Pesticide Residues in Birds and Mammals - Pesticides: Evaluation of Environmental Pollution - page 422

14.4 Insecticides
Insecticides are chemicals developed, produced, and used to control the populations of
insects. Together with the group of rodenticides, they can be considered the most valu-
able pesticides used in agriculture, animal and public health, industry, and households.
However, some representatives of the OP, CB, and pyrethroid groups are also the most
acutely toxic ones of the pesticides for nontarget vertebrates ( Table 14.1 ), and the medium-
to long-term problems of contamination associated with the massive use of the OC
group are still one of the most active and productive areas of research in Environmental
Toxicology today.
14.4.1 Organochlorine Insecticides
Although a long time has passed since the banning of OC insecticides in most parts of
the world, the residues are still present in any kind of biotic or abiotic sample (provided
that a sensitive analytical method is used to detect them). Their bioaccumulatory proper-
ties and capacity to biomagnify and their potential adverse effects on the reproduction
and survival of organisms have stressed the necessity of monitoring their environmental
levels since mid-1960s (Keith 1996; Fisk et al. 2005). The undesirable effects of some of
these chemicals are linked to the occurrence of immunological, pathological, reproduc-
tive, and teratogenic dysfunctions in various vertebrate species. Moreover, some of these
compounds, such as chlordane, chlordecone, p,pʹ-DDT, HCHs, mirex, or toxaphene, are
classified by the IARC as possibly carcinogenic to humans (group 2B) (IARC 2010).
The interference with the endocrine systems of wild animals has received particular
attention in recent times (Vos et al. 2000; Tanabe 2002; Giesy et al. 2003; Porte et al. 2006;
Fossi et al. 2007; Bernanke and Köhler 2009). The International Programme on Chemical
Safety (IPCS) defines endocrine disruptors (EDs) as exogenous substances or mixtures
that alter the function(s) of the endocrine system and consequently cause adverse health
effects in an intact organism, or its progeny, or (sub)populations (Damstra et al. 2002). Such
pollutants can modulate or disrupt the endocrine system via several mechanisms, includ-
ing interfering with hormone synthesis, transport, metabolism, ligand binding, and gene
expression. Reproductive failure, teratogenic effects, and eggshell thinning in animals
exposed to EDs during embryonic development have been discussed extensively (Vos et al.
2000; Damstra et al. 2002; Tanabe 2002; Giesy et al. 2003; Porte et al. 2006; Hotchkiss et al.
2008; Bernanke and Köhler 2009; Sonne 2010).
Due to the biomagnification capacity of recalcitrant POPs, the trophic position has com-
monly been considered the main factor explaining the pollutant concentrations in bird
and mammalian tissues (Dietz et al. 2000; Fisk et al. 2001; Goerke et al. 2004; Alleva et al.
2006; Corsolini 2009; Dhananjayan and Muralidharan 2010; Skarphedinsdottir et al. 2010).
This explains in part the vast use of carnivorous (or piscivorous) species such as birds of
prey, seabirds, or marine mammals for monitoring purposes in environmental toxicology
studies.
Over the past two decades, stable isotope analysis (SIA) has become an important tech-
nique in environmental toxicology and ecotoxicology studies. Although many stable
isotopes can be used, nitrogen-15 ( 15 N/ 14 N expressed relative to a standard, or δ 15 N) and
carbon-13 ( 13 C/ 12 C, or δ 13 C) isotopic signatures have increasingly gained more attention
for unraveling the structures of food webs (Fisk et al. 2001; Elliott 2005; Elliott et al. 2009;
Lavoie et al. 2010). Whereas δ 15 N value is used as an indicator to assess the trophic position