Researchers at Iowa State University tested common industrial cleaning methods on polypropylene flakes used for dairy tubs. They tried physical agitation, sodium hydroxide, ultrasonic vibration, and sodium hydroxide with an industrial detergent. The work appears in Advances in Materials Science and Engineering.
The team found no detectable phthalates or bisphenols after physical agitation alone or agitation with sodium hydroxide. But ultrasonic vibration and sodium hydroxide plus detergent released two phthalates, named DEHP and DCHP, into the wash water. When the researchers simulated reuse of the same wash water for 15 cycles with sodium hydroxide plus detergent, DEHP levels rose: ten times the drinking-water limit after the first wash and 25 times after 15 cycles. The detergent level fell, which suggests the plastic flakes absorbed some cleaner. The study notes health concerns and possible treatments to reduce risks.
Difficult words
- polypropylene — a common plastic used for containers and tubspolypropylene flakes
- phthalate — a chemical added to make plastic flexiblephthalates
- bisphenol — a chemical sometimes found in plasticsbisphenols
- agitation — movement or shaking to clean or mix
- ultrasonic vibration — very fast sound waves used to clean
- detergent — a liquid soap used for cleaning
- absorb — to take in a liquid or substanceabsorbed
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- Would you be worried about chemicals in recycled plastic? Why or why not?
- How could people reduce risks when reusing wash water at a small scale?
- Have you ever washed something many times and noticed the water stayed dirty? Describe that experience.
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