Toxicity and Risk Assessment of Pesticides to Aquatic Fauna

1
Toxicity and Risk Assessment of Pesticides to
Aquatic Fauna

• C. M. Bajet, MF. P. Navarro and L. M. Varca
• CCPTCL, NCPC, UPLB

2
Background Information

• Pesticides often impact nearby aquatic ecosystem
  and catchment basins
• Contamination is through direct water
  contamination or through sediment borne pesticides

3
Background Information

• Sediment borne pesticides affect bottom dwellers
• Pesticides dissolved in water or in suspended
  dissolved OM affect organisms directly living in
  water like fish, shrimp and algae

4
Toxicity testing

• Acute effects measured in animals after a single
  dose or single exposure to a pesticide
• Death/mortality is considered as acute
• LC50 measured concentration of the pesticide in
  water that will kill 50 of test animals
  (24,48,72,96h LC50)
• Inverse relation between toxicity and LC50 values

5
Factors affecting toxicity

• Species
• Age
• Sex
• Condition of the animal
• Water temperature and water quality
• Pesticide formulation
• Several LC50 values may exist for the same
  pesticide

6
Rationale of the Study

• The toxicity to the fish Tilapia nilotica will
  appropriately predict the fish toxicity in the
  tropics
• Algal toxicity will be an indicator of herbicide
  migration
• Shrimp as an aquatic invertebrate will be an
  indicator instead of Daphnia

7
Methodology

• Pesticides tested based on the pesticide
  management survey

• Pyrethroids lambda cyhalothrin, cypermethrin,
  deltamethrin
• Organophosphates profenophos, metamidophos,
  triazophos
• Others imidacloprid, nicosamide
• Herbicides diuron, propanil

8
Methodology Toxicity Testing of Tilapia nilotica

• Tilapia nilotica fingerlings from BFAR
• Size 22 mm
• Weight 1-2 g
• 5 test organisms/ L moderately hard H2O
• Observation time 24, 48, 72 and 96h
• 5-6 concentration range, 3 replicates
• Static conditions

9
Moderately Hard Water (EPA,1989)

• 0.08 g KCl
• 1.2 g of MgSO4 and CaSO4
• 1.92 g NaHCO3
• To be added to 20 L water treated by reverse
  osmosis and aerated for 24H
• Conductivity 280-380 ?S/cm, pH 7.4-7.8 and DO
  gt60 saturation

10
Methodology Toxicity testing in shrimp
(Macrobrachium sp.)

• Shrimps collected from Laguna lake
• Acclimatized and fed in the laboratory
• Tested with pesticides
• Size/weight 1-1.5 g
• 5 test organisms/10 L moderately hard water
• Observation time 24,48,72 and 96h
• 5-6 concentration range, 3 replicates
• Static

11
Results

• Pesticides arranged decreasing order of toxicity
  to Tilapia were as follows
• lambda cyhalothrin as the most toxic followed by
  deltamethrin
• triazophos, methamidophos, cypermethrin,
  profenophos, niclosamide, propanil, diuron and
  imidacloprid.

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Results

• Pyrethroids cypermethrin, deltamethrin and ?
  cyhalothrin
• Organophosphates triazophos and metamidophos were
  all toxic to Tilapia at lt10 ?g/L LC50 (96h).

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Results

• Least toxic was imidacloprid with LC50 (96h)
  101,740 ?g/L followed by diuron (LC50 96h13,620
  ?g/L)
• Diuron is more toxic to rainbow trout (LC50 96h)
  1,950 ?g/L compared to Tilapia

14
Comparative relationship between LC50 (96h)
values of rainbow trout and Tilapia (ug/L).
15
Comparative relationship between LC50 (96h)
values of rainbow trout and LC50 (48h) of Tilapia
(mg/L).
16
Risk assessment based on concentrations detected
from the field

• Low risk to Tilapia at the maximum concentrations
  detected in water
• ? cyhalothrin (lt0.09 ?g/L)
• cypermethrin (1.02 ?g/L)
• deltamethrin (0.03 ?g/L)  

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Risk Assessment Tilapia

• Low risk to Tilapia at the maximum concentrations
  detected in water for
• metamidophos (0.20 ?g/L)
• triazophos (0.15 ?g/L)
• butachlor (0.49 ?g/L).  

18
LC50 of selected pesticides to aquatic
invertebrates (ug/L)
c96h, b48h, a24h
19
LC50 of selected pesticides to aquatic
invertebrates (ug/L)
c96h, b48h, a24h
20
Comparative toxicity to Tilapia and Macrobrachuim
sp.

• Imidacloprid was found to be less toxic to
  shrimps (LC50, 96h) 13,520 ?g/L than to Tilapia
  (LC50, 96h) 101.74 ?g/L
• Deltamethrin and chlorpyrifos were more toxic to
  shrimps than Tilapia

21
Risk assessment of herbicides

• The toxicological impact of the butachlor
  concentrations detected (maximum of 0.49 ?g/L in
  water and 2.92 ?g/kg in sediment) in study sites
  was not assessed.
• LC50 (48h) of butachlor to Tilapia 150 ?g/L
  (Tejada et al, 1993)

22
Toxicity of herbicides to Selenastrum sp.
23
Aquatic toxicity and maximum concentration of
residues in water (ug/L)
 
T tilapia A algae S shrimp
24
Aquatic toxicity and maximum sediment residues
detected (ug/Kg)
T tilapia A algae
25
Summary/Recommendations

• Maximum residues of deltamethrin in water could
  affect Macrobrachium sp.
• Butachlor residues in water will not affect
  Tilapia. No studies on algae.
• Diuron residues (3.15 ?g/L ) in sediment could
  affect algae (EC50 Selenastrum sp. 2.4 ?g/L ,
  EPA database)
• Bioavailability of sediment residues (30.64 ?g/kg
  maximum) of cypermethrin to Tilapia must be
  evaluated (LC50 8.77 ?g/L)