Pyrethroids are about 2,250 times more toxic for insects than mammals. Insects
have more sensitive sodium channels, smaller bodies and low body temperatures.
Moreover, the absorption through the skin in mammals is weak, and they can
metabolise them into non-toxic compounds fast [11].
Human exposition to pyrethroids has been documented studying their metabolites
in urine of German children and teenagers [28], in hair and blood of pregnant women
and meconium of babies [39], in plasma of pregnant women from rural areas of
South Africa [40] and in human milk [25, 33].
A few studies focused on marine organisms including different tissues of
Brazilian dolphins [24, 41], Mediterranean dolphins [42] and wild and edible fish
from Spanish rivers [43].
Seafood production has experimented a 3.2% yearly growth since 1961
[44]. Aquaculture is responsible for half of the seafood production worldwide, and
the world annual fish consumption per capita is about 20 kg. While concern about the
application of pyrethroids in fish farms against fish parasites exists, pyrethroid
ingestion has been reported to be below the accepted daily intake (ADI) [45].
More detailed information of effect of salmon industry in the marine environment
is presented in Chapter “Environmental Risks of Synthetic Pyrethroids Used by the
Salmon Industry in Chile”.
Most of the professional exposure is due to skin absorption. The main effect of
dermal exposition is paresthesia, probably caused by the hyperactivity of cutaneous
nerves, especially on the face. Paresthesia increases with stimuli such as heat,
sunlight, sweat or contact with water [11]. Paresthesia disappears in 12–24 h and
no special treatment is required. However, topical administration of vitamin E can
reduce its symptoms.
Ingestion of pyrethroids causes sore throat, nausea, vomit and abdominal pain in a
few minutes. Mouth ulcers, increased secretion or dysphagia may occur [11]. Inhalation is less important, but it increases when pyrethroids are used in closed spaces.
Systemic effects appear 4–48 h after exposition. The effects usually include dizziness, headache and tiredness. Less frequent effects are palpitations, chest oppression
and blurry sight.
Regarding long-term exposition to pyrethroids at low concentrations, a study in
humans concluded that chronic toxicity of pyrethroids does not cause any specific
symptoms. What could be detected were combinations and correlations of symptoms
caused by the accumulative effect of pyrethroids in nerve tissue such as brain
dysfunction, polyneuropathy, immunosuppression or motor problems due to multiple sclerosis or Parkinson disease [46, 47]. It was also suggested that chronic toxicity
of pyrethroids affect fertility. This hypothesis was proved in rats being administered
small doses of permethrin for a maximum time period of 2 months [48].
On the other hand, these results have been criticised [49] because of the experimental design [50], because pyrethroids were not believed to cause irreversible
effects according to studies on sodium channels [51] or because it was thought that
mammals did not bioaccumulate them [52].
Other studies researched the chronic toxicity of cis-bifenthrin in Daphnia magna
and its cytotoxicity in ovarian cells of Chinese hamster (Cricetulus griseus) and in
human cervical carcinoma cells [53]. The lowest observed effect concentration
10
Ò. Aznar-Alemany and E. Eljarrat
have more sensitive sodium channels, smaller bodies and low body temperatures.
Moreover, the absorption through the skin in mammals is weak, and they can
metabolise them into non-toxic compounds fast [11].
Human exposition to pyrethroids has been documented studying their metabolites
in urine of German children and teenagers [28], in hair and blood of pregnant women
and meconium of babies [39], in plasma of pregnant women from rural areas of
South Africa [40] and in human milk [25, 33].
A few studies focused on marine organisms including different tissues of
Brazilian dolphins [24, 41], Mediterranean dolphins [42] and wild and edible fish
from Spanish rivers [43].
Seafood production has experimented a 3.2% yearly growth since 1961
[44]. Aquaculture is responsible for half of the seafood production worldwide, and
the world annual fish consumption per capita is about 20 kg. While concern about the
application of pyrethroids in fish farms against fish parasites exists, pyrethroid
ingestion has been reported to be below the accepted daily intake (ADI) [45].
More detailed information of effect of salmon industry in the marine environment
is presented in Chapter “Environmental Risks of Synthetic Pyrethroids Used by the
Salmon Industry in Chile”.
Most of the professional exposure is due to skin absorption. The main effect of
dermal exposition is paresthesia, probably caused by the hyperactivity of cutaneous
nerves, especially on the face. Paresthesia increases with stimuli such as heat,
sunlight, sweat or contact with water [11]. Paresthesia disappears in 12–24 h and
no special treatment is required. However, topical administration of vitamin E can
reduce its symptoms.
Ingestion of pyrethroids causes sore throat, nausea, vomit and abdominal pain in a
few minutes. Mouth ulcers, increased secretion or dysphagia may occur [11]. Inhalation is less important, but it increases when pyrethroids are used in closed spaces.
Systemic effects appear 4–48 h after exposition. The effects usually include dizziness, headache and tiredness. Less frequent effects are palpitations, chest oppression
and blurry sight.
Regarding long-term exposition to pyrethroids at low concentrations, a study in
humans concluded that chronic toxicity of pyrethroids does not cause any specific
symptoms. What could be detected were combinations and correlations of symptoms
caused by the accumulative effect of pyrethroids in nerve tissue such as brain
dysfunction, polyneuropathy, immunosuppression or motor problems due to multiple sclerosis or Parkinson disease [46, 47]. It was also suggested that chronic toxicity
of pyrethroids affect fertility. This hypothesis was proved in rats being administered
small doses of permethrin for a maximum time period of 2 months [48].
On the other hand, these results have been criticised [49] because of the experimental design [50], because pyrethroids were not believed to cause irreversible
effects according to studies on sodium channels [51] or because it was thought that
mammals did not bioaccumulate them [52].
Other studies researched the chronic toxicity of cis-bifenthrin in Daphnia magna
and its cytotoxicity in ovarian cells of Chinese hamster (Cricetulus griseus) and in
human cervical carcinoma cells [53]. The lowest observed effect concentration
10
Ò. Aznar-Alemany and E. Eljarrat