April 17, 2013
Emerging contaminants are pollutants that have been recently discovered in the environment and can have adverse effects on both the ecosystem and humans. Ranging in effect from neurotoxin to endocrine disruptors these contaminants can cause reproductive issues and hormone disorders and some become more dangerous as they bioaccumulate up the food chain. Some, but not all of these emerging contaminants are regulated by the EPA and those which are can sometimes be given too high an allowance, causing states to step in and impose stricter standards.
PBB’s and PDBE’s are forms of brominated fire retardants that are used in a variety of commercial products including furniture, electrical devices, and even children’s pajamas. Being hydrophobic and bonding very well to soil particles these chemicals have a tendency to bioaccumulate in the terrestrial ecosystem. (De Wit 2002) These characteristics also allow the chemicals to become a non-point source by binding to airborne particulates and potentially travelling very far, causing difficulty in locating the source of contamination. (ATSDR 2004) PBB’s and PDBE’s have been identified as possible neurotoxins and are known endocrine disruptors. Despite these risks there are no federal guidelines or cleanup standards for these chemicals. (EPA 2010)
Laboratory research has begun to develop potential treatment methods for PBB and PBDE contaminants in the terrestrial ecosystem however. One such study includes the degradation of polybrominated diphenyl ethers by a sequential treatment with nanoscale zero valent iron (nZVI) and aerobic biodegradation. Reductive debromination and oxidation of 1 mg of deca-BDE with 100 mg/vial of nZVI proved highly effective, resulting in a 67% reduction of deca-BDE over a 20 day period. This method could help pave the way to a remediation strategy for highly halogenated pollutants in contaminated sites. (Kim, Y.-M et. al 2012)
Perchlorate is another contaminant, mainly used in the production of munitions, explosives, and found as a product of Chilean fertilizer imports, which poses a threat to terrestrial ecosystems. Unlike PBB’s perchlorate is highly soluble, which greatly increases its potential to leach into groundwater sources. Found in heavy concentrations at military shooting ranges and development sites this chemical commonly enters the ecosystem through mass burnings or burying of old munitions by the military. (ITRC 2005) Perchlorate has been known to infiltrate food supply via groundwater and show up in traceable concentrations, which can affect the thyroid. (FDA 2008) There is federal regulation by the EPA for perchlorates under the Safe Drinking Water Act, though the effectiveness at 15 micrograms per liter permissible is debatable. In contrast the states of Massachusetts and California have stricter standards on perchlorates with permissible levels in water being 2 and 6 micrograms respectively. (CDPH 2010 & Mass. DEP 2006)
In regards to treatment, there are a handful of methods that have been used to remediate perchlorate. Perchlorate can be completely reduced to chloride by acclimated bacteria via cell respiration in fixed-bed bioreactors, although design factors need further investigation. (Kim & Logan 2000) Other off site laboratory methods include ion exchange with perchlorate-selective resins or liquid phase carbon adsorption using granular activated carbon (GAC). On site cleanups have also been underway. The Massachusetts Military Reservation (MMR), a 22,000-acre property sit over an aquifer that has been contaminated by fuel spills and other past activities at MMR’s Otis Air Force Base. One cleanup effort is a program managed by the army that implements technologies such as the aerial magnetometry that assist with the detection of metal objects on or below ground surface.
More extensive research on emerging contaminants can be found via the hyperlink at the beginning of this blog entry.
By Rian Downs & Ryan Gobar
Agency for Toxic Substances and Disease Registry (ATSDR). 2004. Toxicological Profile for Polybrominated Diphenyl Ethers and Polybrominated Biphenyls. www.atsdr.cdc.gov/toxprofiles/tp68.pdf.
California Department of Public Health (CDPH). 2011. Perchlorate in Drinking Water. www.cdph.ca.gov/certlic/drinkingwater/Pages/Perchlorate.aspx
De Wit, C. A. 2002. An Overview of Brominated Flame Retardants in the Environment. Chemosphere. Volume 46. Pages 583 to 624.
Food and Drug Administration (FDA). 2008. U.S. Food and Drug Administration’s Total Diet Study: Dietary intake of Perchlorate and Iodine.
Interstate Technology Regulatory Council (ITRC). 2005. Perchlorate: Overview of Issues, Status, and Remedial Options. www.itrcweb.org/Documents/PERC-1.pdf
Kijung Kim and Bruce E. Logan. Environmental Engineering Science. SEPTEMBER/OCTOBER 2000, 17(5): 257-265. doi:10.1089/ees.2000.17.257.
Kim, Y.-M., Murugesan, K., Chang, Y.-Y., Kim, E.-J. and Chang, Y.-S. (2012), Degradation of polybrominated diphenyl ethers by a sequential treatment with nanoscale zero valent iron and aerobic biodegradation. J. Chem. Technol. Biotechnol., 87: 216–224. doi: 10.1002/jctb.2699
Massachusetts Department of Environmental Protection (DEP). 2006. Perchlorate Information. www.mass.gov/dep/water/drinking/percinfo.htm#stds
U.S. Environmental Protection Agency (EPA). 2010. DecaBDE Phase-out Initiative. www.epa.gov/oppt/existingchemicals/pubs/actionplans/deccadbe.html