Roots, dried fruits, leaves and berries used in traditional Chinese medicine preparations are increasingly contaminated with chemicals, including pesticides and preservatives, experts told RFA during a recent investigation.
Take the wolfberry, or goji berry (lycium barbarum), now popular as a supplement or wellness ingredient around the world. While listings on wholefoods websites outside China now claim to offer "sulfite-free" dried berries, the majority of stock coming out of China is still preserved using sulfites.
"[Sulfur fumigation] is the cheapest form of preservative," Chen Shih-hsiung, an organic agriculture expert on the democratic island of Taiwan, told RFA. "It acts as a preservative, a pesticide and enhances color."
"It's a very common process used by Chinese farmers, and it will be difficult to change that," Chen said.
Taiwan-based food chemistry expert Wang Yuen-chun said the traditional way to preserve herbs and berries is drying them in the sun, but the majority of TCM companies in mainland China now use sulfur fumigation instead, because sun-drying is too labor intensive.
Brightly-colored or light-colored herbs, like sliced white roots and berries, are more likely to have high levels of sulfur, Wang said, because of the color-enhancing effects of fumigation.
Current industry standards agreed between Taiwan, Hong Kong and mainland China limit sulfur dioxide residues in most TCM products to 150 ppm, with some limited to 400 ppm.
But recent tests carried out on TCM medicines imported from China by the Taipei municipal health bureau found that dried winterflower, gentian and tricosanthes all had sulfur dioxide levels in excess of safety standards.
Wang warned that herbs with a high sulfur content will often give off a pungent odor and taste sour or bitter.
"If it has only been lightly treated with sulfur fumigation, you may not notice the smell or taste," he said.
Chen said a low-tech environment and lack of education among herb-growers in China was a major problem.
"A lot of farmers in China have almost no education, and they are working with outdated technology," he said. "It's not so easy for them to upgrade to modern drying methods."
Sulfur dioxide can combine with the residual moisture in dried herbs to make sulfuric acid, which can damage the skin, respiratory and digestive tract and the immune system if ingested over a long period of time, even resulting in lung, liver and kidney damage, Wang said.
Too much sulfur can also neutralize the active ingredients in Chinese medicine by changing the structure of the original compounds, he said.
China is currently the world's largest producer of TCM materials by far, accounting for 90 percent of the global market.
According to a November 2021 article on the Chinese Medicine Net website, more than 60 percent of raw medical materials including codonopsis, angelica, forsythia, jujube, epimedium and astralagus root have failed to pass quality control tests for pharmacopia products due to lack of medicinal value or pesticide residues.
And yet, demand for TCM products is still strong, with an 80 percent increase in the number of applications to register new TCM products since the start of the COVID-19 pandemic.
The scarcity caused by the lack of newly registered suppliers has sent prices skyrocketing, while manufacturers of untested, substandard or fake products are rushing to fill the gap.
In tests of more than 1,000 batches of unregistered TCM herbal preparations in 2020, China’s National Food and Drug Administration found traces of banned pesticides including phorate, carbofuran, DDT, fipronil and BHT.
A profit-driven industry
The problem, according to Chen, is in the profit-driven industrialization of TCM agriculture.
"Traditional Chinese medicine planting uses deep-rooted traditional methods, which states that there's no need for pesticides unless you can see insects, nor for fungicides in the absence of disease, or herbicides in the absence of grass," he said.
"Otherwise, it will lead to disaster in future," said Chen, who calls the industrial use of pesticides "suicide farming."
"It hurts everyone, from the producers to the consumers, and it will leave future generations without farmable land; nobody wins when you use suicide farming methods."
Chen said many TCM herbs have their own insect- and disease-resistant properties.
Dyes are another common substance found in TCM herbs, including Sudan red and other banned red dyes, according to Wang, who says wolfberries and ginseng roots with uneven coloring are more likely to have been sun-dried, while those with a deep, uniform color are more likely to have been dyed.
Among the toxic dyes found in TCM products, Acid Red 73, carmine and Sudan Red are among the most worrying, Wang said.
British studies have shown that six food colorants including carmine can affect children’s intelligence and cause behavioral disorders, while combining easily with heavy metals like arsenic, copper, and lead during the manufacturing process.
Carmine colorants are currently banned in Taiwan, the U.S., Canada and Norway, while they can be used in strictly limited quantities in the EU and Japan, among other countries.
Meanwhile, the International Agency for Research on Cancer (IARC) classifies Sudan Red colorants as carcinogenic to humans or animals.
Chen isn't optimistic about the future of TCM, despite growing his own medicinal herbs at home.
In the end, enough people will be worried about the toxic side-effects to stop buying it. "Chinese medicine will self-destruct," he said.
Translated and edited by Luisetta Mudie.