ACUTE TOXICITY OF PYRITHIONE PHOTODEGRADATION PRODUCTS TO SOME MARINE ORGANISMS

Transcription

1 ACUTE TOXICITY OF PYRITHIONE PHOTODEGRADATION PRODUCTS TO SOME MARINE ORGANISMS International Symposium ON SHIPBUILDING TECHNOLOGY (ISST 2007) - Fabrication and Coatings 6-7 September 2007 Osaka University, Japan T Onduka,, K Mochida, K Ito, A Kakuno and K Fujii, National Research Institute of Fisheries and Environment of Inland nd Sea, Fisheries Research Agency, Japan H Harino, Osaka City Institute of Public Health and Environmental Sciences, Japan

2 Introduction Contents Antifouling paint biocide in Japan Characteristic of pyrithiones (PTs) Experimental Test chemicals, organisms, and methods Result and Discussion Acute toxicity of PTs and photodegradation products Comparison of toxicity of PTs and tributyltin (TBT) in previous study Conclusion Summary and future task

3 Antifouling ing paint biocide Organotin compounds (OTs) such as TBT have been used as antifouling biocides The toxicity of OTs have led to a worldwide ban by the International Maritime Organization Candidate marine antifouling compounds developed as alternatives to OTs Irgarol 1051, diuron, Sea-Nine 211, zinc pyrithione (ZnPT), copper pyrithione (CuPT)

4 Antifouling ing system in Japan Frequency of using PTs : 61% PTs are very frequently used as antifouling booster biocides Dicopper oxide CuPT ZnPT Pyridinetriphenylborane Diuron (%) The frequency of using antifouling biocide in Japan Japan Paint Manufactures Association (2006)

5 Characteristic of Pyrithiones PTs have toxic effects on fresh water organisms Median lethal concentration (LC50)( C50), Median effective concentration (EC50)( : < 462< µg L -1 PTs degrade rapidly in the water column Photolytic half-lives: lives: minutes Hydrolytic half-lives: lives: < days PTs are more stable under dark condition The purpose of this study was to elucidate the effect of the degradation products of PTs on marine organisms

6 Test organisms In the functioning of ecosystem, trophic relations are of prime importance Three marine organisms, representing three trophic levels Alga: Skeletonema costatum Crustacea: Tigriopus japonicus (nauplii) Fish: Pagrus major (weight: g)

7 Test Chemicals Test ChemicalsNSSNNSO3HNONSSNOONSHNSHOPyridine-2- sulfonic-acid (PSA) 2-mercaptopyridine- N-Oxide (POS) 2,2 -dithio-bispyridine-n-oxide ((POS)2) Pyridine-N-Oxide (PO) 2-mercaptopyridine (PS) 2,2 -dithio-bis-pyridine (DPS)NOCuSNOSNOZnSNOSZnPT CuPT

8 Algal growth inhibition test Recommended in the test guidelines of the OECD 201 CuPT: mostly stable ZnPT:100µg/L 7µg/L 30ml f/2 medium Initial cells concentration: 10 4 cells ml -1 Temperature 20 Light source: three ultraviolet screening fluorescent tubes µmol m -2 sec -1, 14hL:10hD In vivo fluorescence of the alga directly with a fluorescence meter 0h 24h 48h 72h Monitor in vivo fluorescence 72-h EC50 value was estimated by probit analysis rate of growth inhibition, nominal concentration

9 Copepod immobilisation test Recommended in the test guidelines of the OECD wells culture plate Filtered seawater Five nauplii / well 4 wells / concentration No feed Test period: 24 hours Under the dark condition Temperature 20 Inability to swim within 15 s after gentle agitation Immobilisation 24-h EC50 value was calculated by probit analysis immobilisation rate, nominal concentration

10 Fish acute toxicity test Recommended in the test guidelines of the OECD L glass aquaria 20 fishes / concentration No feed, Under the dark condition Temperature: Dissolved oxygen: mg L -1 ph: 8.1 0h 24h 48h 72h 96h Change test solution, Monitor mortality 96-h LC50 value was calculated by trimmed Spearman-Karber technique fish mortality, nominal or actual concentration

11 Acute toxicity of pyrithiones Alga Crustacea Fish EC50 EC50 Unit : μg L -1 LC50 CuPT * ZnPT * Previous study TBT * Reported by Mochida et al. (2006); the 96-h LC50 was calculated from the actual concentration Alga : most sensitive Toxicity : CuPT > ZnPT to the crustacea and the fish

12 Discussion of acute toxicity of pyrithiones Toxicity Alga: CuPT = ZnPT Crustacea and fish : CuPT > ZnPT ZnPT reacts with the Cu 2+ in seawater, and convert to CuPT f/2 medium: +1.8µg L -1 (7.1nM) of Cu 2+ in seawater ZnPT the algal test range: µg L -1 ( nM) there was enough Cu 2+ to convert ZnPT to CuPT

13 Acute toxicity of the photodegradation products of pyrithiones Alga Crustacea Fish EC50 EC50 Unit : μg L -1 LC50 POS 1.1 > (POS)2 3.4 >1 250 DPS PS PO > > > PSA > > >

14 Comparison of acute toxicity of photodegradation products and pyrithiones Alga Crustacea Fish EC50 EC50 Unit : μg L -1 LC50 POS 1.1 > (POS)2 3.4 >1 250 DPS PS Pyrithiones CuPT * ZnPT *

15 NNSSOOSOSHH3SNOKinetics of photodegradation products of pyrithiones (POS)2 Redox O Test chemicals transfer different products hν OH - H + POS NOO OH - M n+ ZnPT CuPTNSNOM n+ n O OPOS and (POS)2 can transform to pyrithiones Analytical methods of PTs transfer products in seawater are developing (Seymour and Bailey, 1981)

16 Summary and future task PTs have toxic effects on marine organisms The toxic influence of PTs and some of their photodegradation products on algae Future task The fate of PTs in seawater has to be elucidated The environmental PTs and photodegradation products risk assessments are needed