Review Date: Bispyribac-sodium CAS #: Type Post-emergent aquatic herbicide (selective and systemic) Controls Grasses, sedges and broad-leaved weeds Mode of Action Inhibits the synthesis of the enzyme acetolactate synthase (ALS) required to make specific amino acids vital for plant life. 09/18/2014 125401-92-5 Thurston County Review Summary: The aquatic herbicide active ingredient bispyribac sodium is rated low in hazard and passes Thurston County's pesticide review criteria. MOBILITY Property Value Reference Value Rating 64,000 1 High Soil Sorption (Kd=mL/g) 0.6 to 2 2 High Organic Sorption (Koc=mL/g) 114 2 High Water Solubility (mg/L) Mobility Summary: The hazard for mobility is rated on the potential to move off the site of application with rain or irrigation water. When applied to water, bispyribac-sodium is not expected to bind well to sediment, so its mobility is dictated by the flow of the water body. The hazard for mobility in a water body is not specific to the chemical, therefore it is not rated for this review. PERSISTENCE Property Value Reference Value Rating Vapor Pressure (mm Hg) 0.0000001 mmHg 2 High Biotic or Aerobic Half-life (days) 19 2 Moderate Photolysis Half-life (days) 42 to stable (aquatic) 1 and 2 Moderate to high Terrestrial Field Test Half-life (days) 6.3 1 Low Hydrolysis Half-life (days) Stable 1 High Anaerobic Half-life (days) 88 to 109 2 High Aquatic Field Test Half-life (days) 32 1 Moderate Persistence Summary: Bispyribac-sodium is not expected to dissipate into the air after application and does not break down with interaction with water. After it is applied to water, it will likely take about a month to break down to half of the applied concentration and about three months if it gets into sediment. The hazard for chemical persistence is rated moderate. BIOACCUMULATION Property Value Reference Value Rating Bioaccumulation Factor Value not found Bioconcentration Factor 3 (estimated) 3 Low Octanol/Water Partition Coefficient log Kow = -1.03 1 Low Bioaccumulation Summary: The very low partition coefficient (log Kow = -1.03) and low estimated bioconcentration factor (BCF = 3) indicates a low potential for accumulation in aquatic organisms (References 1 and 3). Thurston County Health Department - 412 Lilly Road NE, Olympia WA 98506 - (www.co.thurston.wa.us/health/ehipm) Ph: 360-867-2664 T.D.D. 360-754-2933 ACUTE WILDLIFE TOXICITY VALUES and Risk Assessment Test Subject Value Reference Toxicity Rating Mammalian (LD50) 2,635 mg/kg 1 Low Avian (LD50) 2,250 mg/kg 1 Low Honey bee or insect (LD50) >141 ug/bee 1 Low Annelida -worms (LC50) >957 mg/kg 1 Low Fish (LC50) >95 mg/L 1 Low Crustacean (LC50) >95 mg/L 1 Low Mollusk (LC50) Value not found Amphibian (LD50 or LC50) Value not found Acute Toxicity Testing and Ecotoxicity Summary: Single-dose toxicity testing indicates that bispyribac-sodium is low in toxicity to mammals, birds, bees, worms, fish and other aquatic organisms (Reference 1). ACUTE HUMAN TOXICITY - Risk Assessment Subject and Scenario Route Dose of Concern Exposure Margin Reference of Safety Risk Rating Infant dietary + water + swimming Oral Value not provided Value not provided 77 5 Low Average adult dietary + water + swimming Oral Value not provided Value not provided 250 5 Low 50 yr old adult dietary + water + swimming Oral Value not provided Value not provided 260 5 Low Other exposures were not evaluated Acute Toxicity Risk Assessment Summary: Risk to infants and adults from oral exposures of bispyribac-sodium was determined to be low in hazard even when the potential exposures from eating treated food, drinking contaminated water and ingestion while swimming in a treated water body were combined. Thurston County Health Department - 412 Lilly Road NE, Olympia WA 98506 - (www.co.thurston.wa.us/health/ehipm) Ph: 360-867-2664 T.D.D. 360-754-2933 CHRONIC HUMAN TOXICITY HAZARDS Property Value Adverse Effect Reference Rating Carcinogenicity No effects up to 7,000ppm No known risk of cancer 4 Low Mutagenicity > 50 ug/plate DNA damage 4 Low Neurotoxicity - (NOAEL) Value not found Endocrine Disruption 10.9 mg/kg/day Testicular atrophy 3 Developmental Toxicity (NOAEL) 100 mg/kg/day Cleft pallet 3 Reproductive Toxicity (NOAEL) >10000 ppm No reproductive effects 3 Chronic Toxicity (NOAEL) 12.3 mg/kg/day Liver and other organ toxicities 3 Rating based on risk Rating based on risk Rating based on risk Chronic Toxicity Hazard Summary: Developmental toxicity was observed in one pup at the same dose that caused significant maternal toxicity (death and premature deliveries). There were no observations of reproductive toxicity in multi-generational testing. The test results indicate that infants and developing fetuses are not more susceptible to the toxic effects of bispyribac sodium. Bispyribac-sodium tested positive for DNA damage although all other mutagenicity tests indicated no significant genetic damage. The California Environmental Protection Agency Department of Pesticide Regulation determined that bispyribac-sodium was not mutagenic (Reference 4). In cancer testing, bispyribac-sodium did not cause tumor formation (Reference 4). The EPA determined that bispyribac-sodium does not pose a cancer risk to humans (Reference 5). CHRONIC HUMAN TOXICITY - Risk Assessment Subject and Scenario Route Dose of Concern Exposure Margin of Reference Risk Safety Rating Long-term exposures are not expected Long-term exposures are not expected Long-term exposures are not expected Long-term exposures are not expected Chronic Toxicity Risk Assessment Summary: Long-term exposures to bispyribac-sodium is not expected from aquatic herbicide use. Metabolites and Degradation Products: Benzoic acid and 2,4-dihydroxy-6-methoxypyrimidine are known soil degradation chemicals (Reference 1). Comments: Bispyribac-sodium may be a skin sensitizer (Reference 1). References 1. International Union of Pure & Applied Chemistry. Pesticide Properties Database. Bispyribac-sodium (Ref: KIH-2023). Record updated February 17, 2014. 2. USEPA. Environmental Fate and Effects Division. Environmental Fate and Ecological Risk Assessment for the Registration of Bispyribac-sodium (Sodium 2,6-bis[(4,6-dimethoxypyramidin-2-yl)oxy]benzoate). August 6, 2001. 3. TOXNET. Toxicology Data Network. National Library of Medicine, Hazardous Substance Database. Bispyribac..Last Revision Date: January 6, 2012. http:// toxnet.nlm.nih.gov. 4. California Environmental Protection Agency, Department of Pesticide Regulation, Medical Toxicology Branch. Summary of Toxicology Data, KIH-2023 (Bispyribac - Sodium). Chemical Code # 5749, Tolerance # 52841. Original date: April 11, 2001. Revised date: 5/23/01. 5. USEPA. Federal Register. Rule. Bispyribac-sodium; Pesticide Tolerance. 2/2/2011. Thurston County Health Department - 412 Lilly Road NE, Olympia WA 98506 - (www.co.thurston.wa.us/health/ehipm) Ph: 360-867-2664 T.D.D. 360-754-2933