Micro/Nanoplastics Effects on Plants
Recently, micro/nanoplastics effects in terrestrial ecosystems have come into focus; a decade ago the research was limited to aquatic systems only. Micro/nanoplastics can affect soil properties with consequent influence on plant growth and activity, either positively or negatively. These effects will vary as a function of plant species, plastic type and, thus, are likely to translate to major changes in plant community. Micro/nanoplastics can be viewed conceptually as a soil physical contaminant that may lower soil bulk density and
FIGURE 1.3 Effect of micro/nanoplastics on plants.
enhance soil drying [26-29]. Slow decomposition of plastic particles due to very high carbon content is known to create microbial immobilization . Major effects of the micro/nanoplastics on plants are summarized in Figure 1.3.
Micro/Nanoplastics Effects on the Food Chain
There is growing concern about the impact of human activities on the whole ecosystem, along with an apprehension that the smaller plastic fraction, through bioaccumulation and trophic transfer, may ultimately contaminate the human population. However, in contrast to the visible presence of massive amounts of litter, there is presently very little understanding about the extent of environmental contamination caused by micro/ nanoplastics. Toxicological effects due to micro/nanoplastics ingestion by humans are still not evident. Presently, it is impossible to assess and control the human exposure to micro- and nanoplastics through food consumption because of the lack of validated methods and standardization on the part of analytical procedures. It must be underlined that the definition of what is intended to be measured is essential for the development of a measurement method, and there is absence of such an internationally accepted definition related to micro/nanoplastic particles. In view of the diversity of particles with respect to size, shape and composition; adsorption of other pollutants and dynamic change of their distribution in our environment based on human activities, the development of fit-for- purpose standardized methods constitutes a challenge .
The calibration of such standard methods requires the use of reference materials, where the type of particle and their concentration is precisely known. Different reference materials for diverse polymers in special matrices should be developed. The adsorption of chemicals and microorganisms or the leaching properties of such materials must accurately mimic the adsorption and leaching properties of plastic particles in the natural environment. Then, comparisons between prepared reference materials and naturally occurring particles can be performed (similar to computability studies which compare incurred serum samples to patient samples in a clinical analysis). Finally, to monitor the contamination caused by micro- and nanoplastics, a significant number of samples must be collected, representative of an environmental area or a population, using standard sampling protocols that avoid further contamination. However, no accurate answer can thus be given, neither to the question of how much microplastic we may consume through a normal diet nor to the question of how it may affect us. Until standardized analytical methods and reference materials are available, the data produced will not be representative and significant .