Urgent Requirement for Environmental Toxicity Data
A new study by Swiss researchers has attempted to predict nanomaterial concentrations in the environment. However, the researchers say more data on environmental toxicity are needed before we can make accurate assessments of potential environmental risks from nanomaterials.
Studies based on real measurements of nanomaterials in the environment are currently almost non-existent, despite the growing use of nanomaterials in commercial products, such as cosmetics, textiles and paints. Therefore, simulations that predict how nanomaterials may be released into the environment, and in what quantities, can be helpful in estimating risks and providing guidance for legislation on the use and disposal of nanomaterials.
The current study focused on modelling environmental concentrations of five types of nanomaterials used in commercial products in the EU, the US and Switzerland: nano-titanium dioxide, nano-zinc oxide, nanosilver, carbon nanotubes and fullerenes. The types of products studied included plastics, textiles, cosmetics, food supplements, paints and consumer electronics.
Environmental concentrations were predicted using a newly developed model. Product life-cycle was divided into various phases from manufacture to waste disposal or recycling, and environmental concentrations were modelled for water, air, soil sediment and groundwater. Where necessary, the researchers accounted for different product life cycles in different countries. In the EU and US, for instance, sewage sludge is spread on soils as fertiliser, but in Switzerland it is incinerated.
In Europe and the US, sludge treated soils and sediments were predicted to hold the highest concentrations of nanomaterials. In Switzerland, effluent from sewage treatment plants and sediment contained the highest concentrations. Concentrations in air were generally predicted to be low.
According to the study, the most common routes by which nanomaterials are released into the environment depend on the type of product in which the nanomaterial is used. Carbon nanotubes, for example, tend to be transferred from manufacturing to waste incineration plants to landfill sites, whereas nano-zinc oxide tends to end up in soils via the spreading of sewage sludge. Titanium dioxide was predicted to accumulate in the highest concentrations overall; nano-titanium dioxide concentrations in sludge treated soils are predicted to have risen to 0.5 mg per kg by 2012, up from 0.1 mg per kg in 2008.
The environmental risks posed by these concentrations could not be accurately estimated as there is a lack of toxicity data. The researchers say more data are urgently needed, particularly for nano-forms of silver, titanium dioxide and zinc oxide, which may pose a risk to aquatic life.
The results agree well with the limited data that are available from studies providing actual measurements of environmental concentrations. However, the researchers stress the need to eliminate uncertainties in their model by improving current knowledge about the volumes of nanomaterials used in different products and about the specific types of nanomaterials studied. For instance, nanotubes and fullerenes vary in their properties according to their specific forms. They also suggest building regional databases containing region-specific product life-cycle information.
Source: Environmental Expert /...
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