The control group, consisting of resident physicians, will use non-disposable plastic tableware (NDPT) provided by hospital canteens for two months.

The exposure group, also comprising resident physicians, will use disposable plastic tableware (DPT) made of polystyrene, provided by the same hospital canteens for two months

Microplastic release from the daily use of disposable plastic materials (e.g., plastic boxes) when holding hot food or drink.

In this study, the researchers utilized the Chinese version of the Depression Anxiety Stress Scales-21 (DASS-21), a widely recognized and reliable instrument for assessing depression, anxiety, and stress. This comprehensive tool is divided into three sections, each dedicated to evaluating the levels of depression, anxiety, and stress, respectively. The depression scale scores range from 0 to 21, with normal scores falling below 4. Anxiety scores also range from 0 to 21, with normal scores below 3. For stress, scores range from 0 to 18, with scores below 7 considered normal. Higher scores on any of these scales indicate elevated levels of depression, anxiety, or stress. In this research, the DASS-21 was employed to monitor the variations in anxiety and depression-like behaviors among the two groups, both at baseline and after the treatment period.

The gut microbiota encompasses the microorganisms residing in the human gastrointestinal tract. Microbial diversity refers to the variety of different species present in the gut microbiome. In this study, DNA extraction from fecal samples is carried out in two primary steps. Initially, the sample undergoes purification using multiple reagents and centrifugation. This process isolates the microbes by removing other fecal components. The next step involves lysing bacterial cells; this is achieved by incubating the samples in lysis buffer with agitation. Subsequently, the extracted DNA is amplified through techniques such as multiple displacement amplification. A 16S rRNA primer is then selected for gene sequencing. The sequences obtained from the 16S rRNA will be analyzed to ascertain the gut microbial diversity at the species level.