Nanosilver:
Health Effects
Silver nanoparticles are the most common commercialized nano technological
product on the market. Due to its unique antibacterial properties, silver
nanoparticles have been hailed as a breakthrough germ killing agent
and have been incorporated into a number of consumer products such as
clothing, kitchenware, toys and cosmetics. Many consider silver to be
more toxic than other metals when in nanoscale form and that these particles
have a different toxicity mechanism compared to dissolved silver. Scientists
have concluded that nanoparticles can pass easily into cells and affect
cellular function, depending on their shape and size. However, little
has been done to evaluate these interactions and their health impacts
on humans. Preliminary research with laboratory rats has found that
silver nanoparticles can traverse into the brain, and can induce neuronal
degeneration and necrosis (death of cells or tissue) by accumulating
in the brain over a long period of time. Other potential harmful effects
include the generation of dangerous radicals that injure cells by attacking
DNA, proteins and membranes. Due to their size, these particles can
readily penetrate the body and cells through various routes.
Routes of Exposure
Inhalation:
Nanoparticles can become airborne easily due to their size and mass.
When inhaled, nanoparticles can go deeper into the lungs reaching more
sensitive areas. There they inflame the lungs, which must work harder
in attempts to remove the foreign particles. It is still unknown whether
these particles can be removed by the lungs or whether they remain as
deposits within lung tissue. Research is still ongoing to investigate
whether nanosize particles cause pulmonary inflammation as well as systemic
effects, and whether they translocate from the lungs to other organs
such as the liver, kidney or brain.
Skin Absorption:
This route of exposure occurs mainly through cosmetics, sunscreens,
textiles and clothing imbedded with silver nanoparticles. Nano particles
are known to be absorbed by the skin. Broken skin, or skin with cuts
and wounds, may give rise to easier and direct absorption of nanoparticles
into the blood stream and translocation in the body. The fate and effects
of these particles on, and within the skin and human body are not clearly
understood. Other problems still to be investigated include the interference
with resident microflora on the skin.
Ingestion:
This type of exposure can come about through hand to mouth transfer
of particles from products imbedded with nano silver or from food and
food packaging. Ingestion of particles can also arise due to respiratory
clearing actions of inhaled particles. Little to no information is available
for the fate and effects of silver nanoparticles within the digestive
track. However, observations in laboratory animals have documented that
uptake of particles from the digestive track into the lymphatic and
circulatory systems can occur. Uptake also seems to primarily occur
in the intestines and is dependent on size. While the health impacts
are still unknown, the fact that the digestive process utilizes beneficial
bacteria to assist in the digestive process, the presence of silver
nanoparticles may undoubtedly have an adverse impact of these native
bacterial populations.
Nanosilver in Food
Nanotechnologies
have been employed in food production, processing and packaging. The
Project on Emerging Nanotechnologies at the Woodrow Wilson International
Center for Scholars has followed the progress of the use of nanotechnologies
in the food industry. According to their 2008 report entitled “Assuring
the Safety of Nanomaterials in Food Packaging: The regulatory process
and key issues,” nanoparticles raise safety questions different
from those raised by conventional scale version of the same material.
Many food
packaging materials have been incorporating nanoparticles, especially
silver nanoparticles, to prolong the shelf life and safety of packaged
food from microbial agents. Researchers are developing ‘smart
packaging’ that would be able to tell if the packaged food becomes
contaminated, as well as respond to changes in environmental conditions
and self-repair holes and tears. Other nanoparticles have been known
to be included in food to enhance flavor, improve emulsification and
nutrient availability. Nanosized herbicides, fertilizers and other agrichemicals
are also being developed to improve the efficiency of growing crops.
While these advances in technology are promising and exciting, the fate
and impacts of these particles have not been equally studied. There
are major concerns that silver nanoparticles can migrate from packaging
and into foods, exposing consumers to risks that are not yet known.
Many of these products are not labeled to alert the consumer to the
use of nanoparticles in the product and thus taking away the consumer’s
right to choose whether to avoid these products or not. A lack of governmental
oversight and regulation on this new technology further compounds the
problem of a lack of data and safety testing.
