000828 - forsvar - revised text
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Environmental Risk Assessment of Antimicrobials
Hans-Christian Holten Lützhøft
Section of Environmental ChemistryDepartment of Analytical and Pharmaceutical Chemistry
The Royal Danish School of Pharmacy
Demand from the European Community (EMEA, 1998)
Antimicrobial discharge can be expected after medication due to limited effluent treatment at the fish farm resulting in possible exposure to the environment
Why Bother?
Environmental Occurrence
Overview of Performed Tasks
Outline Main objective The antimicrobials Environmental fate Environmental effects Exposure scenarios Environmental risk assessment
Main Objective Assess the aquatic environmental risk associated with
application of antimicrobials in freshwater fish farming
The Antimicrobials
Physical Chemical Properties
Physical Chemical Properties
Application Treat infections among fish in fish farming
Enteric red mouth disease Furunculosis Vibriosis
Fry mortality syndrome
FLU, OXA, SAFSDZ/TMPAMX, OTC
AMX, OTC
OXA and SDZ/TMP are commercially available as medicated feed
Consumption in Danish Fish Farming, kg
Year OXAa SDZa TMPa AMXb OTCb Otherb Total1994 700 1,000 200 6 94 132 2,1321995 906 1,241 248 78 67 242 2,7821996 511 845 169 141 27 177 1,8701997 587 1,677 335 132 16 181 2,928
a: Viuf (Personal communication), b: Data from 3 counties (Danske amter, Personal communication), Other:dimetridazole (antiprotozoal), florfenicol, metronidazole, sulfamerazine, and antimicrobials as such.
Compared with other Countries
mg/kg (fish) mg/L (effluent)Country 1987 1994 1997 1995Scotlanda - 40 8 naNorwayb 885 7 - naDenmarkc - 61 84 0.7USAd - - - 4a: Baird et al. (Personal communication), b: Markestad and Grave (1997), c: Viuf (Personal communication)and Danske amter (Personal communication), d: Vicari et al., (Personal communication), -: not available,na: not applicable.
Biotic Fate Low oral bioavailability (ca. 10%)a
Various degrees of biotransformationb
Mainly excreted as parent compoundsc
a: Bjørklund and Bylund (1991); b: Grondel et al. (1989), Ishida (1992), Tan and Wall (1995); c: Bergsjø et al. (1979), Rogstad et al. (1991), Ishida (1992), Tan and Wall (1995)
Preliminary Environmental Assessment
Low oral bioavailability and low biotransformation result mainly in excretion of a parent compound
The principal exposure is to the aquatic environment, however the distribution is widely pH-dependent
Environmental exposure of biological active chemicals may affect non-target organisms
Environmental Fate
Environmental Processes
Objectives Determine distribution coefficients (DDOC) of 4-quinolones
between dissolved organic carbon (DOC) and water using SPME-HPLC analysis
What influence does pH have?
pH?
DOC?
N
F
CH3
COOHO
N
OCOOH
CH3
O
ON
FO
COOH
NHN
F
Holten Lützhøft et al. (Accepted)
Principles of SPME Negligible depletion solid phase
microextraction (nd-SPME)
Kinetic extraction approach Measurement of the free concentration
MXMX
MXMXFibreXFibre
Interaction with DOC
Chemical Log KOW Log KOC from QSARa Log DDOC
FLU 1.7b 1.7 3.40.27c
OXA 1.0d 1.0 3.90.05c
SAF - - 4.80.01c
DDT 6.9e 6.8 5.60.18f
HxCBz 5.7e 5.6 5.00.05f
PeCBz 5.2e 5.1 4.50.03f
a: Di Toro (1985), b: Takács-Novák and Avdeef (1996), c: Holten Lützhøft et al. (Accepted) III, d: HoltenLützhøft et al. (2000) II, e: Bruijn et al. (1989), f: Urrestarazu Ramos et al. (1998).
pH-Dependent Interaction with DOC
N
F
CH3
COOHO
pKa=6.5
FLU
N
OCOOH
CH3
O
O pKa=6.9
OXA
2 3 4 5 6 7 83
4
5
6
SAF
OXAFLU
pH
Log
DDO
C
N
FO
COOH
NHN
F
pKa=6.8
pKa=4.1
SAF
pKa=8.6
Conclusions DDOC values for the investigated 4-quinolones appeared to
be remarkably high
DDOC values for the investigated 4-quinolones were shown to be pH dependent, suggesting electrostatic interactions to work in the system
Summary of Environmental Fate
Log DSED values of 2.3-2.7a
Similar physical chemical properties for sulphadiazine and amoxicillin suggest log DSED in the same range
Photodegradation is negligibleb
Non-biodegradablec
Oxytetracycline is biodegradable in freshwater sediment slurries (t½: 2-8 days)
a:Lai et al. (1995), Holten Lützhøft (Unpublished); b: Lunestad et al. (1995); c: Hektoen et al. (1995), Lai et al. (1995)
Environmental Effects
Objectives Investigate the suitability of using the standard test algae
Selenastrum capricornutum to represent micro-algae for evaluation of antimicrobials, e.g. ISO (1989) and EMEA (1998)
Establish toxicity data for antimicrobials towards algae
Holten Lützhøft et al. (1999)
Tested Algae Microcystis aeruginosa (freshwater cyanobacteria) Rhodomonas salina (marine cryptophycean) Selenastrum capricornutum (freshwater green algae)
BacteriaProcaryoticNo nucleus0.5-2.0 µm
No photosynthesis
Modified from Brock and Madigan (1991)
CyanobacteriaProcaryoticNo nucleus0.5-60 µm
Photosynthesis
AlgaeEucaryotic
Nucleus2-200 µm
Photosynthesis
Overview of Acute Effect Data
0,1
1
10
100
1000
AMX SAF FLU SDZ OXA OTC TMP
LC50
, mg/
L
a: Migliore et al. (1997); b: Andersen (1999), Andersen (Personal Communication); c: Andersen (1999), Wollenberger et al. (2000), Halling-Sørensen et al. (In press); d: Andersen (1999), Halling-Sørensen et al. (In press)
: NOEC
Artemia sp.a A. tonsab
B. reriodD. magnac
Overview of Chronic Effect Data
0,0001
0,001
0,01
0,1
1
10
100
1000
10000
AMX SAF FLU SDZ OXA OTC TMP
EC50
, mg/
L
: NOEC
a: Backhaus et al. (2000); b: Holten Lützhøft et al. (1999) IV; c: Wollenberger et al. (2000)
V. fischeria M. aeruginosab R. salinab
S. capricornutumb D. magnac
Conclusion Environmental evaluation of antimicrobials requires tests
of cyanobacteria
The effect concentrations are comparable to concentrations of antimicrobials found in the environment
Exposure scenarios
Overview of Exposure Scenarios
PECs
Environmental Risk Assessment
Procedure to Derive PNEC Constant assessment factor approach proposed by the
OECDa and EMEAb
Assessment factor depends on quality of data i.e. acute/chronic, NOEC/EC50, trophic levels
a: OECD (1992); b: EMEA (1998)
Factor AssessmentEC or NOECLowest PNEC 50
0
50
100
NOEC
Chronic Acute
EC50
AF=10
Log C
AF=100
NOEC
Effe
ct, %
EC50
Assessment FactorsThree trophic levels Less than three trophic levels
0
50
100
Log C
AF=1,000
NOEC
EC50
Effe
ct, %
PNECs
Risk Quotients
PNECPECRQ
Main Objective
Assess the aquatic environmental risk associated with application of antimicrobials in freshwater fish farming
Environmental Ranking
TMP OTC SDZ SAF OXA FLU AMX
Harmless understudied scenarios
More studiesrequired RQ
10-3 10-2 10-1 1 101 102 103
I would like to thank ... Sven Erik Jørgensen and Bent Halling-Sørensen for the
thorough supervision during my Ph.D. project the last 3-4 years