## 4 Hazard
### Ecological Systems, Including Marine and Soil  
Harms to ecological systems often generate over time the conditions for general harms to humans. Five years ago, assessment of the environmental hazards of NMs was in its infancy. The knowledge on NMs' impacts on aquatic organisms was more advanced, although very many gaps still existed [50; 51; 52]. Most work was focussed on a few freshwater species (daphnids, some fish species and single-celled pelagic algae) and some microbial systems. Since that time this primary and exploratory research work has expanded to cover a wider range of phyla, although with variable incidence, and a wide range of endpoints.  
Only five years ago very few papers existed at the time using terrestrial organisms as test species, and this gap was also very acute regarding impacts on plants [52].  
Discussions on the importance of characterisation of the relevant properties of NMs for environmental studies were also in very early stages. Environmental scientists were learning rapidly from human toxicologists drawing on the wealth of knowledge from the respiratory toxicology community, especially on ultrafine particles.  
Exposure characterisation in the soil matrix is not a simple matter and special methods will need developing [10]. A core problem is that we cannot detect nanoparticles against the massive background of other particulates in the soil. The authors were party to the review of methods that had become available for nanoparticles characterisation in complex matrices, including soil [13]. Much progress had been made, with techniques like Scanning Electron Microscopy with an Energy Dispersive X-Ray Analyser (SEM-EDX), x-ray spectroscopy using synchrotron radiation, but also single-particle Inductively coupled plasma mass spectrometry (SP-ICP-MS) and flow field-flow fractionation coupled to ICP-MS (F-FFF-ICP-MS).  
**Recommendation 24**: Regarding soil we recommend that research priority is given to the following: development of new methods for nano-characterisation in soil and tissues (including cheaper methods for use in standard testing schemes); assessment of nanomaterial evolution in soil system; method development for better assessment of actual exposure of soil organisms to NMs; assessment of the nanomaterial characteristics driving their potential accumulation in food chains; the development of effect-markers to address mode-of-action in soil organisms; coupling of nanomaterial properties to their fate in soil, and effects in organisms (short to medium term).  
Knowledge is also required on fluxes or rates instead of distribution coefficients on which models for chemicals are often dependent. Important rates include rates of sedimentation, re-suspension, bioaccumulation, deposition and run-off fluxes. More information is needed on agglomeration, behaviour of agglomerates, sinks _i.e._, local accumulation, and understanding of what happens at the interfaces between water and sediments and water and biological surfaces.  
**Recommendation 25**: There is some urgency for funded research into future cumulative impacts of NMs (especially metallic NMs) on marine phytoplankton, which are vital to life on earth since they produce about 50% of oxygen and are a major atmospheric carbon sink [53; 54; 55].  
**Recommendation 26**: For the scientific design of ecotoxicology studies a multi-partner approach is essential. Even simple assays can generally not completely be addressed by a single partner.