3.7 Other Effects
Recent systematic reviews and meta-analyses have associated prenatal or childhood
indoor exposure to insecticides, assessed as a class, to an increased risk of leukemia
and brain tumors in children [76–82]. Possible association between the use of the
common pyrethroid insecticide, permethrin, and various types of cancer has been
more particularly evaluated in several epidemiological studies, mostly based on the
US Agricultural Health Study cohort. Negative or inconclusive results were reported
[77, 83–88]. Pooled analysis of large agricultural worker cohorts from France, the
USA, and Norway found moderate association between chronic use of deltamethrin
and elevations in risks of non-Hodgkin lymphoid malignancies (subtypes) [89].
The consequences of pyrethroid exposure on coronary heart disease [90], body
mass index [91, 92], hematological parameters [93], genetic damage [94–97],
rheumatoid arthritis [98], and prediabetes [99, 100] were infrequently examined.
4 Conclusions
A growing number of epidemiological studies have been carried out to investigate
the health impact of long-term environmental and occupational exposures to
pyrethroids.
Suggestive association between pyrethroid exposure and various respiratory and
neurologic effects has been reported in adults in a few recent studies. Most of them
addressed occupational exposures (e.g., agricultural workers), with self-reported
uses. These exposure conditions may be specific and may not be readily generalizable to chronic environmental exposures of the adult population at relatively low
levels. In addition, neurological findings were not consistent across studies and
overall evidence remains limited yet. Regarding the thyroid function, no or weak
changes in relation with pyrethroid exposure have been reported in the studies
conducted so far.
Numerous earlier epidemiological studies have focused on the male endocrine
and reproductive system, and some of them have suggested that pyrethroids may
have potential deleterious effects on different male sexual characteristics [1, 101,
102]. In line with this hypothesis, several cross-sectional studies published in the last
few years found an association between environmental pyrethroid exposure and
decreased sperm quality and sperm DNA damages. However, the inconsistencies
across all results available still prevent strong conclusions.
A great deal of attention has also been devoted to the consequences of environmental exposure to pyrethroids during pregnancy. Most existing studies, of which
those currently reviewed, found weak evidence of adverse effects on general birth
outcomes including birth weight and length and gestational age. Past and present
studies on child neurodevelopment and behavior (i.e., infants to grade schoolers)
were relatively consistent. The negative effects related to prenatal pyrethroid
Human Risk Associated with Long-Term Exposure to Pyrethroid Insecticides
295
Recent systematic reviews and meta-analyses have associated prenatal or childhood
indoor exposure to insecticides, assessed as a class, to an increased risk of leukemia
and brain tumors in children [76–82]. Possible association between the use of the
common pyrethroid insecticide, permethrin, and various types of cancer has been
more particularly evaluated in several epidemiological studies, mostly based on the
US Agricultural Health Study cohort. Negative or inconclusive results were reported
[77, 83–88]. Pooled analysis of large agricultural worker cohorts from France, the
USA, and Norway found moderate association between chronic use of deltamethrin
and elevations in risks of non-Hodgkin lymphoid malignancies (subtypes) [89].
The consequences of pyrethroid exposure on coronary heart disease [90], body
mass index [91, 92], hematological parameters [93], genetic damage [94–97],
rheumatoid arthritis [98], and prediabetes [99, 100] were infrequently examined.
4 Conclusions
A growing number of epidemiological studies have been carried out to investigate
the health impact of long-term environmental and occupational exposures to
pyrethroids.
Suggestive association between pyrethroid exposure and various respiratory and
neurologic effects has been reported in adults in a few recent studies. Most of them
addressed occupational exposures (e.g., agricultural workers), with self-reported
uses. These exposure conditions may be specific and may not be readily generalizable to chronic environmental exposures of the adult population at relatively low
levels. In addition, neurological findings were not consistent across studies and
overall evidence remains limited yet. Regarding the thyroid function, no or weak
changes in relation with pyrethroid exposure have been reported in the studies
conducted so far.
Numerous earlier epidemiological studies have focused on the male endocrine
and reproductive system, and some of them have suggested that pyrethroids may
have potential deleterious effects on different male sexual characteristics [1, 101,
102]. In line with this hypothesis, several cross-sectional studies published in the last
few years found an association between environmental pyrethroid exposure and
decreased sperm quality and sperm DNA damages. However, the inconsistencies
across all results available still prevent strong conclusions.
A great deal of attention has also been devoted to the consequences of environmental exposure to pyrethroids during pregnancy. Most existing studies, of which
those currently reviewed, found weak evidence of adverse effects on general birth
outcomes including birth weight and length and gestational age. Past and present
studies on child neurodevelopment and behavior (i.e., infants to grade schoolers)
were relatively consistent. The negative effects related to prenatal pyrethroid
Human Risk Associated with Long-Term Exposure to Pyrethroid Insecticides
295