Plastic pollution is a growing global crisis, with a staggering 79% of plastic waste ending up in landfills or the natural environment. As the world grapples with this challenge, the role of recycling has become increasingly crucial. However, a recent study has uncovered a concerning issue – the mechanical recycling of plastic through shredding can release a vast number of microscopic and nanoscopic plastic particles into the air, potentially exposing workers to significant health risks.
The research, conducted by a team from the University of California, Los Angeles (UCLA), examined the emission and physicochemical properties of these airborne microplastics and nanoplastics generated during the shredding process. Their findings shed light on a previously overlooked aspect of plastic recycling and its potential consequences for human health and the environment.
Uncovering the Hidden Dangers of Plastic Recycling
As the world’s plastic production has skyrocketed, the need for effective waste management has become increasingly pressing. Mechanical recycling, which involves shredding and regranulation, is the most common method for processing plastic waste, with an expected global processing capacity of 55 million tons by 2030. However, this study reveals that the shredding process can release a staggering number of microplastics and nanoplastics into the air, posing a significant threat to the health of workers involved in the recycling process.
Measuring the Emissions: From Submicron to Micron Sizes
The researchers employed advanced particle monitoring instruments to quantify the concentration and size distribution of the airborne particles generated during the shredding of three common types of plastic: polyethylene terephthalate (PET), polypropylene (PP), and high-density polyethylene (HDPE). They examined both waste and new, unused plastics to understand how the emissions varied throughout a product’s life cycle.
The results were alarming. During the shredding process, the number concentrations of particles in the submicron (10-420 nm) and micron (0.3-10 μm) size ranges were up to 2,910 times higher than the pre-shredding background levels. The maximum concentrations of particles within the 10-420 nm range reached a staggering 1,300,000 particles per cubic centimeter (particles/cm³), while the maximum concentrations of particles within the 0.3-10 μm range reached 2,000 particles/cm³. In comparison, the average background levels were just 700 particles/cm³ for the submicron range and 2 particles/cm³ for the micron range.
Fig. 1
Unraveling the Physicochemical Properties of the Airborne Particles
The researchers further investigated the physical and chemical characteristics of the airborne particles, shedding light on their potential impact on human health. They found that the particles exhibited a wide range of morphologies, from twisted and warped shapes to fiber-like structures and clusters of smaller fragments.
The elemental composition analysis revealed the presence of not only carbon and oxygen (the main components of plastic polymers) but also various additives and contaminants, such as aluminum, copper, calcium, silicon, and sodium. These additional elements can be attributed to the labels, adhesives, and increased additives incorporated into the waste plastic, as well as potential adsorption of environmental pollutants.
Interestingly, the waste plastics consistently generated higher emissions and contained more elements compared to their new, unused counterparts. This suggests that the recycling of waste plastics may pose an even greater risk to worker health due to the accumulation of these additional substances.
Fig. 2
The Threat to Worker Health: Nanoplastics and Respiratory Risks
The study’s findings are particularly concerning when considering the potential health impacts of exposure to these airborne microplastics and nanoplastics. Smaller particles, especially those in the 10-30 nm range, have the highest deposition fraction in the alveoli (the tiny air sacs in the lungs) and can potentially cross into the bloodstream, posing a significant threat to worker health.
Previous research has shown that particle size, shape, and surface properties can affect their interactions with living organisms and their ability to cause adverse effects. The diverse morphologies and chemical compositions of the particles generated during shredding make it challenging to generalize their potential toxicity, underscoring the need for further investigation.
Addressing the Challenge: Toward Safer Plastic Recycling
This study highlights the urgent need to address the emission of microplastics and nanoplastics during the mechanical recycling of plastic. The researchers emphasize the importance of implementing adequate engineering control measures and the use of personal protective equipment to safeguard workers during shredding activities.
Furthermore, the findings suggest that the recycling of waste plastics may require special consideration, as the increased additives and contaminants in these materials can lead to higher emissions and potentially greater health risks. Exploring alternative recycling methods or developing strategies to minimize the release of these microscopic particles could be crucial steps in ensuring the safety of workers and the broader environment.
As the world continues to grapple with the plastic pollution crisis, this research sheds light on a previously overlooked aspect of the problem. By addressing the hidden dangers of plastic recycling, we can work towards a more sustainable and safer future for all.
Author credit: This article is based on research by S. Swinnerton, J. Su, Candace S. J. Tsai.
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