# Project 4 - Design Principles and Field-Deployable Models for Economical Remediation of Dioxin-Contaminated Sites

> **NIH NIH P42** · MICHIGAN STATE UNIVERSITY · 2022 · $322,331

## Abstract

PROJECT SUMMARY: Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs, also abbreviated as
PCDD/F) are among the most challenging environmental contaminants. Over the past 20 years, anaerobic
microorganisms such as Dehalococcoides mccartyi and enrichments have been shown to use a number of
PCDD/Fs as electron acceptors. Under laboratory conditions, the respiration rates of these organohalide
respiring bacteria (OHRB) yield PCDD/F half-lives of the order of months to a few years. Hence, OHRB, if
stimulated, can play a larger role in attenuating PCDD/Fs in situations where more intrusive solutions such as
dredging and capping are not practicable because of cost or other factors. The ability of D. mccartyi to respire
PCDD/Fs is closely linked to the high numbers of cobalt-containing proteins (mostly reductive dehalogenases -
RdhAs), the genes and proteins associated with the salvaging pathway for cobalamins, and hydrogenases - to
utilize the electron donor (H2). All three are critical subunits of the respiration complex. Cobalamins are corrinoids
(compounds containing four reduced pyrrole rings with cobalt at the center of the ring) with 5,6-
dimethylbenzimidazol (5,6-DMBI) as the lower ligand. A Cbl with cyanide as the upper ligand of cobalt is called
CN-Cbl or vitamin B12 (B12). All PCDD/F respirers known so far are auxotroph for Cbl. They cannot synthesize
Cbl and must salvage it using the Cbl salvage pathway. Yet, Chloroflexi – the phylum all D. mccartyi belong to
has the highest number of cobalt-containing genes (mostly rdhs) among all known bacteria and archaea. The
potential for the presence of OHRB at the two Superfund sites - Tittabawassee and Saginaw Rivers, MI (TR/SR),
and Passaic River, NJ (PR) is high. Our work has already identified a dominant phylotype, PRdAO, at the PR
site. Overall, these OHRB combined with amendments including activated carbon (AC), hydrogen release
compounds (HRC), and B12 have the potential to reduce the overall toxicity equivalency quotient (TEQ) and
health risks associated with PCDD/Fs. Such AC-based approaches are already being implemented for other
organohalides such as polychlorinated biphenyls. Integrative mathematical models play a key role in developing
optimal solutions for PCDD/F remediation. Accordingly, this project has the following four specific aims: i)
Quantify the parameters for integrative remediation of PCDD/Fs in the presence of exogenous B12, HRC, D.
mccartyi, and AC, ii) Identify native OHRB and Rdhs-mediated pathways for dechlorination and detoxification of
PCDD/Fs at the TR/SR/PR Superfund sites, iii) Determine the effect of AC, bioaugmentation, and salinity on
native PCDD/F-dechlorinating OHRB, dechlorination pathways, and rates in microcosms, iv) Develop and
validate site-specific integrative remediation models for PCDD/F involving biotic and abiotic interventions. This
new comprehensive model integrates the collective knowledge into a mathematical tool for predicting reduction
i...

## Key facts

- **NIH application ID:** 10353534
- **Project number:** 2P42ES004911-27A1
- **Recipient organization:** MICHIGAN STATE UNIVERSITY
- **Principal Investigator:** SYED A. HASHSHAM
- **Activity code:** P42 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $322,331
- **Award type:** 2
- **Project period:** 1997-04-01 → 2027-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10353534

## Citation

> US National Institutes of Health, RePORTER application 10353534, Project 4 - Design Principles and Field-Deployable Models for Economical Remediation of Dioxin-Contaminated Sites (2P42ES004911-27A1). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10353534. Licensed CC0.

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