Transformation of Silver Nanoparticles in Sewage Sludge

From Environmental Protection Online

Carol Potera

Carol Potera, based in Montana, has written for EHP since 1996. She also writes for Microbe, Genetic Engineering News, and the American Journal of Nursing.

Citation: Potera C 2010. Transformation of Silver Nanoparticles in Sewage Sludge. Environ Health Perspect 118:a526-a527. doi:10.1289/ehp.118-a526a
Online: 01 December 2010

The release and environmental fate of nanoparticles throughout the life cycle of “nanoenabled” goods is an area of growing research interest. In the first known field study of the fate of silver nanoparticles in the wastewater treatment system, researchers now report these nanoparticles transform into silver sulfide in the sludge produced by sewage treatment plants.1 This new information about the life cycle of silver nanoparticles provides a starting point for further exploring their impact on the environment.

Silver has been used as an antimicrobial agent for millennia,2 and the increased surface area offered by the nanoparticle form of the metal offers greater germ-killing capacity.3 Today, manufacturers add silver nanoparticles to hundreds of consumer products, including food storage containers, clothing, computer keyboards, cosmetics, pillows, cell phones, and medical appliances.4

Silver is water soluble, so contact with any type of moisture—such as a bath or a spin in the washing machine—washes some out and sends it into wastewater systems. “We wanted to know what form of silver enters the environment after it goes down the drain and passes through sewage treatment plants,” says Michael Hochella, a geochemist at Virginia Polytechnic Institute and State University and director of natural and incidental nanoparticles for the multi-institute Center for the Environmental Implications of NanoTechnology.5

Sludge from sewage treatment facilities can end up as landfill or soil amendments in agricultural fertilizers, or it can be burned in incinerators. In 2006 and 2007 the U.S. Environmental Protection Agency (EPA) analyzed sewage sludge samples from 74 municipal wastewater treatment facilities nationwide and tested for 28 metals, including silver (which was detected in all the samples).6 Through the EPA, Hochella and postdoctoral fellow Bojeong Kim obtained frozen samples of sludge from a Midwest facility. They suspected it would contain the nanosilver particles now used in consumer products—although the EPA’s goal in sampling was simply to obtain national estimates of the concentrations of selected analytes, not identify nanoparticles.


Numbers of Goods Containing Silver Nanoparticles4
Kim developed analytical methods to determine the size, chemistry, and atomic structure of silver nanoparticles in the samples. The samples tested high in silver, but the silver could not be attributed to an industrial source. Scanning transmission electron microscopy revealed the nanoparticles were 5–20 nm in diameter and formed small, loosely packed aggregates no more than 100 nm in size. Energy-dispersive X-ray spectrometry showed that sulfur (which is produced by microorganisms that digest sewage) combined with the silver in a 2:1 ratio, and the crystal structure confirmed the formation of silver sulfide nanoparticles.1

The results underscore the complexity of environmental fate. “What we start with is not what ends up in the environment,” Hochella says. The researchers don’t know how many silver nanoparticles were introduced to the wastewater treatment plants or how much incoming nanosilver ended up as silver sulfide nanoparticles. However, Kim notes that no pure silver nanoparticles were found in the sludge.

In general, silver sulfide is highly insoluble and settles out of water.7 But no one knows if silver sulfide nanoparticles behave in the same way. Properties of metals can change dramatically as particle size decreases.3 “It’s hard to predict whether the solubility of nanoparticles will increase, decrease, or stay the same,” Kim says. The bioavailability, toxicity, and reactivity of silver sulfide nanoparticles also are unknown.

If silver sulfide nanoparticles do prove toxic, the environmental implications could be unfavorable. Antimicrobial nanoparticles could adversely impact desirable microorganisms that decompose waste in sewage treatment plants, says Murray McBride, director of the Cornell Waste Management Institute. Furthermore, McBride says, nanosized silver sulfide applied to agricultural land could oxidize in soils and release toxic silver ions that kill beneficial soil microorganisms. On the other hand, one study of laboratory-grown Pseudomonas putida biofilms indicated some bacteria bind silver ions, potentially rendering them less toxic.8

References and Notes Top
1. Kim B, et al. Environ Sci Technol 44(19):7509–7514. 2010. doi:10.1021/es101565j Find this article online
2. Alexander JW Surg Infect (Larchmt) 10(3):)289–292. 2009. doi:10.1089/sur.2008.9941 Find this article online
3. Chen X, Schluesener HJ Toxicol Lett 176(1):1–12. 2008. doi:10.1016/j.toxlet.2007.10.004 Find this article online
4. The Project on Emerging Nanotechnologies. Nanotechnology Consumer Product Inventory. Washington, DC:The Woodrow Wilson International Center for Scholars (2010). Available: http://tinyurl.com/5sa88q [accessed 3 Nov 2010].
5. Funded by the National Science Foundation and the U.S. Environmental Protection Agency, the Center for the Environmental Implications of NanoTechnology is a consortium of scientists from Duke University, Carnegie Mellon University, Howard University, Virginia Polytechnic Institute and State University, the University of Kentucky, and Stanford University who study the biological, environmental, and ecological consequences of nanomaterials.
6. EPA. Targeted National Sewage Sludge Survey Statistical Analysis Report. EPA-822-R-08-018. Washington, DC:Office of Water, U.S. Environmental Protection Agency (2009). Available: http://tinyurl.com/33mlma4 [accessed 3 Nov 2010].
7. Lytle PE Environ Toxicol Chem 3(1):21–30. 1984. Find this article online

Crystalline silica dust study

Workers who manually grind concrete surfaces need better protection from crystalline silica dust, according to research from the University of Toledo in Ohio and the Center for Construction Research and Training in Silver Spring, MD.

Dust control methods, including general ventilation, local exhaust ventilation and wet grinding, reduced silica dust concentrations. However, no combination of factors or control methods brought the eight-hour exposure level to below the recommended level of 0.025 mg/m³, which study researchers said indicates the need for refined controls or respirators.

The study appeared in the December issue of the Journal of Occupational and Environmental Hygiene.

Press Release – FAA Proposes $140,000 Civil Penalty Against K-Mart

Tue Nov 23, 2010 5:54 am (PST)

Press Release – FAA Proposes $140,000 Civil Penalty Against K-Mart,Inc.

For Immediate Release November 19, 2010 Contact: Kathleen BergenPhone: 404-305-5100WASHINGTON – The Federal Aviation Administration is proposing a$140,000 civil penalty against K-Mart, Inc., of Royal Oak, Mich., forallegedly violating Department of Transportation hazardous materials regulations.The FAA alleges K-Mart offered two packages to UPS for transportation by air from Caguas, Puerto Rico to its returned goods center in McDonough,Ga.

The first shipment, Sept. 21, 2009, contained 15 three-ounce containers of nail color, which is classified as paint, a flammable liquid. The second shipment, Oct. 26, 2009, contained 18 five-ounce containers of aerosol sun block, a flammable gas. Neither shipment was declared to contain hazardous materials.

K-Mart allegedly offered the shipments for transportation by air when they were not packaged, marked, classed, described, labeled or in condition for shipment as required by regulations. UPS employees at the Louisville sort center discovered both packages leaking. K-Mart, Inc., has 30 days from receipt of the FAA's civil penalty letter to respond to the agency.

USFA Releases Thanksgiving Day Fires in Residential Buildings Report

Nov 12, 2010

The Federal Emergency Management Agency's (FEMA) U.S. Fire Administration (USFA) issued a special report recently examining the characteristics of Thanksgiving Day fires in residential buildings. The report, Thanksgiving Day Fires in Residential Buildings, was developed by USFA's National Fire Data Center.

The report is part of the Topical Fire Report Series and is based on 2006 to 2008 data from the National Fire Incident Reporting System (NFIRS). According to the report, an estimated 2,000 Thanksgiving Day fires in residential buildings occur annually in the United States, resulting in an estimated average of five deaths, 25 injuries, and $21 million in property loss.

The leading cause of all Thanksgiving Day fires in residential buildings is, by far, cooking. In addition, these fires occur most frequently in the afternoon hours from noon to 4 p.m. Smaller, confined fires account for 71 percent and larger, nonconfined fires account for 29 percent of Thanksgiving Day fires in residential buildings. Finally, smoke alarms were not present in 20 percent of nonconfined Thanksgiving Day fires that occurred in occupied residential buildings.

The topical reports are designed to explore facets of the U.S. fire problem as depicted through data collected in NFIRS. Each topical report briefly addresses the nature of the specific fire or fire-related topic, highlights important findings from the data, and may suggest other resources to consider for further information. Also included are recent examples of fire incidents that demonstrate some of the issues addressed in the report or that put the report topic in context.


To view the report, click here

From ohsonline.com

"position entails work of considerable difficulty"

If you want brevity in your position descriptions for any of our EHS related classifications, you might consider this recent offering from the city of West Allis.

Thanks to Bob Grieshaber for the submission.

AT&T Building Leaks 1,000 Gallons Of Diesel Fuel

Emergency generators can leak!!

Posted: 7:35 pm PDT October 2, 2010
SAN JOSE, Calif. -- About one thousand gallons of diesel fuel have spilled from a ten-story building and into a storm drain and surrounding concrete in San Jose Saturday evening, a fire captain said.

Firefighters responded to a 5:15 p.m. call that fuel had been leaking out of an AT&T Corp. building at South Almaden Blvd., San Jose fire Captain Barry Stallard said.
On the building's roof, arriving crews discovered an engine -- meant to power the building in the event of an outage -- was inexplicably leaking diesel fuel into the roof's drain and down to the street, Stallard said.

The drain has leaked fuel into the nearby sewage system and onto a surrounding concrete recreational area where people jog.

The engine has a fuel capacity of about 100 gallons, Stallard said, but is connected to tanks in the building parking lot that hold about 50,000 gallons.

The building operates AT&T's 911 hub, which is used to route residents' emergency calls to local dispatchers. It also operates standard phone service.

Service has not been affected by the spill, Stallard said.

Almaden Boulevard is closed between West San Fernando and West Santa Clara streets, Stallard said.

No injuries have been reported.

Crews are continuing to respond to the incident with no estimation of when the oil will stop leaking or when the roads will be reopened.

From http://www.ktvu.com

Washington University to Pay Fine for Hazardous Issues

Posted 27 Sep 2010

Washington University in St. Louis is paying a $15,000 civil penalty over what the federal government calls "hazardous waste management issues."

The school also will spend at least $45,000 on a supplemental project to help clean local high school laboratories of hazardous waste, the U.S. Environmental Protection Agency said.

Washington University’s hazardous waste problems at the school’s Danforth and School of Medicine campuses were uncovered through inspections conducted in April 2008.

Inspections found violations for failure to make hazardous waste determinations and for operating a treatment, storage and disposal facility without a proper permit. There also were "issues related to the storage of hazardous waste beyond legal time limits," failure to properly label hazardous waste storage containers, and failure to manage waste lamps among the problems, the EPA said.

As part of a settlement, the school will spend a minimum of $45,000 on a supplemental environmental project to address hazardous waste issues in 12 high schools within the St. Louis Public Schools District.

The university agreed to conduct ongoing clean-out operations at laboratories at the two campuses, the EPA said.

*For more information on news about waste and recycling go to www.wasterecyclingnews.com

From: http://veoliaes-ts.com/buzz-newsletters/September2010/3