Nanosilver
Nanosilver
Underlying this discussion so far is the assumption that what we're doing actually matters—that the amount of silver, including nanosilver, that's released into the environment and our bodies from consumer and hospital products is significant in relationship to background levels in the environment.
The Silver Nanotechnology Working Group isn't so sure that's the case. Nanosilver production has been estimated at 2.8–20 tons per year in the United States and 250–312 tons worldwide. Volpe says this represents a minor component of overall silver production—estimated by the silver industry to exceed 31,250 tons —and of silver volumes in the environment.
Thus, Volpe says, new applications of nanosilver are not expected to have a significant impact on the level of silver demand over the next 10–15 years, even though many applications may achieve significant commercial success. The NRDC, in contrast, argues that "if nanosilver proves to be much more toxic than conventional silver, the smaller quantities released will not necessarily cause less harm."
Luoma noted in Silver Nanotechnologies and the Environment that silver is rare in the Earth's crust and background concentrations extremely low. "Thus," he wrote, "the addition of only a small mass of silver to a water body from human activities will result in proportionally large deviations from the natural conditions." But he also pointed out that "the environmental chemistry of silver metal influences bioavailability and toxicity in complex ways."
Actual production data for nanosilver are not publicly available. Lowry believes the only way to get an accurate handle on how much nanosilver is entering the environment now and years down the line is to develop a comprehensive inventory of synthesis and production data. "With that kind of process, we can figure out what the loading on our waterways would be," he says. "But without an inventory, it's really hard to understand what our concentrations are. … If you don't know what the loading will be, you don't know what the environmental concentrations will be.
Getting a Handle on the Numbers
Underlying this discussion so far is the assumption that what we're doing actually matters—that the amount of silver, including nanosilver, that's released into the environment and our bodies from consumer and hospital products is significant in relationship to background levels in the environment.
The Silver Nanotechnology Working Group isn't so sure that's the case. Nanosilver production has been estimated at 2.8–20 tons per year in the United States and 250–312 tons worldwide. Volpe says this represents a minor component of overall silver production—estimated by the silver industry to exceed 31,250 tons —and of silver volumes in the environment.
Thus, Volpe says, new applications of nanosilver are not expected to have a significant impact on the level of silver demand over the next 10–15 years, even though many applications may achieve significant commercial success. The NRDC, in contrast, argues that "if nanosilver proves to be much more toxic than conventional silver, the smaller quantities released will not necessarily cause less harm."
Luoma noted in Silver Nanotechnologies and the Environment that silver is rare in the Earth's crust and background concentrations extremely low. "Thus," he wrote, "the addition of only a small mass of silver to a water body from human activities will result in proportionally large deviations from the natural conditions." But he also pointed out that "the environmental chemistry of silver metal influences bioavailability and toxicity in complex ways."
Actual production data for nanosilver are not publicly available. Lowry believes the only way to get an accurate handle on how much nanosilver is entering the environment now and years down the line is to develop a comprehensive inventory of synthesis and production data. "With that kind of process, we can figure out what the loading on our waterways would be," he says. "But without an inventory, it's really hard to understand what our concentrations are. … If you don't know what the loading will be, you don't know what the environmental concentrations will be.
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