Nanoplastics release from polystyrene foam containers

Polystyrene (PS) foam is widely used in instant noodle containers, which exhibit a larger amount of nanoplastic (NP) release compared to other disposable plastic containers. The released NP particles can be absorbed into the body through ingestion and may adversely affecting the human body. The notable release of PS-NP particles is attributed to the properties of the PS foam unit cells. Each PS foam unit cell is very thin, and the extent of expansion and damage to these cells significantly influences the NP particle release. When the water in contact with the container exceeds the maximum service temperature (MST, >70℃), the PS foam becomes vulnerable. Furthermore, the thicker the foam, its expansion leads to greater damage to the unit cells. Notably, for commercial containers in contact with oil-fried noodles, damage to unit cells was observed when in contact with 99℃ water. In addition, 10⁴ times more (1.46 ± 0.59)× 10¹² particles/m² were released compared to non-oil contact containers. Residual oil from the fried noodles can destroy unit cells with high temperature. This highlights that oil is an important contributor to nanoparticle release, suggesting that PS foam containers are unsuitable for food packaging, especially for foods containing oil.