Environmental Engineering Reference
In-Depth Information
parative study of the disappearance of booster biocides from natural sea
water containing the diatom
Amphora coeffeaeformis
[13] concluded that Ir-
garol 1051 and diuron were not easily degraded even after 8 weeks, whereas
chlorothalonil was unlikely to persist and SeaNine 211 was easily degraded.
In another study [14], the authors demonstrated that the toxicity of Sea-
Nine 211 and zinc pyrithione to
Acartia tonsa
declined rapidly through either
rapid degradation or partitioning to sediments. Half-lives of Irgarol 1051
(100 d), dichlofluanid (18 h), chlorothalonil (1.8 d), SeaNine 211 (
<
24 h), zinc
pyrithione (
<
24 h), TCMTB (740 h) and zineb (96 h) have been reported [10].
Further details on the mechanisms of degradation are provided in the re-
views [9, 10] and the other chapters of this topic.
Zinc pyrithione (the zinc chelate of 2-pyridinethiol-1-oxide) is unusual as
it is reported to transchelate with copper to form copper pyrithione (which
also acts as a booster biocide) [15]. Both zinc and copper pyrithiones are
considered to degrade rapidly.
Toxicological properties of the compounds have been reviewed [9, 11] and
are detailed in the chapter by Yamada within this volume. Marine plants ap-
pear particularly vulnerable to many of these biocides. The first published
study on the herbicidal properties of the booster biocides was by Dahl and
Blanck [16] on the toxicity of Irgarol 1051 to periphyton communities. Long-
term effects were detected at 0.25 to 1 nM (63 to 250 ng L
-1
), which is within
the range of concentrations reported for coastal waters. Later studies [17-19]
have confirmed the vulnerability of algae
phytoplankton to booster biocides,
and especially corals through damage to their endosymbiotic microalgae
(zooxanthellae) [20]. Subsequent to the review by Konstantinou and Alba-
nis [9], some other papers address algal toxicity [21-23]. Using natural pop-
ulations of phytoplankton, Readman et al. [21] report toxic effects of Irgarol
at low concentrations (Fig. 4) with an EC50 (72 h) of 70 ng L
-1
.Again,this
concentration is well within the range of concentrations reported in coastal
waters.
Within the ACE Project, endocrine disruption was also assessed. Based on
an evaluation of potentially suitable test systems, it was decided to apply the
ER-CALUX (estrogen responsive-chemically activated luciferase expression)
assay to determine (anti) estrogenicity. None of the antifoulants selected (Ir-
garol 1051, SeaNine, chlorothalonil, diuron, dichlofluanid, maneb and ziram)
showed a strong estrogenic response.
The critical feature in risk evaluation of the booster biocides relates to
persistence and toxicity. Although substantial information has been accrued,
some authors [24] consider that additional data is still required to properly
evaluate the risks associated with the widespread use of Irgarol 1051, di-
uron, SeaNine 211 and chlorothalonil. These authors caution against the use
of TCMS pyridine, TCMTB and dichlofluanid and, again, identify a lack of
appropriate data. In their initial risk evaluation, zinc pyrithione and zineb
appear the least hazardous options for the aquatic environment.
/
