Does salt contain plastic particles?

On November 3, the reporter went to Xi'an Powder Lane China Resources Wanjia Supermarket, Ximen Wal-Mart Supermarket, and Songguang Supermarket in Guangbei Road to sample and purchase salt. They found that the salt sold in these supermarkets is the same brand, with 350 grams of seaweed iodized salt. 200 grams of low sodium and iodized salt in the package. Among them, the powder lane Huarun Wanjia, Ximen Woolma two kinds of packaging, and the pine forest supermarket on Guangbei Road only has 350 grams of seaweed iodized salt.
On the afternoon of November 3, the reporter sent the samples to the Chemical Experiment Teaching Center of Xi'an Jiaotong University. After the experimenter gave the salt sample number, put it into 5 beakers, then add distilled water to dissolve it, and prepare 5 parts of salt saturated solution.
Professor Tang Yuhai introduced that plastic particles are insoluble in water, and if the salt is fully dissolved, if plastic particles are suspended in water or deposited on the bottom of the beaker.
At 2:30 pm on November 4, five beakers that were fully dissolved and allowed to stand for about 20 hours were placed on the experimental console. Careful observation with the naked eye, except for some bubbles on the walls of individual beakers, the salt solution in the five beakers was clear and transparent, and no suspended particles or precipitates were found.
Professor Tang Yuhai said that this means two situations: one is that there are no plastic particles in the five samples, and the other is the presence of plastic particles but the particle size is too small for the naked eye to observe.
Subsequently, Teacher Li Jianjun sampled each sample separately with a straw and placed it under a microscope. In the case of the eyepiece 16 times and the objective lens 40 times, that is, the magnification of 640 times, the presence of foreign matter particles in the sample salt solution was not found.
Is the microscope magnification too low, or does it require a more sophisticated method to test?
According to the situation reported in the media report on November 3, this article by East China Normal University studied salt from three different sources, sea salt, lake salt and well salt/rock salt. The experimental method is roughly “microscopically seeing particle size, Fourier infrared The spectrum looks at the components."
Professor Tang Yuhai said that although infrared spectrometers can be used for more detailed analysis, the premise is that there must be a certain amount. The sample salt solution did not see the presence of plastic particles under a 640-fold microscope, and such an amount could not be analyzed by an infrared spectrometer. If you want to make a more detailed observation, you may need to use a tunneling microscope. But plastic is a macromolecular structure. If it reaches such a small level, it is basically negligible. In addition, since plastics cannot be absorbed by the human body, even if a small amount of plastic particles enter the human body, most of them can be excreted.
Foreign media reports that the salt micro-plastic data is seriously inaccurate
On the issue encountered in the experiment, on November 5, the reporter of Huashang Daily contacted the Propaganda Department of the Party Committee of East China Normal University. The staff sent an article to the Huashang Daily titled “Marine micro-plastic pollution, the environment that the world had to face together. The article of the question is a reply. The article is written by Professor Li Daoji, the State Key Laboratory of Coastal Research at East China Normal University. Professor Li is also the earliest expert in the research of micro-plastics in the marine environment.
Professor Li Daoji explained in the article that the foreign media reported that the news reports on micro-plastics in salt were inaccurate. The study focused on the approach of marine microplastics into the human food web, which was received by the international environmental science journal Environmental Science & Technology and published online August 20. On August 28th, Scientific American published a news report on Chinese salt containing microplastics based on online papers. The title and some of the texts highlight the "Chinese salt" and "Chinese consumers" do not rule out the purpose of attracting readers. The data on micro-plastics referenced in this report is seriously inaccurate. The maximum salt salt per kilogram in the original text is 681, but the report is about 1200 per pound (should be 308 per pound), which is inconsistent with the data and opinions in the paper.
Professor Li Daoji believes that micro-plastics are ubiquitous in the environment. For example, researchers found that up to 400 micro-plastics per kilogram of honey, up to 13,000 per kilogram of soft tissue in Canadian cultured mussels.
In contrast, the microplastics obtained from salt are minimal. Salt micro-plastics are just an example of the impact of living products on micro-plastics and are a warning to everyone.