Chemical Compound Migration in Drinking Water Stored in Polypropylene Bottles

Abstract

Plastic bottles are commonly used for storing drinking water. However, limited knowledge exists regarding the migration of chemicals from plastic into water. In Sri Lanka, children often use reusable polypropylene (PP) plastic bottles for keeping water they use throughout the day. This study aimed to investigate the migration of chemicals and microplastic particles (MPs) into water stored for 24 hours in new PP plastic bottles and, to determine the effect of temperature on this migration. We tested 24 one-liter PP plastic bottles keeping distilled water and citric acid solutions at temperatures of 10◦C, 27◦C, 50◦C, and 80◦C after washing them with distilled water at 40◦C. Experiments were conducted in triplicate, and all samples, including three bottle-washed water, were tested for pH and filtered using membrane filter papers (0.2 μm pore size). MPs were captured upon Nile red staining and fluorescent images, and MPs in all filtered samples were counted using an orange lens under UV light (420-470 nm BLUE GG495: ORANGE) with a stereo microscope. Results revealed that MPs in the range of 1-100 μm were present in both solutions at all temperatures. The number of MPs migrating to drinking water was increased with temperature (p < 0.05). We observed a decline of water pH in all stored distilled water bottles under different temperatures. PP bottle-washed water samples showed a significant pH difference, but no apparently significant pH difference in citric acid samples. After 10 weeks, tap water stored in PP bottles showed decrease in pH and increase in electrical conductivity (EC) along with temperature. These results suggest that PP bottles storing different drinkables enhance the leaching of plasticrelated compounds. Further the findings opens the needs of further research to identify potential unknown chemical migrations supported by pH and EC changes, as well as toxicological assessing of the relevance and risk of the MPs and other leachable identified.