities as well as state agencies and others. What do you plan to do during the next reporting period to accomplish the goals? We will focus on the development of pastic film-based samplers for field monitoring of pesticides in streams for water quality protection and understand how pesticides move from sites of applications via runoff to urban streams.

Impacts
What was accomplished under these goals? We have carried out research to develop sampling and analytical methods to quantify the bioavailability of pesticides and other stronglt hydrophobic compounds in water and sediment, and we have also conducted investigation on fate and transport of pesticides in urban environments in relation to use of pesticides for structural and landscape pest control.

Publications

• Type: Journal Articles Status: Published Year Published: 2013 Citation: Cui, X.Y., P. Mayer, and J. Gan. 2013. Methods to assess bioavailability of hydrophobic organic contaminants: Principles, operations, and limitations. Environmental Pollution 172: 223-234.
• Type: Journal Articles Status: Published Year Published: 2013 Citation: Cui, X.Y., and J. Gan. 2013. Comparing sorption behavior of pyrethroids between formulated and natural sediments. Environmental Toxicology & Chemistry 32: 1033-1039.
• Type: Journal Articles Status: Published Year Published: 2013 Citation: Bao, L.J., JF. Jia, J. Crago, E.Y. Zeng, D. Schlenk, and J. Gan. 2013. Assessing bioavailability of DDT and metabolites in marine sediments using solid phase microextraction with performance reference compounds. Environmental Toxicology & Chemistry 32: 1946-1953.
• Type: Journal Articles Status: Published Year Published: 2013 Citation: Jiang, W.Y., A. Soeprono, M. Rust, and J. Gan. 2013. Ant control efficacy of pyrethroids and fipronil on outdoor concrete surfaces. Pest Management Science DOI 10.1002/ps.3555

Progress 01/01/12 to 12/31/12

Outputs
OUTPUTS: Pesticides are widely used by homeowners and commercial applicators for residential landscape maintenance and structural pest control. Pesticides used in residential areas have been shown to contribute to surface water contamination in urban watersheds. To better understand the processes contributing to urban pesticide runoff, we have continued our research on pesticide fate and transport on urban hard surfaces such as concrete. We have completed experiments under field conditions using concrete slabs at the UC South Coast Research and Education Center in Irvine, CA, and sampling and analysis of dust on driveway, sidewalk and street for urban-use pesticides. The research findings have been communicated to California Department of Pesticide Regulation, and disseminated at regional and national meetings. PARTICIPANTS: Weiying Jiang, Ph.D. student, Environmental Science graduate program, UC Riverside, CA; Fred Ernst, Staff Scientist, UC Riverside; Ruben Reif-Lopez, Postdoctoral Scientist, UC Riverside; Partner organization: California Department of Pesticide Regulation (Kean Goh, Xuyang Zhang, Frank Spurlock, and Cheryl Gill); Collaborators: Department of Entomology, UC Riverside (Les Greenberg, and Mike Rust); UC Cooperative Extension Orange County (Darren Haver) TARGET AUDIENCES: The scientific community; regulators such as EPA and California Department of Pesticide Regulation; chemical companies such as Syngenta, Bayer, DuPont and Dow AgroSciences; professional pesticide applicators; watershed managers; and the general public. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
We have discovered that the main form of pesticides transferred into runoff water from concrete surfaces was as attachment to fine particles that likely originated from the weathering of concrete surfaces and deposition of dust particles from surrounding areas. We also observed that pesticides such as pyrethroids and fipronil were quickly transformed to other products on concrete surfaces when exposed to sunlight under outdoor conditions. Some of the degradation intermediates, including 3-phenoxybenzoic acid (3-PBA) from pyrethroids, and sulfone, sulfide and desulfinyl derivatives of fipronil, all possess biological activity. In another study, we collected dust samples on the surface of pavement in communities in the city of Riverside, and measured pesticide occurrence. Current-use insectides such as pyrethroids and fipronil, were found in most dust samples. These findings have important implications. The finding that pesticides are mainly associated with fine particles suggests that preventsion of off-site movement of loose particles would be key to mitigating pesticide runoff in residential areas. Transformation of pesticides to other biologically active compounds is a novel observation, which dictates that more attention should be directed to understanding the role of hardscapes in contaminant cycling in the environment. Mechanisms for the observed transformations, including importance of catalytic reactions and photolysis, should be further investigated. The source of pesticides in dust should be further explored.

Publications

• 1). Jiang, W.Y., D. Haver, M. Rust, and J. Gan. 2012. Runoff of pyrethroid insecticides from concrete surfaces following simulated and natural rainfalls. Water Research 46: 645-652.
• 2). Jiang, W.Y., and J. Gan. 2012. Importance of fine particles in pesticide runoff from concrete surfaces and its prediction. Environmental Science & Technology 46: 6028-6034.

Progress 01/01/11 to 12/31/11

Outputs
OUTPUTS: Pesticides are widely used by homeowners and commercial applicators for residential landscape maintenance and structure pest control. Pesticides used in residential areas have been shown to contribute to surface water contamination in urban watersheds. To better understand the processes contributing to urban pesticide runoff, we have continued our study on pesticide behavior on urban hard surfaces such as concrete. We have completed experiments under field conditions using concrete slabs at the UC South Coast Research and Education Center in Irvine, CA. The research findings have been communicated to California Department of Pesticide Regulation, and disseminated at regional and national meetings. PARTICIPANTS: Participants: Weiying Jiang, Ph.D. student, Environmental Science graduate program, UC Riverside, CA. Partner organization: California Department of Pesticide Regulation (Kean Goh, Xuyang Zhang, Frank Spurlock, and Cheryl Gill) Collaborators: Department of Entomology, UC Riverside (Les Greenberg, and Mike Rust); UC Cooperative Extension Orange County (Darren Haver) TARGET AUDIENCES: The scientific community; regulators such as EPA and California Department of Pesticide Regulation; chemical companies such as Syngenta, Bayer, DuPont and Dow AgroSciences; professional pesticide applicators; watershed managers; and the general public. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
We found that the main form of pesticides transferred into runoff water from concrete surfaces was as attachment to fine particles that likely originated from the weathering of concrete surfaces and deposition of dust particles from surrounding areas. We also observed that pesticides such as pyrethroids and fipronil were quickly transformed to other products on concrete surfaces when exposed to sunlight under outdoor conditions. Some of the degradation intermediates, including 3-phenoxybenzoic acid (3-PBA) from pyrethroids, and sulfone, sulfide and desulfinyl derivatives of fipronil, all possess biological activity. These findings have important implications. The finding that pesticides are mainly associated with fine particles suggests that prevention of off-site movement of loose particles would be key to mitigating pesticide runoff in residential areas. Transformation of pesticides to other biologically active compounds is a novel observation, which dictates that more attention should be directed to understanding the role of hardscapes in contaminant cycling in the environment. Mechanisms for the observed transformations, including importance of catalytic reactions and photolysis, should be further investigated.

Publications

• Jiang, W., J. Gan, and D. Haver. 2011. Sorption and desorption of pyrethroid insecticide permethrin on concrete. Environmental Science & Technology 45: 602-607.
• Jiang, W.Y., D. Haver, M. Rust, and J. Gan. 2012. Runoff of pyrethroid insecticides from concrete surfaces following simulated and natural rainfalls. Water Research 46: 645-652.
• Jiang, W.Y., and J. Gan. 2012. Importance of fine particles in pesticide runoff from concrete surfaces and its prediction. Environmental Science & Technology (in review)

Progress 01/01/10 to 12/31/10

Outputs
OUTPUTS: Pesticides are widely used by homeowners and commercial applicators for residential landscape maintenance and structure pest control. Pesticides used in residential areas have been shown to contribute to surface water contamination in urban watersheds. Along with researchers from UC Davis, we have monitored occurrence of current-use insecticides, including all pyrethroids and fipronil, from eight neighborhoods in Sacramento and Orange County, for over two years. Fipronil and its metabolites, as well as bifenthrin, cypermethrin, and some other pyrethroids, have been frequently found in residential runoff under dry and wet weather conditions. To further understand the processes contributing to such runoff transport, we have completed a study to understand pesticide sorption, persistence, and runoff potential from urban hard surfaces such as concrete. Commonly used insecticides have been found to persist for a long time on concrete with potential to contaminate passing runoff water. In a more recent study (with minor revision suggested by ES&T), we characterized sorption and desorption of permethrin, the most used pyrethroid insecticide, on concrete surfaces, to understand its availability for contaminating runoff water. Sorption of 14C-permethrin to concrete was rapid, and the sorption isotherm was linear, with surface area-normalized Kd of 1.91 mL/cm2. When small permethrin-treated concrete cubes (14 by 14 by 8 mm) were subjected to 300-h sequential desorption, both the parent compound and total 14C showed an initial rapid desorption followed by prolonged slow desorption. Meanwhile, permethrin became more resistant to desorption as the pesticide contact time on the concrete increased. When desorption was performed 1 and 7 d after the treatment, the desorbed permethrin after 300 h was 34.1% and 23.7% of the spiked amount, respectively, as compared to 56.2% for the freshly spiked samples. The decreased desorption was partially attributed to permethrin decomposition on the alkaline concrete. However, even after 300 h, over 20% of the applied 14C still remained in the concrete. Therefore, when pesticide-treated concrete surfaces come in contact with runoff water, elevated concentrations may be expected initially, while the extended desorption implies a potential for sustained contamination. PARTICIPANTS: Kean Goh, Xuyang Zhang, Frank Spurlock, and Cheryl Gill, California Department of Pesticide Regulation; Les Greenberg and Mike Rust, Department of Entomology, UC Riverside, CA; Weiying Jiang, Ph.D. student, Environmental Science graduate program, UC Riverside, CA. TARGET AUDIENCES: The scientific community; regulators such as EPA and California Department of Pesticide Regulation; chemical companies such as Syngenta, Bayer, DuPont and Dow AgroSciences; professional pesticide applicators; watershed managers; and the general public. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
The environmental fate and behavior of pesticides has been well studied in systems such as agricultural soil. In contrast, little is known about the retention, transformation and availability of pesticides in artificial systems such as urban hard surfaces. Understanding the fate and availability of pesticides on urban hard surfaces such as concrete will provide critical information needed for better managing pesticide use in urban environments to minimize the negative impact on the environment, including contamination of surface water downstream. We have been working with California Department of Pesticide Regulation on a range of studies to investigate pesticide sorption, persistence and availability for contaminating runoff water. We have also beening conducting research at the South Coast Research and Education Center (SCREC) in Irvine, CA, which serves as a location for public outreach and education. So far we have presented our research findings at Society of Environmental Toxicology and Chemistry meetings, and Americal Chemical Society meetings. We have also published one article in Environmental Toxicology & Chemistry, with the second manuscript in review (with minor revision) in Environmental Science and Technology. In addition, we have collaborated with Dr. Les Greenberg and Dr. Mike Rust in a study evaluating pesticide runoff from residential homes with different pesticide formulations or treatments. We have published a joint paper in Pest Management Science.

Publications

• 1). Jiang, W., K. Lin, D. Haver, S. Qin, F. Spurlock, and J. Gan. 2010. Wash-off potential of urban use insecticides on concrete surfaces. Environmental Toxicology and Chemistry 29: 1203-1208.
• 2). Greenberg, L., M.K. Rust, J.H. Klotz, D. Haver, J.N. Kabashima, S. Bondarenko and J. Gan. 2010. Impact of ant control technologies on insecticide runoff and efficacy. Pest Management Science 66: 980-986.

Progress 01/01/08 to 12/31/08

Outputs
OUTPUTS: Pyrethroids are insecticides commonly used in both agricultural and urban environments. Residues of pyrethroids are frequently found in bed sediments in regions such as California in the United States, and as such sediment toxicity from pyrethroid contamination is an emerging concern. Pyrethroids are highly hydrophobic, and toxicity from sediment-borne pyrethroids is expected to depend closely on their desorption rate. In the present study, we evaluated the effect of aging on desorption kinetics of sediment-borne pyrethroids. Two sediments spiked with four pyrethroids were incubated for 7, 40, 100, and 200 d at room temperature. Desorption measured using sequential Tenax extractions was well described by a three-compartment model. The estimated rapid desorption fraction (F_rapid) decreased quickly over time and was accompanied by an increase of the very slow desorption fraction (F_vs). The aging effect on desorption kinetics followed a first-order model, with half-lives for the decrease in F_rapid for all four pyrethroids in both sediments ranging from two to three months. When coupled with degradation, the estimated half-lives of the rapidly desorbing fraction (thus, the potentially bioavailable concentration) were  two months for all four pyrethroids. Two field-contaminated sediments displayed distinctively different desorption kinetics. The sediment with fresh residues exhibited rapid desorption, while the other sediment containing aged residues was highly resistant to desorption. The observation that desorption of pyrethroids decreased quickly over contact time implies that the bioavailability of sediment-borne pyrethroids may diminish over time, and that the use of non-selective extraction methods may lead to overestimation of the actual sediment toxicity from pyrethroid contamination. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Many environmental contaminants are strongly hydrophobic and tend to associate with the bed sediment. Acute and chronic aquatic toxicities from sediment contamination are an emerging concern. The toxicity of a sediment-borne contaminant depends on its desorption and bioavailability, which changes over time. In this study, we constructed the desorption kinetics curves of selected pyrethroids from sediments after the sediment and pesticide were in contact for different lengths of time. The desorption curves were fitted to a three-phase model to estimate the rapidly desorbing fraction F_rapid that reflects (bio)availability. The results showed that as the contact time increased from 7 to 200 d, F_rapid quickly decreased, suggesting that aging decreased the availability of pyrethroids in sediments. Although the conventional half-lives for the test compounds were from 30 to over 600 d, when expressed in the rapidly desorbable concentrations, the half-lives decreased to less than 2 months for all compounds. Therefore, as pesticide residues "age" in the environment, their toxicity would decrease faster than what may be indicated by the total chemical concentration. This finding may have important implications for risk assessment of these compounds in the environment.

Publications

• 1. Xu, Y.P., F. Spurlock, Z.J. Wang, and J. Gan. 2007. Comparison of five methods for measuring sediment toxicity of hydrophobic contaminants. Environmental Science and Technology 41: 8394-8399. 2. Hunter, W., Y.P. Xu, F. Spurlock, and J. Gan. 2008. Using disposable polydimethyl-siloxane (PDMS) fibers to assess the bioavailability of permethrin in sediment. Environmental Toxicology and Chemistry 27: 568-575. 3. Xu, Y.P., J. Gan, Z.J. Wang, and F.C. Spurlock. 2008. Effect of aging on desorption kinetics of sediment-associated pyrethroids. Environmental Toxicology & Chemistry 27: 1293-1301. 4. Yang, Y., W. Hunter, S. Tao, and J. Gan. 2008. Relationships between desorption intervals and availability of sediment-borne hydrophobic contaminants. Environmental Sciences and Technology 42: 8446-8451. 5. Hunter, W., Y. Yang, F. Reichenberg, P. Mayer, and J. Gan. 2009. Measuring pyrethroids in sediment porewater using matrix-solid phase microextraction. Environmental Toxicology and Chemistry 28: 36-43. 6. Yang, Y., W. Hunter, S. Tao, and J. Gan. 2009. Effects of black carbon on pyrethroid bioavailability in sediments. Journal of Agricultural and Food Chemistry 57: 232-238.

Progress 01/01/07 to 12/31/07

Outputs
OUTPUTS: Pyrethroids are insecticides commonly used in both agricultural and urban environments. Residues of pyrethroids are frequently found in bed sediments in regions such as California in the United States, and as such sediment toxicity from pyrethroid contamination is an emerging concern. Pyrethroids are highly hydrophobic, and toxicity from sediment-borne pyrethroids is expected to depend closely on their desorption rate. In the present study, we evaluated the effect of aging on desorption kinetics of sediment-borne pyrethroids. Two sediments spiked with four pyrethroids were incubated for 7, 40, 100, and 200 d at room temperature. Desorption measured using sequential Tenax extractions was well described by a three-compartment model. The estimated rapid desorption fraction (Frapid) decreased quickly over time and was accompanied by an increase of the very slow desorption fraction (Fvs). The aging effect on desorption kinetics followed a first-order model, with half-lives for the decrease in Frapid for all four pyrethroids in both sediments ranging from two to three months. When coupled with degradation, the estimated half-lives of the rapidly desorbing fraction (thus, the potentially bioavailable concentration) were about two months for all four pyrethroids. Two field-contaminated sediments displayed distinctively different desorption kinetics. The sediment with fresh residues exhibited rapid desorption, while the other sediment containing aged residues was highly resistant to desorption. The observation that desorption of pyrethroids decreased quickly over contact time implies that the bioavailability of sediment-borne pyrethroids may diminish over time, and that the use of non-selective extraction methods may lead to overestimation of the actual sediment toxicity from pyrethroid contamination. PARTICIPANTS: Project Leader: Jay Gan Cooperators: Frank Spurlock (California Department of Pesticide Regulation), Kean Goh (California Department of Pesticide Regulation), Lorence Oki, Anthony O'Geen (UC Davis), Darren Haver, John Kabashima, Julie Newman (UCCE) Technical Support: Postdocs: Svetlana Bondarenko, Yiping Xu, Kunde Lin, Laura Delgado; Ph.D. students: Mae Nillos, Sujie Qin, Wesley Hunter, Robert Budd, Yu Yang, Weiying Jiang TARGET AUDIENCES: Scientific community Farm advisors and extension specialists regulators agrochemical companies PROJECT MODIFICATIONS: Nothing significant to report

Impacts
Many environmental contaminants are strongly hydrophobic and tend to associate with the bed sediment. Acute and chronic aquatic toxicities from sediment contamination are an emerging concern. The toxicity of a sediment-borne contaminant depends on its desorption and bioavailability, which changes over time. In this study, we constructed the desorption kinetics curves of selected pyrethroids from sediments after the sediment and pesticide were in contact for different lengths of time. The desorption curves were fitted to a three-phase model to estimate the rapidly desorbing fraction Frapid that reflects (bio)availability. The results showed that as the contact time increased from 7 to 200 d, Frapid quickly decreased, suggesting that aging decreased the availability of pyrethroids in sediments. Although the conventional half-lives for the test compounds were from 30 to over 600 d, when expressed in the rapidly desorbable concentrations, the half-lives decreased to less than 2 months for all compounds. Therefore, as pesticide residues "age" in the environment, their toxicity would decrease faster than what may be indicated by the total chemical concentration. This finding may have important implications for risk assessment of these compounds in the environment.

Publications

• Bondarenko, S., F. Spurlock, and J. Gan. 2007. Analysis of pyrethroids in sediment porewater solid-phase microextraction (SPME). Environmental Toxicology & Chemistry 26: 2587-2593.
• Zheng, W., J. Gan, S.K. Papiernik, and S.R. Yates. 2007. Identification of volatile/semi-volatile products derived from cis-1,3-dichloropropene chemical remediation by thiosulfate. Environmental Science and Technology 41: 6454-6459.
• Xu, Y.P., F. Spurlock, Z.J. Wang, and J. Gan. 2008 Comparison of five methods for measuring sediment toxicity of hydrophobic contaminants. Environmental Science and Technology 41: 8394-8399.
• Hunter, W., Y.P. Xu, F. Spurlock, and J. Gan. 2008. Using disposable polydimethyl-siloxane (PDMS) fibers to assess the bioavailability of permethrin in sediment. Environmental Toxicology and Chemistry 27:568-575.
• Lao, W.J., and J. Gan. 2007. Hold-up volume and its application in estimating effective phase ratio and thermodynamic parameters on a polysaccharide-coated chiral stationary phase. Journal of Separation Science 30: 2590-2597.
• Zhao, M.R., Y. Zhang, W.P. Liu, C. Xu, R.M. Wang, and J. Gan. 2008. Estrogenic activity of lambda-cyhalothrin in the MCF-17 human breast carcinoma cell line. Environmental Toxicology and Chemistry 27: 1194-1200.
• Lao, W.J., and J. Gan. 2008. Characterization of column hold-up volume with static and dynamic methods on an immobilized polysaccharide-based chiral stationary phase. Chromatographia 67: 3-7.
• Mangiafico, S., J. Newman, D. Merhaut, J. Gan, L.S. Wu, J.H. Lu, B. Faber, and R. Evans. 2008. Evaluation of detention and recycling basins in managing nutrient and pesticide runoff from nurseries. HortScience 43: 393-398.
• Xu, Y.P., J. Gan, Z.J. Wang, and F.C. Spurlock 2008. Desorption kinetics and aging influence of sediment-associated pyrethroids. Environmental Toxicology & Chemistry 27: 1293-1301.
• Haruta, S., W.P. Chen, J. Gan, J. Simunek, A.C. Chang, and L. Wu. 2008. Leaching risk of N-nitrosodimethylamine (NDMA) in soil receiving reclaimed wastewater. Ecotoxicology and Environmental Safety 69: 374-380.
• Qin, S.J., and J. Gan. 2007. Abiotic enantiomerization of permethrin and cypermethrin: Effect of organic solvents. Journal of Agricultural and Food Chemistry 55: 5734-5739.
• Wang, L.M., W.P. Liu, C.X. Yang, Z.Y. Pan, J. Gan, C. Xu, M.R. Zhao, and D. Schlenk. 2007. Enantioselectivity in endocrine disruption potential and uptake of bifenthrin. Environmental Science and Technology 41: 6124-6128.
• Nillos, M.G., G. Rodriguez-Fuentes, J. Gan, and D. Schlenk. 2007. Enantioselective acetylcholinesterase inhibition of the organophosphorus insecticides profenofos, fonofos and crotoxyphos. Environmental Toxicology and Chemistry 26: 1949-1954.
• Zhu, Y.F., Z.M. Xie, J.M. Xu, and J. Gan. 2007. Metsulfuron-methyl adsorption-desorption in variably charged soils from Southeast China. Fresenius Environmental Bulletin 16:1363-1367.
• Lin, K.D., F. Zhang, S.S. Zhou, W.P. Liu, and J. Gan. 2007. Stereoisomeric separation and toxicity of nematicide fosthiazate. Environmental Toxicology and Chemistry 26: 2339-2344.
• Yang, W.C., J. Gan, W. Hunter, and F. Spurlock. 2007. Bioavailability of permethrin and cyfluthrin in surface waters with low levels of dissolved organic matter. Journal of Environmental Quality 36: 1678-1685.
• Budd, R., S. Bondarenko, D. Haver, J. Kabashima, and J. Gan. 2007. Occurrence and bioavailability of pyrethroids in sediment in a mixed land use watershed. Journal of Environmental Quality 36: 1006-1012.
• Lin, K.D., C. Xu, S.S. Zhou, W.P. Liu, and J. Gan. 2007. Enantiomeric separation of imidazolinone herbicides using chiral high performance liquid chromatography. Chirality 19: 171-178.
• Gadepalli, R.S., J. Rimoldi, F. Fronczek, M. Nillos, J. Gan, X. Deng, G. Rodriguez-Fuentes, and D. Schlenk. 2007. Synthesis of fenthion sulfoxide and fenoxon sulfoxide enantiomers: Effect of sulfur chirality on acetylcholinesterase activity. Chemical Research in Toxicology 20:257-262.
• Wang, H.Y., Q.F. Ye, J. Gan, and L.C. Wu. 2007. Biodegradation of Cry1Ab protein from Bt transgenic rice in aerobic and flooded paddy soils. Journal of Agricultural and Food Chemistry 55:1900-1904.

Progress 01/01/06 to 12/31/06

Outputs
Bioavailability of synthetic pyrethroids: Residues of synthetic pyrethroids were recently found in urban and agricultural streams, especially in the bed sediment. Given the increased use of pyrethroids and their broad spectrum aquatic toxicity, sediment toxicity from pyrethroid contamination is an emerging concern. Due to their outstanding hydrophobicity, the actual toxicity of a pyrethroid is regulated by its phase distribution and bioavailability. In 2006 we shifted our research focus on this topic to phase distribution and bioavailability of pyrethroids in sediment and sediment porewater. We have several studies in progress and will report their outcomes in the coming year. The following is a brief summary of a few finished studies on this subject. 1). Effect of suspended sediment on pyrethroid acute toxicity: While pyrethroids display very high acute toxicities to water-column organisms in laboratory tests, environmental water samples typically contain suspended sediment (SS) that reduces the freely dissolved pyrethroid concentration, hence pesticide bioavailability. Consequently, phase distribution plays an important role in pyrethroid aquatic toxicology. In this study, we evaluated the effects of SS on the toxicity of four widely used pyrethroid insecticides to Ceriodaphnia dubia. In all assays, LC50 values consistently increased with increasing SS, demonstrating the inhibitory effect of SS on pyrethroid toxicity. The LC50s in the 200 mg/L SS solutions were 2.5-13 times greater than those measured in sediment-free solutions. Results from this study suggest that the inhibitory effect of SS must be considered in estimating exposures to pyrethroids in aquatic systems. The SPME methodology may be used effectively to measure the bioavailable concentration and to predict the actual ecotoxicological effects of pyrethroids. 2). Effect of dissolved organic matter on pyrethroid bioavailability: In this study we evaluated the effect of dissolved organic matter (DOM) on the pyrethroid uptake by and acute toxicity to water-column invertebrates using permethrin as a model compound. During the bioassays, we simultaneously measured the freely dissolved pesticide concentration using polydimethylsiloxane (PDMS) fibers as a biomimetic surrogate. The presence of DOM consistently decreased permethrin uptake and increased its LC50. For instance, in a pond water containing DOM at 10 mg/L, LC50 of permethrin to Ceriodaphnia dubia increased from 0.56 to 1.03 ug/L while bioaccumulation factor (BAF) by Daphnia magna decreased by 56%. Pesticide accumulation on the PDMS fiber closely mimicked that pesticide uptake by D. magna. These results indicate that the inhibitory role of DOM should be considered when developing toxicologically relevant water quality limits and monitoring protocols for permethrin and likely other pyrethroids in runoff effluents and surface streams that ubiquitously contain DOM.

Impacts
Contamination of surface streams by synthetic pyrethroids appears to be an emerging water quality issue in California and likely in other regions. Pyrethroid products are in widespread use in both urban and agricultural environments. Although pyrethroids have high aquatic toxicity, their strong adsorption may significantly affect their phase distribution and ultimately their actual toxicity. Our studies so far have provided both methods as well as insights to understand such interactions. The results may be used by the regulatory communities in establishing water quality criteria and monitoring schemes.

Publications

• Yang, W.C., F. Spurlock, W.P. Liu, and J. Gan. 2006. Effects of dissolved organic matter on the bioavailability and toxicity of permethrin to aquatic invertebrates. Journal of Agricultural and Food Chemistry 54: 3967-3972.
• Yang, W.C., W. Hunter, J. Gan and F. Spurlock. 2006. Effect of suspended solids on bioavailability of synthetic pyrethroids. Environmental Toxicology and Chemistry 25: 1585-1591.
• Yang, W.C., F. Spurlock, W.P. Liu, and J. Gan. 2006. Inhibition of aquatic toxicity of synthetic pyrethroids by suspended sediment. Environmental Toxicology and Chemistry 25: 1913-1919.