# The Microplastics Cycle: An In-Depth Look at a Complex Topic
## 2 The Microplastics Cycle
### Microplastics in Land  
Plastics have become prevalent, in part due to their portability, durability, light weight, and low cost, and the diversity of uses within residential, medical, and industrial settings [21]. Despite the fact that the design and manufacturing of microplastics and majority of its uses occurs on land, the research on the impact of plastic waste and microplastics on soil and landfills is considerably less extensive than that on water sources. (In 2022, 499 papers published on microplastics related to soil, sludge, compost, and land fill, among the total 2402 microplastic research articles. Using the Web of Science database, an extensive search was conducted employing the keywords'microplastics and landfills','microplastics and sludge', and'microplastics and compost' in the title, abstract, author keywords, and keywords plus fields). Plastics and microplastics captured in the soil may undergo multiple transformations, including degradation, before reaching water sources [22; 23]; however, these transformations vary depending on a variety of factors such as temperature, rainfall, soil type, type of microbes in soil, chemical composition of soil, etc. [24; 25]. In light of this, it is crucial to comprehend the plastics and microplastics present in landfills and soil, as well as their repercussions on soil and ecosystems. The presence of microplastic (MP) particles has been detected in various commonly consumed items derived or processed on land, including sugar (0.44 particles/g), honey (0.10 particles/g), salt (0.11 particles/g), alcohol (32.27 particles/L), bottled water (94.37 particles/L), tap water (4.23 particles/L), and ambient air (9.80 particles/m\({}^{3}\)) [26; 27]. According to [PERSON] and [PERSON] [28], there is an estimated annual deposition of a substantial amount of microplastics in North American agricultural soils, ranging from 44,000 to 300,000 tons. This expansion of focus to include agricultural contexts highlights the presence and potential impact of microplastics in these specific settings. European farmlands have been associated with a comparable estimate ranging from 63,000 to 430,000 tons, as reported by [PERSON], [PERSON], et al. in 2016 [29]. These studies highlight just one route of exposure people have to microplastics as they move through the environment in the land, water, and air, and enter our food chain. Furthermore, the potential for plants to concentrate plastic particles and then be ingested by animals adds another dimension to this intricate matter. The utilization of plastic film is a common technique in agriculture for the purpose of preserving fodder, which plays a crucial role in the diets of dairy and beef cattle [30]. Furthermore, it is common practice to encase hay bales with mesh or twine in order to maintain their shape. This practice involves the use of plastics, which are incorporated into feed preservation techniques for animals that are raised for food production. This method increases the likelihood of migration of microplastics or additives from feed packaging into animal feed. It is worth mentioning that there have been documented cases in scientific research, where bisphenol products (BPs) have been detected in animal feed. These BPs are believed to originate from packing materials such as polypropylene (PP) and polyethylene (PE) [31]. The infiltration of polycyclic aromatic hydrocarbons (PAHs) into the solid feed of cows serves as a significant indication of the likelihood for these pollutants to permeate the milk generated by these livestock, as emphasized by [PERSON] et al. [32]. The number of publications published by various nations on the same topics as those mentioned above is shown on the global map (Figure 2). Using the Web of Science Core Collection database, we combed through all 1405 papers published up to 2022. The search pattern included all conceivable permutations of the word associated with each of four land-related terms. The studies were combed for location and publication date information.