Three hundred million tons of plastic are produced annually. Due to photodegradation, plastic breaks down into microplastics, ranging in size from 1 µm to 999 µm. Their minuscule size allows them to be readily transported and to infiltrate terrestrial and aquatic environments. This research investigated the effects of microplastics in the soil on the soil itself, as well as on the health of Lactuca sativa var. longifolia, commonly known as the lettuce plant. A group of lettuce was grown in soil with a 10% concentration of microplastics, and a control group in plain soil. After 49 days, the plant height, biomass, and root length were examined, together with the water holding capacity of the soils. To visualize whether microplastics were taken in by the lettuce plants, fluorescent microplastics were added to the soil of another experimental group. After 19 days, these plants were cleaned thoroughly, mashed up, and tested for the presence of fluorescent beads. Results showed that microplastics increased the water holding capacity of soil by 29%, that plants grew 17.9% taller in soil with microplastics, and that the differences in dry biomass and root length between the experimental and the control groups were statistically insignificant. Black light analysis for fluorescence showed that microplastics got carried along with plant matter. Although microplastics in the soil seem to positively benefit the soil and somephysical characteristics of the plants, the fact that microplastics tenaciously adhere to the lettuce may render lettuce unsafe to consumers.
