INSERM: In an article published in the journal Environment International, researchers from Inserm (Inserm Unit 1085 – IRSET, the Institute of Research in Environmental and Occupational Health, Rennes), in association with the Laboratory for Developmental and Educational Psychology, LPDE (Rennes 2 University), provide new evidence of neurotoxicity in humans from pyrethroid insecticides, which are found in a wide variety of products and uses. An increase in the urinary levels of two pyrethroid metabolites (3-PBA and cis-DBCA) in children is associated with a significant decrease in their cognitive performances, particularly verbal comprehension and working memory. This study was carried out on nearly 300 mother and child pairs from the PELAGIE cohort (Brittany).
Pyrethroids constitute a family of insecticides widely used in a
variety of sectors: agriculture (various crops), veterinary
(antiparasitics) and domestic (lice shampoo, mosquito products). Their
mode of action involves blocking neurotransmission in insects, leading
to paralysis. Because of their efficacy and relative safety for humans
and mammals, they have replaced older compounds (organochorides,
organophosphates, carbamate) considered more toxic.
Exposure of children to pyrethroids is common.
different to adult exposure, due to the closer proximity of children to
ground-level dust (which stores pollutants), more frequent
hand-to-mouth contact, lice shampoos, etc. In children, pyrethroids are
mainly absorbed via the digestive system, but are also absorbed through
the skin. They are rapidly metabolised in the liver, and mainly
eliminated in the urine as metabolites within 48 hours.
Given these elements and the mode of action (neurotoxicity) of
pyrethroid insecticides, the researchers proposed the hypothesis of a
possible effect of these contaminants on the nervous system and its
development in children.
Contribution of the PELAGIE mother-child cohort
Pregnancy is also an important period of life for the future health
of the child. For this reason, the researchers studied the PELAGIE
mother-child cohort established between 2002 and 2006, which monitors
3,500 mother-child pairs. This cohort simultaneously considers exposure
to pyrethroid insecticides during foetal life and childhood.
A total of 287 women, randomly selected from the PELAGIE cohort and
contacted successfully on their child’s sixth birthday, agreed to
participate in this study.
Two psychologists visited them at home. One assessed the child’s
neurocognitive performances using the WISC scale (verbal comprehension
index, VCI, and working memory index, WMI). The other psychologist
characterised the family environment and stimuli that might have had a
role on the child’s intellectual development, collected a urine sample
from the child, and collected dust samples.
Exposure to pyrethroid insecticides was estimated by measuring levels
of five metabolites (3-PBA, 4-F-3-PBA, cis-DCCA, trans-DCCA and
cis-DBCA) in urine from the mother (collected between the 6th and 19th
weeks of pregnancy) and from the child (collected on his/her 6th
A decrease observed in child cognitive performances
Results show that an increase in children’s urinary levels of
two metabolites (3 PBA and cis-DBCA) was associated with a significant
decrease in cognitive performances, whereas no association was
observed for the other three metabolites (4-F-3-PBA, cis-DCCA and
trans-DCCA). With respect to metabolite concentrations during pregnancy,
there was no demonstrable association with neurocognitive scores.