26 Jan 2018
Study of Environmental Impact of Nanosilver in Consumer Products
On 20 December 2017, the European Commission reported on a study about the environmental impact of silver nanoparticles released from 15 commonly used consumer products. Hong Kong manufacturers may be increasingly using nanoparticles in their products (particularly textiles and toys), which may make the results of the study relevant and useful.
Nanosilver particles are used, e.g., in wound dressings to prevent infection, or in textiles for keeping clothes fresh due to their antibacterial and antifungal properties. They can be applied for coating surfaces of electronics, textiles, metals, woods, ceramics, glass, papers, or mixed into plastic resins.
The reasoning behind this study is the general suspicion that the use of nanoparticles could be toxic to humans and the environment. Unlike previous studies dealing with the release of nanoparticles under various conditions, this new study focuses on both environmental and life-cycle impacts in order to assess the overall impact of the products that contain them.
Fifteen products were chosen based on their commercial availability. Six of them were purchased and nine were modelled based on previous literature. The purchased products were: four types of wound dressing, one plastic food container and one sock containing silver nanoparticles (sock no. 1). The modelled products were: one fleece baby blanket, one plastic children’s cup, one cuddly toy, one medical mask, one medical cloth, one towel, one T-shirt, one resealable plastic food storage bag and another sock (sock no. 2) of a different composition.
The researchers examined environmental impacts from the silver extraction and refining process itself, the impacts of manufacturing and the impacts of nanomaterial release.
The impact of silver mining on the environment materialises in emissions (smog and release of arsenic ions into the groundwater) and the heating needed for processing contributes to global warming and fossil-fuel depletion. The manufacturing processes were analysed with regard to their electricity consumption and chemical use.
Releases into the water would be subject to waste-water treatment, which filters out more than 90% of silver, the researchers found. However, the ecotoxicity impacts of previous steps in the life cycle had to be taken into consideration.
In general, the researchers concluded that the contribution of nanosilver to the products’ overall environmental impact may be marginal in the context of the products’ other components. Therefore, the degree of concentration of nanosilver in a product was a decisive aspect for determining the overall impact of the product.
While those products with nanosilver concentrations below 0.005% showed minimal to negligible impacts associated with nanosilver, for those products with concentrations of 0.005% to 3%, the contribution of nanosilver was highly dependent on the composition of the products. However, concerning products with concentrations above 10%, nanosilver impacts dominated all environmental categories.
The researchers also compared the particles released relative to the initial nanosilver concentration for each product. Releases from one of the wound dressings of up to 5% of the overall nanosilver content were the highest (by percentage) due to the solubility of the product when in contact with solutions.
Releases from textiles depended highly on their production method and on the way the nanosilver was incorporated, with higher releases where particles were surface-bound.
Releases from food packaging amounted to up to 2% of overall content, although by mass the food container released most nanomaterials at 7.92 mg. The study deduced that solid polymer materials release more silver during washing than fibrous materials.
The study concluded that the potential environmental benefits of nanosilver use should be taken into account. Advantages of nano-enabled products are usually not achievable with conventional products, which makes a direct comparison difficult.
The study highlights that prospective assessments of new technologies should be carried out prior to their commercialisation in products in order to examine their environmental impact and guide their development.