Environmental Engineering Reference
In-Depth Information
of fi elds. Notwithstanding these extraordinary measures, fi eld personnel found dead birds in 33 of
44 fi elds searched on ten of the 11 farms monitored. Personnel found 30 species (25 birds, four
mammals and one reptile) dead or debilitated in the fi elds. Of the carcasses recovered in the fi elds,
42% were more than 18 metres from the edge of the cultivated area or in the treated area. Personnel
recovered fresh carcasses up to 15 days post-application that had detectable carbofuran residues.
Finding these fresh carcasses so long after application was especially signifi cant given the observa-
tions that confi rmed considerable scavenging activity. The high level of scavenging, in turn, suggests
that the searchers missed many carcasses. Laboratory personnel detected carbofuran residues in the
upper gastrointestinal tract of 81% of 58 birds analysed. Residue levels ranged from 0.6 ppm in a
savannah sparrow (
Passerculus sandwichensis
) to 208 ppm in a white-throated sparrow (
Zonotrichia
albicollis
). A third (11/32) of the samples analysed contained normal brain cholinesterase levels. The
fi ndings of normal cholinesterase levels in such a high proportion of casualties reaffi rmed that thor-
ough investigation of fi eld incidents should be based on a 'weight of evidence approach' rather than
any single factor (see Chapter 2). After this study, the State of Virginia denied registration of granular
carbofuran, just ahead of a negotiated settlement between the US EPA and FMC, the manufacturer.
8.2.2 Reported incidents where the product was applied according
to label directions
Given the notable amount of fi eld data implicating granular carbofuran in bird kills, we will make
only a brief summary of the kill record. One can fi nd more details in the sources cited in this section
and via other resources. Farmers and bystanders rarely detect and report bird kills, and when these
kills are reported, the information recorded with the kills is often inadequate. This is exemplifi ed by
an entry in the Pesticide Incidents Monitoring System (PIMS) of the US EPA (1979):
00/00/71 WI [Wisconsin] In an agricultural incident carbofuran was a suspect factor
in an undescribed bird kill. No conclusions about pesticide involvement were drawn
from the investigation. One owl was suspected of containing residues; laboratory
results were not reported.
This example is given, not to denigrate the efforts of the US EPA in compiling relevant pesticide
information, but rather to point to the real diffi culty involved in assembling kill information from
multiple sources. We must emphasise that even in the United States and Canada, few State and
provincial governments have adequate resources to detect, investigate, and document fi sh and wild-
life kills of any type.
Similarly, many kills reported by the National Wildlife Health Laboratory (formerly part of the
US Fish and Wildlife Service (US FWS), now part of the US Geological Survey, USGS) are often
described as '
carbamate toxicosis suspected
' leaving the reader to ponder on the chemical involved.
In a 1988 survey of 351 farmers in Québec, 5% of the individuals contacted reported having encoun-
tered bird mortality in their fi elds. In nine cases, farmers that were contacted volunteered the identity
of the chemical responsible; three of those nine cases were carbofuran kills. All cases involved toxic
rodenticides or cholinesterase-inhibiting insecticides (J.L. DesGranges, Canadian Wildlife Service,
personal communication).
Kill reports are especially inadequate to deal with the diffuse mortality of breeding songbirds that
is expected from the use of granular carbofuran (Mineau 1988). These birds are on territories and
found at low density around agricultural fi elds.
Despite their repetitive nature, we will briefl y review some of the documented kill incidents to:
1) confi rm the experimental fi ndings under operational conditions, 2) offer evidence for crops and
situations not directly tested, and 3) provide useful supplementary data such as residue profi les in
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