3.4 Prenatal Exposure and Outcomes at Birth
and in Childhood
Several birth cohort studies and a small number of large case-control studies have
assessed the relationship between pyrethroid exposure during pregnancy and common outcomes at birth, i.e., gestation duration, preterm birth, birth weight and
height, and head circumference (Table 4). They mainly provided no or modest
evidence of potential effects on non-occupationally exposed populations. To notice,
one of the largest case-control studies suggested that exposure to two or more
pyrethroids during the first or second trimester of pregnancy may increase the risk
of spontaneous preterm birth [36]. Pesticide exposure was based on the proximity of
mother’s residence with pesticide application sites. This finding was not replicated in
a similar case-control study also based on California birth records [37]. In the
VHEMBE South Africa birth cohort (Venda Health Examination of Mothers, Babies
and their Environment), two urinary metabolites of pyrethroids (i.e., cis-DCCA and
DBCA) measured at delivery were negatively associated with body weight and body
mass index (BMI) in boys at 1 and 2 years of age [34]. Possible contribution of
exposure to pyrethroids and other environmental factors during childhood (e.g.,
pesticide spray at home) was not controlled. Moreover, no effect was observed on
these outcomes at birth [33, 35].
A few case-control studies, mostly by the same team, have examined potential
association between risk of selected birth defects and residential proximity with
agricultural pyrethroid applications during early pregnancy (Table 4). No association
was found with the pyrethroid group, but there were elevated odd ratios for two
specific pyrethroids, cyfluthrin (craniosynostosis) and lambda-cyhalothrin (heart
defects) [39–41]. The authors considered that their studies added to the scant
literature on this topic but that further verification and inquiry were needed before
firm conclusions on individual chemicals teratogenicity.
3.5 Neurological Outcomes (Adult Exposure)
Several cross-sectional studies have examined the neurologic effects of long-term
occupational exposure to pyrethroids in agricultural workers or pesticide applicators
(Table 5). A broad spectrum of symptoms and functions has been assessed with
different tools and indicators (e.g., medical diagnosis of symptoms, performance in
neurobehavioral tests). Pyrethroid exposure was ascertained by history exposure
questionnaires, except from one study which relied on urinary biomarkers [52]. Interpretation is limited due to the paucity of data and the small sample size in a number
of these studies.
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and in Childhood
Several birth cohort studies and a small number of large case-control studies have
assessed the relationship between pyrethroid exposure during pregnancy and common outcomes at birth, i.e., gestation duration, preterm birth, birth weight and
height, and head circumference (Table 4). They mainly provided no or modest
evidence of potential effects on non-occupationally exposed populations. To notice,
one of the largest case-control studies suggested that exposure to two or more
pyrethroids during the first or second trimester of pregnancy may increase the risk
of spontaneous preterm birth [36]. Pesticide exposure was based on the proximity of
mother’s residence with pesticide application sites. This finding was not replicated in
a similar case-control study also based on California birth records [37]. In the
VHEMBE South Africa birth cohort (Venda Health Examination of Mothers, Babies
and their Environment), two urinary metabolites of pyrethroids (i.e., cis-DCCA and
DBCA) measured at delivery were negatively associated with body weight and body
mass index (BMI) in boys at 1 and 2 years of age [34]. Possible contribution of
exposure to pyrethroids and other environmental factors during childhood (e.g.,
pesticide spray at home) was not controlled. Moreover, no effect was observed on
these outcomes at birth [33, 35].
A few case-control studies, mostly by the same team, have examined potential
association between risk of selected birth defects and residential proximity with
agricultural pyrethroid applications during early pregnancy (Table 4). No association
was found with the pyrethroid group, but there were elevated odd ratios for two
specific pyrethroids, cyfluthrin (craniosynostosis) and lambda-cyhalothrin (heart
defects) [39–41]. The authors considered that their studies added to the scant
literature on this topic but that further verification and inquiry were needed before
firm conclusions on individual chemicals teratogenicity.
3.5 Neurological Outcomes (Adult Exposure)
Several cross-sectional studies have examined the neurologic effects of long-term
occupational exposure to pyrethroids in agricultural workers or pesticide applicators
(Table 5). A broad spectrum of symptoms and functions has been assessed with
different tools and indicators (e.g., medical diagnosis of symptoms, performance in
neurobehavioral tests). Pyrethroid exposure was ascertained by history exposure
questionnaires, except from one study which relied on urinary biomarkers [52]. Interpretation is limited due to the paucity of data and the small sample size in a number
of these studies.
274
A.-M. Saillenfait and S. Malard