inhalation exposure at typical air levels, with inhalation contributing 5–10% of the
total exposure [50]. Pyrethroid air concentration is in steady state with household
dust levels. Bradman et al. measured air concentrations indoors and outdoors along
with house dust levels in the homes of 20 children and only found measurable levels
of cis-permethrin in the air, while several other pyrethroids were present in the house
dust [37]. Tulve et al. measured indoor and outdoor air, wipe samples from play
areas, levels on socks, and in food for 14 pyrethroids, piperonyl butoxide, and
2 other pesticides in the homes of 9 children (Table 3) [39]. Most pyrethroids
were detected more frequently in indoor air than outdoor air, and the median and
maximum concentrations were higher [39] in the indoor air samples. They also
found correlations between the wipe samples and the indoor air levels for multiple
pyrethroids across the homes.
Since dust can be resuspended by movement in a home, Zhou et al. used a robot to
simulate a toddler’s movement and observed that the movement increased particulate pyrethroid air concentrations [51]. They measured twice the permethrin air
concentrations near the moving robot at a toddler’s breathing zone height compared
to levels at an indoor stationary sampler collected simultaneously. They also found
differences in the air concentration when the robot resuspended dust from a vinyl
floor (65 and 143 ng/m
3 , stationary and robot sample, respectively) compared to a
carpeted floor (34 and 61 ng/m
3 , stationary and robot sample, respectively). This
study demonstrated the need for caution when using indoor air concentrations rather
than personal air concentration measurements to estimate pyrethroid inhalation
exposure.
7 Urinary Metabolites of Pyrethroids
Once inhaled, pyrethroids are metabolized in the body and excreted with many
compounds having half-lives of just hours. A list of common pyrethroids and their
metabolites is given in Table 4 [48, 52]. Several pyrethroids have the same metabolites, e.g., 3-BPA, cis-DCCA, and trans-DCCA, so while the presence of these
metabolites in urine indicates that there was likely an exposure to a pyrethroid, it
does not confirm which specific pyrethroid was present nor the exposure route. The
metabolites are predominantly excreted as sulfate and glucuronide conjugates in the
urine. The urinary metabolite levels have been used to evaluate exposure models.
Several studies have used the US EPA Stochastic Human Exposure and Dose
Simulation (SHEDS)-Multimedia model to predict the relative contributions of
pyrethroid exposures across all routes and compare the results to urinary 3-PBA
levels [50, 53, 54]. While there was a strong correlation between the total exposure
predicted and the urinary 3-PBA levels, only a small percentage of the cumulative
exposure was calculated to be via inhalation, and the inhalation exposure was not
correlated to the urinary levels across the entire population studies.
Time series changes in urinary levels of trans-DCAA and 3-PBA were shown to
be related application of permethrin in an agricultural settings to workers exposed
238
C. P. Weisel
total exposure [50]. Pyrethroid air concentration is in steady state with household
dust levels. Bradman et al. measured air concentrations indoors and outdoors along
with house dust levels in the homes of 20 children and only found measurable levels
of cis-permethrin in the air, while several other pyrethroids were present in the house
dust [37]. Tulve et al. measured indoor and outdoor air, wipe samples from play
areas, levels on socks, and in food for 14 pyrethroids, piperonyl butoxide, and
2 other pesticides in the homes of 9 children (Table 3) [39]. Most pyrethroids
were detected more frequently in indoor air than outdoor air, and the median and
maximum concentrations were higher [39] in the indoor air samples. They also
found correlations between the wipe samples and the indoor air levels for multiple
pyrethroids across the homes.
Since dust can be resuspended by movement in a home, Zhou et al. used a robot to
simulate a toddler’s movement and observed that the movement increased particulate pyrethroid air concentrations [51]. They measured twice the permethrin air
concentrations near the moving robot at a toddler’s breathing zone height compared
to levels at an indoor stationary sampler collected simultaneously. They also found
differences in the air concentration when the robot resuspended dust from a vinyl
floor (65 and 143 ng/m
3 , stationary and robot sample, respectively) compared to a
carpeted floor (34 and 61 ng/m
3 , stationary and robot sample, respectively). This
study demonstrated the need for caution when using indoor air concentrations rather
than personal air concentration measurements to estimate pyrethroid inhalation
exposure.
7 Urinary Metabolites of Pyrethroids
Once inhaled, pyrethroids are metabolized in the body and excreted with many
compounds having half-lives of just hours. A list of common pyrethroids and their
metabolites is given in Table 4 [48, 52]. Several pyrethroids have the same metabolites, e.g., 3-BPA, cis-DCCA, and trans-DCCA, so while the presence of these
metabolites in urine indicates that there was likely an exposure to a pyrethroid, it
does not confirm which specific pyrethroid was present nor the exposure route. The
metabolites are predominantly excreted as sulfate and glucuronide conjugates in the
urine. The urinary metabolite levels have been used to evaluate exposure models.
Several studies have used the US EPA Stochastic Human Exposure and Dose
Simulation (SHEDS)-Multimedia model to predict the relative contributions of
pyrethroid exposures across all routes and compare the results to urinary 3-PBA
levels [50, 53, 54]. While there was a strong correlation between the total exposure
predicted and the urinary 3-PBA levels, only a small percentage of the cumulative
exposure was calculated to be via inhalation, and the inhalation exposure was not
correlated to the urinary levels across the entire population studies.
Time series changes in urinary levels of trans-DCAA and 3-PBA were shown to
be related application of permethrin in an agricultural settings to workers exposed
238
C. P. Weisel