4 research outputs found
Metabolites of Organophosphate Flame Retardants and 2‑Ethylhexyl Tetrabromobenzoate in Urine from Paired Mothers and Toddlers
As a result of the polybrominated
diphenyl ether (PBDE) ban in
the mid-2000s, the chemical flame retardant market has moved toward
alterative compounds including chlorinated alkyl and nonchlorinated
aryl organophosphate flame retardants (OPFRs) as well as aromatic
brominated compounds such as Firemaster 550 (FM550). Recent studies
have shown that the OPFRs and Firemaster 550 components are frequently
detected in polyurethane foams and in indoor dust. Some OPFRs are
considered carcinogenic and/or neurodevelopmental toxicants, and children’s
exposure to these compounds is a concern. OPFRs are readily metabolized
and excreted in the urine as their dialkyl and diaryl compounds which
function as biomarkers for OPFR exposure. Limited research has shown
that adults are broadly exposed to OPFRs, but nothing is known about
children’s exposure. Similarly, 2-ethylhexyl-2,3,4,5-tetrabromobenzoate
(EH-TBB), a FM550 component, is metabolized to tetrabromobenzoic acid
(TBBA). The current study measured levels of bisÂ(1,3-dichloro-2-propyl)
phosphate (BDCIPP), bisÂ(1-chloro-2-propyl) phosphate (BCIPP), diphenyl
phosphate (DPHP), 2 alkylated DPHPs, and TBBA in urine collected in
2013 from 21 US mother-toddler pairs. BDCIPP, DPHP, and ip-DPHP were
detected in 100%, 98%, and 96% of all individuals, whereas BCIPP and <i>tert</i>-butyl-DPHP (tb-DPHP) were only detected in 8% and 13%.
Further, TBBA was detected in 27% of adults but 70% of children. Overall,
children had higher urinary levels of BDCIPP, DPHP, ip-DPHP, and TBBA
as compared to their mothers, suggesting higher exposure. For example,
on average, BDCIPP levels in children were 4.9 times those of mothers.
BDCIPP and DPHP levels in mother’s urine were also significantly
correlated with levels in children’s urine, suggesting similar
exposure routes, likely in the home environment. Various potential
predictors of OPFR exposure were assessed using a questionnaire. In
children some predictors of hand-mouth exposure were associated with
elevated BDCIPP and DPHP levels (e.g., less frequent hand washing
for BDCIPP). Overall, these trends are consistent with higher flame
retardant levels in children as a result of increased hand-mouth behavior
and elevated dust exposure
Brominated Flame Retardants in Placental Tissues: Associations with Infant Sex and Thyroid Hormone Endpoints
Background: Brominated flame retardants (BFRs) are endocrine disruptors that bioaccumulate in the placenta, but it remains unclear if they disrupt tissue thyroid hormone (TH) metabolism. Our primary goal was to investigate associations between placental BFRs, TH levels, Type 3 deiodinase (DIO3) activity and TH sulfotransferase (SULT) activities. Methods: Placenta samples collected from 95 women who delivered term (>37 weeks) infants in Durham, NC, USA (enrolled 2010–2011) were analyzed for polybrominated diphenyl ethers (PBDEs), 2,4,6-tribromophenol (2,4,6-TBP), THs (T4, T3 and rT3), and DIO3 and TH SULT activities. Results: PBDEs and 2,4,6-TBP were detected in all placenta samples. PBDEs were higher in placental tissues from male infants compared to female infants, with 2,4,6-TBP and BDE-209 levels approximately twice as high. Among male infants, placental BDE-99 and BDE-209 were negatively associated with rT3 placental levels. For female infants, placental BDE-99 and 2,4,6-TBP were positively associated with T3 concentrations. DIO3 activity was also significantly higher in placental tissues from male infants compared to females, while 3,3’-T2 SULT activity was significantly higher in placental tissues from females compared to males. Among males, several PBDE congeners were positively correlated with T3 SULT, while BDE-99 was negatively associated with T3 SULT among females. Associations generally remained after adjustment for potential confounding by maternal age and gestational age at delivery. Conclusions: These results suggest BFRs accumulate in the placenta and potentially alter TH function in a sex-specific manner, a possible mechanism to explain the sex-dependent impacts of environmental exposure on children’s growth and development. More research is needed to elucidate the effects of BFRs on placenta function during pregnancy, as well as the biological consequences of exposure and thyroid disruption
Brominated Flame Retardants in Placental Tissues: Associations with Infant Sex and Thyroid Hormone Endpoints
Background: Brominated flame retardants (BFRs) are endocrine disruptors that bioaccumulate in the placenta, but it remains unclear if they disrupt tissue thyroid hormone (TH) metabolism. Our primary goal was to investigate associations between placental BFRs, TH levels, Type 3 deiodinase (DIO3) activity and TH sulfotransferase (SULT) activities. Methods: Placenta samples collected from 95 women who delivered term (>37 weeks) infants in Durham, NC, USA (enrolled 2010–2011) were analyzed for polybrominated diphenyl ethers (PBDEs), 2,4,6-tribromophenol (2,4,6-TBP), THs (T4, T3 and rT3), and DIO3 and TH SULT activities. Results: PBDEs and 2,4,6-TBP were detected in all placenta samples. PBDEs were higher in placental tissues from male infants compared to female infants, with 2,4,6-TBP and BDE-209 levels approximately twice as high. Among male infants, placental BDE-99 and BDE-209 were negatively associated with rT3 placental levels. For female infants, placental BDE-99 and 2,4,6-TBP were positively associated with T3 concentrations. DIO3 activity was also significantly higher in placental tissues from male infants compared to females, while 3,3’-T2 SULT activity was significantly higher in placental tissues from females compared to males. Among males, several PBDE congeners were positively correlated with T3 SULT, while BDE-99 was negatively associated with T3 SULT among females. Associations generally remained after adjustment for potential confounding by maternal age and gestational age at delivery. Conclusions: These results suggest BFRs accumulate in the placenta and potentially alter TH function in a sex-specific manner, a possible mechanism to explain the sex-dependent impacts of environmental exposure on children’s growth and development. More research is needed to elucidate the effects of BFRs on placenta function during pregnancy, as well as the biological consequences of exposure and thyroid disruption
Temporal Trends in Exposure to Organophosphate Flame Retardants in the United States
During the past decade,
use of organophosphate compounds as flame
retardants and plasticizers has increased. Numerous studies investigating
biomarkers (i.e., urinary metabolites) demonstrate ubiquitous human
exposure and suggest that human exposure may be increasing. To formally
assess temporal trends, we combined data from 14 U.S. epidemiologic
studies for which our laboratory group previously assessed exposure
to two commonly used organophosphate compounds, trisÂ(1,3-dichloro-2-propyl)
phosphate (TDCIPP) and triphenyl phosphate (TPHP). Using individual-level
data and samples collected between 2002 and 2015, we assessed temporal
and seasonal trends in urinary bisÂ(1,3-dichloro-2-propyl) phosphate
(BDCIPP) and diphenyl phosphate (DPHP), the metabolites of TDCIPP
and TPHP, respectively. Data suggest that BDCIPP concentrations have
increased dramatically since 2002. Samples collected in 2014 and 2015
had BDCIPP concentrations that were more than 15 times higher than
those collected in 2002 and 2003 (10<sup>β</sup> = 16.5; 95%
confidence interval from 9.64 to 28.3). Our results also demonstrate
significant increases in DPHP levels; however, increases were much
smaller than for BDCIPP. Additionally, results suggest that exposure
varies seasonally, with significantly higher levels of exposure in
summer for both TDCIPP and TPHP. Given these increases, more research
is needed to determine whether the levels of exposure experienced
by the general population are related to adverse health outcomes