1 evaluation of water contamination from consumer product uses rick reiss sot dc spring symposium...

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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