2,4-Dichlorophenoxyacetic Acid Analysis of Risks to Endangered and Threatened Salmon and Steelhead December 1, 2004 Shannon Borges Cara Dzubow Greg Orrick Ann Stavola Environmental Field Branch Office of Pesticide Programs Summary 2,4-D is a widely used herbicide applied to many crop sites and non-crop sites in the Pacific Northwest. Acid and amine salt forms of 2,4-D are "practically non-toxic" to “slightly toxic,” while ester forms of 2,4-D are “slightly toxic” to “highly toxic” to fish. Some forms of 2,4-D may lead to adverse acute and chronic effects. Some esters are “moderately toxic” to freshwater invertebrates, which may be sources of food for salmonids. All forms of 2,4-D that were tested had relatively high toxicity to vascular plants, which could lead to loss of cover for salmonid adults and young. Terrestrial uses of 2,4-D in the Pacific Northwest pose no direct or indirect risk to fish. 2,4-D acid and amine salts pose an indirect risk to fish when used on rice crops and for aquatic weed control. 2,4-D esters pose acute and chronic risk directly and indirectly when used for aquatic weed control. This endangered species risk assessment is developed for Federally listed Pacific salmon and steelhead. The findings of the Office of Pesticide Program’s Environmental Risk Assessment developed for non-target fish and wildlife as part of the reregistration process are applied to determine the potential risks to the 26 listed threatened and endangered Evolutionarily Significant Units (ESUs) of Pacific salmon and steelhead. We determined that use on terrestrial crops of 2,4-D will cause no effect to any ESUs when used according to labeled application directions. When used on rice, 2,4-D may affect but is not likely to adversely affect 4 ESUs, but will have no effect on 22 ESUs. Aquatic weed control usage information for 2,4-D is too deficient to perform an analysis for each ESU. However, we determined that any use of 2,4-D on aquatic weeds may affect threatened and endangered salmon and steelhead of all 26 ESUs. Introduction Page 1 of 102 This analysis was prepared by the US Environmental Protection Agency (EPA) Office of Pesticides Programs (OPP) to evaluate the risks of 2,4-D to threatened and endangered Pacific salmon and steelhead. Problem Formulation: The purpose of this analysis is to determine whether the registration of 2,4-D as an herbicide for use on various treatment sites may affect threatened and endangered (T&E or listed) Pacific anadromous salmon and steelhead and their designated critical habitat. Scope: Although this analysis is specific to listed Pacific anadromous salmon and steelhead and the watersheds in which they occur, it is acknowledged that 2,4-D is registered for uses that may occur outside this geographic scope and that additional analyses may be required to address other T&E species in the Pacific states as well as across the United States. We understand that any subsequent analyses, requests for consultation and resulting Biological Opinions may necessitate that Biological Opinions relative to this request be revisited, and could be modified. Page 2 of 102 Contents Section Page 1. Background 7 2. Description and use of 2,4-D 16 a. Chemical overview 16 b. Registered uses 17 c. Application rates and methods 18 d. 2,4-D usage 25 3. General aquatic risk assessment for endangered and threatened salmon and steelhead 34 a. Aquatic toxicity of 2,4-D 34 b. Environmental fate and transport 48 c. Incidents 52 d. Estimated and actual concentrations of 2,4-D in water 53 e. Water quality criteria 61 f. Recent changes in 2,4-D registrations 61 g. Existing protections 61 h. Discussion and general risk conclusions for 2,4-D 63 4. Description of Pacific salmon and steelhead Evolutionarily Significant Units relative to 2,4-D use sites 69 5. Specific conclusions for Pacific salmon and steelhead ESUs 98 6. References 100 Attachments A. Quantitative Usage Analysis for 2,4-D B. EFED Risk Assessment for the RED for 2,4-D (draft EFED chapter) C. 2,4-D Master Label D. Washington State Use Summary E. EFED Tier II Aquatic Exposure Assessment F. Representative Labels Tables Table Table Title Page Number Number 1 Qualitative descriptors for categories of fish and aquatic 8 invertebrate toxicity 2 Risk-quotient criteria for fish and aquatic invertebrates 14 3 Labeled crops and application methods/equipment for 2,4-D 19 4 Labeled crops and maximum application rates for 2,4-D 20 Page 3 of 102 Table Table Title Page Number Number 5 Nationwide 2,4-D usage from most of 1992 through 2000. 25 6 Reported usage of 2,4-D in California, 1993-2000 (Total acres) 28 7 Reported usage of 2,4-D in California 1993-2002 (Total pounds 28 of active ingredient) 8 Usage of 2,4-D by crop or site in California in 2001 28 9 Major usage of 2,4-D in Washington 32 10 Acute toxicity of 2,4-D TGAI to freshwater fish 34 11 Acute toxicity of 2,4-D formulated products to freshwater fish 35 12 Freshwater fish early life-stage and life-cycle toxicity under flow 36 through conditions using TGAI 13 Acute toxicity of 2,4-D TGAI and formulated products to non­ 37 target invertebrates 14 Chronic toxicity of 2,4-D TGAI to freshwater invertebrates 38 15 Toxicity of 2,4-D TGAI and formulated products to nontarget 38 aquatic plants 16 Acute toxicity of 2,4-D TGAI and formulated products to 39 estuarine and marine fish 17 Chronic toxicity of 2,4-D TGAI to estuarine and marine fish 40 18 Acute toxicity of 2,4-D to estuarine and marine invertebrates 41 19 Acute toxicity of 2,4-D TGAI to freshwater fish 42 20 Acute toxicity of 2,4-D formulated products to freshwater fish 42 21 Chronic toxicity of 2,4-D TGAI to freshwater fish 43 22 Acute toxicity of 2,4-D TGAI and formulated products to non­ 43 target invertebrates 23 Chronic toxicity of 2,4-D acid formulated products to freshwater 44 invertebrates 24 Acute toxicity of 2,4-D formulated products to estuarine and 44 marine fish Page 4 of 102 Table Table Title Page Number Number 25 Acute toxicity of formulated products containing 2,4-D and other 45 active ingredients to freshwater and marine fish (Toxdata) 26 Acute toxicity of formulated products containing 2,4-D and other 45 active ingredients to freshwater and marine fish (AQUIRE) 27 Acute toxicity of formulated products containing 2,4-D and other 46 active ingredients to freshwater and marine invertebrates 28 Toxicity of formulated products containing 2,4-D and other 47 active ingredients to freshwater and marine plants 29 Half-lives of various 2,4-D chemical moieties under three 50 metabolic conditions 30 1 in 10 year estimated environmental concentrations of 2,4-D in 54 the Pacific Northwest 31 Pesticide residues of 2,4-D reported in surface water (SW) and 57 groundwater (GW) in NAWQA summary publications for HSUs contained within Washington, Oregon, Idaho, and California 32 California DPR database pesticide residue concentrations for 58 surface waters (1990-2003) 33 Aquatic organism risk quotient calculations for 2,4-D acid and 64 amine salts 34 Aquatic organism risk quotient calculations for 2,4-D rice 68 applications and aquatic weed control 35 Usage of 2,4-D on rice in counties located within the California 71 Coastal Chinook Salmon ESU 36 Usage of 2,4-D on rice in counties located within the Central 72 Valley Spring-Run Chinook Salmon ESU 37 Usage of 2,4-D on rice in counties located within the Sacramento 75 River Winter-Run Chinook ESU 38 Usage of 2,4-D on rice in counties located within the Sacramento 89 River Winter-Run Chinook ESU 39 Summary conclusions on specific ESUs of salmon and steelhead 99 for 2,4-D use on rice Page 5 of 102 Figures Figure Figure Title Page Number Number 1 Estimated annual agricultural 2,4-D usage 18 Page 6 of 102 1. Background Under section 7 of the Endangered Species Act, the Office of Pesticide Programs (OPP) of the U S Environmental Protection Agency (EPA) is required to consult on actions that ‘may affect’ federally listed endangered or threatened species or that may adversely modify designated critical habitat. Situations where a pesticide may affect a fish, such as any of the salmonid species listed by the National Marine Fisheries Service (NMFS), include either direct or indirect effects on the fish. Direct effects result from exposure to a pesticide at levels that may cause harm. Acute Toxicity - Relevant acute data are derived from standardized toxicity tests with lethality as the primary endpoint. These tests are conducted with what is generally accepted as the most sensitive life stage of fish, i.e., very young fish from 0.5-5.0 grams in weight, and with species that are usually among the most sensitive. These tests for pesticide registration include analysis of observable sublethal effects as well. The intent of acute tests is to statistically derive a median effect level; typically the effect is lethality in fish (LC50) or immobility in aquatic invertebrates (EC50). Typically, a standard fish acute test will include concentrations that cause no mortality, 100% mortality, and no observable sublethal effects. By looking at the effects per each test concentration, a dose-response curve can be derived to help statistically predict the effects likely to occur at various pesticide concentrations; a well done test can even be extrapolated, with caution, to concentrations below those tested (or above the test concentrations if the highest concentration did not produce 100% mortality).