3.2 Thyroid Function
The relationships between farm-related exposures to different classes of pesticides
and thyroid disease and/or thyroid hormone disruption have been examined in a
series of recent studies using the cohort of the US Agricultural Health Survey
(Table 2) [13–16, 18]. Weak association between long-term use of permethrin
applied to crops and an increased risk of hypothyroidism was found among female
spouses of farmers aged over 60 years [14]. No significant effect was found for
permethrin applicators. Although they were conducted with large sample sizes over
long time periods, these studies presented several limitations, including self-report of
pesticide uses and lack of doctor diagnosis confirmation.
Regarding environmental exposures, no association was found between thyroid
hormone levels and the urinary pyrethroid metabolite 3-PBA, in a representative
sample of individuals from the US National Health and Nutrition Examination
Survey [17], and in Japanese pregnant women [19] and prenatally exposed
neonates [18].
3.3 Reproductive Effects
Several cross-sectional studies have evaluated the impact of environmental exposure
to pyrethroids on male reproductive health (Table 3). In all studies, assessment relied
on a single semen or blood sample and on the single measure of one (3-PBA) or
several pyrethroid metabolites in urine. A series of studies conducted in men
recruited in fertility clinics showed associations between pyrethroid urinary metabolites (3-PBA, cis-DCCA, and/or trans-DCCA) and sperm quality [31], DNA
damages [27–29], and testosterone levels [31]. However, it is not clear if these
results may apply to the general population. In contrast to these findings, urinary
concentrations of 3-PBA were not found to be associated with sexual hormones and
semen parameters in men from the Japanese general population [30, 32] and/or
occupationally exposed to pyrethroids [25].
Comparatively, a relatively small number of epidemiological studies have been
published on the possible association of pyrethroid exposure and female reproductive health. Biomarkers of pyrethroids were primarily used to confirm exposure. A
variety of outcomes of interest has been evaluated in single studies (Table 3).
Although limited, data available suggest that more attention should be paid to time
to pregnancy [21], female reproductive hormones [22], and girl puberty [23],
especially at higher levels of pyrethroid exposure.
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A.-M. Saillenfait and S. Malard
The relationships between farm-related exposures to different classes of pesticides
and thyroid disease and/or thyroid hormone disruption have been examined in a
series of recent studies using the cohort of the US Agricultural Health Survey
(Table 2) [13–16, 18]. Weak association between long-term use of permethrin
applied to crops and an increased risk of hypothyroidism was found among female
spouses of farmers aged over 60 years [14]. No significant effect was found for
permethrin applicators. Although they were conducted with large sample sizes over
long time periods, these studies presented several limitations, including self-report of
pesticide uses and lack of doctor diagnosis confirmation.
Regarding environmental exposures, no association was found between thyroid
hormone levels and the urinary pyrethroid metabolite 3-PBA, in a representative
sample of individuals from the US National Health and Nutrition Examination
Survey [17], and in Japanese pregnant women [19] and prenatally exposed
neonates [18].
3.3 Reproductive Effects
Several cross-sectional studies have evaluated the impact of environmental exposure
to pyrethroids on male reproductive health (Table 3). In all studies, assessment relied
on a single semen or blood sample and on the single measure of one (3-PBA) or
several pyrethroid metabolites in urine. A series of studies conducted in men
recruited in fertility clinics showed associations between pyrethroid urinary metabolites (3-PBA, cis-DCCA, and/or trans-DCCA) and sperm quality [31], DNA
damages [27–29], and testosterone levels [31]. However, it is not clear if these
results may apply to the general population. In contrast to these findings, urinary
concentrations of 3-PBA were not found to be associated with sexual hormones and
semen parameters in men from the Japanese general population [30, 32] and/or
occupationally exposed to pyrethroids [25].
Comparatively, a relatively small number of epidemiological studies have been
published on the possible association of pyrethroid exposure and female reproductive health. Biomarkers of pyrethroids were primarily used to confirm exposure. A
variety of outcomes of interest has been evaluated in single studies (Table 3).
Although limited, data available suggest that more attention should be paid to time
to pregnancy [21], female reproductive hormones [22], and girl puberty [23],
especially at higher levels of pyrethroid exposure.
266
A.-M. Saillenfait and S. Malard