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expert reaction to study looking at pyrethroid insecticides in pregnancy and in children, and childhood behavioural difficulties

Researchers publishing in the Occupational & Environmental Medicine investigated the associations between metabolite measures of prenatal and childhood exposure to pyrethroid insecticides and behavioural skills in 6-year-olds. A Before the Headlines analysis accompanied these comments.


Prof Sir David Spiegelhalter, Winton Professor for the Public Understanding of Risk, University of Cambridge, said:

“The evidence presented is extremely weak, and the few reported positive associations could well be due to chance.

“The authors first carry out 60 standard statistical tests, and only find one ‘significant’ association, whereas three would be expected just by chance alone.  They then do 30 more sensitive statistical tests, and find two positive, but also one negative, associations – all the rest of the tests show no good evidence of a link between metabolite and behaviours.

“Although the press release claims that “children with the highest levels of metabolites in their urine were around three times as likely to display abnormal behaviour”, this finding was not at the highest level of metabolite, and was not statistically significant.”


* ‘Behavioural disorders in 6-year-old children and pyrethroid insecticide exposure: the PELAGIE mother-child cohort’ by Jean-François Viel et al. published in Occupational & Environmental Medicine on Wednesday 1 March 2017. 


Declared interests

Prof Sir David Spiegelhalter: “No conflicts of interest.”

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