The large number and diversity of organohalogen compounds
(OHCs)
occurring in the environment poses a grand challenge to analytical
chemists. Since no single targeted method can identify and quantify
all OHCs, the size of the OHC “iceberg” may be underestimated.
We sought to address this problem in municipal wastewater treatment
plant (WWTP) sludge by quantifying the unidentified fraction of the
OHC iceberg using targeted analyses of major OHCs together with measurements
of total and extractable (organo)halogen (TX and EOX, respectively;
where X = F, Cl, or Br). In addition to extensive method validation
via spike/recovery and combustion efficiency experiments, TX and/or
EOX were determined in reference materials (BCR-461 and NIST SRMs
2585 and 2781) for the first time. Application of the method to WWTP
sludge revealed that chlorinated paraffins (CPs) accounted for most
(∼92%) of the EOCl, while brominated flame retardants and per-
and polyfluoroalkyl substances (PFAS) accounted for only 54% of the
EOBr and 2% of the EOF, respectively. Moreover, unidentified EOF in
nonpolar CP extracts points to the existence of organofluorine(s)
with physical–chemical properties unlike those of target PFAS.
This study represents the first multihalogen mass balance in WWTP
sludge and offers a novel approach to prioritization of sample extracts
for follow-up investigation.