cypermethrin, and cyfluthrin [21]. Even though the same compounds were also
detected in the dissolved phase, their relative abundance differed from that of the
particles. Comparison of the suspended/dissolved concentration ratio to the soilwater partition constant showed that bifenthrin was not at equilibrium and in excess
in the particles [21]. In contrast, dissolved+particulate samples collected in two
others rivers of Southern California during low flow period showed much lower
concentrations, and only bifenthrin and permethrin were detected [20].
Generally, the past and on-going water survey programs setup in California have
yielded an important and valuable amount of data on the occurrence of pyrethroids.
These studies demonstrated that one or two pyrethroids were frequently present in
whole water samples, and that the dominant active compound differed in space and
time (both years and seasons), reflecting the distinct agricultural targets, shifts in
usages, and emissions from urban pest control [11, 19]. A metadata analysis gave the
integrated view that cyhalothrin and bifenthrin were the compounds most frequently
exceeding Regulatory Threshold Levels in surface freshwater of the USA and
reached higher maxima in concentration [2].
In developing countries, the impact of current-use pesticides on freshwater
quality is a growing concern, and an increasing literature documents pyrethroids in
Asian water bodies, whereas reports on Africa are still too scarce [34]. Together with
hundreds of other micro-pollutants, two pyrethroids were monitored in rivers and
canals flowing through Vietnamese large cities and showed occasionally very high
permethrin concentrations [23]. Cypermethrin and permethrin also dominated in the
dissolved phase and in suspended particles of an urban creek, close to Guangzhou
(Southern China, [25]). In GuanTin reservoir close to Beijing, deltamethrin was the
more frequently detected pyrethroid insecticide in spring [24]. In streams and rivers
of a rice cultivation area in the Philippines, cyhalothrin, cypermethrin, and
deltamethrin were frequently detected, at concentrations exceeding water quality
thresholds in half of the samples [48]. In Pakistan, deltamethrin and permethrin were
close to water quality threshold in winter samples [26].
In European Rivers, permethrin was detected in the UK [27], cyhalothrin and
cypermethrin in dissolved water and suspended particles of seven streams of Central
Germany, especially after rain events [31]. Cypermethrin was the most frequently
detected pyrethroid in the dissolved phase of the Ebro Delta (Spain), where rice is
cultivated [28, 29]. Cypermethrin and deltamethrin concentrations varied in space
and time, with peaks in concentration at the end of May followed by an apparent
removal within 3 weeks [28, 29]. This finding demonstrated, by in situ observations,
the fast degradation of pyrethroids in freshwater. In another Spanish rice paddy area,
cypermethrin, bifenthrin, esfenvalerate, and cyhalothrin were present in most surface
and groundwater total water samples analyzed [30], with the number of pyrethroids
detected and their concentrations exceeding those measured in the Ebro Delta. In
addition to broadcast on paddy fields, urban emissions through waste water treatment plant emissaries were likely responsible for this contamination. Despite a more
restricted literature on European waters than for American ones, pyrethroid residues
occur in agricultural freshwater environments and their concentrations may exceed
90
L. Méjanelle et al.
detected in the dissolved phase, their relative abundance differed from that of the
particles. Comparison of the suspended/dissolved concentration ratio to the soilwater partition constant showed that bifenthrin was not at equilibrium and in excess
in the particles [21]. In contrast, dissolved+particulate samples collected in two
others rivers of Southern California during low flow period showed much lower
concentrations, and only bifenthrin and permethrin were detected [20].
Generally, the past and on-going water survey programs setup in California have
yielded an important and valuable amount of data on the occurrence of pyrethroids.
These studies demonstrated that one or two pyrethroids were frequently present in
whole water samples, and that the dominant active compound differed in space and
time (both years and seasons), reflecting the distinct agricultural targets, shifts in
usages, and emissions from urban pest control [11, 19]. A metadata analysis gave the
integrated view that cyhalothrin and bifenthrin were the compounds most frequently
exceeding Regulatory Threshold Levels in surface freshwater of the USA and
reached higher maxima in concentration [2].
In developing countries, the impact of current-use pesticides on freshwater
quality is a growing concern, and an increasing literature documents pyrethroids in
Asian water bodies, whereas reports on Africa are still too scarce [34]. Together with
hundreds of other micro-pollutants, two pyrethroids were monitored in rivers and
canals flowing through Vietnamese large cities and showed occasionally very high
permethrin concentrations [23]. Cypermethrin and permethrin also dominated in the
dissolved phase and in suspended particles of an urban creek, close to Guangzhou
(Southern China, [25]). In GuanTin reservoir close to Beijing, deltamethrin was the
more frequently detected pyrethroid insecticide in spring [24]. In streams and rivers
of a rice cultivation area in the Philippines, cyhalothrin, cypermethrin, and
deltamethrin were frequently detected, at concentrations exceeding water quality
thresholds in half of the samples [48]. In Pakistan, deltamethrin and permethrin were
close to water quality threshold in winter samples [26].
In European Rivers, permethrin was detected in the UK [27], cyhalothrin and
cypermethrin in dissolved water and suspended particles of seven streams of Central
Germany, especially after rain events [31]. Cypermethrin was the most frequently
detected pyrethroid in the dissolved phase of the Ebro Delta (Spain), where rice is
cultivated [28, 29]. Cypermethrin and deltamethrin concentrations varied in space
and time, with peaks in concentration at the end of May followed by an apparent
removal within 3 weeks [28, 29]. This finding demonstrated, by in situ observations,
the fast degradation of pyrethroids in freshwater. In another Spanish rice paddy area,
cypermethrin, bifenthrin, esfenvalerate, and cyhalothrin were present in most surface
and groundwater total water samples analyzed [30], with the number of pyrethroids
detected and their concentrations exceeding those measured in the Ebro Delta. In
addition to broadcast on paddy fields, urban emissions through waste water treatment plant emissaries were likely responsible for this contamination. Despite a more
restricted literature on European waters than for American ones, pyrethroid residues
occur in agricultural freshwater environments and their concentrations may exceed
90
L. Méjanelle et al.