**Abstract**

Microplastics (MPs), which have recently threatened living organisms, are widely distributed throughout the world's fresh waters, oceans, and seas. HDPEs and PETs are produced and used in significant quantities in plastics. High-density polyethylene (HDPE) and polyethylene terephthalate (PET), which can survive in the natural environment for many years, are resistant to thermal, mechanical, and biological effects. This study examined the current developments in the sources of high-density polyethylene microplastics (mHDPE) and polyethylene terephthalate microplastics (mPET), and their disposal and properties. mHDPE and mPET microplastics consist of several sources, including their debris that breaks down their waste into smaller pieces as a result of physical and chemical processes, as well as micro-sized pieces of plastic commonly applied in personal care products or synthetic textiles. mHDPE and mPET pollution has become an important environmental problem with the potential to harm human health by entering the human and animal food chain. mHDPEs and mPETs, which enter the living organism through ingestion, inhalation, and dermal contact in general, adversely affect the cellular mechanisms in different parts of the body. In addition, they are decomposed into free radicals by the effects of external factors such as light and temperature, as well as biological agents and chemical wastes in the environment, which significantly affects the sustainability of the ecological environment.

**Keywords:** microplastic, waste, pollution, environment, properties, application
