Pesticide Residues in Birds and Mammals - Pesticides: Evaluation of Environmental Pollution - page 430

14.4.2 Organophosphorus and Carbamate Insecticides
Cholinesterase-inhibiting compounds such as OP and CB insecticides (some representatives
also with acaricide and nematicide activities) have largely replaced the OC group. They are
often considered nonpersistent products in the environment; thus, they have a low potential
for bioaccumulation and biomagnification but a high potential for acute toxicity (Poppenga
2007). Moreover, due to their extensive use in agriculture for crop protection and in many
other areas and situations, such as golf courses, forestry, gardens, and in veterinary medi-
cine for parasite control on livestock and because some products remain quite toxic for days
or weeks after application, continuous unwanted exposure to OPs and CBs occur.
Among the most vulnerable of nontarget species are birds, for which lethal episodes are
frequently reported in the literature (Henny et al. 1987; Newton 1998; de Snoo et al. 1999;
Goldstein et al. 1999; Fleischli et al. 2004; Kwon et al. 2004; Pain et al. 2004; Wobeser et al.
2004; Muzinic 2007; Berny and Gaillet 2008; Elliott et al. 2008; Hernández and Margalida
2008; Guitart et al. 2010b; Otieno et al. 2010; Novotný et al. 2011). One of the worst and latest
episodes occurred in the pampas (grasslands) of Argentina between 1995 and 1996, when
the inadequate use of monocrotophos was responsible for the deaths of an estimated 5095
Swainson's hawks ( Buteo swainsoni ), which represented approximately 1% of the world popu-
lation of this raptor species at the time (Goldstein et al. 1999). In the United States, the lethal
risk to birds has generally declined over the period between 1991 and 2003 in most crops,
which was attributed to a replacement of the more toxic insecticides, largely OP and CB
products (Mineau and Whiteside 2006). Of 24 different pesticides identified in avian mortali-
ties in the United States, the most frequent were famphur (18%), carbofuran (15%), diazinon
(12%), and fenthion (5.1%), with Falconiformes reportedly being killed most frequently (49%
of all die-offs) but Anseriformes found dead in the greatest numbers (64% of 8877 recovered
carcasses) (Fleischli et al. 2004). In Spain, a review of the analytical data pooled from various
institutions indicated that 58 wild birds, including 10 cinereous vultures and one Spanish
imperial eagle, were poisoned by different pesticides between 1990 and 2005, especially by
aldicarb and carbofuran (27.59% each) and methomyl (8.62%) (Martínez-Haro et al. 2008).
Moreover, there is growing concern that exposure to AChE-inhibiting insecticides may
also have negative sublethal effects on avian populations by affecting the physiological and
behavioral responses, including the loss of orientation in migratory birds (Strum et al. 2010).
Lethal cases in mammals, some primary and other secondary poisonings, have also
been reported (Goldstein et al. 1999; Wobeser et al. 2004; Wang et al. 2007; Martínez-Haro
et al. 2008; Berny et al. 2010; Guitart et al. 2010a,b; Novotný et al. 2011). The illegal use of
anticholinesterase pesticides in Canada between 1967 and 2002 was reviewed by Wobeser
et al. (2004), and coyotes ( Canis latrans ), red foxes, and striped skunks ( Mephitis mephitis )
were implicated in many of the episodes. Novotný et al. (2011) reported cases in Eurasian
otters with carbofuran and cases in wild boars ( Sus scrofa ) and bisons ( Bison spp.) with
methomyl in the Czech Republic.
The best diagnosis of poisoning with OPs and CBs is the measurement of AChE activ-
ity in the brain, which is best correlated with morbidity and mortality than chlolinesterase
inhibition in the plasma or blood. As a general rule, it is considered that a 20% decrease in
activity is indicative of abnormal exposure, while lethal intoxication is usually associated
with a 50% decline, although these figures can be lower or higher depending on the situation
(Goldstein et al. 1999; Mineau and Tucker 2002; Wobeser et al. 2004). In particular, species,
age, sex, reproductive condition, nutritional status, and sample handling and laboratory
techniques have been demonstrated to introduce some variability (Mayack and Martin
2003; Maul and Farris 2004). At least for Northern cardinals ( Cardinalis cardinalis ), Maul