DESCRIPTION

The Problem With PCBs

Polychlorinated Biphenyls (PCBs) are long lasting toxic pollutants spread through the environment. These PCBs harm human health, cause ecological damage and prevent economic and recreational use of the surrounding environment. They do so even when dispersed at low concentrations through bioaccumulation: low levels in the environment lead to the buildup of dangerous concentrations in fish and other animals higher up the food chain. In humans, PCBs are suspected carcinogens and can have harmful effects to the endocrine, cardiovascular, and neurological systems [1Agency for Toxic Substances and Disease Registry. (2023). Polychlorinated Biphenyl Toxicity. Center for Disease Control. https://www.atsdr.cdc.gov/csem/polychlorinated-biphenyls/adverse_health.html]

The current methods of PCB disposal involve removal of the source, followed by either incineration or containment [2Environmental Protection Agency. (2023). Policy and Guidance for Polychlorinated Biphenyls. https://www.epa.gov/pcbs/managing-remediation-waste-polychlorinated-biphenyls-pcbs-cleanups]. Incineration is usually applied to PCB containing manufactured materials and highly contaminated soils and is not environmentally friendly, while containment only leaves the toxins as a "problem for later" and does not degrade them [2Environmental Protection Agency. (2023). Policy and Guidance for Polychlorinated Biphenyls. https://www.epa.gov/pcbs/managing-remediation-waste-polychlorinated-biphenyls-pcbs-cleanups , 3Helena I. Gomes, H. I. Gomes, Celia Dias-Ferreira, C. Dias-Ferreira, & Alexandra B. Ribeiro, A. B. Ribeiro. (2013). Overview of in situ and ex situ remediation technologies for PCB-contaminated soils and sediments and obstacles for full-scale application. Science of the total environment, 445-446, 237-260. doi: 10.1016/j.scitotenv.2012.11.098 ]. Incineration is not easily applied to environments with widely-dispersed PCBs at lower concentrations, which is the case for most sites today. Therefore, methods involving bioremediation - harnessing living organisms as a factory for capturing and degrading toxins - are a promising potential way to address this problem at lower costs and on larger scales.

Our solution: Byephenyl

Our project aims to provide a method to address low level concentrations in a cost effective manner. We plan to do this by eventually transforming cyanobacteria to generate chlorine-targeting dehalogenases and biphenyl reductases. Biofilms can be an effective collector of PCBs in water solutions, by enabling them to also destroy the pollutant we can provide a system which can clean a constant flow of water. However, the first task, which we focus on in this project, is developing the dehalogenase protein that has a higher activity for the polychlorinated biphenyls. We plan to use protein modeling software to design mutations in an existing dehalogenase sequence, and test its activity experimentally.

What prompted us to consider this was looking at a different problem in our state. Nitrogen and phosphate pollution from wastewater treatment can generate harmful algal blooms, which are removed via biofilm systems. Installation of this technology at a Chesapeake Bay wastewater treatment plant to remove nutrient pollution was also found to capture 97% of the PCBs moving through that treatment plant [4Williams, M. (2020, May 4). Wastewater treatment plants use technology to tackle a lingering chemical. Chesapeake Bay Program. https://www.chesapeakebay.net/news/blog/wastewater-treatment-plants-use-technology-to-tackle-a-lingering-chemical ]. Biofilm's PCB capturing potential is well demonstrated, to the point that they are used as a method to measure PCB levels in the environment via accumulation [5Wong, S. and B. Era-Miller. (2019). Quality Assurance Project Plan: Measuring PCBs in Biofilm, Sediment, and Invertebrates in the Spokane River: Screening Study. Publication No. 19-03-103. Washington State Department of Ecology, Olympia. https://fortress.wa.gov/ecy/publications/SummaryPages/1903103.html ].

We decided to focus on the problem given its significance to our home state of Washington. Washington State Department of Ecologies identifies 519 sites in our state that are contaminated with PCBs and are either waiting for treatment or currently being cleaned up.

Our state has multiple Superfund sites (areas of extreme pollution) due to PCB release. There are 6 Superfund Sites in and around Seattle, 5 of which are contaminated with toxic levels of PCBs [6Environmental Protection Agency. (2023). Search for superfund sites where you live. Department of Interior. https://www.epa.gov/superfund/search-superfund-sites-where-you-live ]. These sites leach pollution into our waters contaminating the aquatic and marine environments.

The Bigger Picture

PCBs are the cause of a majority of our freshwater fish consumption advisories, and the reason for nearly all of the marine consumption which prevents communities from taking use of our state's natural resources [7Washington State Department of Health. Fish Consumption Advisories in Washington State. https://doh.wa.gov/data-and-statistical-reports/washington-tracking-network-wtn/fish-advisories/fish-consumption-advisories-washington-state ]. This is particularly harmful to tribal nation members who consume fish at a higher rate than other residents and so are more at risk from the toxic effects of PCB bioaccumulation [8Miller, M. and Schick, T. (2022, Nov 22). The US promised tribes they would always have fish, but the fish they have pose toxic risks. Oregon Public Broadcasting and Propublica. https://www.propublica.org/article/how-the-us-broke-promise-to-protect-fish-for-tribes ].

The PCB problem is ongoing, these chemicals despite being banned are still being generated and harm is still being caused and will continue to be. PCB metabolizing biofilms have the potential to be a cost effective cleanup solution for Washington State and around the world.

Citations

  1. Agency for Toxic Substances and Disease Registry. (2023). Polychlorinated Biphenyl Toxicity. Center for Disease Control. https://www.atsdr.cdc.gov/csem/polychlorinated-biphenyls/adverse_health.html
  2. Environmental Protection Agency. (2023). Policy and Guidance for Polychlorinated Biphenyls. https://www.epa.gov/pcbs/managing-remediation-waste-polychlorinated-biphenyls-pcbs-cleanups
  3. Helena I. Gomes, H. I. Gomes, Celia Dias-Ferreira, C. Dias-Ferreira, & Alexandra B. Ribeiro, A. B. Ribeiro. (2013). Overview of in situ and ex situ remediation technologies for PCB-contaminated soils and sediments and obstacles for full-scale application. Science of the total environment, 445-446, 237-260. doi: 10.1016/j.scitotenv.2012.11.098
  4. Williams, M. (2020, May 4). Wastewater treatment plants use technology to tackle a lingering chemical. Chesapeake Bay Program. https://www.chesapeakebay.net/news/blog/wastewater-treatment-plants-use-technology-to-tackle-a-lingering-chemical
  5. Wong, S. and B. Era-Miller. (2019). Quality Assurance Project Plan: Measuring PCBs in Biofilm, Sediment, and Invertebrates in the Spokane River: Screening Study. Publication No. 19-03-103. Washington State Department of Ecology, Olympia. https://fortress.wa.gov/ecy/publications/SummaryPages/1903103.html
  6. Environmental Protection Agency. (2023). Search for superfund sites where you live. Department of Interior. https://www.epa.gov/superfund/search-superfund-sites-where-you-live
  7. Washington State Department of Health. Fish Consumption Advisories in Washington State. https://doh.wa.gov/data-and-statistical-reports/washington-tracking-network-wtn/fish-advisories/fish-consumption-advisories-washington-state
  8. Miller, M. and Schick, T. (2022, Nov 22). The US promised tribes they would always have fish, but the fish they have pose toxic risks. Oregon Public Broadcasting and Propublica. https://www.propublica.org/article/how-the-us-broke-promise-to-protect-fish-for-tribes