To protect phones from scratches, people slip them into all kinds of cases. Little do they know, while this safeguards their phones, it harms themselves.
On September 14th, the investigative team from CCTV's "Is It True?" program purchased three common types of phone cases—plastic, silicone, and leather—from street vendors and department stores. These were sent to the Indoor Air Testing Lab at Tsinghua University's Building Environment Testing Center for analysis.Analysis revealed that under average temperatures during normal phone use, these cases release toxic formaldehyde. Leather cases emitted the highest levels at 0.25 milligrams per cubic meter—more than double the national indoor air standard.The investigation also found that plastic cases bought from street vendors released the highest levels of benzene at 0.0494 mg/m³, while leather cases purchased from shopping malls released the least at 0.0191 mg/m³. However, neither exceeded the national indoor air standard of 0.11 mg/m³.
Journalists conducted follow-up investigations and found that most phone cases sold at roadside stalls and small shops lacked standardized product information, with some merely wrapped in plastic bags as packaging. Nearly all these cases emitted varying degrees of pungent odors, and some exhibited color bleeding.Dong Jinshi, Secretary-General of the International Food Packaging Association and Deputy Secretary-General of the Beijing Environmental Science Society, stated that formaldehyde is indeed present in some phone cases, originating from two sources: 1. Most phone cases are made of plastic, silicone, or leather, materials that typically require formaldehyde during synthesis. Residual formaldehyde remains in a free state within the case and can volatilize into the environment regardless of heat exposure.2. Complex designs like leather flip cases require processes such as bonding, printing, and color fixation. Adhesives often contain urea-formaldehyde resins that may decompose at high temperatures. "Currently, there are no national standards for phone cases, leading to a chaotic market. Some unregulated manufacturers cut costs by adding auxiliary materials that may produce additional harmful substances when the phone heats up."Benzene and formaldehyde, classified as carcinogens by the World Health Organization, are volatile organic compounds that can be released from phone cases.Zhang Jinliang, a researcher at the Institute of Environmental Pollution and Health at the Chinese Research Academy of Environmental Sciences, explained that beyond carcinogenic effects, prolonged low-level exposure to formaldehyde can cause headaches, dizziness, fatigue, and weakened immunity, along with symptoms like drowsiness, memory loss, neurasthenia, and depression.Chronic exposure to benzene may damage the blood and nervous systems. Zhang emphasized that China currently lacks testing standards for phone case products, making it impossible to determine if their emissions meet requirements. The experiments mentioned in this article were conducted in sealed chambers, differing from real-world usage environments, so there is no need for excessive alarm.Since phones are typically held close to the head during use and generate heat, which accelerates the release of harmful substances, the risk of inhaling these substances remains. In fact, phone cases do not extend the device's lifespan. Data indicates that cases impair heat dissipation; the same phone model lasts over three years without a case but only up to two years with one. Thus, most phone cases are unnecessary.Dong Jinshi advises consumers that if they insist on using a case, they must be cautious about purchasing channels and follow the rule of "look, smell, and feel." First, avoid overly brightly colored cases, as vivid hues may indicate high heavy metal content. Prolonged contact can allow these metals to enter the body through the skin, potentially damaging the kidneys and liver. Second, be wary of cases emitting pungent odors or causing eye irritation.Finally, avoid cases that feel excessively soft or hard, or those that shed color, as these may contain residual benzene-based organic solvents from manufacturing. Opt for genuine leather or silicone cases from reputable manufacturers instead of plastic alternatives. Additionally, make calls, play games, or watch videos in well-ventilated areas; use earphones during calls; and minimize children's exposure to phone cases.