Appendix A: Final Risk Assessment For Diquat Bromide The Water Quality Program NOVEMBER 2002 Publication Number 02-10-046 Appendix A: Final Risk Assessment For Diquat Bromide Prepared by: Kathleen Emmett Washington State Department of Ecology The Water Quality Program NOVEMBER 2002 Publication Number 02-10-046 For additional copies of this document contact: Department of Ecology Publications Distribution Center P.O. Box 47600 Olympia, WA 98504-7600 Telephone: (360) 407-7472 The Department of Ecology is an equal opportunity agency and does not discriminate on the basis of race, creed, color, disability, age, religion, national origin, sex, marital status, disabled veteran's status, Vietnam Era veteran's status, or sexual orientation. If you have special accommodation needs or require this document in an alternative format, please call the secretary of the Watershed Management Section at 360-407-6404. The TTY number is 711 or 1-800-833-6388 TABLE OF CONTENTS Section: Label Description & History 1 Section 2: Chemical Characteristics 35 Section 3: Environmental Fate 47 Section 4: Environmental Effects 129 Section 5: Human Health Effects 355 Diquat Volume 4, Section 1 LABEL DESCRIPTION & HISTORY 29 PAGES SEIS Risk Assessments of Aquatic Herbicides: Study No. 00713 Diquat - LABEL DESCRIPTION & HISTORY Vol. 4, Sec. 1 – Page 1 SEIS Risk Assessments of Aquatic Herbicides: Study No. 00713 Vol. 4, Sec. 1 – Page 2 Diquat - LABEL DESCRIPTION & HISTORY TABLE OF CONTENTS TABLE OF CONTENTS ................................................................................................................ 3 1.0 REGISTRATION STATUS............................................................................................. 5 1.1 DIQUAT AS AN AQUATIC HERBICIDE..................................................................... 5 1.1.1 Registration Requirements ............................................................................................ 5 1.1.2 Registration and Permitting History .......................................................................... 6 1.1.3 Risk Assessment (For a more detailed analysis see Section 4.1.10.2.5) ...................... 7 1.1.4 Registration Labels .................................................................................................... 9 1.1.4.1 Current Labels........................................................................................................ 9 1.1.4.2 Historical Labels.................................................................................................... 9 1.1.4.3 Label Restrictions.................................................................................................. 9 1.1.3.4 Labeled Use..........................................................................................................11 1.1.3.5 Effectiveness Controlling Specific Aquatic Plant Species................................... 11 1.1.3.6 Other Concerns.................................................................................................... 12 1.1.4 Maintaining the Current Registration.......................................................................... 13 REFERENCES.............................................................................................................................. 14 LIST OF TABLES ........................................................................................................................ 17 LIST OF APPENDICES ............................................................................................................... 24 SEIS Risk Assessments of Aquatic Herbicides: Study No. 00713 Diquat - LABEL DESCRIPTION & HISTORY Vol. 4, Sec. 1 – Page 3 SEIS Risk Assessments of Aquatic Herbicides: Study No. 00713 Vol. 4, Sec. 1 – Page 4 Diquat - LABEL DESCRIPTION & HISTORY 1.0 REGISTRATION STATUS This section describes the historic and current federal labels and typical uses. It also summarizes application rates, weeds controlled and reports on current practices undertaken by licensed Washington applicators. The final section describes research underway, including rate and application technology and proposed new labeling. 1.1 DIQUAT AS AN AQUATIC HERBICIDE 1.1.1 Registration Requirements In order to register a pesticide with the EPA for use in the United States, the active ingredient and its formulations must be tested for mammalian toxicity, physical chemistry, environmental fate, effects on ground water, and eco-tox effects. Work must also be done to demonstrate the expected magnitude of residue on edible products and residues in water. After this data is generated, it is submitted to various branches of EPA for review. If EPA finds that the product does not pose significant risk to humans, livestock, or wildlife and has a favorable environmental persistence and degradation profile, a registration will be granted. With that registration, the manufacturer has permission to sell the product in the United States. However, each state may have its own separate registration process which may be more stringent than the EPA’s registration process. Washington State’s registration procedure requires that the applicant submit a copy of the market label and a copy of the confidential statement of formula. The Washington State Department of Agriculture (WSDA) reviews these submittals for compliance with state and federal requirements. If these requirements are filled, the product will be registered by the state unless it presents an unusual hazard to the environment. Studies conducted for submission to EPA since 1987 must be conducted in compliance with Good Laboratory Practice (GLP) regulations as specified in 40 CFR (Code of Federal Regulations) 160. These regulations are designed to improve the quality of records keeping and prevent fraud. They specify what records must be kept and how long they must be kept. They also specify how long analytical standards must be kept, how often they must be re-characterized and storage conditions. Furthermore they provide guidelines on how to determine the length of time that organic and inorganic reagents, solvents and biological samples can be kept, and under what conditions they should be stored. Also, GLPs provide guidance on how the integrity of the biological samples can be determined. For practical purposes, GLPs insure the integrity of the data. They allow for the reconstruction and interpretation of data within the study. WSDA has registered diquat for use under several labels, but the only registered formulation for use in public waterways is Reward® Landscape and Aquatic Herbicide. This product contains 37.3% active ingredient (3.73 pounds diquat dibromide/gallon) which is equal to 20% cation equivalents (2.0 pounds diquat cation/gallon). Diquat products registered by WSDA and except for Reward, are restricted in their use “for application to ponds, lakes and drainage ditches where there is little or no outflow of water and which are totally under the control of the products user include: No. Product Registered with the WSDA EPA Registration No. Name of Company 1 Misty Weed Trol® VF 8123-37-10807 Amrep Inc. SEIS Risk Assessments of Aquatic Herbicides: Study No. 00713 Diquat - LABEL DESCRIPTION & HISTORY Vol. 4, Sec. 1 – Page 5 2 Opti-Gro Aqua Trim II 8123-37-66114 Check-Mark 3 Sea-Cide® Aquatic Weed Killer 8123-37-40208 Drummond Amer. Corp. 4 Weedtrine® D 8959-9 Applied Biochemists Inc. 5 Share Quick Kill® Non-Selective 10088-13-11547 Share Corp. Vegetation Killer 6 Total Solutions Eliminator® 10088-13-68562 Total Solutions 7 Zeneca* Diquat® Herbicide 10182-353 Zeneca* Ag Products Inc. 8 Reward® Landscape and Aquatic 10182-404 Zeneca* Ag Products Inc. Herbicide * Zeneca Diquat products are now sold by Syngenta Diquat® initially received Federal registration for control of submersed and floating aquatic weeds in 1962 and completed the Registration Eligibility Decision (RED) process on February 18, 2000. In addition to controlling watermilfoil, diquat is known to be particularly effective against water-lettuce (Pistia stratiotes), duckweed (Lemna spp.), cattails (Typha spp.), and Salvinia spp. Very few aquatic herbicides are effective in controlling these species of aquatic macrophytes (Gallagher and Haller, 1990 and Reward® LA label, 2000). 1.1.2 Registration and Permitting History In the state of Washington, applications of aquatic herbicides and algaecides are performed by WSDA licensed applicators under a state permit system. Ecology manages this system and uses a 2001 Supplemental Environmental Impact Statement (SEIS) for diquat, copper compounds, glyphosate, endothall, 2,4-D and fluridone as well as manual, mechanical and biocontrol methods as guidance for writing permits for aquatic weed and algae control (Ecology, 2001). The state permitting system is a result of six agencies working together to develop a statewide integrated pest management system for aquatic plants and noxious emergent vegetation. The goal of this system is to ensure that the most effective and least environmentally damaging management alternatives will be used. Ecology is responsible for issuing short-term modifications (STMs) to the water quality standards. These are required for management activities such as use of pesticides, mechanical or other control methods that might cause excess turbidity or violate other provisions of the water quality standards. Ecology is also responsible for ensuring consistency of proposals with rules and regulations designed to protect groundwater, shorelands, wetlands, air quality,