Environmental fate and toxicity
Nanomaterials can get into the environment at any stage of their lifecycle, from the production of the raw material, when using a product containing nanomaterials or when that product is recycled or turned into waste.
But what happens to these small particles once they get into the environment, where do they end up and can they be harmful?
The potentially negative effects of nanomaterials depend on their properties such as particle size and surface area and the properties of the environment they end up in. For example, pH levels, temperature or the presence of salts or other substances.
Properties of nanomaterials steer their effects in the environment
Understanding the nano-specific properties of these materials is needed to reliably assess any negative impacts they might have on the environment.
Very often, even at the same time, nanoparticles have several ongoing ageing processes in the environment, for example chemical transformation which can change their transport, fate and ultimately their ecotoxicological profile and bio-accumulative potential.
All these factors make it difficult to predict the effects of nanomaterials in different environments and a realistic hazard and risk assessment is more challenging than for conventional chemicals.
Advances in science close knowledge gaps
Constant progress has been made during the last decade in the field of environmental fate and behaviour of nanomaterials. This has led to closing many of the existing knowledge gaps.
Test guidelines and guidance documents developed through the OECD for conventional chemicals are also applicable to nanomaterials. More needs to be done though to create specific requirements that fully capture nano-specific characteristics.
In most cases, standard toxicity tests such as the OECD test guidelines deliver reliable hazard estimates. These tests normally look at effects during a certain life stage or throughout the entire life of an organism.
However, some results from research projects in non-standard tests revealed for a few cases effects over multiple generations within a species or population. Here for some aquatic invertebrates or soil organisms such as worms or plants, the parental generation showed little or no effects, but the growth, reproduction or physiology of the offspring were affected.
More research is needed to better understand how these generational effects can be covered by current risk assessment frameworks.
Miniature ecosystem to understand wider environmental impact
Researchers are working on new approaches to help understand longer term impact. One example is a mesocosm-based risk assessment. A mesocosm is a miniature ecosystem that tries to copy a certain environmental habitat with key species.
The goal is to determine exposure and hazard in a single experiment and during several generations.
One drawback is that analytical methods to monitor nanoparticles in mesocosms and other simpler tests are often not sensitive enough to fully capture their behaviour – information that is crucial to link the effects with the properties of nanomaterials.