1 evaluation of water contamination from consumer product uses rick reiss sot dc spring symposium...
TRANSCRIPT
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Evaluation of Water Contamination from Consumer Product Uses
Rick Reiss
SOT DC Spring Symposium
April 15, 2010
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Introduction
Many consumer products are disposed of down residential drains
Transported into sewer systems and potentially released into the environment Contaminate waterways leading to risk to aquatic species Potentially make its way into drinking water
Sorb to sludge in sewage treatment plants Some sludge is used as biosolids for agricultural amendment Potential for terrestrial exposures
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Factors Affecting Potential Risks
Quantities used Methods of disposal Dilution into waterway Physicochemical properties
Binding to organic matter Aquatic degradation
Toxicity to aquatic organisms
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Summary of Reconnaissance Studies
USGS has performed surveys in streams, surface water sources of drinking water, and groundwater Found a variety of antimicrobials, fragrances, flavoring
chemicals, pesticides, plasticizers, cosmetics, etc.
However, the low levels of most detections raises questions about whether there is a risk
Many potential chemicals have not been measured
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CASE STUDY #1 – TRICLOSAN AQUATIC EXPOSURES
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Approach
Triclosan (2,4,4’-trichloro-2’-hydroxydiphenyl ether) is a broad spectrum bactericide Generally low human toxicity, but high toxicity to algae Recent studies address estrogenic activity
Used soaps, detergents, surface cleansers, disinfectants, cosmetics, pharmaceuticals, and oral hygiene products.
Most (~95%) of the uses are disposed of down residential drains
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Purpose of the Study
Estimation of the distribution of triclosan concentrations in reaches following WWTP discharge. Based on: Characteristics of reaches Discharge mass from WTTP Physicochemical properties
Estimation of risk to aquatic organisms based on most sensitive species in phylogenic groups.
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Significant Factor Affecting Loading: Dilution at Outfall
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Factors Affecting Triclosan Loading into Rivers
Triclosan loading into river Influent concentration Removal efficiency in WWTP
Physical properties of river Dilution pH Suspended sediment concentration Organic carbon content of sediment
Physicochemical properties
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Development of an Aquatic Exposure Model
Steady-state model accounting for ionization, sorption with suspended sediment, and complexation with dissolved organic carbon (DOC).
Downstream dissipation modeled from results of die-away studies.
Probabilistic inputs developed for effluent concentration, pH, stream velocity, suspended sediment concentration (including organic carbon content), and DOC concentration
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Characteristics of Reaches
EPA’s Clean Water Needs Survey contains extensive data for WWTP facilities. Mean flow, low flow, velocity, pH, and discharge volume
Of the 16,024 WWTPs in 1996, sufficient data were available for 11,010 facilities.
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Mean Flow Dilution at WWTPs
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Low Flow Dilution (One in 10 years)
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Triclosan Removal in Wastewater Treatment Plants
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Wastewater Treatment Removal
Significant removal due to high sorption to sludge
Removal rates: Activated sludge: 94 to 96 percent (4 plants) Trickling filter: 58 to 96 percent (4 plants)
Distribution of U.S. treatment plants: (1) activated sludge: 86%, (2) trickling filter: 12%, and (3) primary treatment: 2%.
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Physicochemical Properties of Triclosan
Property Value
Molecular Weight 289.6
Water Solubility 12 mg/L
Dissociation constant (pKa) 8.14 at 20oC
Vapor pressure 7x10-4 Pa at 25oC
Partition coefficient (log Kow) 4.8
Aerobic biodegradation in soil 17.4-35.2 day half-life
Aqueous photolysis 41-min half-life at pH of 7 and 25oC
Adsorption to suspended solids (Koc) 47,454 mg/g
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Correlation Between Suspended Sediment and Organic Carbon Content
0
1
10
100
0 1 10 100 1,000 10,000
Suspended Sediment Concentration (mg/L)
Per
cent
age
Org
anic
Car
bon
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Triclosan Die-Away Studies
Triclosan dissipation in an 8 kilometer stretch of Cibalo Creek in south central Texas (Morrall et al.): Half-life, dilution-corrected, was 12.8 hours. Half-life, including dilution, was 5 hours
Measured triclosan dissipation in the River Aire in the U.K. (Sabaliunus et al.): Half-life, including dilution, was 3.3 hours
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Summary of Probabilistic Analysis
Data on stream characteristics for 11,010 reaches obtained from Needs survey for both mean and low flow dilutions.
Suspended sediment and DOC concentration from USGS data, and organic carbon content from correlation.
Environmental fate properties of triclosan (e.g., sorption).
Die-away rate
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Estimated Concentrations at Discharge Point
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Lowest NOECs Across Species Class
Species NOEC (ppb)
Acute fish (bluegill sunfish, fathead minnow) 100
Acute aquatic invertebrates (Ceriodaphnia dubia)
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Algae (Scenedesmus subspicatus) 0.67
Aquatic plants (Lemna gibba) 62.5
Chronic fish (rainbow trout) 34
Chronic aquatic invertebrates (Daphnia magna) 40
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Margins of Safety at Outfall (Low Flow)
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Margins of Safety 5 Miles Downstream, Low Dissipation (Low Flow)
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Margins of Safety 5 Miles Downstream, High Dissipation (Low Flow)
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Summary of Case Study
There should be no direct effects to fish, plants or invertebrates due to triclosan exposures from WWTPs
There may be some effects to algae for reaches where the dilution is low (or when the dilution is low)
Uncertainties exist regarding degradates of triclosan in water, particularly due to photolysis
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CASE STUDY #2 – TRICLOSAN TERRESTRIAL EXPOSURES
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Introduction
Triclosan has a high potential to sorb with organic matter
Sludge is wastewater treatment plants is very rich in organic matter
Some wastewater sludge is used as soil amendments in agriculture
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Exposure Pathways
Direct exposure Earthworms Soil microorganisms Terrestrial plants
Secondary exposures Consumption of earthworms (birds and mammals) Fish exposed in water from wastewater effluent (birds and
mammals)
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Triclosan Concentrations in Sludge
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Endpoint Values for Risk AssessmentSpecies Value
Birds, acute (bobwhite quail) LD50 = 862 mg/kg
Birds, subchronic (bobwhite quail) LD50 = 577 mg/kg/day
Mammals, acute (rats) LD50 = 3700 mg/kg
Mammals, chronic (hamsters) NOEL = 75 mg/kg/day
Earthworms NOEL >1026 mg/kg
Microorganisms HA50 = 236 mg/L
Soil respiration and nitrification NOEL = 1 mg/kg
Cucumbers NOEC = 1 mg/kg (pre-emergent study in relevant soil)ED50 = 0.74 mg/kg (shoot dry weight in sand)
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Key Factors in the Exposure Assessment
Assumed soil amendment rates 0.5-2.0 kg/m2/year
Soil degradation rate 35 day half-life
Bioconcentration factors in fish and earthworms
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Predicted Environmental Concentrations
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Margins of Safety for Secondary Fish Exposure
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Margins of Safety for Secondary Exposure from Earthworms
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Margins of Safety for Terrestrial Plants
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Conclusions
Everything must go somewhere! Especially things that don’t degrade quickly and/or stick to
organic matter
Risk assessment methods can be applied to address potential exposures in aquatic and terrestrial environments Can be used to differentiate real risks from mere exposures