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1 Evaluation of Water Contamination from Consumer Product Uses Rick Reiss SOT DC Spring Symposium April 15, 2010.

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Presentation on theme: "1 Evaluation of Water Contamination from Consumer Product Uses Rick Reiss SOT DC Spring Symposium April 15, 2010."— Presentation transcript:

1 1 Evaluation of Water Contamination from Consumer Product Uses Rick Reiss SOT DC Spring Symposium April 15, 2010

2 2 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

3 3 Factors Affecting Potential Risks  Quantities used  Methods of disposal  Dilution into waterway  Physicochemical properties  Binding to organic matter  Aquatic degradation  Toxicity to aquatic organisms

4 4 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

5 5 CASE STUDY #1 – TRICLOSAN AQUATIC EXPOSURES

6 6 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

7 7 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.

8 8 Significant Factor Affecting Loading: Dilution at Outfall

9 9 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

10 10 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

11 11 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.

12 12 Mean Flow Dilution at WWTPs

13 13 Low Flow Dilution (One in 10 years)

14 14 Triclosan Removal in Wastewater Treatment Plants

15 15 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%.

16 16 Physicochemical Properties of Triclosan PropertyValue Molecular Weight289.6 Water Solubility12 mg/L Dissociation constant ( pK a )8.14 at 20 o C Vapor pressure7x10-4 Pa at 25 o C Partition coefficient (log K ow )4.8 Aerobic biodegradation in soil day half-life Aqueous photolysis41-min half-life at pH of 7 and 25 o C Adsorption to suspended solids ( K oc )47,454 mg/g

17 17 Correlation Between Suspended Sediment and Organic Carbon Content

18 18 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

19 19 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

20 20 Estimated Concentrations at Discharge Point

21 21 Lowest NOECs Across Species Class SpeciesNOEC (ppb) Acute fish (bluegill sunfish, fathead minnow)100 Acute aquatic invertebrates ( Ceriodaphnia dubia ) 50 Algae ( Scenedesmus subspicatus )0.67 Aquatic plants ( Lemna gibba )62.5 Chronic fish (rainbow trout)34 Chronic aquatic invertebrates ( Daphnia magna )40

22 22 Margins of Safety at Outfall (Low Flow)

23 23 Margins of Safety 5 Miles Downstream, Low Dissipation (Low Flow)

24 24 Margins of Safety 5 Miles Downstream, High Dissipation (Low Flow)

25 25 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

26 26 CASE STUDY #2 – TRICLOSAN TERRESTRIAL EXPOSURES

27 27 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

28 28 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)

29 29 Triclosan Concentrations in Sludge

30 30 Endpoint Values for Risk Assessment SpeciesValue 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 EarthwormsNOEL >1026 mg/kg MicroorganismsHA50 = 236 mg/L Soil respiration and nitrificationNOEL = 1 mg/kg CucumbersNOEC = 1 mg/kg (pre-emergent study in relevant soil) ED50 = 0.74 mg/kg (shoot dry weight in sand)

31 31 Key Factors in the Exposure Assessment  Assumed soil amendment rates  kg/m 2 /year  Soil degradation rate  35 day half-life  Bioconcentration factors in fish and earthworms

32 32 Predicted Environmental Concentrations

33 33 Margins of Safety for Secondary Fish Exposure

34 34 Margins of Safety for Secondary Exposure from Earthworms

35 35 Margins of Safety for Terrestrial Plants

36 36 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


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