Abstract
Microplastics (MPs) refers to plastic particles of 5 mm or less that exist in the environment such as the atmosphere and ocean. Therefore, there is concern about human exposure by various routes. However, even today, the effects on the human have not been clarified. It is known that the surface of MPs existing in the various environments is chemically deteriorated by external factors such as UV rays and waves. Therefore, it is essential to evaluate the biological effects in consideration of the deterioration state. Therefore, we first prepared a standard product that imitated the deterioration state of MPs in the environments. Furthermore, using them, we attempted to evaluate the effects of MPs on cells by cytotoxicity tests.
Polyethylene (PE), which has the highest production volume, was selected as the standard product for MPs. By irradiating the PE powder sample with UV rays of 172 nm, degraded PE with a chemically deteriorated surface was prepared. In addition, it was confirmed that the prepared degraded PE could be present in the environment by comparing with the sample collected from the environment. Next, using the obtained standard product, a cytotoxicity test by MTT assay was performed. As cell lines, RAW264.7 and THP-1, which are immune cells, and A549, HaCaT, and Caco-2, which are epithelial cells of lung, skin, and intestine, were selected. As a result, concentration-dependent cytotoxicity was observed only in degraded PE in all cell lines. This indicates that PE has different effects on cells depending on the presence or absence of deterioration.
