## 3 Presence of Micro- and Nanoplastics in Environmental Matrices and Food
### Water  
Water serves as a major route for the ingestion of plastic pollutants, particularly in drinking water, including tap water, commercial bottled water, and beverages made with tap water.  
MPs and NPs can occur at various stages as contaminants of drinking water, but the isolation and analysis of nano-sized particles are complex, and data regarding their  
Figure 1: Possible routes for human exposure to plastic particles.  
occurrence are often unavailable [14; 15; 16]. In drinking water treatment plants, plastic particles are mostly detected as fibers [14; 16; 17; 18] or as spherical and fragmented particles of 1-50 um in treated water [19] and bottled water, with mean concentrations of 4.23 MPs/L and 94.37 MPs/L, respectively [20]. Note that the abundance of plastic particles increases as their size decreases [21]. [PERSON] et al. [22] reported a relatively high volume of spherical nanoparticles derived from PET bottled water ranging from 60 nm to 5300 um, but little is known about the occurrence of nano-scale plastics in drinking water systems, mainly due to the methodological difficulties mentioned above.  
MPs and NPs have also been extensively documented in various aquatic environments [23], including marine waters [24], surface water bodies [25; 26; 27], and wastewaters [28; 29]. Plastic debris in the Sargasso Sea was first reported in 1972 [30], and since then, numerous studies have emphasized how human activities have transformed marine waters into the ultimate repositories for plastic waste and how plastic particles of different dimensions accumulate throughout various trophic levels and transport through the entire food web, not only in the marine environment [31]. NPs were quantified in lakes and streams in Siberia (mean 51 \(\mu\)g/L) and Sweden (mean 563 \(\mu\)g/L) [32], and particularly, NPs \(<\) 200 nm were found in river waters with average concentrations ranging from 5 to 336 \(\mu\)g/L in Austria and Thailand, respectively. Moreover, NPs were detected in marine environments from 4.2 to 9.25 \(\mu\)g/L in the Netherlands and China [23], and, intriguingly, in the Greenland ice core and in Antarctic Sea ice, where the average concentrations of the NPs were 13.2 ng/mL or ranged from 37.7 to 67 ng/mL, respectively [33].  
Municipal wastewater treatment plants act as primary receptors of MPs and NPs, originating from landfills, industrial effluents, civil discharge (especially fibers from washing machines), and stormwater before discharge into open waterways [34; 35; 36]. Water stirring, mixing, and pumping generate shear forces, potentially causing MP fragmentation and NP generation. Mechanical impellers, for example, can fragment MPs from 75 to 300 \(\mu\)m into smaller particles averaging 0.74-1.88 \(\mu\)m, to the point that NPs released post-wastewater treatment are at least 40 times higher than the initial NP/MP levels [37]. Over 95% of MPs \(>\) 300 \(\mu\)m are removed through primary and secondary treatments, but to reach a 98% removal efficacy, tertiary treatment is required [34; 38], which many plants lack. Despite this, it is estimated that around 65 million MPs \(<\) 300 \(\mu\)m could still be discharged into receiving water bodies daily, even with the maximum removal efficacy, due to the vast volume of wastewater treated globally each day [39], raising concerns about the quality of open water environments.