Evaluation of Airborne Exposures Associated with Grinding Applications of Plastic-composited Brick

This study investigated potential exposures to airborne particles generated from manual grinding or cutting applications of bricks, with a focus on plastic-composited bricks. As an emerging technology, construction bricks made from plastic waste present a method of recycling plastics and addressing the accumulation of plastic waste in the environment. However, little is documented on the environmental and occupational health aspects of plastic-composited bricks. To simulate practical activities, three types of plastic-composited bricks and a concrete brick were grinded in an enclosure using a 4.5-inch hand grinder. Particle number concentrations and size distributions were monitored to evaluate emitted particles which could migrate into the operator’s breathing zones once being released into the environment. The maximum particle concentrations emitted in the enclosure with simulated activities across all types of bricks were 5.3 × 106 particles/cm3 in the 10-420 nm size range and 6,100 particles/cm3 in the 0.3-10 μm size range which were approximately 3-4 orders of magnitude larger than the laboratory ambient level. Emitted airborne particles and the studied bricks were characterized to identify morphology and elemental compositions. Images taken using scanning electron microscopy (SEM) of brick particles showed various particle sizes and shapes, including flat elongated particles and small round particles. Energy dispersive X-ray spectroscopy (EDX) analysis showed that aerosolized and scraped plastic-composited brick and concrete brick particles contain various mineral and metal elements in addition to the main of C and O, ranging from 71.9-82.5% of C and 20.4-25.6% of O. Si was detected as high as 2.5% on both bricks. Additional elements detected at percentages under 1% of responses were Fe, Al, Ti, K, Cr, Ca, Na, Mg, B, and Cu. B and Cu were only detected in the concrete brick; Ti and Cr were only found in the plastic-composited bricks. Possible exposure to Si, Al, Ti, and Cr has been correlated with adverse health outcomes including carcinogenicity. Additionally, the plastic-composited bricks produced smaller sized particles on average compared to the concrete brick. This could result in a higher potential for cytotoxicity with particles to travel deeper into airways. Overall, the enormous numbers of particles generated from the experiments and small particle sizes suggest that brick grinding and cutting may migrate thousands to millions of inhalable and respirable particles into the environment and reach the operator’s breathing zone while performing their tasks. Furthermore, the various elements observed may be linked to negative health effects individually or through combined toxic effects. The findings suggest proceeding with caution and adding appropriate safeguards when workers are utilizing plastic-composited bricks.