Will the plastic coating on the inner wall of the paper cup harm human health?

Disposable paper cups have become standard in coffee shops, fast food restaurants and daily life due to their lightness and low cost. However, in recent years, the controversy over "the plastic coating on the inner wall of paper cups may release harmful substances" has continued to ferment. While enjoying the convenience, consumers can't help but worry: Are these seemingly harmless paper cups quietly threatening our health?
The "invisible identity" of paper cup coating
The vast majority of disposable paper cups on the market are not pure paper products. In order to block liquid penetration, manufacturers will coat the inner wall of the paper cup with a layer of plastic film (usually polyethylene PE or polylactic acid PLA). This coating is relatively stable at room temperature, but when it comes into contact with high-temperature liquids (such as hot coffee and hot tea), plastic molecules may migrate due to thermodynamic effects.
A study in the journal "Environmental Science and Technology" in 2020 pointed out that PE-coated paper cups containing 95°C hot water can release about 25,000 microplastic particles within 1 hour, accompanied by a small amount of bisphenol A (BPA) analogs. Although the single intake of these substances is negligible, whether long-term accumulation is harmful to the human body remains to be further verified.
Toxicity controversy: disagreements in the scientific community
Scholars who support "low risk" believe that the polyethylene used in paper cup coatings is a food contact safety material certified by the FDA, with stable chemical properties and a release amount far below the safety threshold under normal use. For example, the European Food Safety Authority (EFSA) stipulates that the daily tolerable BPA intake of the human body is 4 micrograms per kilogram of body weight, while the migration amount in a cup of hot drink is usually less than 0.1 micrograms.
However, skeptics cite animal experimental evidence to point out that long-term exposure to microplastics may cause intestinal inflammation, endocrine disruption and even cell damage. A study by Dutch scholars in "International Environment" in 2022 showed that microplastics have been detected in human blood, some of which may be related to food packaging materials. Although there is no direct evidence to prove its pathogenicity, the "potential risk" cannot be ignored.
Industry practice and consumer misunderstandings
In order to avoid risks, paper cup manufacturers are trying to replace traditional PE coatings with polylactic acid (PLA). PLA is derived from renewable resources such as corn starch, is biodegradable and has better heat resistance. However, the cost of PLA is 30%-50% higher than that of PE, and its degradation requires industrial composting conditions, resulting in a slow promotion process.
On the other hand, consumers often fall into two major misunderstandings:
Mistakenly using paper cups for microwave heating: the inner coating of paper cups may melt under high microwave temperatures, releasing higher doses of microplastics;
Reusing paper cups: paper cups have a loose structure and are prone to breeding bacteria after repeated use, and the risk increases after the coating is damaged.
How to use paper cups safely?
Control the temperature of liquids: Try to use paper cups for low-temperature or room-temperature drinks, and avoid contact with high-temperature liquids above 85°C;
Choose uncoated paper cups: Some brands have launched "plastic-free coating" paper cups, using beeswax or water-based barriers instead;
Support reusable containers: Bring your own stainless steel or glass cups to reduce dependence from the source.