1 20 januari 2011

Tamiflu in the environment

Caroline MoermondCharles BodarLonneke van LeeuwenMark MontfortsBianca van de VenSuzanne WuijtsMonique van der AaAns Versteegh

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What is Tamiflu?● Tamiflu = oseltamivir

● Antiviral drug which slows the spreading of viral cells through the body

● Registered in Europe (EMA) in 2002

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Why a risk assessment?● Swine flu (‘Mexicaanse griep’) – questions raised about

environmental impact of flu-related medication● In the original risk assessment for authorisation, pandemic use and

drinkwater quality were not taken into account● Advice for the ministry of Environment (VROM) at sept. 1, 2009

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Properties of tamiflu● Oseltamivir ethylester phosphate transforms in the body

first into pro-drug: oseltamivir ethylester then into active compound: oseltamivir-acid

● In urine: ethylester:acid 1:4● Log Kow = 1.21 for ethylester; log Kow = 0.006 for acid● Very soluble, low sorption to organic matter● Almost no hydrolysis or photolysis● DT50 in water-sediment system is 86 days● No degradation in surface water in the dark during 60 days● very persistent!

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Environmental risk assessment - general● For human pharmaceuticals, risk assessment is performed according

to EMA guideline● Two phases:

– Phase 1: estimation of exposure› If trigger value of 0.01 µg/L in surfacewater is met phase 2› If compound is a hormone always phase 2

– Phase 2: environmental fate and effects analysis› Base set of fate and effects data› Risk assessment for surface water, ground water, and STP› If necessary (sorption) also risk assessment for sediment and soil

● Effect characterisation:

PNEC

PEC

ionconcentrateffectnopredicted

ionconcentrattalenvironmenedictedPr

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Estimation of exposure● Predicted Environmental Concentration (PEC)

– EMA guideline gives a basic calculation which can be refined using the prevalence of the disease

factordilutionpersonperwastewaterofamountdaily

npenetratiomarketoffractiondosedailyimummaxwaterPECsurface

● Fraction of market penetration is default 0.01 (1%)● For oseltamivir: daily dose is 150 mg/day for curative use and 75 mg/day for preventive use

PECsurfacewater using default values: 0,70 µg/L use by 30% of inhabitants of a region: PECsurfacewater = 20.9 µg/L 1 µg/L if 1.5% of all inhabitants is treated.

● (Almost) no degradation in sewage treatment plant!

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Estimation of exposure – are these values realistic?

EMA default exposure scenario 0.7 µg/L

EMA exposure scenario with 30% use 20.9 µg/L

Singer et al, 2007 34 µg/L

KWR calculations for river Rhine during pandemic use 1-10 µg/L

UK drinking water inspectorate model calculations(Watts and Crane Associates, 2007)

Max 107 µg/L

Industry models (Straub, 2009) Max 98 µg/L

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Estimation of exposure – are these values realistic?

EMA default exposure scenario 0.7 µg/L

EMA exposure scenario with 30% use 20.9 µg/L

Rivers in Japan during ‘normal’ flu season (Söderström et al., 2009)

Max 60 ng/L

STP effluent in Japan 2008/2009 flu season (Ghosh et al., 2010a)

Max. 293 ng/L

Rivers in Japan 2008/2009 flu season (Ghosh et al., 2010a)

Max. 190 ng/L

STP influent in Japan 2009/2010 flu season (Ghosh et al., 2010b)

Max. 460 ng/L

STP influent Rhine catchment area sept. ’09 (Prasse et al.,. 2010)

Max. 53 ng/L

River in Germany, sept. ’09 (Prasse et al., 2010) Max. 38 ng/L

River Rhine, Germany, sept. ’09 (Prasse et al., 2010) Max. 160 ng/L

Measurements agreed very well with modeled concentrations

Influence from manufacturing plants?

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Estimation of effects: Single species toxicity tests

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Estimation of effects: criteria for toxic effects● Chronic ecotoxicity studies required by EMA guideline, because

exposure is also chronic

● NOEC = no effect concentration● LOEC = lowest effect concentration● LC50 = concentration at which 50% of the test animals has died

(L=lethal)● EC50 = concentration at which 50% of the animals show an effect

(behaviour, growth, reproduction, etc.)

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Criteria for toxic effects

-1 0 1 2 30

25

50

75

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concentration (log scale)

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L(E)50

-1 0 1 2 30

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% s

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val

L(E)50

control 1 2 3 4 50

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NOEC

treatment

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control 1 2 3 4 50

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NOEC

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Estimation of effects

algae

+ +

crustacea fish

Aquatic ecosystem?

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Estimation of effects● Predicted No Effect Concentration (PNEC):

PNEC = lowest NOEC / 10

● Use of assessment/extrapolation factor, covering:– intra- and inter-species variation– short-term to long-term extrapolation– intra- and inter-laboratory variation– lab-to-field extrapolation

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Risk characterisation of surface- and groundwater

● PEC/PNEC < 1: negligible risk● PEC/PNEC > 1: potential risk

● Oseltamivir in surface water:– Worst-case PEC: 20.9 µg/L– PNEC based on lowest NOECs (≥ 1000 µg/L) = ≥ 100 µg/L PEC/PNEC = ≤ 0.21

● Oseltamivir in ground water:– Worst-case PEC: 20.9 µg/L / 4 = 5.2 µg/L – PNEC based on lowest NOECs (≥ 1000 µg/L) = ≥ 100 µg/L PEC/PNEC = ≤ 0.05 no risk for direct ecotoxicity

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Risk characterisation – sewage treatment plants● PEC for sewage treatment plants is factor 10 higher than

PECsurfacewater (no dilution) PEC = 209 µg/L

● Respiration-inhibition test (OECD 209) was not performed

● Biodegradation tests showed no effect on micro-organisms at 200 µg/L PNEC = ≥200 / 10 = ≥ 20 µg/L

● Another study showed an effect at 360 µg/L ● PEC/PNEC = ≤ 10.5 potential risk

● There are indications that tamiflu may have an effect on microbial biofilms

● Combined effect of antibiotics and tamiflu unclear

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Risk characterisation – drinking water● No guidance in EMA guideline● No general drinking water standard for pharmaceuticals

(Drinkwaterrichtlijnen 98/83/EG and 75/440/EEG)● Because of the enzymatic mode of action, the compound belongs to

the group of pesticides Pesticide drinking water standards: 0.1 µg/L

● General signal value for alle anthropogenic compounds: 1 µg/L● Expected concentrations of tamiflu during pandemic use are above

these values.

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Risk characterisation – drinking water● Is this a problem?

– Oseltamivir does not sorb to organic carbon active carbon filtration will not remove oseltamivir

– Other types of filtration may remove oseltamivir, but data are scarce

– The safety margin between the calculated concentrations and human toxicological effect values is large enough not to expect effects.

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Antiviral resistance formation● Out of scope of this risk assessment● But: EC50 for influenza virus is 80-230 ng/L (Gubareve et al.,

2001; Monto et al. 2006).

EMA default exposure scenario 0.7 µg/L

EMA exposure scenario with 30% use 20.9 µg/L

Rivers in Japan during ‘normal’ flu season (Söderström et al., 2009)

Max 60 ng/L

STP effluent in Japan 2008/2009 flu season (Ghosh et al., 2010a) Max. 293 ng/L

Rivers in Japan 2008/2009 flu season (Ghosh et al., 2010a) Max. 190 ng/L

STP influent in Japan 2009/2010 flu season (Ghosh et al., 2010b) Max. 460 ng/L

STP influent Rhine catchment area sept. ’09 (Prasse et al.,. 2010) Max. 53 ng/L

River in Germany, sept. ’09 (Prasse et al., 2010) Max. 38 ng/L

River Rhine, Germany, sept. ’09 (Prasse et al., 2010) Max. 160 ng/L

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Questions?