Plastic pollution has become a global crisis, and recycling is touted as a crucial solution. However, a recent study has uncovered a concerning discovery – the mechanical recycling of plastic through shredding can release vast quantities of airborne microplastics and nanoplastics, posing significant health risks to workers. This research sheds light on the hidden dangers of a process that is widely used in the recycling industry. The findings highlight the need for stricter safety measures and further investigation into the impact of these tiny plastic particles on human health and the environment. Microplastics and nanoplastics are emerging as a growing concern, and this study provides valuable insights into their generation during a common recycling practice.
Plastic Pollution and the Rise of Recycling
The global production of plastic has skyrocketed in the past century, leading to a waste management crisis. While only 9% of global plastics are recycled, the demand for recycling is increasing as the world seeks solutions to the plastic pollution problem. Mechanical recycling, which involves shredding and regranulation, is the most common method for processing plastic waste and is expected to process almost 55 million tons of plastic globally by 2030.
Uncovering the Hidden Dangers of Plastic Shredding
A recent study conducted by researchers from the University of California, Los Angeles (UCLA) has revealed a concerning discovery – the shredding of plastic during mechanical recycling can release vast quantities of airborne microplastics and nanoplastics. These tiny plastic particles, ranging from 10 to 420 nanometers (nm) in size, can be inhaled by workers, potentially exposing them to significant health risks.
The researchers investigated the emission and physicochemical properties of microplastics and nanoplastics generated during the shredding of three common types of plastic: polyethylene terephthalate (PET), polypropylene (PP), and high-density polyethylene (HDPE). They found that the number concentrations of these particles were 3 to 2,910 times higher during periods of shredding compared to pre-shredding background levels.
Alarming Concentrations of Airborne Microplastics and Nanoplastics
The study’s findings are particularly alarming. The maximum concentrations of particles within the 10-420 nm size range, across all six categories of plastic (waste and new), ranged from 22,000 to 1,300,000 particles per cubic centimeter (particles/cm³) during shredding, compared to average background levels of 700 particles/cm³. For the 0.3 to 10 micrometer (μm) size range, the maximum concentrations ranged from 24 to 2,000 particles/cm³ during shredding, compared to average background levels of 2 particles/cm³.
These findings suggest that workers engaged in plastic shredding activities could be exposed to alarmingly high concentrations of airborne microplastics and nanoplastics, particularly in the 10-100 nm size range, which are known to have the highest deposition fraction in the alveoli of the lungs.
Waste Plastics Generate Higher Emissions than New Plastics
The study also found that waste plastics consistently generated higher emissions of microplastics and nanoplastics than their new, unused counterparts. This is attributed to the presence of additional elements, such as adhesives, labels, and increased additives, in the waste plastic samples.
The elemental composition analysis revealed the presence of various elements, including aluminum, copper, calcium, silicon, and sodium, which are commonly used as plastic additives to improve physical properties, color, and durability. The waste plastics had a higher number of these additional elements compared to the new plastics, contributing to the increased emissions.
Diverse Particle Morphology and Potential Health Risks
The study also examined the morphology of the airborne particles using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The researchers found that the particles exhibited a wide range of shapes and sizes, with some exhibiting rod-like features. This diversity in particle morphology is significant, as research suggests that rod-like particles with larger aspect ratios can reach the deeper regions of the respiratory system, potentially posing greater health risks.
Furthermore, the zeta potential measurements indicated that the airborne particles generated during shredding may have a tendency to agglomerate, further complicating their behavior and potential impact on human health.
Implications and Future Directions
The findings of this study have important implications for the recycling industry and worker safety. The high concentrations of airborne microplastics and nanoplastics generated during plastic shredding highlight the need for stricter safety measures and engineering controls to protect workers from exposure.
The researchers emphasize the importance of further research to document the levels of airborne particulate matter present at mechanical recycling facilities and to investigate the potential health risks associated with the inhalation of these tiny plastic particles. Understanding the physicochemical properties and behavior of microplastics and nanoplastics is crucial for assessing their impact on human health and the environment.
As the world continues to grapple with the plastic pollution crisis, this study serves as a wake-up call, reminding us that the solutions we seek, such as recycling, may come with their own set of hidden dangers that require careful examination and mitigation.
This article is based on research by S. Swinnerton, J. Su, Candace S. J. Tsai.
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