More research on silver nanoparticles

Last October 18 we wrote about silver nanoparticles that “Silver is an environmental contaminant and the study reinforces that care needs to be taken in any use of silver as a disinfectant to avoid collateral environmental damage.”

A new report from researchers at Duke University and elsewhere indicates that our October report may have been at least a little bit of an understatement.

Silver nanoparticles are metallic silver in the form of extremely small dust particles. A range of nanoparticles are among the new tools being developed by researchers around the world. Nanoparticles often have properties that are different from, and sometimes more intense than, the macro scale materials from which they are derived.

The article from the Duke University team is entitled Low Concentrations of Silver Nanoparticles in Biosolids Cause Adverse Ecosystem Responses under Realistic Field Scenario. The team set out to study the environmental activity of silver nanaoparticles in sewage sludge applied to farm fields. The questions the team sought to answer were:

  1. What is the environmental fate of Ag (silver) under this exposure scenario?
  2. How do realistic additions of AgNPs (silver nanoparticles) affect plant productivity, microbial community composition, and microbially-mediated biogeochemical cycling?
  3. To what extent are the fate and biological impacts of AgNPs distinct in magnitude or direction from those of Ag+ (silver ions)?

The conclusions:

  1. An estimated 60% of the average 5.6 million tons of biosolids produced each year in the United States is land applied. Results show that biosolids amended with AgNPs at environmentally relevant concentrations and added to a diverse terrestrial ecosystem caused ecosystem-level impacts. Specifically, the AgNP treatment led to an increase in N2O fluxes, changes in microbial community composition, biomass, and extracellular enzyme activity, as well as species specific effects on aboveground plant biomass.
  2. While AgNPs may be transformed in biosolids through oxidation and sulphidation, they still had an impact on plants and microbes.
  3. Several species of plants take up Ag from AgNPs in soils, though the extent to which different plant species accumulated Ag varied greatly. Uptake and incorporation of Ag into plant biomass suggests the potential for transfer of Ag up the food chain.

The researchers point out that additional research is needed to better understand how silver nanoparticles interact with the environment and with various species. However, having seen several such research papers and presentations, GallonDaily will be bold enough to suggest that the vultures are gathering around the question of the environmental safety of silver nanoparticles.

The article by Benjamin Colman of the Department of Biology and the Center for the Environmental Implications of Nanotechnology at Duke University, and others, is available at no cost at


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