atmosphere, some of them have the potential for long range transport as
pentachorinated PCBs, 4–5 rings PAHs and DDD (Fig. 2). In comparison to those
legacy pollutants and hydrocarbons, current-use pesticides such as pyrethroids are
often reported in one environmental phase, chiefly dissolved freshwater phase or
riverine sediments. Both dissolved phase and suspended particles [31] or suspended
particles and sediments [14] or dissolved water phase and sediments [24, 27, 28, 33]
are considered jointly in order to assess combined risks for the water ecosystem and
for the benthic ecosystem. Future research efforts should address their multiphase
partitioning, including the atmosphere, to elucidate their capacity to affect proximate
or distant ecosystems from their primary sources. The advective transport of pyrethroids has been largely addressed only in relation to their dispersion by river flow
notably during storm events. However, the partition between dissolved pyrethroids
and particles is specifically addressed by one study, showing that for this particular
site, a diffusive flux of bifenthrin existed from the particles toward the dissolved
water [21].
8 Future Research Integration
Because of their rapid decay, pyrethroids are reported above detection levels in areas
and at times closed to their point sources, and a global appraisal is still missing. It can
be foreseen that pyrethroids might threaten biodiversity in some geographical areas
where data is still lacking to date. Most croplands are indeed not studied for
pyrethroids (Africa, Brasil, etc., see review [62]). In African market, esfenvalerate
was the highest pesticide residue in fruits and vegetables, and allethrin was also
detected, attesting for their use [80–83]. Ukraine, Pakistan, Turkey, Paraguay, and
India registered the larger pyrethroid use while environmental informations on
pyrethroid occurrence are mainly lacking for those countries [7, 26].
Pyrethroids are degraded in the environment so that they are not conspicuously
detected, with the exception of some agricultural or urban areas. Their high degradation rates with respect to legacy pollutants support the belief that they are unlikely
to persist in the environment. However, extension of cropland and of urbanized
space will likely result into an increase in pyrethroid uses and emissions, because
better alternatives to control pests are still lacking. In the case where the rate of
inputs of pyrethroids would compensate for their degradation, pyrethroid occurrence
may become more continuous and their behavior may then be assimilated to that of
“quasi persistent organic pollutants”, with secondary transport evading them away
from their application area. In California, past and current monitorings have demonstrated that there is a persistent threat to aquatic ecosystems because of current-use
pesticides, with an increasing share by pyrethroids [19].
In conclusion, the shift to current-use pesticides demands a better understanding
of the occurrence of pyrethroids in developing countries where the market shares are
the highest. The partition, transport, and degradation fluxes of pyrethroids need to be
Fate of Pyrethroids in Freshwater and Marine Environments
101
pentachorinated PCBs, 4–5 rings PAHs and DDD (Fig. 2). In comparison to those
legacy pollutants and hydrocarbons, current-use pesticides such as pyrethroids are
often reported in one environmental phase, chiefly dissolved freshwater phase or
riverine sediments. Both dissolved phase and suspended particles [31] or suspended
particles and sediments [14] or dissolved water phase and sediments [24, 27, 28, 33]
are considered jointly in order to assess combined risks for the water ecosystem and
for the benthic ecosystem. Future research efforts should address their multiphase
partitioning, including the atmosphere, to elucidate their capacity to affect proximate
or distant ecosystems from their primary sources. The advective transport of pyrethroids has been largely addressed only in relation to their dispersion by river flow
notably during storm events. However, the partition between dissolved pyrethroids
and particles is specifically addressed by one study, showing that for this particular
site, a diffusive flux of bifenthrin existed from the particles toward the dissolved
water [21].
8 Future Research Integration
Because of their rapid decay, pyrethroids are reported above detection levels in areas
and at times closed to their point sources, and a global appraisal is still missing. It can
be foreseen that pyrethroids might threaten biodiversity in some geographical areas
where data is still lacking to date. Most croplands are indeed not studied for
pyrethroids (Africa, Brasil, etc., see review [62]). In African market, esfenvalerate
was the highest pesticide residue in fruits and vegetables, and allethrin was also
detected, attesting for their use [80–83]. Ukraine, Pakistan, Turkey, Paraguay, and
India registered the larger pyrethroid use while environmental informations on
pyrethroid occurrence are mainly lacking for those countries [7, 26].
Pyrethroids are degraded in the environment so that they are not conspicuously
detected, with the exception of some agricultural or urban areas. Their high degradation rates with respect to legacy pollutants support the belief that they are unlikely
to persist in the environment. However, extension of cropland and of urbanized
space will likely result into an increase in pyrethroid uses and emissions, because
better alternatives to control pests are still lacking. In the case where the rate of
inputs of pyrethroids would compensate for their degradation, pyrethroid occurrence
may become more continuous and their behavior may then be assimilated to that of
“quasi persistent organic pollutants”, with secondary transport evading them away
from their application area. In California, past and current monitorings have demonstrated that there is a persistent threat to aquatic ecosystems because of current-use
pesticides, with an increasing share by pyrethroids [19].
In conclusion, the shift to current-use pesticides demands a better understanding
of the occurrence of pyrethroids in developing countries where the market shares are
the highest. The partition, transport, and degradation fluxes of pyrethroids need to be
Fate of Pyrethroids in Freshwater and Marine Environments
101