Microplastic Release from Hot Beverage Cups
New research indicates that heat significantly increases the release of microplastics from disposable hot beverage cups. The study, coauthored and published in the Journal of Hazardous Materials: Plastics, investigated how various cups behave when exposed to hot liquids.
Microplastics are plastic fragments ranging from approximately 1 micrometer to 5 millimeters. They can originate from the breakdown of larger plastic items or be released directly from products during normal use, eventually entering the environment, food, and human bodies. The long-term health implications of microplastics in human bodies require further research.
Temperature and Material Factors
A meta-analysis of 30 peer-reviewed studies on common plastics like polyethylene and polypropylene identified temperature as a key factor in microplastic release. Increased liquid temperature generally correlates with increased microplastic release, with reported releases ranging from hundreds to over 8 million particles per liter. Soaking time was not a consistent driver, suggesting the initial liquid temperature is more critical than how long the drink remains in the cup.
Further experiments tested 400 polyethylene and plastic-lined paper coffee cups at 5°C (cold) and 60°C (hot).
- Material: Plastic-lined paper cups released fewer microplastics than all-plastic cups at both temperatures.
- Heat: For all-plastic cups, switching from cold to hot water increased microplastic release by approximately 33%. Consuming 300 milliliters of coffee daily from a polyethylene cup could result in ingesting 363,000 microplastic particles annually.
High-resolution imaging revealed that all-plastic cups have rougher internal surfaces compared to plastic-lined paper cups. This rougher texture facilitates particle detachment. Heat accelerates this process by softening the plastic and causing expansion and contraction, which creates more surface irregularities that fragment into the drink.
Risk Mitigation
To manage microplastic exposure from hot beverages, using reusable cups made of stainless steel, ceramic, or glass is recommended, as these materials do not shed microplastics. If disposable cups are necessary, plastic-lined paper cups are indicated to shed fewer particles than all-plastic cups, though neither is entirely microplastic-free.
Reducing the initial temperature of hot liquids before they contact plastic-lined containers can also decrease physical stress on the plastic lining and potentially lower microplastic exposure.