Drinking hot beverages from paper cups poses health risks, a study has found.
In the 15 minutes it takes for (hot) coffee or tea to be consumed the microplastic layer on the cup degrades and releases 25,000 micron-sized particles into the hot beverage."
Sudha Goel, Study Lead Author and Assistant Professor, Indian Institute of Technology
"An average person drinking three regular cups of tea or coffee daily, in a paper cup, would end up ingesting 75,000 tiny microplastic particles which are invisible to the naked eye," she adds.
Globally, some 264 billion paper cups were produced in 2019 for consuming food and beverages such as tea, coffee, chocolate, soft drinks, and soups, according to the Imarc Group, an international market research company.
According to Imarc, consumers use paper cups because of hectic lifestyles and busy schedules, with the demand spurred by the rising trend of takeaway services and ready-to-eat food across the globe. Paper cups also do not require cleaning and can be easily discarded after use.
But the IIT researchers say there is a price to be paid for the convenience. "Microplastics act as carriers for contaminants like ions, toxic heavy metals such as palladium, chromium and cadmium, as well as organic compounds that are hydrophobic (water repelling) and can cross over into the animal kingdom," says Sudha. "When ingested regularly over time, the health implications could be serious."
Sudha's team poured ultra-pure (MilliQ) water at 85—90 degrees Celsius into paper cups and allowed it to sit for 15 minutes before analysing it under a fluorescence microscope for microplastics. The plastic linings were separately examined for changes in physical, chemical and mechanical properties.
The results were startling, says Sudha. "We could confirm the release into the MilliQ water of microplastic particles as well as submicron-sized particles using a scanning electron microscope — a disposable paper cup exposed to hot liquid for 15 min will have approximately 10.2 billion submicron sized particles."
Further, using ion chromatography, the researchers observed ion transfer into the water from the paper cups, confirming that microplastics could be released into hot beverages.
Most disturbingly, says Sudha, analysis of the plastic films showed the presence of heavy metals in the liners.
"This study shows that careful consideration needs to be done before the promotion of replacements for bio-hazardous products and environmental pollutants. We have been quick to replace plastics cups and glasses with disposable paper cups," said IIT-Kharagpur director, Virendra Tewari, in a statement. Tewari suggests a return to traditional, disposable terracotta cups that are still used in many parts of India.
According to Sudha, the convenience of paper cups is such that it is hard to find a suitable replacement, especially in modern office settings where paper cups go with coffee-vending machines.
"There is definitely a push factor from the companies that install and maintain coffee or tea vending machines that are ubiquitous in offices," says Goutham Y, chief of the Chennai-based Ecolife, a group of environmental entrepreneurs with a mission to replace petroleum-based products with biodegradable and environment- and health-friendly counterparts.
"Apart from ingesting microplastics, as outlined in the IIT study, paper cups leave behind thin plastics that contaminate the environment," says Goutham. Disposable paper cups do not decompose in a landfill and cannot be recycled so that there is a continuous and growing demand for them that can only be met by further deforestation."
Goutham says Ecolife is researching on non-petroleum, plant-based films that can be used to coat paper cups such as polybutylene succinate that are biodegradable but admits that the environment-friendly cups are twice as costly as the regular ones now in use.
According to Goutham, the wayside tea and coffee stalls in India typically have such small margins on sales that they serve their beverages in the cheapest possible cups, often lined with wax, which can be even more dangerous for consumers than plastic liners.
"About the only way to get people to use safer materials is for the government to be proactive and reduce taxes on the manufacture of paper cups and perhaps even subsidise them, given the havoc they can play on the health of unsuspecting populations," Goutham says.
The study is due to be published February 2021 in the Journal of Hazardous Materials but is already available online.
Ranjan, V. P., et al. (2020) Microplastics and other harmful substances released from disposable paper cups into hot water. Journal of Hazardous Materials. doi.org/10.1016/j.jhazmat.2020.124118.