burden in the mothers’ muscle. While the limited number of samples prevents an
in-depth argumentation for that, the evidence show that pyrethroids penetrated
the placental membrane and bioaccumulated in the developing foetus in every pair.
In a previous section of this chapter (Sect. 3.3), it has been shown that pyrethroids
are also found in human milk, thus transferred to lactating babies judging by what
has been proved for dolphins.
5 Final Remarks
Bioavailability is the first step to bioaccumulation. Based on desorption kinetic from
sediment, cyfluthrin was the most bioavailable compound, while λ-cyhalothrin was
the less bioavailable of the assessed pyrethroids [29]. Cypermethrin, esfenvalerate
and permethrin were in the most bioavailable half of the list, fenpropathrin and
fluvalinate were around the centre, and bifenthrin and tetramethrin were in the less
bioavailable half. The literature indicates that the bioavailability of pyrethroids,
with percentages of desorption between 9 and 36%, is considerably lower than
that of POPs such as PBDEs, DDT and HBCD, with values over 70%.
Bioaccumulation of pyrethroids had been disregarded in the past to
the mammalian capacity of metabolizing them. However, evidence of their
bioaccumulation has been reported in several publications. Evidence of
bioaccumulation in marine mammals was first found in samples of Franciscana
dolphins from Brazil [7]. Total pyrethroid concentrations ranged from 7.04
to 68.4 ng/g lw. Permethrin showed the highest concentrations, reaching up to
54.6 ng/g lw. The other compounds in decreasing order of concentrations were
cypermethrin, tetramethrin, deltamethrin, fluvalinate, λ-cyhalothrin, fenvalerate,
cyfluthrin and bifenthrin, the latter at levels below 3 ng/g lw.
A trend of pyrethroid concentrations according to the dolphins’ age was
suggested. High concentrations were found in calves due to pyrethroids accumulated
via maternal transfer. Concentrations could dilute with the dolphins growth
and rise again from dietary intake. Finally, adult individuals would metabolize
pyrethroids decreasing their concentration. Greater pyrethroid concentrations
were reported in urban areas, except for deltamethrin, which had been used
in rural areas to control stored grain insects.
A similar study with striped dolphins from the Spanish Mediterranean detected
bifenthrin, cyhalothrin, deltamethrin, permethrin and tetramethrin in most samples
[8]. Mean total pyrethroid concentration was 300 Æ 932 ng/g lw. The environmental
differences between the Mediterranean Sea and the Atlantic Ocean might account
for the levels in striped dolphin compared to the Brazilian ones. The western
Mediterranean Sea had already been identified as a contamination hotspot for marine
mammals [38]. Concentrations of pyrethroids in Mediterranean striped dolphins
were comparable to those of PBDEs and PAH and higher than those of HBB and
dechloranes, but lower than PCB and DDT levels [39–42].
Bioavailability and Bioaccumulation of Pyrethroid Insecticides in Wildlife and. . .
219
in-depth argumentation for that, the evidence show that pyrethroids penetrated
the placental membrane and bioaccumulated in the developing foetus in every pair.
In a previous section of this chapter (Sect. 3.3), it has been shown that pyrethroids
are also found in human milk, thus transferred to lactating babies judging by what
has been proved for dolphins.
5 Final Remarks
Bioavailability is the first step to bioaccumulation. Based on desorption kinetic from
sediment, cyfluthrin was the most bioavailable compound, while λ-cyhalothrin was
the less bioavailable of the assessed pyrethroids [29]. Cypermethrin, esfenvalerate
and permethrin were in the most bioavailable half of the list, fenpropathrin and
fluvalinate were around the centre, and bifenthrin and tetramethrin were in the less
bioavailable half. The literature indicates that the bioavailability of pyrethroids,
with percentages of desorption between 9 and 36%, is considerably lower than
that of POPs such as PBDEs, DDT and HBCD, with values over 70%.
Bioaccumulation of pyrethroids had been disregarded in the past to
the mammalian capacity of metabolizing them. However, evidence of their
bioaccumulation has been reported in several publications. Evidence of
bioaccumulation in marine mammals was first found in samples of Franciscana
dolphins from Brazil [7]. Total pyrethroid concentrations ranged from 7.04
to 68.4 ng/g lw. Permethrin showed the highest concentrations, reaching up to
54.6 ng/g lw. The other compounds in decreasing order of concentrations were
cypermethrin, tetramethrin, deltamethrin, fluvalinate, λ-cyhalothrin, fenvalerate,
cyfluthrin and bifenthrin, the latter at levels below 3 ng/g lw.
A trend of pyrethroid concentrations according to the dolphins’ age was
suggested. High concentrations were found in calves due to pyrethroids accumulated
via maternal transfer. Concentrations could dilute with the dolphins growth
and rise again from dietary intake. Finally, adult individuals would metabolize
pyrethroids decreasing their concentration. Greater pyrethroid concentrations
were reported in urban areas, except for deltamethrin, which had been used
in rural areas to control stored grain insects.
A similar study with striped dolphins from the Spanish Mediterranean detected
bifenthrin, cyhalothrin, deltamethrin, permethrin and tetramethrin in most samples
[8]. Mean total pyrethroid concentration was 300 Æ 932 ng/g lw. The environmental
differences between the Mediterranean Sea and the Atlantic Ocean might account
for the levels in striped dolphin compared to the Brazilian ones. The western
Mediterranean Sea had already been identified as a contamination hotspot for marine
mammals [38]. Concentrations of pyrethroids in Mediterranean striped dolphins
were comparable to those of PBDEs and PAH and higher than those of HBB and
dechloranes, but lower than PCB and DDT levels [39–42].
Bioavailability and Bioaccumulation of Pyrethroid Insecticides in Wildlife and. . .
219