9:15 AM - 9:30 AM
[MZZ51-02] “Hidden organohalogen” in mammals: Analysis of extractable organohalogens and contributions of identified/unidentified compounds
Keywords:Halogen, Persistent organic pollutants, Mammals, NAA, Unidentified organohalogen
Several organohalogen compounds are known as persistent organic pollutants (POPs) and regulated due to their persistence, bioaccumulation, and toxicity. Many unidentified organohalogen (organochlorine and organobromine) compounds are found in animals. The determination of organically bound chlorine (Cl) and bromine (Br) along with the individual analysis of organohalogen compounds enables us to estimate the proportions of Cl and Br mass in the identified compounds. Low-molecular-weight compounds (< 1,000 g/mol) can include unidentified compounds with POP-like properties. In this study, we extracted the samples using organic solvents and fractionated the extracts into low- and high-molecular-weight fractions. We determined the concentrations of extractable organochlorine (EOCl) and extractable organobromine (EOBr) in each fraction by neutron activation analysis (NAA). The identified Cl and Br were calculated from the reported or measured concentrations of identified organohalogen compounds and the mass balance of identified/unidentified Cl and Br in the low-molecular-weight fractions were investigated [Mukai et al. (2021) Sci. Tot. Environ. 756, 143843].
Liver samples were collected from cats (n = 3, males), raccoon dogs (n = 3, males), and striped dolphins (n = 3, males). Freeze-dried sample was subsequently extracted with 10 mL of acetone, 10 mL of acetone/hexane (1:1, v/v), and 10 mL of hexane using a focused ultrasonic processor. Aliquot of crude extract was washed to remove the inorganic Cl and Br by partitioning the crude extracts between 5% Na2SO4 solution and a mixture of methyl tert-butyl ether and hexane (1:1, v/v). The organic phase was subjected to fractionation by gel permeation chromatography (GPC). The first 120 mL of the eluate was considered the high-molecular-weight fraction and the second 120 mL was considered the low-molecular-weight fraction. The Cl and Br concentrations were determined by NAA. Fractionated extract was placed in a polyethylene bag with a paper filter and dried at normal temperature and pressure. Cl and Br in identified compounds (identified Cl and Br) were calculated from the reported or measured concentrations.
EOX-H and EOX-L were defined by EOX (X = Cl or Br) in the high- and low-molecular-weight fractions, respectively. According to the lipid weight-based concentrations of EOX-L and EOX-H, the EOCl concentrations exceeded the EOBr concentrations in all fractions for all species. Although the EOCl-L concentrations did not differ among the species, the EOBr-L and EOBr-H concentrations differed markedly among the species. Especially, striped dolphins had significantly higher EOBr-L levels. The ratio of EOCl-L to EOCl-H was similar in the three species, while the ratios of EOBr-L to EOBr-H differed markedly: 0.092 (cats), 0.34 (raccoon dogs), and 1.3 (striped dolphins). The mean proportion of Cl contributed to EOCl-L by identified compounds (PCBs and chlorinated pesticides) was greatest in the striped dolphins (80%) followed by the raccoon dogs (16%) and cats (1.5%). The proportion of Br that PBDEs contributed to EOBr-L was >50% in two cats, while it was <6% in other specimens. This suggests that PBDEs are a dominant source of EOBr-L in two cats, which are exposed to PBDEs used as flame retardants.
Unidentified organochlorine that is associated with low-molecular-weight compounds is abundant in the cat and raccoon dog, suggesting the abundance of unidentified organochlorine compounds from terrestrial environment. Unidentified organobromine is abundant in the striped dolphin, suggesting the abundance of unidentified organobromine compounds from marine environment. We investigated the mass balance of identified and unidentified X in EOX-L. This showed that EOX levels and compositions were different among species and between halogens. The application of EOX analysis with individual analysis should help to clarify the presence of “hidden organohalogen” (unidentified EOX) in the environment.
Liver samples were collected from cats (n = 3, males), raccoon dogs (n = 3, males), and striped dolphins (n = 3, males). Freeze-dried sample was subsequently extracted with 10 mL of acetone, 10 mL of acetone/hexane (1:1, v/v), and 10 mL of hexane using a focused ultrasonic processor. Aliquot of crude extract was washed to remove the inorganic Cl and Br by partitioning the crude extracts between 5% Na2SO4 solution and a mixture of methyl tert-butyl ether and hexane (1:1, v/v). The organic phase was subjected to fractionation by gel permeation chromatography (GPC). The first 120 mL of the eluate was considered the high-molecular-weight fraction and the second 120 mL was considered the low-molecular-weight fraction. The Cl and Br concentrations were determined by NAA. Fractionated extract was placed in a polyethylene bag with a paper filter and dried at normal temperature and pressure. Cl and Br in identified compounds (identified Cl and Br) were calculated from the reported or measured concentrations.
EOX-H and EOX-L were defined by EOX (X = Cl or Br) in the high- and low-molecular-weight fractions, respectively. According to the lipid weight-based concentrations of EOX-L and EOX-H, the EOCl concentrations exceeded the EOBr concentrations in all fractions for all species. Although the EOCl-L concentrations did not differ among the species, the EOBr-L and EOBr-H concentrations differed markedly among the species. Especially, striped dolphins had significantly higher EOBr-L levels. The ratio of EOCl-L to EOCl-H was similar in the three species, while the ratios of EOBr-L to EOBr-H differed markedly: 0.092 (cats), 0.34 (raccoon dogs), and 1.3 (striped dolphins). The mean proportion of Cl contributed to EOCl-L by identified compounds (PCBs and chlorinated pesticides) was greatest in the striped dolphins (80%) followed by the raccoon dogs (16%) and cats (1.5%). The proportion of Br that PBDEs contributed to EOBr-L was >50% in two cats, while it was <6% in other specimens. This suggests that PBDEs are a dominant source of EOBr-L in two cats, which are exposed to PBDEs used as flame retardants.
Unidentified organochlorine that is associated with low-molecular-weight compounds is abundant in the cat and raccoon dog, suggesting the abundance of unidentified organochlorine compounds from terrestrial environment. Unidentified organobromine is abundant in the striped dolphin, suggesting the abundance of unidentified organobromine compounds from marine environment. We investigated the mass balance of identified and unidentified X in EOX-L. This showed that EOX levels and compositions were different among species and between halogens. The application of EOX analysis with individual analysis should help to clarify the presence of “hidden organohalogen” (unidentified EOX) in the environment.