An industry study showed that some well-known food products in China fail to meet national safety standards for external packaging.
Insiders predict that such scandals are unlikely to be avoided in the short term because of lax enforcement.
Dong Jinshi, executive vice-president of the International Food Packaging Association, said its tests found many paper cups for instant noodles and milk tea have excessive fluorescent whitening agent on their outside packaging.
His conclusion was based on the association's three-month study, which ended this month.
The study looked at 84 well-known food products purchased from local supermarkets and convenience stores in Beijing and Shanghai, as well as Guangdong, Zhejiang and Jiangsu provinces.
For instance, 24 food products, or 80 percent of the total samples taken in Beijing, were found to have excessive fluorescent whitening agent, according to the study.
Many popular products that have been on supermarket shelves for many years were listed as being substandard, it said.
Fluorescent whitening agent is a type of organic compound used to make paper white, but it may cause cancer after people ingest it over time.
"Although the inner packages of the samples were all right, consumers still are at risk of absorbing the chemical, when they touch the packages outside," he said.
By Friday afternoon, no food enterprises involved in the study said they plan to pull their products off store shelves.
Uni-President Enterprises (China) Investment, a major producer of instant noodles, disputed the study's results on Friday, saying "all paper cups for its instant noodles met the national standards on packaging", according to an announcement on its website.
Hou Xingfu, an official from Jinmailang Food Product, another company listed in the report, also defended the safety of the packaging.
"The paper cups for our products are made by professional packaging companies. We will conduct an investigation as soon as possible," Hou was quoted as saying by the website china.com.cn on Thursday.
Duan Yujing, a staff member in charge of quality supervision from the International Food Packaging Association, offered her own thoughts about why the packaging was unsafe.
"It is very likely that the substandard packages were made from recycled paper or even wastepaper that is not suitable for packaging food and drinks, because of their lower costs," Duan said.
The price of raw paper, which is suitable for packaging food after processing, is about 10,000 yuan ($1,570) a ton, almost twice as much as that of recycled paper, she said.
Since the country's current regulations have not clarified that outside packaging should also meet the same standards as inside packaging, many enterprises exploited the loophole, she said.
Zhang Jun, a 35-year-old resident of Beijing, is taking a stand after seeing the report.
"I believed both inside and outside packages for food and drink must be made from qualified paper for public health. I will try to avoid buying those products from now on because of the scandal," Zhang said.
Meanwhile, only one of the 25 tested samples of paper cups in the provinces and municipalities met the country's new standards for printed patterns, the study showed.
The new rule, which came into effect in June, required that colored patterns on paper cups cannot be within 15 mm from a cup's lip or 10 mm from its bottom for health concerns.
The rule, which does not include details on penalties for offenders, cannot have a big effect in the near future, said a manager from a local paper cup company in Beijing, who only provided his surname Li.
"But my company has already followed the new regulation for business concerns, since many of our products are sold to those high-end consumers, such as in restaurants and coffee stores, who are concerned about health issues," he said.