水研センター研報，第21号，31−45，平成19年
Bull. Fish. Res. Agen. No. 21, 31‑45, 2007

総説

Behaviour, Occurrence, and Aquatic Toxicity of New Antifouling
Biocides and Preliminary Assessment of Risk to Aquatic Ecosystems
Hisashi YAMADA*

Abstract Paints containing biocides prevent the adhesion of organisms to the hulls of
ships, and are hazardous to aquatic ecosystems. I reviewed published literature reporting the behaviour, occurrence, and toxicity in aquatic environments of the organotin-free
new antifouling biocides. Our analysis included the representative alternative new biocides;
2,4,5,6-tetrachloro-isophthalonitrile（chlorothalonil）, N -dimethyl-N-phenylsulphamide（dichlofluanid）,1（3,4-dichlorophenyl）-3,3-dimethylurea（diuron）,2-methylthio-4-t-butylamino-6-cyclopropylamino-s-triazine（Irgarol 1051）, 4,5-dichloro-2-（n-octyl）-4-isothiazoline（Sea Nine 211）,2（thiocyanomethylthio）benzothiazole（TCMTB）, bis-（1-hydroxy-2（1H）-pyridinethionate-O,S）zinc（zinc pyrithione, ZnPT）, zinc ethylene bis-（dithiocarbamate）（zineb）, pyridinetriphenylboron（PK）, and bis-（1-hydroxy-2（1H）-pyridinethionate-O,S）copper（copper pyrithione,
CuPT）. These new biocides are classified as toxic to very toxic according to guidelines of
the Organization for Economic Co-operation and Development, with toxicity values similar
to those of TBT. The new biocides are decomposed by hydrolysis, photolysis, and biologicalactivity and thus are less persistent in the environment than TBT, but low vapour pressure
limits their evaporation. Because of medium octanol-water coefficient（Kow）and organiccarbon partitioning coefficient（Koc）values, these new biocides, except for zineb, ZnPT, and
CuPT, tend to be distributed in both seawater and sediments but have low bioaccumulation
in aquatic organisms. Chlorothalonil, dichlofluanid, diuron, Irgarol 1051 and its degradation
product, 2-methylthio-4-tert-butylamino-6-amino-s-triazine（M1）, and Sea Nine 211 have beenfound in natural waters, with higher concentrations in marinas and small harbours for fishing boats than in coastal waters, but insufficient data are available to assess contaminationby these biocides. The reported concentrations of Irgarol 1051, M1, and Sea Nine 211 exceed
their respective predicted no-effect concentration values, especially in marinas and fisheryharbours, suggesting that these new biocides are already harming aquatic ecosystems insome areas. Further research is needed to assess the ecotoxicological risks of these biocides
and to develop methods for estimation of their concentrations in ambient water.
Key words : TBT-free antifouling paint, biocide, fate in environment, toxicity, risk assessment, aquatic organisms

Introduction

to the hulls of ships, is a crucial aspect of ship
maintenance and the effective operation of marine

Prevention of biofouling, the adhesion of organisms

vessels. Many antifouling paints have been developed

2007年 月12日受理（Received on March 12, 2007）*
中央水産研究所 〒236-8648 横浜市金沢区福浦2−12−4（National Research Institute of Fisheries Science, 2-12-4, Fukuura, Kanazawa, Yokohama 236-8648, Japan）

Hisashi YAMADA
and widely used. Cuprous oxide‑based paints werealonitrile（chlorothalonil）, N -dimethyl-N-phenyl-

used until around 1965, when they were replacedsulphamide（dichlofluanid）, 1-（3,4-dichlorophenyl）

with paints containing organotin compounds,-3,3-dimethylurea（diuron）, 2-methylthio-4-t-butyl-

most commonly tributyltin（TBT）or triphenyltinamino-6-cyclopropylamino-s-triazine（Irgarol 1051）,（TPT）, which effectively control biofouling by a4,5-dichloro-2-（n-octyl）-4-isothiazoline（Sea Nine 211）,wide variety of organisms. It has become apparent,

2-（thiocyanomethylthio）benzothiazole（TCMTB）,

however, that organotin compounds are hazardous tobis-（1-hydroxy-2（ 1H）-pyridinethionate-O,S） zincaquatic environments. These organotin compounds（zinc pyrithione, ZnPT）, and zinc ethylene bis-

are poorly biodegradable and thus remain in the（dithiocarbamate）（zineb）. Reported values ofenvironment for a long time. Moreover, theseoctanol-water coefficient（Kow）, solubility, andcompounds are highly toxic to aquatic organisms, so

estimated organic carbon partitioning coefficientbioaccumulation is a concern.

（Koc） for these compounds are summarized

In Japan, the use of organotin compounds in

i n T a b l e 1 . H a r i n o（ 2 0 0 4 ） s u m m a r i z e d t h eantifouling paints has been regulated by thephysicochemical properties of the new biocides

Chemical Substances Control Law, which prohibits

pyridinetriphenylboron（PK）and bis-（1-hydroxy-2

the manufacture, import, and sale of organotin（ 1 H ）-p y r i d i n e t h i o n a t e - O , S ） c o p p e r（ c o p p e rcompounds, and by notifications and otherpyrithione, CuPT）（Table 1）. Most of these newforms of administrative guidance together withbiocides have been used as pesticides（herbicides

controls on use that are voluntarily imposed by

and fungicides）; however, Sea Nine 211, CuPT, andvarious organizations. The Marine Environment

PK were produced for use as antifouling biocides

Protection Committee of the International Maritime（Fig. 1）.

Organization has been exploring a world-wide

PK（Hokko Chemical Industry）was introduced

prohibition of the application of organotins ascommercially as an alternative biocide in 1993.

antifouling biocides and in October 2001 adopted theLimited physicochemical data are available forInternational Convention on the Control of Harmful

this compound; therefore, it is difficult to assess its

Antifouling Systems on Ships, which resulted in a

impact on aquatic environments.

ban on the application of organotin-based antifouling

Vapour pressures of chlorothalonil, dichlofluanid,

paints. Therefore, a number of organotin-free

Irgarol 1051, diuron, and Sea Nine 211 are 0 076 mPa

antifouling paints have been developed. In addition（25 ℃）, 0 016 mPa（20 ℃）, 0 089 mPa, 0 41 mPa

to cuprous oxide, several organic chemical（50 ℃）, and 0 98 mPa（25 ℃）, respectively. These

substances, such as 2-mercaptopyridine N-oxide zincvalues are lower than that of TBTO, and indicating

salt, are used as biocides in organotin-free antifoulingthat these new biocides tend to mainly remain in thepaints. Few studies have been undertaken on either

liquid phase.

the fate in the aquatic environment or the harmful

Diuron is the most soluble of the new biocides（35effects on aquatic organisms of these new antifoulingmg/L）. The solubilities of Sea Nine 211, TCMTB,

biocides.

ZnPT, and Irgarol 1051 are 14 mg/L, 10.4 mg/L, 8

Author investigated ecotoxicological information

mg/L, and 7 mg/L, respectively; these compounds

available in published literature to estimate theh a v e g r e a t e r s o l u b i l i t y t h a n c h l o r o t h alonil,

harmful effects of these new biocides on aquatic

dichlofluanid, and CuPT.

organisms and the marine environment.

The log Kow values of the new biocides ranged
from 0 6 to 4 0. Chlorothalonil has the highest（logPhysicochemical properties

Kow of 4 0）, and zineb has the lowest（log Kow of
0 6）. In spite of the low solubilities of ZnPT and

Two studies（Thomas 2001a; Harino 2004）

CuPT, both have low log Kow values of 0 9（Table

provided data on representative new biocides1）, suggesting that these new biocides may not be（Table 1）. Thomas（2001a）listed 8 representative

bioconcentrated to high concentrations in aquaticnew biocides（Fig. 1）, 2,4,5,6-tetrachloro-isophthorganisms.

Ecotoxicological Risk Assessment of New Antifouling Biocides

Fig. 1. The constitutional formula of representative new biocides.

Hisashi YAMADA
2＊Table 1. Physico-chemical properties of new biocides1＊ and bis（tributyltin）oxide（TBTO）

Log Koc values estimated by the equation（logChlorothalonil is rapidly photodegraded by

Koc = log Kow ‑ 0 21）（Karickhoff, 1981）are also

sunlight, with a half-life ranging from 1 to 48 hshown in Table 1. Log Koc values of chlorothlonil,

according to photodegradation measurements indichlofluanid, diuron, Irgarol 1051, Sea Nine 211, andseveral natural waters. Chloro-1,3-dicyanobenzene

TCMTB ranged from 2 9 to 3 8, and were sameand benzamide are produced as photodegradation

order of TBTO. The log Koc values of zineb（0 6）,

products（Sakkas

ZnPT（0 7）, and CuPT（0 7）, were comparatively

found to be slower than photodegradation, with alow. The medium Koc values of the new biocides

half-life of 8 to 9 days（Walker

such as chlorothalonil suggest that these biocides., 2002a）. Biodegradation was1988）.

Dichlofluanid

as well as TBTO may exist in both water andThomas（2001a） reviewed the degradation of

sediments; whereas biocides with low Koc values,

dichlofluanid in the natural environment, andsuch as zineb, ZnPT, and CuPT, may exist mainly inreported a half-life of 18 h, which is relatively rapid

water. Galvindegradation.

（1998）reported that ZnPT and

CuPT exist in sediments as copper and manganese

Diuroncomplexes.

Harino（2004） reported that no half-life data
were available on diuron. Ellis and Camper
Degradation（1982） reported that more than 80% of diuron
was degraded in seawater within 27 days, with

Author reviewed degradation processes, including

most of the degradation due to biological activity;

photolysis, hydrolysis, and biodegradation, for thephotodegradation had only a minor effect. Under

new biocides.

aerobic conditions, the primary degradation products

Chlorothalonil

of diuron are 3-（3,4-dichlorophenyl）-1-methyl urea,

Ecotoxicological Risk Assessment of New Antifouling Biocides
3,4-dichlorophenyl urea, and 3-（3,4-dichloroaniline）,

A half-life of 96 h was observed in hydrolysis

whereas the primary anaerobic degradation productexperiments at pH 10 and 20 ℃ .

is 3（4-chlorophenyl）-1,1 -dimethylurea.

ZnPT and CuPT

Irgarol 1051

Comprehensive studies on degradation of ZnPT

Many researchers（Liu, 1997; Okamura,and CuPT（Turley2000） found that the

2002a; Okamura and Sugiyama, 2004）have studiedhydrolysis half-life of CuPT in sterilized artificial

the degradation of Irgarol 1051. Liu（1997）

seawater is 12 9 days. Results of a seawater

demonstrated that Irgarol 1051 is degraded by white

die-away experiment indicated that at an initial

rot fungus（） to 2-

CuPT concentration of 52 μg/L, the half-life withmethylthio-4-tert-butylamino-6-amino-s-triazine（M1）respect to biodegradation is approximately 4 days

through N-dealkylation of a cyclopropyl group fromin seawater and 7 h in river water. CuPT is also

the cyclopropylamino side-chain at the 6-position ofsensitive to light, with a reported photolysis half-life

the s-triazine ring. M1 is not degraded further byof 29 1 min.

and appears to accumulate as an

The reported hydrolysis half-life of ZnPT is >90

end degradation product in aquatic environments.

days, and ZnPT also biodegrades in seawater, with

Irgarol 1051 is also transferred to M1 bya half-life of approximately 4 days. Like CuPT, ZnPT

Hg-catalyzed hydrolysis（Liu1999a）and by

has high sensitivity to light; its reported half-life isphotolysis（Okamura, 2002a）. The photodegradation

17 5 min under a filtered xenon arc lamp and <2of Irgarol 1051 is stimulated by dissolved organic

min under natural sunlight.

materials such as humic and fulvic substances

These results suggest that ZnPT and CuPT（Okamura and Sugiyama, 2004）. The Irgarol 1051

are mainly degraded by photolysis in aquatic

half-life（Harino 2004）ranged from 36 to 273 days.

environments. Pyridine sulfonic acid is produced

These results suggest that Irgarol 1051 is fairly

from ZnPT and CuPT as a degradation products.

stable in aquatic environments.

PK

Sea Nine 211

There are no available data on PK hydrolysis

Sea Nine 211 undergoes hydrolysis, photolysis, andbiodegradation. Shadeor biodegradation in the aquatic environment.

（1993）reported that

Photodegradation of PK dissolved in artificial

Sea Nine 211 is stable in sterile water at pH 7 but

seawater and subjected to UV radiation（254 nm, 5 5

is hydrolyzed under acidic and alkaline conditions.

W）（Amey and Waldron, 2004）was very rapid andHarino（2004）reported that biodegradation is rapid

in <1 h led to boric acid production by elimination of

in seawater, with a half-life ranging from <0 5 to >30

pyridine and phenol.

days; N-octyl ozamic acid, 4,5-dichlorothiazole, andIn summary, the information on the degradation

N-octyl carbamic acid are produced as the primaryof these new antifouling biocides suggests that

degradation products.

these new biocides are not stable compared with

TCMTB
Laboratory results by Brownlee

the previously used TBT. Because of their more
（1992）

indicated that TCMTB is rapidly degraded into

rapid degradation, these new biocides pose less of anenvironmental risk than TBT.

2-mercaptobenzothiazole and 2-（ methylthio）
benzothiazole. TCMTB is easily degraded byConcentrations in the Aquatic Environment

photolysis, with a reported half-life of <0 5 h, and has
a reported biodegradation half-life of 740 h in natural

Chlorothalonil

waters.

Chlorothalonil concentrations in seawater were

Zineb

studied in coastal areas of the United Kingdom

Zineb is known to degrade rapidly through（Thomas2002; Voulvoulis

2000）.

hydrolysis to 5,6-dihydro-3H-imidazo-（2,1-c）

Chlorothalonil was not detected in seawater from

-1,2,4-dithiazole-3-thion, ethylene diisothiocyanate,

Southampton（Thomasand ethylenethiourea（Hunter and Evans, 1991）.

of Blackwater Estuary, however, concentrations

2002）. In seawaterHisashi YAMADA<0.0002 ‑ 0.00138 μg/L were reported by Voulvoulis; 1997; Thomas

2001b）, the Irgarol 1051

（2000）.

concentration in seawater ranged from <0 001 to

Dichlofluanid

0 682 μg/L. The concentrations were higher inDichlofluanid was detected in coastal waters in
Greece（Sakkas

2002b）and Spain（Martinez2001） in concentrations ranging from<0.001 to 0 284 μg/L and from <0 002 to 0 76 μg/L,

the marinas than in coastal waters. The highest
concentration of 0 682 μg/L was measured in amarina in Humber.
The Irgarol 1051 concentrations measured at

respectively.

marinas in the North Sea and the Baltic Sea were

Diuron0.011 ‑ 0.17 μg/L and 0.08 ‑ 0.44 μg/L, respectively

The concentration of diuron in seawater wasdetermined by Thomas（Biselli

2000）. In general, concentrations were（2001b）at the southhigher in the Baltic Sea than in the North Sea. The

coast of the United Kingdom（Southampton andconcentrations measured in marinas in Germany

Sutton Harbour）. In Southampton, the concentration

were similar to those in the marinas of France andin seawater ranged from 0.004 to 6 742 μg/L in

the United Kingdom.

marinas and harbours and from <0.001 to 0.465 μg/L

The Irgarol 1051 concentrations from 0 03 to 0 4

in estuarine water. The concentrations in Sutton

μg/L were reported at marinas in estuarine areas ofHarbour ranged from 0 001 to 0 334 μg/L. Harino

Sweden. This substance has been detected not only

（2005）measured concentrations of diuron inin seawater but in terrestrial water samples taken

seawater in Osaka Port, Japan, that ranged from
0 013 to 0 35 μg/L.

from marinas in the lakes of Switzerland.
In Japan, Okamura

Irgarol 1051

（2000a） and Liu（1999b）conducted surveys of environmental

The concentrations of Irgarol 1051 in the coastal

contamination in the Seto Inland Sea. Irgarol 1051

waters of Japan, Canada, France, the Unitedand its degradation product M1 were detected

Kingdom, Germany, and Sweden and in the lakes ofin the seawater but not in sediment. Irgarol 1051

Switzerland are summarized in Table 2. Irgarol 1051

concentrations in seawater ranged from below

was not detected in seawater samples taken fromthe detection limit to 0 296 μg/L, with the higher

4 locations in Canada, including Vancouver. It wasconcentrations being detected in marinas and small

detected, however, in the coastal waters of France,

fishing ports located in the prefectures of Hiroshima,

the United Kingdom, Germany, Sweden, and Japan

Okayama, Hyogo, and Kagawa（Table 5）. M1 has

and in samples taken from marinas in the lakes ofbeen detected in seawater taken in the Seto Inland

Switzerland.

Sea, and M1 concentrations in seawater ranged fromThe concentrations in seawater samples taken

below the detection limit to 1 27 μg/L. These resultsin France ranged from below the detection limit toindicate that MI concentrations tend to be higher

1 7 μg/L, with the highest values being measured

than those of Irgarol 1051 and that M1 remains

for samples taken in the marinas of the Cotein aquatic environments for a longer period thand Azur region（Readan

Irgarol 1051.

measured by Tolosa

1993）. Irgarol 1051 was（1996）at marinas, ports,

Irgarol 1051 concentrations in seawater wereand beaches; the concentrations were 0 022 ‑ 0 64

found to be higher in marinas and small fishingμg/L, 0 0138 ‑ 0 264 μg/L, and <0 0015 ‑ 0 017 μg/L,

ports where pleasure boats and small fishing vessels

respectively. The concentrations at marinas wereare moored than in large ports used by ocean-goinghigher than those at ports and beaches. The

vessels. Irgarol 1051 concentrations are also higher

concentrations determined by Readan

in Europe（France, the United Kingdom, Germany,（. 1993）

did not differ from those reported by Tolosa（1996）. These results suggest that the annual
variation of concentrations is not significant.
In a United Kingdom survey covering 7 coastal
areas（Gough; 1994; Zhou

; 1996; Scarlett

and Sweden）than in Japan. These results indicatethat antifouling paints containing Irgarol 1051 are
predominantly used on pleasure boats and small
fishing vessels, and they are used in greater volumes
in the European countries than in Japan.

Ecotoxicological Risk Assessment of New Antifouling Biocides
Table 2. Concentration of Irgarol 1051 and its degradation products（M1）in water at various regions.

Hisashi YAMADA
Irgarol 1051 concentrations in sediments were
measured by Biselli（2000）in the North Sea

and Baltic Sea and by Albanis

Sea Nine 211 is acutely toxic to phytoplankton
at concentrations of 13 9 ‑ 32 μg/L, to crustacean（2002）in thespecies at concentrations of 4 7‑1 312 μg/L, tocoastal area of Greece. The concentrations ranged

bivalves at a concentration of 850 μg/L, and to fishfrom 3 to 25 μg/kg dry weight in the North Sea, 4species at concentrations of 2 7 ‑ 20 5 μg/L（Table

to 220 μg/kg dry weight in the Baltic Sea, and less3）. From these data, author conclude that thisthan the detection limit to 338 μg/kg dry weightcompound exhibits weaker acute toxicity to bivalvesin Greece. Concentrations were particularly high inthan other aquatic organisms such as phytoplankton

the sediments of marinas, a tendency similar to thatand fish. Based on these acute toxicity values,

observed in seawater.

Sea Nine 211 is classified as very toxic to toxic

Sea Nine 211
Thomasaccording to the OECD guidelines.
（2001b）reported that Sea Nine

Chronic toxicities of Sea Nine 211 to

211 was not detected in seawater and sediments

and sheepshead minnows（

collected at marinas on the south coast of the United

are reported to occur at concentrations of 1 2 μg/L

Kingdom in 1998. On the other hand, Martinez

and 6 μg/L, respectively（Table 4）. The 28 d LC50

（2001）reported that Sea Nine 211 was detected）

to rainbow trout larvae is 14 μg/L（Okamura,at concentrations ranging from 0 26 to 3 7 μg/L in2002）, leading to fears that the chronic toxicity ofseawater from the Spanish Mediterranean. Sea Nine

Sea Nine 211 is equivalent to that of other antifouling

211 was detected in the coastal areas of Greece atcompounds such as ZnPT, CuPT, and PK.

concentrations ranging from <0 0063 to 0 049 μg/L
（Sakkas2002b）and in Osaka Port in Japan（Harino2005）from <0 0003 to 0 0055 μg/L.

ZnPT and CuPT
Published literature contains very little data on
the acute toxicity of ZnPT and CuPT to aquatic

TCMTB, ZnPT, CuPT, and PK

organisms（Table 3）. The respective toxicity values

Thomas（2004） reported that theirof ZnPT are reported to be 2 06 ‑ 28 μg / L for

monitoring studies did not detect chlorothalonil,

phytoplankton（Shipbuilding Research Association ofdichlofluanid, ZnPT, Sea Nine 211, or TCMTB in

Japan, 2002）,29 ‑ 34 μg/L for（Shipbuilding

seawater in the United Kingdom. Harino

Research Association of Japan, 2002）, and 2 6 ‑ 400（2005）also reported that ZnPT and CuPT were not

μg/L for fish species（Shipbuilding Researchdetected in seawater collected in Osaka Port, Japan.

Association of Japan, 2002）. CuPT exposure causes

I found no literature reporting concentration of PK

acute toxicity leading to decreased phytoplankton

in aquatic environments.

g r o w t h a t c o n c e n t r a t i o n s o f 2 8 ‑ 3 5 μg / L（Shipbuilding Research Association of Japan, 2002）,

Harmful effects of new biocides on aquaticorganisms

immobilization at 22 μg/L（Shipbuilding
Research Association of Japan, 2002）, and decreased
survival of fish species at 4.3 ‑ 7.67 μg/L
（Shipbuilding

Chlorothalonil

Research Association of Japan, 2002）. Mochida

Acute toxicity of chlorothalonil to（2006）recently studied the acute toxicity of CuPT

andand ZnPT to toy shrimp（

are summarized in Table 3. The 48 h EC50 toand red sea bream（））; 96 h LC 50 s

ranged from 97 to 129 μg/L, and the 96 h

to red sea bream were 9 3 μg/L for CuPT and

LC50 to fish species ranged from 69 to 76 μg/L.

98 2 μg/L for ZnPT. On the other hand, 96 h

Acute toxicities to crustacean and fish species

LC50s of CuPT and ZnPT were 2 5 and 120 μg/L,

are significant, and areaccordingrespectively, for toy shrimp. Although the available

to Organization for Economic Co-operation andtoxicity data are limited, they indicate that CuPTDevelopment（OECD） ecotoxicity classification

exhibits greater acute toxicity to fish and shrimp

guidelines（OECD, 1996）.

species than does ZnPT. Toxicological data on ZnPTSea Nine 211very toxic

and CuPT evaluated on the basis of the OECD

Ecotoxicological Risk Assessment of New Antifouling Biocides
classification guidelines correspond to the
toxic

very

definition, suggesting that both compounds

are highly toxic to aquatic organisms.

Mochida（2006） examined the toxicities

of pyrithione compounds（ZnPT and CuPT） in
the presence of copper ions. The presence ofIn organotin-free antifouling paints, the pyrithione

Cu 2+ did not change the acute toxicity of CuPT

compounds（ZnPT and CuPT）are usually used in

but significantly increased the acute toxicity of

combination with cuprous oxide, and their acute

ZnPT. According to Mochidatoxicity may change with the presence of copper.

enhancement of toxicity by Cu

Table 3. Acute toxicity of new biocides to aquatic organisms

Table 4. Chronic toxicity of new biocides to aquatic organisms（2006）, the2+is attributable toHisashi YAMADA
conversion of ZnPT to more toxic CuPT.

bacterial growth even at a concentration of 50,000

ZnPT has significant effects on the embryogenesis

μg/L（Okamura

2000a）. The 24 h LC50 ofof fish species, and an early life-stage toxicological

Irgarol 1051 to crustacean species is reported to

study in which fertilized eggs were exposed to ZnPT

range from 5 700 to 12 000 μg/L（Okamura

confirmed deformities in the spinal curvature of fish

2000a）. It inhibits mobilization（48 h EC50）at a

larva after hatching（Goka, 1999）. For rainbow trout

concentration of 8 100 μg/L（Ciba-Geigy, 1995）. The

larvae, Okamura（2002b）obtained 28 d LC50

48 h LC50 to oyster larvae is 3 200 μg/L, whereas

values of 4 6 μg/L for ZnPT and 1.3 μg/L for CuPT

the 96 h LC50 to fish species ranges from 790 μg/L

（Table 4）. These toxicity values raise the concern

for rainbow trout to 4 000 μg/L for zebrafish（Hallthat both compounds may exhibit high chronic

Jr.

toxicity to fish species.

1999）.

The EC50 for inhibition of phytoplankton growth

ZnPT and CuPT are degraded in the aquatic

ranges from 0.1 to 2 3 μg/L. Irgarol 1051 is very

environment to pyridine sulfonic acid. The acutetoxic to seaweed; germination and development

toxicities of pyridine sulfonic acid were as follows;of spores is inhibited at concentrations ranging

120 h LC50 to freshwater algae was 28 900 μg/L,from 0.6 to 5.9 μg/L（Okamura

48 h EC50 towas >122 000 μg/L, andconstitutional formula of Irgarol 1051 resembles that96 h LC50 to fish species was 57 100 ‑ >127 000of triazine herbicides; therefore, it seems reasonableμg/L（Table 3）. The acute toxicities of pyridinethat Irgarol 1051 is remarkably more toxic to aquatic

sulfonic acid were weaker than those of the parent

vegetation such as phytoplankton and seaweed thancompounds, ZnPT and CuPT. These results suggest

to marine animals such as crustaceans and fish.

that toxicities of ZnPT and CuPT decrease in theprocess of degradation.

2000b）. The

Based on the ecotoxicity classification guidelines（OECD, 1996）, Irgarol 1051 acute toxicity values toPKphytoplankton and aquatic animals（crustaceans andBecause of its recent development for use asfish）correspond to the definition of very toxic anda biocide in antifouling paints, only limited data

toxic , respectively.

are available on the harmful effects of PK on

As shown in Table 5, the 72 h EC50 of M1 toaquatic organisms（Table 3）: the 72 h EC50 to thephytoplankton growth ranged from 1 9 to 46 μg/L

phytoplankton（Okamurais 2.15 μg/L

2000a）. The 96 h EC50 of M1 to（Shipbuilding Research Association of Japan,1999）,

the germination and development of the spores of

the 96 h LC50 to shrimp（

seaweed ranged from 1 7 to 130 μg/L（Okamura）is

149 μg/L（Shipbuilding Research Association of, 2000b）, whereas it is acutely toxic to crustacea

Japan, 1999）, and the 96 h LC50 to red sea bream（（

11 000 μg/L（Okamura）is 242 μg/L（Shipbuilding Research） species at concentrations of
2000a）. EC50 and

Association of Japan, 1999）. Although the acute

LC50 values of M1 are 10 times greater than those

toxicity of PK is weaker than that of ZnPT andof the parent compound. Although the toxicity of

CuPT, it is classified as very toxic according to

Irgarol 1051 decreases as the compound is degraded,

the OECD toxicity guidelines.

its degradation product M1 is classified as toxic

The 28 d LC50 of PK is 42 μg/L based on 28-day
rearing experiments using rainbow trout larvae（Okamura,according to the OECD ecotoxicity classifications.
The chronic toxicity of Irgarol 1051 was evaluated2002）. This value is equivalent toby an early life-stage toxicity test using rainbow

that of ZnPT and CuPT. These results raise a great

trout（embryo to larval stage）（Table 6）. A noconcern of this compound s harmful effect on aquaticobserved effect concentration of 4 02 μg/L wasorganisms.

determined by the inhibition of larval growth

Irgarol 1051

during 60 days after hatching（Hall Jr.

Acute toxicity of Irgarol 1051 and its degradation

Chronic toxicity and acute toxicity values revealed

1999）
.

product M1 to various aquatic organisms arethat the acute/chronic toxicity ratios of Irgarol

summarized in Table 5. Irgarol 1051 does not affect1051 to rainbow trout ranged from 3 to 100. This

Ecotoxicological Risk Assessment of New Antifouling Biocides
Table 5. Acute toxicity of Irgarol 1051 and its biodegradation products（M1）to aquatic organisms

Table 6. Chronic toxicity of Irgarol 1051 to shrimp and fish.

ratio is similar to that of numerous other chemical

which is equivalent to that of the TBT（Koyama andsubstances such as lindane, PCP, DDT, and dieldrin.

Shimizu, 1992; Horiguchi and Shimizu, 1992; IMO,

In summary, despite the paucity of data on the1997）.

toxicity of the new antifouling biocides to aquaticorganisms, available published data suggest that

Preliminary risk assessment

Irgarol 1051 is toxic to phytoplankton and seaweed
and that CuPT and ZnPT are highly toxic to marine

The predicted no effect concentration（PNEC）

animals. The acute toxicity of these new biocides

was tentatively estimated from the lowest acuteis found to be in the order of micrograms per liter,

toxicity value by the OECD method. In accordanceHisashi YAMADA
with OECD method, the uncertainty factor of 100

The higher EC / PNEC was recognized in marinas

was used to calculate PNEC. The values of PNEC for

and fisheries harbours, raising concerns that theseseveral new biocides are shown in Table 7 together

biocides are already harming the aquatic ecosystem,with the observed concentrations of these biocides

especially in marinas and fisheries harbours. The

in natural waters.

concentrations of Irgarol 1051, M1, and Sea Nine

The highest concentration found in natural water

211 in seawater collected at coastal areas such as（EC）and PNEC of chlorothalonil, was 0 00138 μg/L

beaches were significantly lower than PNEC values.

and 0 69 μg/L, respectively. EC / PNEC ratio wasHazardous impacts by these new biocides seem

0 002, and EC was two orders of magnitude lower

restricted to particular areas such as marinas andthan the PNEC value. Although the available data

fisheries harbours, where many pleasure boats

on chlorothalonil concentrations in natural waters

and/or fishing boats are moored.

are very limited, these results suggest that its

Harino（2005）did not detect pyrithione

hazardous impact on the aquatic environments cancompounds（ZnPT and CuPT）in the seawater ofbe considered small.

Osaka Port, Japan. These Osaka port results indicate

The PNEC was 0 016 μg/L for Irgarol 1051, 0 19

that hazardous impact of pyrithione compounds are

μg/L for M1 , and 0 027 μg/L for Sea Nine 211. The

not yet a concern. The limited published data on

ECs of Irgarol 1051 ranged from 0 264 to 1 7 μg/L,

the concentrations of PK preclude evaluation of theand EC / PNEC ratio fell between 5 33 and 106 25.

hazardous impact of PK on the marine ecosystem,

The EC was one or two orders magnitude higher

and further studies are needed.

than PNEC in marinas. The ECs of 1 21 and 1 27
μg/L were observed in M1, and was EC / PNEC

Conclusion

ratio was estimated as 6 37 or 6 68. The EC / PNEC
ratio of Sea Nine 211 ranged from <0 01 to137.

The low vapour pressure of the new biocides inTable 7. Preliminary risk assessment of several new biocides to aquatic organisms by comparing PNEC
with the highest concentration in natural waters.

Ecotoxicological Risk Assessment of New Antifouling Biocides
water limits their evaporation. Because of medium

booster biocide contamination in Greek marine

Kow and Koc values, the new biocides, except

sediments.

, 48, 475‑485.

zineb, ZnPT, and CuPT, tend to be distributed in

Amey, R. L. and Waldron, C., 2004 : Efficacy andboth seawater and sediments, and they are hardly

chemistry of BOROCIDETMP triphenyl

bioconcentrated in aquatic organisms.

boron‑pyridine, a non‑metal antifouling biocide.

The new biocides are decomposed by hydrolysis,

Proceedings of International Symposium on

photolysis, and biological activity. Thus they are less

Antifouling Paint and Marine Environment

stable than TBT and do not persist for a long time

（InSAfE）,234‑243.

in aquatic environments. These new biocides are

Biselli, S., Bester, K., Huhnerfuss, H. and Fent, K.,classified as toxic or very toxic by the OECD

2000 : Concentration of the antifouling compoundclassification guideline, and show almost the same

Irgarol 1051 and of organotins in water andtoxicity as TBT.

sediments of German North and Baltic Sea.

Chlorothalonil, dichlofluanid, diuron, Irgarol 1051

, 40, 233‑243.

and its degradation product M1, and Sea Nine 211

Brownlee, B. G., Carey, J. H., MacInnis, G. A. andhave been detected in natural waters, with higher

Pellizzari, I. T., 1992 : Aquatic environmental

concentrations in marinas and small harbours forc h e m i s t r y o f 2 ‑（ t h i o c y a n o m e t h y l t h i o ）fishing boat than in coastal waters. Research on the

benzothiazole and related benzothiazoles.
, 11, 1153‑1168.

occurrence in seawater in Japan was carried out
only by Harino

who did not detect pyrithione

compounds. Detailed surveys are needed to clarify
the present extent of contamination by the new
biocides.

Ciba-Geigy Co., 1995 : Irgarol 1051 in antifouling
paints. Technical Information Bulletin.
Ellis, P. and Camper, N., 1982 : Aerobic degradationof diuron by aquatic microorganisms.

The reported concentrations of Irgarol 1051, M1,

B17, 277‑288.

and Sea Nine 211 in natural waters exceed the PNEC

Ernst, W., Doe, K., Jonah, P., Young, J., Julien,

values, particularly in marinas and fishery harbours.

G. and Hennigar, P., 1991 : The toxicity of

Igarol 1051, M1, and Sea Nine 211 are causing

chlorothalonil to aquatic fauna and the impact ofa hazardous impact on the aquatic ecosystem

its operational use on a pond ecosystem.
, 21, 1‑9.

in marinas and fishery harbours. To assess the
ecotoxicological risk of the new biocides in detail,Galvin, R. M., Melland, J. M. R. and Montoya, M. R.,

further research on toxicity and the development

1998 : A contribution to the study of the naturalof methods for estimating concentrations in naturaldynamics of pyrithione（Ⅱ）, deactivation bywaters are needed.

direct chemical and absorptive oxidation.
, 4, 61‑64.

Acknowledgements

Goka, K., 1999 : Embryotoxicity of zinc pyrithione,
an antidandruff chemical, in fish.

I am grateful to Dr. Kazufumi Takayanagi（Seikai,

Section A, 81, 81‑83.

National Institute of Fisheries Science, Fisheries

Gough, M. A., Forthergill, J., Hendrie, J. D., 1994 : A

Reasech Agency）for his advice and critical readings

survey of southern England coastal waters forof this paper. Thanks are also due to Mr. Toshimitu

the s-triazine antifouling compound Irgarol 1051.

Onzuka（National Research Institute of Fisheries, 28, 613‑620.

and Environment of Inland Sea, Fisheries Reasech
Agency）for his assistance in preparing a figure.

Hall Jr., L. W., Giddings, J. M., Solomon, K. R., andBalcomb, R., 1999 : An ecological risk assessment
for use of Irgarol 1051 as an algaecide for

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