Environmental Engineering Reference
In-Depth Information
carbofuran in North America have been written (e.g., National Research Council of Canada (NRCC)
1979; Eisler 1985) but without the level of detail provided here on the bird impacts.
In December 1995, the Canadian regulatory authorities cancelled all silica-based granular for-
mulations and ordered the manufacturer to conduct fi eld trials on the corncob formulations. FMC
Corporation, in concert with the Bayer Corporation, carried out these trials in early 1997 and sub-
mitted the results in the autumn of 1997 to government regulators. In December 1998, the Pest
Management Regulatory Agency (the new regulatory authority following a 1996 reorganisation of
the pesticide registration system in Canada) announced a full cancellation of all granular registra-
tions because of unacceptable risks to birds.
In December 1995, the regulatory authorities also cancelled some uses of the fl owable carbofuran
after results of a study showed that the product was adversely affecting the endangered burrowing
owl (
Athene cunicularia
). This effect occurred despite the very low application rate of 132 grams of
active ingredient per hectare (denoted as g ai/ha). This is revisited later in Section 8.4.2.3. However,
the regulators allowed continued use for corn and potatoes, notwithstanding the higher application
rates on these crops and the fact that carbofuran use had caused avian mortality at these rates and
on similar sites. The Pest Management Regulatory Agency (PMRA), Canada's regulatory authority,
re-opened its review of the remaining uses of carbofuran along with several other carbamate pesti-
cides in 2002. In July 2009, in step with US EPA proceedings, the PMRA proposed the cancellation
of all remaining uses of carbofuran. This complete cancellation of all carbofuran registrations was
fi nalised in December 2010. The PMRA cited unacceptable risks to human health and to the environ-
ment and stated that these risks could not be mitigated.
Chapter 2 provided a discussion of the diagnosis and forensic aspects of kills caused by carbo-
furan. Most of the documents referenced in the present chapter report cholinesterase inhibition
levels in brain and residues in gastrointestinal tracts of casualties. Our emphasis is also on birds,
however, several of the studies reviewed, especially some of the industry-led studies, also report
incidental kills of mammals, reptiles and amphibians. We caution the reader that the information that
follows has been collated from a very large body of incident reports which vary tremendously both in
quality and detail. To ensure full disclosure and minimise confusion, we have tried to include specifi c
information such as number of deaths, species, and residue levels detected, or even whether or not
samples were analysed for residues where those were not reported.
8.2 Impacts from the sandcore (silica) granular formulations
The evidence that granular carbofuran causes extensive wildlife mortality comes from supervised
fi eld trials, various monitoring efforts (e.g., in Virginia and California) and kill incidents usually
reported by farmers and members of the public.
8.2.1
Supervised fi eld trials and surveillance exercises
Field trials under experimental control usually offer better evidence than kill reports because the
investigators (1) strictly monitor the pesticide applications and (2) report carcass search efforts
and other critical parameters to help identify sources of bias. The principal disadvantage of fi eld
studies, especially those that rely on fi nding carcasses, is that the studies often have a low
power of problem detection (Mineau and Collins 1988). However, investigators usually do fi nd
dead birds, even in poorly designed studies of granular carbofuran. FMC contracted three stud-
ies (FMC 1983; 1986a; 1986b) to fulfi ll requirements for re-registration of the product in the
United States. Balcomb, Bowen, Wright et al. (1984) conducted an additional study to confi rm the
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