Evaluation of airborne exposures associated with grinding applications of plastic-sand composite bricks

• Experimental findings suggest that brick grinding and cutting may migrate thousands to millions of inhalable and respirable particles into the environment • Airborne particles emitted from plastic waste bricks may generate toxic elements that pose hazards to the environment and humans including Si, Al, Ti, and Cr • Plastic waste bricks may offer benefits towards environmental impacts and construction industries owing to less silicon content, less water absorption, and being cheaper to produce • Downside of plastic waste bricks are potential health risks from extremely high concentration of nanoparticles as small as 0.1 μm (100 nm) Construction bricks made from plastic waste present an emerging method of recycling plastics, but there is little documentation on the potential health risks associated with plastic waste bricks. To examine particle emission hazards, this study evaluated micro- and nano- sized particles emitted from plastic-sand composite bricks when operators are cutting or grinding them. We utilized three plastic-sand composite bricks which were composed from a mixture of high-density polyethylene (HDPE) waste plastics and sand in the following ratios, 30% waste plastic with 70% sand, 90% waste plastic with 10% sand, and 100% waste plastic. Common exposures were simulated by grinding plastic-sand composite bricks in an enclosure. The resulting particle emissions were as many as 5.3 × 10 6 particles/cm 3 in the 10-420 nm size range and 6,100 particles/cm 3 in the 0.3-10 μm size range. Energy dispersive X-ray spectroscopy (EDX) analysis showed that brick particles contained various elements including Si, Al, Ti, and Cr. Exposure to these elements has been correlated with adverse health outcomes including carcinogenicity. The results suggest that brick grinding and cutting may migrate thousands to millions of ultrafine inhalable and respirable particles into the environment and the operator’s breathing zone while performing tasks. The small size of nanoscale particles poses a higher potential for respirable particle hazard; these findings suggest adding appropriate controls when operators are utilizing plastic-sand composite bricks. Emitted particle characteristics may vary with different brick compositions, and nanoparticle occupational exposure limits do not exist yet; these limitations suggest taking caution in extrapolation and highlight the need for further research. Environmental Implication Plastic waste bricks offer a method of recycling the extra plastic and decreasing brick production costs by using cheaper waste materials. Plastic-sand composite bricks may offer benefits towards environmental impacts, human health and construction industries owing to less silicon content, less water absorption, and cheaper to produce compared with the traditional concrete blocks, while also presenting potential health risks in terms of the extremely high concentration of nanoparticles as small as 0.1 μm (100 nm) being released into the environment.