contaminated soils, brought an important discussion about global transport dynamics
of persistent organic pollutants (POPs) [85–87]. This approach was proposed around
the 1990s in a period of increasing banning of organochlorine pesticides in industrialized countries but with their continued use in tropical and subtropical countries
[85, 88]. The use of degradation profiles of chiral POPs as tracers of their sources is
still required for monitoring global contamination. There is evidence of increased
secondary emissions of POPs into the atmosphere, including industrial pollutants,
such as polychlorinated biphenyls (PCBs), due to rising temperatures and melting in
Arctic regions in the face of global climate change [86, 89].
As described for some organochlorines, pyrethroid stereoselectivity is potentially
suitable for environmental signature interpretation. Considering the greater toxicity
of specific enantiomers, the finding of contamination profiles in different environmental compartments can be a fundamental tool for more accurate risk assessments.
4.1 Pyrethroid Stereoisomerism on Environmental Samples
Over the last several decades, pyrethroids have been increasingly used as an
alternative to more toxic and persistent pesticides, such as organochlorines, organophosphates and carbamates. However, reports on pyrethroid contamination in
aquatic mammals and atmospheric air from mountains of biosphere reserve of the
Atlantic Forest demonstrate their persistence in the environment and their long range
of contamination [90, 91].
Therefore, a more extensive investigation is required considering the fate and the
possible impacts of these compounds in the environment.
Pyrethroid stereoisomerism on environmental samples must be interpreted considering some relevant points: (1) the current limitation on the number of published
works, since in many studies, the results are presented only with the sum of isomers;
(2) the occurrence of different commercial formulations must be checked to avoid
misunderstandings regarding the profile found in the environment; and (3) the
multiple chiral centres in pyrethroids generate up to four peaks in an achiral
stationary phase and up to eight peaks in a chiral phase, which require an adequate
peak resolution during the analytical procedures for the subsequent profile
comparison.
Some previous studies have presented the enantiomeric factor (EF) as a means to
discuss the environmental dynamics of pyrethroids, which includes their degradation/persistence pattern in environmental samples [90, 92, 93]. Depending on the
analysis, EF can be calculated to compare enantiomeric pairs (cis- and transdiastereomers) or single enantiomers (R- and S-enantiomers). EF is calculated
through the equation (EF ¼ A sp /A T ), where A sp is a specific stereoisomer chromatographic peak area and A T is the sum of peak areas of all structurally related
stereoisomers present in the sample [90, 93]. In equal proportion, each diastereomer
of Type I pyrethroids is expressed as EF ¼ 0.5 or 50%. In Type II pyrethroids, an
equal proportion of each diastereomer is expressed as EF ¼ 0.25 or 25% due to the
Stereoselectivity and Environmental Behaviour of Pyrethroids
165
of persistent organic pollutants (POPs) [85–87]. This approach was proposed around
the 1990s in a period of increasing banning of organochlorine pesticides in industrialized countries but with their continued use in tropical and subtropical countries
[85, 88]. The use of degradation profiles of chiral POPs as tracers of their sources is
still required for monitoring global contamination. There is evidence of increased
secondary emissions of POPs into the atmosphere, including industrial pollutants,
such as polychlorinated biphenyls (PCBs), due to rising temperatures and melting in
Arctic regions in the face of global climate change [86, 89].
As described for some organochlorines, pyrethroid stereoselectivity is potentially
suitable for environmental signature interpretation. Considering the greater toxicity
of specific enantiomers, the finding of contamination profiles in different environmental compartments can be a fundamental tool for more accurate risk assessments.
4.1 Pyrethroid Stereoisomerism on Environmental Samples
Over the last several decades, pyrethroids have been increasingly used as an
alternative to more toxic and persistent pesticides, such as organochlorines, organophosphates and carbamates. However, reports on pyrethroid contamination in
aquatic mammals and atmospheric air from mountains of biosphere reserve of the
Atlantic Forest demonstrate their persistence in the environment and their long range
of contamination [90, 91].
Therefore, a more extensive investigation is required considering the fate and the
possible impacts of these compounds in the environment.
Pyrethroid stereoisomerism on environmental samples must be interpreted considering some relevant points: (1) the current limitation on the number of published
works, since in many studies, the results are presented only with the sum of isomers;
(2) the occurrence of different commercial formulations must be checked to avoid
misunderstandings regarding the profile found in the environment; and (3) the
multiple chiral centres in pyrethroids generate up to four peaks in an achiral
stationary phase and up to eight peaks in a chiral phase, which require an adequate
peak resolution during the analytical procedures for the subsequent profile
comparison.
Some previous studies have presented the enantiomeric factor (EF) as a means to
discuss the environmental dynamics of pyrethroids, which includes their degradation/persistence pattern in environmental samples [90, 92, 93]. Depending on the
analysis, EF can be calculated to compare enantiomeric pairs (cis- and transdiastereomers) or single enantiomers (R- and S-enantiomers). EF is calculated
through the equation (EF ¼ A sp /A T ), where A sp is a specific stereoisomer chromatographic peak area and A T is the sum of peak areas of all structurally related
stereoisomers present in the sample [90, 93]. In equal proportion, each diastereomer
of Type I pyrethroids is expressed as EF ¼ 0.5 or 50%. In Type II pyrethroids, an
equal proportion of each diastereomer is expressed as EF ¼ 0.25 or 25% due to the
Stereoselectivity and Environmental Behaviour of Pyrethroids
165