Environmental Release Of Microplastics Eight Typicalfrom Disposable Medical Devices And Assessment Of Their Toxic Effects

With the acceleration of urbanization and industrialization,a large number of plastic products are produced and discharged into the environment.Plastics in environmental media will age and degrade under the influence of ultraviolet light,high temperature and mechanical friction,forming new pollutants-microplastics.At present,the widespread presence of microplastics in the environment has triggered a series of environmental and public health problems,bringing new challenges to environmental protection.In recent years,the level of healthcare in China has been progressing,and the amount of medical waste generated has been increasing year by year.Among these medical wastes,medical plastics occupy a considerable proportion.Unlike ordinary plastics,medical plastics need to go through a high-temperature sterilization process before being buried or recycled on-site,which provides the basic conditions for the release of a large number of microplastics.It is worth noting that microplastics have not been included in the testing indexes of China’s waste gas and waste water emission standards,which led to this project.In this study,all eight typical disposable medical devices in the Measures for the Supervision and Administration of Disposable Sterile Medical Devices issued by the State Council were selected as research objects.Utilizing the Caenorhabditis elegans,taking microplastics as the main body throughout the beginning and the end,a series of studies were carried out around real samples and real environments,and the main research contents are summarized as follows:(1)Mechanisms and patterns of microplastic release from disposable medical devices:The environmental release mechanisms and patterns of microplastics in different disposable medical devices have been clarified using various characterization techniques.The quantity and particle size of microplastics released from disposable medical devices are directly related to the changes of their surface physical and chemical properties.The material itself is the key to the change of physical and chemical properties.Compared with PVC-based disposable medical devices,polypropylene-based disposable medical devices released more microplastics with smaller particle sizes.In addition,we also explored the microplastic release pattern of the same type of disposable medical devices under different parameter conditions(temperature,time),which provides new experimental evidence and ideas for the selection of parameters for autoclave sterilization in the future.(2)Assessment and comparison of toxic effects of three types of microplastics:a)Real sample microplastics:Nematodes were exposed to real sample microplastics released from disposable medical devices,and the changes of nematode endpoints such as nerve,reproduction and lifespan were detected in order to reveal the influence of the toxic effects of real sample microplastics on nematodes.The real sample microplastics showed differences in toxicity at different concentrations and materials with dose effects.This may be related to the material,particle size and quantity of these secondary microplastics.It is worth noting that at lower concentrations,microplastics are the main cause of toxicity,but at higher concentrations,the combined toxic effects of microplastics and other pollutants need to be considered.In terms of mechanism investigation,altered intestinal permeability of nematodes is considered to be the key to the differences in toxicity.b)Standardized microplastics:A dose effect of microplastic toxicity was determined by examining the changes in developmental,locomotor and reproductive endpoints of nematodes after exposure to different concentrations of standardized microplastics.The changes in neural,reproductive and lifespan endpoints of standard microplastics with different particle sizes were evaluated,and the rule that the smaller the particle size,the more toxic the microplastic was was found to be.The distribution of microplastics of different particle sizes in nematodes was observed under fluorescence microscope by orange and green fluorescent microplastics.Among them,100 nm microplastics could break through the intestinal barrier and cause the change of intestinal permeability.Finally,the changes of nematode oxidative stress indicators after exposure to different particle size microplastics were explored to explain the toxicity differences of different particle size microplastics.c)Aged microplastics in the seawater:The ageing mechanism of microplastics in the seawater has been determined by various characterization,which is mainly related to carbon bond breaking and benzene removal.It was clarified that aged microplastics in the seawater release secondary microplastics of different shapes and sizes,and can enter the nematode gut for accumulation.Differences in toxicity between fresh and aged microplastics were found,and the neurotoxicity and reproductive toxicity of aged microplastics were significantly enhanced,which was related to the accumulation of microplastics in the intestine and oxidative stress.(3)Environmental interactions between microplastics and microbiological:The phenomenon of interaction between microbiological and microplastics was discovered,and a system for stable reproduction of this phenomenon was developed.We also observed the whole process of interaction under the microscope using fluorescent microplastics and fluorescent microbial strains.We demonstrated that the interaction between microbiological and microplastics promotes short-term uptake of microplastics by nematodes,but does not exacerbate the toxicity of microplastics.In addition,we preliminarily explored the preference of microbiological to colonize the surface of microplastics by sampling real lake water for incubation at a total of 11 sampling sites in four lakes in Hefei city area,and explored the differences in bacterial flora between the microplastic interaction group and the lake water background by using 16s seq,which showed that microplastic surfaces were colonized mostly by harmful bacteria and bacteria that used plastics as a carbon source.The findings in this chapter reveal the interactions between microplastics and microorganisms,which may also be important vectors for harmful bacteria in real-world environments.In summary,this study reveals the aging mechanism and microplastic release pattern of disposable medical devices.we further comparatively evaluates the toxic effects of three types of microplastics.In addition,we preliminarily explores the interactions and effects of microplastics and microbiological.It provides new experimental evidence for a more comprehensive understanding of the health risks of microplastics in real environments,and provides theoretical references for the establishment of subsequent standards for the production,use and disposal of plastic-related medical devices.