Safety of silver nanoparticles
Safety of silver nanoparticles
Nanomaterial safety
It has been shown scientifically that silver nanoparticles are constantly released from bulk pieces of metallic silver (1). This process happens at a room temperature and the only thing required is humidity. This means that people have been in contact with silver nanoparticles for ages without even realizing it. Everytime one uses a silver spoon or wears silver jewelry it is in contact with AgNPs.
Scientists have undertaken extensive studies on nanosilver. These results were summarised and published in OECD (2) and WHO (3) reports.
In animal based studies, it has been demonstrated that even extremely high doses (2000 mg for kg of bodyweight) have no acute adverse effect on our health when used externally. The same results were obtained, when silver nanoparticles were tested for irritation (on skin and eye) and sensitization on skin.
OECD and WHO reports suggest that silver nanoparticles may be harmful, if they are inhaled or ingested repeatedly. Animal studies suggest that no-observed-adverse-effect level (NOAEL) for repeated exposure is less than 30 mg for kilogram of bodyweight per day. For an average human (70 kg) this would translate to 2.1 g of silver intake. In humans it is known that internal chronic use of silver nanoparticles can cause argyria (skin discoloration). This condition can develop when silver is being used internally. One study suggests that “Argyria becomes clinically apparent after a silver retention approximating an equivalent of 8 g” (4). Therefore we do not recommend inhaling or ingesting excessive amounts of silver nanoparticles.
Two human health surveillance studies showed that working with silver nanoparticles can be safe. If silver nanoparticles are manufactured using wet methods, the workers exposure to silver nanoparticles was 10 to 100 times lower than the current occupational limit for silver.