Pesticide Residues in Birds and Mammals - Pesticides: Evaluation of Environmental Pollution - page 431

and Farris (2005) concluded that monitoring of the plasma cholinesterase reactivation with
pyridine-2-aldoxime methochloride (2-PAM) appeared to be a more sensitive indicator
of exposure than the diagnostic threshold. Using this biomarker of toxic effect, it is not
easy to distinguish between OPs and CBs, although some differences in the reactivation
of the phosphorylated and carbamylated enzymes exist and can be used (Smith et al. 1995;
Mineau and Tucker 2002; Wobeser et al. 2004).
Chemical monitoring is rarely used for these insecticides and metabolites, and usu-
ally only for forensic purposes and analyzing preferentially the gastrointestinal contents
(Goldstein et al. 1999; Fleischli et al. 2004; Kwon et al. 2004; Pain et al. 2004; Wobeser et al.
2004; Muzinic 2007; Wang et al. 2007; Berny and Gaillet 2008; Elliott et al. 2008; Otieno et al.
2010). Determination of the AChE activity in the plasma, as a nondestructive biomarker,
can be extensively (and nonexpensively) used to monitor “normal” exposition in different
bird groups, related to environmental stress from typical agricultural pesticide application
regimes (Wilson et al. 2001; Maul and Farris 2005; Martínez-Haro et al. 2007; Vergara et al.
2008; Strum et al. 2010) or in “special” circumstances as during locust control operations of
large areas (Fildes et al. 2006).
Many lethal episodes in birds are related to granular formulations, which present a seri-
ous hazard to birds. Microgranules and granules are always used for the most toxic pesti-
cides, such as the OPs, chlorpyrifos, disulphoton, ethoprop, fonofos, and phorate, and the
CBs, aldicarb and carbofuran (Kendall and Smith 2003; Elliott et al. 2008; Martínez-Haro
et al. 2008; Otieno et al. 2010). Birds eat granules exposed on the soil surface, mistaking
them for food or grit. Elliott et al. (2008) found in Canada 211 waterfowl corpses, dead from
primary poisoning (average AChE inhibition in brain being 74%, range 69%-78%), and 15
raptors, mainly bald eagles, dead from secondary poisoning, after granular application
of fonofos. In Canada, the use of granular insecticides in agriculture was found linked to
population declines of several bird species, including the American robin ( Turdus migrato-
rius ), the horned lark ( Eremophila alpestris ), the house sparrow ( Passer domesticus ), and the
mourning dove ( Zenaida macroura ) (Mineau et al. 2005).
Due to the wide and extensive use, it is not unsuspected that the residues of these insec-
ticide compounds may appear in the milk in dairy cattle. In Mexico, of 96 milk samples
examined by GC for 13 OP insecticides, eight (12%) contained residues exceeding established
maximum residue limits (MRL) for dichlorvos (n = 5 samples), phorate, chlorpyrifos, and
chlorfenvinphos (n = 1, each) (Salas et al. 2003). In Italy and Spain, none of the 298 and 242
milk samples examined, respectively, contained detectable levels of OPs above the MRL fixed
by the European Commission, although, for example, residues of chlorpyriphos, dichlorvos,
or coumaphos were found (Gazzotti et al. 2009; Melgar et al. 2010). Sengupta et al. (2010)
reported levels of OP pesticides, mainly dimethoate and malathion, in the range of 11-98 ng/g
WW in meat samples of cow, goat, and chicken collected from five locations in India.
14.4.3 Pyrethroid Insecticides
Synthetic pyrethroids have their origins in the naturally occurring insecticides in pyre-
thrum extracts, collectively called pyrethrins, which are obtained from the flowers of the
chrysanthemum species ( Chrysanthemum cinerariaefolium ). Pyrethroids were developed to
increase the photostability and residence time in environmental conditions of pyrethrins
while retaining some other interesting characteristics, such as a rapid neurotoxicant insec-
ticidal activity and a relatively low acute mammalian toxicity (Anadón et al. 2009). Thus,
pyrethroids are considered relatively persistent compounds, which show very low water