was also described for 1R-enantiomers of cis-/trans-permethrin, fenpropathrin and
lambda-cyhalothrin after soil incubation and by using a bacterial consortium isolated
from Brazilian savannah [50–52].
Considering the different groups of soil organisms, earthworms play an important
role in the dynamics of organic matter and in the maintenance of soil structure in
addition to ecological and environmental functions [17, 34]. Among the widely
occurring pyrethroids in soils, cypermethrin has been predominant [33]. In an acute
toxicity assay (filter paper contact) with earthworms Eisenia fetida exposed to alphacypermethrin (1R-cis-αS and 1S-cis-αR enantiomers), high toxicity of 1R-cis-αS
enantiomer was observed with LC 50 ¼ 49.5 ng cm
À2 [34]. The toxicity was
approximately threefold higher compared to racemic alpha-cypermethrin and
33-fold higher compared to the 1S-cis-αR enantiomer (Table 2).
Although E. fetida and E. andrei are earthworm species widely used in toxicological assessments, the preferential use of Eisenia spp. may underestimate impacts
to other worm species on the environment. In a study comparing the response
of enzymatic biomarkers with E. andrei and Lumbricus rubellus exposed to
deltamethrin (1R-cis-αS), a greater susceptibility of L. rubellus was observed
[35]. In addition, LC 50 (48 h) ¼ 0.11 μg cm
À2 to L. rubellus was fivefold lower
than observed in tests with E. andrei (Table 2). According to these studies,
cis-isomers with the same configuration (1R-cis-αS) were toxic to earthworms in a
concentration range between nanograms and micrograms per cm
À2 . Additionally,
the single isomer with cis-configuration esfenvalerate (2S-αS), which has a different
molecular structure (there is no cyclopropane ring) with a chiral centre on C-2, was
approximately fourfold more toxic to E. fetida than racemic fenvalerate (Table 2)
[28]. In the specific case of fenvalerate, its insecticidal activity is related to the 2-S
configuration, which is structurally compatible with the 1-R configuration of the
cyclopropane ring that also presents high insecticidal action [15, 53].
In addition to the differences between compounds, including their chemical
structures and their spatial arrangements, the soil matrix presents great variation
related to such physicochemical characteristics as pH, redox potential, soil moisture,
soil texture and organic matter content [44]. Among soil parameters, organic matter
content plays an important role in pyrethroid sorption on soils, which directly affects
their bioavailability and environmental fate [54]. Soil characteristics also influence
the diversity and abundance of soil microbiota, including its catabolic activity related
to important functions, such as nutrient cycling and pyrethroid biodegradation
[55, 56].
Although there is some progress in studies approaching enantioselectivity by soil
microbiota and earthworms, to the best of our knowledge, there is a lack of studies
considering other soil organisms, such as the enchytraeids Enchytraeus albidus and
Enchytraeus crypticus, and soil arthropods, such as the collembolans Folsomia
candida and Folsomia fimetaria, and the soil mite Hypoaspis aculeifer [57].
Considering the impacts on organisms of different trophic levels, such as
detritivore species (e.g. earthworms) and predators (e.g. Hypoaspis aculeifer), an
enantioselective approach will be an important step for more precise risk assessments, aiming to protect and maintain soil functions.
160
C. E. T. Parente et al.
lambda-cyhalothrin after soil incubation and by using a bacterial consortium isolated
from Brazilian savannah [50–52].
Considering the different groups of soil organisms, earthworms play an important
role in the dynamics of organic matter and in the maintenance of soil structure in
addition to ecological and environmental functions [17, 34]. Among the widely
occurring pyrethroids in soils, cypermethrin has been predominant [33]. In an acute
toxicity assay (filter paper contact) with earthworms Eisenia fetida exposed to alphacypermethrin (1R-cis-αS and 1S-cis-αR enantiomers), high toxicity of 1R-cis-αS
enantiomer was observed with LC 50 ¼ 49.5 ng cm
À2 [34]. The toxicity was
approximately threefold higher compared to racemic alpha-cypermethrin and
33-fold higher compared to the 1S-cis-αR enantiomer (Table 2).
Although E. fetida and E. andrei are earthworm species widely used in toxicological assessments, the preferential use of Eisenia spp. may underestimate impacts
to other worm species on the environment. In a study comparing the response
of enzymatic biomarkers with E. andrei and Lumbricus rubellus exposed to
deltamethrin (1R-cis-αS), a greater susceptibility of L. rubellus was observed
[35]. In addition, LC 50 (48 h) ¼ 0.11 μg cm
À2 to L. rubellus was fivefold lower
than observed in tests with E. andrei (Table 2). According to these studies,
cis-isomers with the same configuration (1R-cis-αS) were toxic to earthworms in a
concentration range between nanograms and micrograms per cm
À2 . Additionally,
the single isomer with cis-configuration esfenvalerate (2S-αS), which has a different
molecular structure (there is no cyclopropane ring) with a chiral centre on C-2, was
approximately fourfold more toxic to E. fetida than racemic fenvalerate (Table 2)
[28]. In the specific case of fenvalerate, its insecticidal activity is related to the 2-S
configuration, which is structurally compatible with the 1-R configuration of the
cyclopropane ring that also presents high insecticidal action [15, 53].
In addition to the differences between compounds, including their chemical
structures and their spatial arrangements, the soil matrix presents great variation
related to such physicochemical characteristics as pH, redox potential, soil moisture,
soil texture and organic matter content [44]. Among soil parameters, organic matter
content plays an important role in pyrethroid sorption on soils, which directly affects
their bioavailability and environmental fate [54]. Soil characteristics also influence
the diversity and abundance of soil microbiota, including its catabolic activity related
to important functions, such as nutrient cycling and pyrethroid biodegradation
[55, 56].
Although there is some progress in studies approaching enantioselectivity by soil
microbiota and earthworms, to the best of our knowledge, there is a lack of studies
considering other soil organisms, such as the enchytraeids Enchytraeus albidus and
Enchytraeus crypticus, and soil arthropods, such as the collembolans Folsomia
candida and Folsomia fimetaria, and the soil mite Hypoaspis aculeifer [57].
Considering the impacts on organisms of different trophic levels, such as
detritivore species (e.g. earthworms) and predators (e.g. Hypoaspis aculeifer), an
enantioselective approach will be an important step for more precise risk assessments, aiming to protect and maintain soil functions.
160
C. E. T. Parente et al.