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Bio 430: Chemicals in the environment

Bio 430: Chemicals in the environment. Jeffrey Jenkins Department of Environmental and Molecular Toxicology Oregon State University. Chemical fate: transformation and transport within and between Soil-Air-Water-Biota. Source: U.S. Geological Survey. interception. wash off.

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Bio 430: Chemicals in the environment

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  1. Bio 430: Chemicals in the environment Jeffrey Jenkins Department of Environmental and Molecular Toxicology Oregon State University

  2. Chemical fate: transformation and transport within and between Soil-Air-Water-Biota Oregon State University Source: U.S. Geological Survey

  3. interception wash off Oregon State University

  4. Oregon State University

  5. Chemical fate in the environment Molecular interactions (physical-chemical properties, reactivities) Environmental factors (Temperature, pH, light intensity, ion composition and strength, microbial activity, natural organic matter, etc.) Environmental processes (e.g. air/water exchange, sorption/desorption, chemical, photochemical and biological transformation) Oregon State University

  6. Chemical fate in the environment Transport and mixing processes Dynamic behavior in a natural system (mathematical models and field investigations) Oregon State University

  7. Chemicals in the Environment • Initial distribution to environment (manufacture and use): • emission in: air-soil-water-biota compartments • Transformation: degradation/metabolism • Redistribution- transport in and between compartments: • diffusion/advection-dispersion/mass transport Oregon State University

  8. Chemicals in the Environment • Understanding chemical fate, what scale? • Local scale: site-specific inputs, potential for off-site transport. • Watershed scale: integration of site-specific inputs and transport, particular emphasis on water quality. • Regional scale: integration of watershed-airshed chemical inputs and redistribution, long range transport of persistent compounds. Oregon State University

  9. Range of ESA Listed Salmon Oregon State University

  10. Pesticides in the Environment • Initial distribution in the environment: • method of application • timing of application • frequency of application • amount of active ingredient • formulation (other ingredients) Oregon State University

  11. Initial distribution sunlight temperature Persistence and Mobility organic matter soil pH moisture soil texture Environmental Fate Environmental Behavior of Pesticides in Soils Oregon State University

  12. Pesticide Fate and Transport • Physical-chemical properties: • Water solubility • Vapor Pressure • Kd (soil/water partition coefficient) • Henrys Law Constant • Soil half-life • Foliar half-life Oregon State University

  13. Oregon State University

  14. Soil sorption Oregon State University

  15. Soil sorption • To account for different soil types and organic matter content the Kd is normalized for % organic carbon. * decimal equivalent Oregon State University

  16. Soil Properties that Influence Leaching and Runoff • Permeability • Water table conditions • Organic matter content • Clay content Oregon State University

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  18. Course textured soils and other soil conditions that result in preferential flow paths must also be considered. Oregon State University

  19. Pesticides in Ground and Surface Water Oregon State University

  20. water soil particle concentration concentration of pesticide of pesticide in sorbed to soil solution Pesticides in surface water • Mass transfer primarily in the dissolved phase, will vary with pesticide’s solubility in water and soil sorption. Oregon State University

  21. Partitioning between soil compartments(soil, water air) Oregon State University

  22. Oregon State University

  23. Atmospheric Transport Zones Oregon State University

  24. Oregon State University

  25. Oregon State University

  26. Volatile loss as Percent Applied Oregon State University

  27. Pesticide Fate • Field dissipation: sum of chemical and biological processes including: • Chemical degradation1 • Biological degradation (microbial + plant)1 • Photodegradation2 • Volatilization • 1Approximated with a 1st order rate constant • 2Approximated with a psuedo 1st order rate constant Oregon State University

  28. Pesticide degradation half-life • Half-life = the amount of time it takes the parent compound to decay to half its original amount • Half-life in an environmental compartment: (soil-air-water-biota) sum of all degradation and transport pathways Oregon State University

  29. Pesticide degradation half-life Oregon State University

  30. Sunlight photolysis of an aqueous suspension of nitrofen Oregon State University

  31. Chemical and microbial degradation of chloroanilines Oregon State University

  32. LD50:lethal dose for ½ the test animals NOAEL Oregon State University

  33. Aldicarb degradation pathways and LD50 values (rat acute oral) Oregon State University

  34. Pesticide Properties used to evaluate fate in the Environment Oregon State University

  35. Chemical fate determines exposure to humans and aquatic life Oregon State University

  36. 13.4 million lbs of pesticides used annually in OregonWhat are the risks and who decides? • Federal Insecticide, Fungicide, and Rodenticide Act regulates pesticide manufacture, use, storage, and disposal (benefit-risk balancing statute.) • Under Authority of the Clean Water Act, ODEQ has the authority to set pesticide water quality standards for waters of the state (TMDLs). • Under the Endangered Species Act NMFS and USFWS have the authority to set rules deemed necessary to prevent more species declines under a provision called “Four D.” • EPA, NMFS, and USFWS have “overlapping” jurisdiction with regards to pesticide use and the Endangered Species Act. Oregon State University

  37. EPA Risk Assessment Risk = f (exposure, toxicity) Source: Purdue University Pesticides Program Oregon State University

  38. Pesticide Risk Assessment • RFD: The Reference Dose is the amount of a pesticide residue a person could consume daily for 70 years with no harmful non-cancer effects. Oregon State University

  39. Pesticide Risk Assessment • The RFD is determined by dividing the NOAEL by a safety factor, usually between 100 and 1000, • to account for uncertainty in extrapolating from animal studies and to protect sensitive individuals, including infants and children. Oregon State University

  40. Quantitative Assessment of Health Risks of Pesticides in Drinking Water MCL - The Maximum Contaminant Level permissible in water which is delivered to any user of a public water system (Safe Drinking Water Act; ~50 pesticides have MCLs) HA - Health Advisory: EPA guidance for drinking water contaminants based on lifetime exposure and non-carcinogenic endpoints. HA is derived from the DWEL. DWEL - Drinking Water Equivalent Level, based on the Reference Dose (RfD) and assuming 70 Kg person drinks 2 liters per day over a lifetime. The DWEL has been adjusted assuming that drinking water comprises 20% of the allowable daily intake. Oregon State University

  41. Pesticide Risk Assessment: Wildlife • What is the toxicity of the pesticide and it’s degradates to wildlife? Acute toxicity (high dose-short exposure) Chronic toxicity (low dose-long exposure) Most sensitive adverse effect Sensitive sentinel species Oregon State University

  42. EPA Pesticide Aquatic Risk: Wildlife Toxicity Assessment • Laboratory tests are used to determine the NOAEL in representative species. • The hazard quotient is the ratio of the NOAEL to the expected environmental concentration. • If the hazard quotient is greater than 1.0, the potential exists for adverse ecological effects. Oregon State University

  43. Use of models for evaluating hazards associated with chemicals in the environment • Models use a systems approach to understanding complex phenomenon. • Computer based environmental models present a conceptual framework and a mathematical formulation of fate and transport between compartments (soil, air, water, biota) based upon scientific principles. Oregon State University

  44. Environmental fate models • PRZM and EXAMS (EPA) • CalTOX (California EPA) • Fugacity Model Levels I, II, III (Mackay) • Gaussian plume models (EPA, NOAA) • http://www.lanl.gov/orgs/d/d4/movies.shtml Oregon State University

  45. Fugacity Model for Biphenyl Oregon State University

  46. Fugacity Model for Biphenyl Oregon State University

  47. Hazard Identification Dose-Response Assessment Exposure Risk Characterization How Do We Assess Risk? • Follow the National Academy of Sciences (NAS) four-step risk assessment paradigm*: * From the National Research Council’s Risk Assessment in the Federal Government: Managing the Process, 1983. Oregon State University

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