Remediating Soil Lead with Fish Bones
Kris S. Freeman
Kris S. Freeman has written for Encarta encyclopedia, NIH, ABCNews.com, and the National Park Service. Her research on the credibility of online health information appeared in the June 2009 IEEE Transactions on Professional Communication.
Environ Health Perspect 120:a20-a21 (2012). http://dx.doi.org/10.1289/ehp.120-a20a [online 01 January 2012]
Fish bones are made of the phosphate mineral apatite, which readily combines with lead to form pyromorphite, a stable crystalline mineral that can’t be absorbed by the human digestive system.1,2 Now researchers are using fish bones and other phosphate-rich amendments to remediate lead in urban soils. “We have seen reduction in bioaccessibility in some lab samples up to fifty percent within just a few weeks of treatment,” says Steve Calanog of the U.S. Environmental Protection Agency (EPA), who is overseeing an agency project using fish bones to clean up soils in the South Prescott neighborhood of Oakland, California.3
In situ and laboratory tests have shown that phosphates can also immobilize other potentially toxic metals, including copper, zinc, cadmium, and uranium.1,4,5,6,7,8 In one of these studies, lead concentrations in soil leachate treated with fish bones dropped from 0.28 mg/L to 0.00065 mg/L within weeks.6,7 Unlike phosphate fertilizers, the apatite in fish bones does not run off the soil.2 Fish bones also are being used as a phosphate source for lead remediation projects in other urban areas, including a pilot project in New Orleans, Louisiana, funded by the U.S. Department of Housing and Urban Development.9
Excessive blood lead can cause delays in neurological and physical development in children, and high blood pressure, kidney problems, and cancer in adults. Lead added to house paints and fuels decades ago still lingers in urban neighborhoods across the country, and children can be exposed through the soil in yards and playgrounds. Total lead levels in soils tested in the Oakland/San Francisco Bay area average 300–600 ppm, according to Calanog. The U.S. EPA considers lead in bare soil in play areas to be a hazard at a concentration of 400 ppm,10 and the California Office of Environmental Health Hazard Assessment has estimated that exposure to a soil lead concentration of 80 ppm will produce an increase in blood lead of up to 1 μg/dL.11 In South Prescott, which is adjacent to the AMCO Chemical Superfund site, total soil lead levels average 843 ppm, with some spots reaching 2,500 ppm.3
The 2-year, $4-million South Prescott project is part of a growing trend to treat soils contaminated with lead and other heavy metals in place, rather than removing and replacing soils or capping them with asphalt or concrete, techniques that require dump sites to store contaminated soils as well as sources of uncontaminated soils for replacement. “Lead contamination is a pervasive problem, and our traditional ways of responding are neither economically nor ecologically sustainable,” Calanog says.
Phosphate immobilization is not recommended for sites with lead levels above 4,000 ppm, such as those heavily contaminated with lead paint, according to Rufus Chaney, a research agronomist with the U.S. Department of Agriculture Environmental Management and Byproduct Utilization Laboratory. Chaney has worked on soil remediation projects in South Prescott, Baltimore, and other urban neighborhoods, and on the development of less expensive tests for measuring levels of bioaccessible lead.12
In South Prescott, workers till 3 pounds of fish bones into each square foot of property treated, then cover the freshly tilled soil with 3–6 inches of clean soil and plants.3 Many project workers are hired locally through the Cypress Mandela Training Center, a pre-apprenticeship program in West Oakland. Workers receive health and safety and lead-abatement training, and they wear personal protective equipment, including respirators, Calanog says.
The fish bones used in South Prescott come from commercial processing of pollock into fillets, fish sticks, and artificial crab meat. Catfish farms are another possible source of fish bones for remediation, according to Judith Wright, the geologist whose studies of fossilized fish bones13 inspired her invention (U.S. Patent #6217775) of the process of using fish bones to remediate heavy metals. Wright, owner of PIMS NW, Inc., supplies the cleaned fish bones for projects such as that at South Prescott. Bones from weight-bearing animals, such as cattle, contain the same chemical form of apatite as do fish bones but in a more highly crystallized form that combines less readily with metals, Wright says.
“Many amendments other than fish bones can also be used for phosphate immobilization,” Chaney says. Indeed, the EPA, U.S. Army Corps of Engineers, U.S. Department of Defense, and other agencies have tested numerous synthetic, mined, and organic sources of phosphates for remediation, including mineral apatite, rock phosphate, soluble phosphate fertilizers, and biosolids compost from treated sewage.1,4,5,6,7,8 Calanog says many of these possible amendments are fairly accessible in terms of cost, but the beauty of the fish bones, according to Wright, is that they’re free of contaminants. Using fish bones also avoids ecological issues involved with mining phosphates, and the bones will not dissolve but “will remain in place to stabilize metals for millennia,” she says.2
Chaney favors the use of organic amendments such as composts that are high in iron, as well as phosphates. Whereas phosphates transform lead into other compounds, iron compounds physically bind with lead through adsorption, a process in which one compound adheres to the surface of another. When lead molecules adsorb to iron-based compounds such as ferrihydrite, he says, they are no longer soluble and can’t be absorbed through the lining of the small intestine. Without realizing it, many urban gardeners are already remediating their soils by adding fertilizers and composts that contain phosphates and iron. “Only about five to ten percent of lead in urban gardens is bioavailable, compared to fifty to sixty percent in urban soils elsewhere,”12 Chaney says.
- Miretzky P, Fernandez-Cirelli A.. Phosphates for Pb immobilization in soils: a review. Environ Chem Lett 6(3):121–133. 2008. http://dx.doi.org/10.1007/s10311-007-0133-y.
- Wright J, et al. PIMS Using Apatite II™: How It Works To Remediate Soil and Water. In: Sustainable Range Management-2004, Hinchee RE, Alleman B, eds. Columbus, OH:Battelle Press (2004). In: Proceedings of the Conference on Sustainable Range Management, 5–8 Jan 2004, New Orleans, LA. Available: http://www.pimsnw.com/files/1howapatiteiiworks30.pdf [accessed 12 Dec 2011].
- EPAWest Oakland Lead Cleanup. San Francisco, CA:U.S. Environmental Protection Agency, Region 9 (Jul 2011). Available: http://www.epaosc.org/sites/5604/files/West%20Oakland%207_11%20Book.pdf [accessed 12 Dec 2011].
- Allen HL IV, et alThe Use of Soil Amendments for Remediation, Revitalization, and Reuse. Washington, DC:Office of Superfund Remediation and Technology Innovation, U.S. Environmental Protection Agency (Sep 2007). Available: http://www.clu-in.org/conf/tio/ecoresources3_120507/resources/OSWER-Soil-Amendments-FINAL%5B10-4-07%5D.pdf [accessed 12 Dec 2011].
- Brown S, et al. Effect of biosolids processing on lead bioavailability in an urban soil. J Environ Qual 32(1):100–108. 2003. http://dx.doi.org/10.2134/jeq2003.1000.
- Conca J, Wright J. PIMS: a simple technology for clean-up of heavy metals and radionuclides throughout the world. In: Baca TE, Florkowski T, eds. The Environmental Challenges of Nuclear Disarmament. New York, NY:Springer-Verlag (1999).
- Wright J, et al.Arlington, VA:Environmental Security Technology Certification Program, U.S. Department of Defense (Jun 2006):ESTCP Cost and Performance Report. PIMS™: Remediation of Soil and Groundwater Contaminated with Metals Available: http://www.pimsnw.com/files/Cost&PerformanceReport2005.pdf [accessed 12 Dec 2011].
- Tardy BA, et al.Washington, DC:Environmental Quality and Technology Program, U.S. Army Corps of Engineers (Sep 2003):Chemical Stabilization of Lead in Small Arms Firing Range Soils Available: http://el.erdc.usace.army.mil/elpubs/pdf/trel03-20.pdf [accessed 12 Dec 2011].
- HUDWashington, DC:U.S. Department of Housing and Urban Development (1 Mar 2011):HUD Awards Nearly $8 Million for Asthma Intervention and to Protect Thousands of Children from Health Hazards in Their Homes [press release] Available: http://portal.hud.gov/hudportal/HUD?src=/press/press_releases_media_advisories/2011/HUDNo.11-025 [accessed 12 Dec 2011].
- EPA Residential Lead Hazard Standards—TSCA Section 403 [website]. Washington, DC:U.S. Environmental Protection Agency (updated 8 Nov 2010). Available: http://epa.gov/lead/pubs/leadhaz.htm [accessed 12 Dec 2011].
- OEHHA Revised California Human Health Screening Levels for Lead. Sacramento, CA:Integrated Risk Assessment Branch, Office of Environmental Health Hazard Assessment, California Environmental Protection Agency (Sep 2009). Available: http://oehha.ca.gov/risk/pdf/LeadCHHSL091709.pdf [accessed 12 Dec 2011].
- Zia MH, et al.Environ Pollut. In vitro and in vivo approaches for the measurement of oral bioavailability of lead (Pb) in contaminated soils: a review. Environ Pollut 159(10):2320–2327; http://dx.doi.org/10.1016/j. envpol.2011.04.043.
- The Wright J, et al. 1987. Geochim Cosmochim Acta. Paleoredox variations in ancient oceans recorded by rare earth elements in fossil apatite. Geochim Cosmochim Acta 51(3):631–644 (1987); http://dx.doi.org/10.1016/0016- 7037(87)90075-5.
This month EHP’s Children’s Health section highlights recent laboratory research about health effects of early-life exposures. By showing causative linkage between specific exposures and various health outcomes in animal models, toxicologists help to confirm associations found in observational human studies. Together, toxicologists and epidemiologists build the scientific evidence base used by risk assessors and regulators to protect children’s health.
Learn more about rigor and transparency in scientific publishing at the 2017 SOT Annual Meeting and ToxExpo, as EHP Editor-in-Chief Sally Perreault Darney chairs and speaks at an Informational Session titled “Addressing Rigor and Transparency in Research and Journal Publication.” At the session, scheduled for Wednesday, March 15, at 5:00 PM in Room CC 314, Sally will talk about interdisciplinary challenges for rigor and reproducibility in environmental health research. More details are available in the SOT 2017 Conference Program.