Advisory Committee on Pesticides Annual Report 2001

<strong>Advisory</strong> <strong>Committee</strong> on Pesticides Annual Report 2001
risk to wildlife and recommended approval for the use on winter oilseed
rape as proposed. The <strong>Committee</strong> also recommended that the approval holder
be required to implement a user education scheme to minimise further any
environmental effects.
Clomazone
Clomazone is a new isoxazolidinone herbicide that acts by inhibition of
biosynthesis of photosynthetic pigments in plants. The ACP considered
applications for approval of two products ‘Centium 50 WP’, a wettable powder
(WP), and ‘Centium 360 CS’, a capsule suspension (CS), for residual control
of broad-leaved weeds in winter oilseed rape.
Clomazone was rapidly and extensively absorbed, metabolised and excreted
in the rat, mainly via urine. Very little unmetabolised parent compound
was excreted and a large number of metabolites were identified,
mostly hydroxylated derivatives of the parent compound, especially
5-hydroxyclomazone.
8
The active substance is classifiable as ‘Harmful if swallowed and by inhalation’
based on acute oral and inhalational studies in rats.
The <strong>Committee</strong> agreed that the main toxicological effect was liver enlargement
and that the acceptable daily intake (ADI) should be based on the no
observed adverse effect level (NOAEL) of 12.5 mg/kg bodyweight (bw)/day)
from a one-year dog study. With a 100-fold assessment factor, this gave an
ADI of 0.13 mg/kg bw/day. It was also considered appropriate that the shortterm
systemic admissible operator exposure level (AOEL) should be derived
in the same way. An acute reference dose (ARfD) of 0.3 mg/kg bw/day was
agreed based on the NOAEL of 30 mg/kg bw/day for maternal toxicity in a
rabbit teratogenicity study, with a 100-fold assessment factor. Members agreed
that there were no apparent concerns in relation to genotoxicity,
carcinogenicity or reproductive toxicity.
Residue trials indicated that clomazone residues were present below the limit
of quantification (LOQ) in oilseed rape at harvest, and calculations indicated
that the consumer exposure would be acceptable. The exposures of operators
from use of ‘Centium 50 WP’ were considered acceptable if protective gloves
were worn when handling the product. For ‘Centium 360 CS’ coveralls and
protective gloves should be required when handling the product. Exposures
of bystanders and workers were regarded as acceptable. ‘Centium 360 CS’
was classifiable as a skin sensitiser on the basis of a Buehler test, and the ACP