Is the herbicide glyphosate carcinogenic? The EU is divided
In March of this year, the International Agency for Research on Cancer (IARC) raised the carcinogenic risk of the herbicide "glyphosate" (Glyphosate, sold in Taiwan under the product name "Niannianchun") from "possibly carcinogenic (Group 2B)" to "probably carcinogenic (Group 2A)", indicating that some studies have already pointed to glyphosate's carcinogenic effects on humans, but after the European Food Safety Authority (EFSA) re-evaluated the relevant studies, it reached a completely opposite conclusion, holding that glyphosate is unlikely to be a carcinogen, and at the same time adjusted glyphosate's acceptable daily intake (ADI) from 0.3 mg per kg of body weight per day to 0.5 mg.
Wu Kun-Yu, a professor at National Taiwan University's College of Public Health, said that it is very common for different international organizations to hold differing views on the same pesticide, and now that EFSA's conclusion is opposite to that of IARC, it is bound to spark debate internationally, and IARC is very likely to restart its assessment within a certain period of time.
International Agency for Research on Cancer: Glyphosate increases cancer risk
Glyphosate, also known as Niannianchun, has a killing effect on any plant and is cheap, at about 100 yuan per liter, making it one of the most widely used non-selective herbicides in the world, and Taiwan is no exception. According to statistics from the Weed Science Society of the Republic of China, in 2013 glyphosate sales in Taiwan reached as much as 3643 metric tons, ranking first among non-selective herbicides.
However, because "non-selective" means that spraying it on crops will cause phytotoxicity, glyphosate in Taiwan is mostly applied to fallow fields or weeds between fields.
Glyphosate was originally classified by IARC as "possibly carcinogenic," meaning that international studies had already shown that glyphosate can cause cancer in animals. As studies indicated that people who come into contact with glyphosate over the long term due to occupational exposure have an increased risk of developing non-Hodgkin lymphoma, and with further concerns that it may cause gene mutations and gene damage, IARC in March of this year upgraded glyphosate to the "probably carcinogenic" category.
European Union: Past studies ignored mammals' own background rates
So why did EFSA and IARC reach opposite conclusions? According to the full report released by EFSA on November 12, although some experiments concluded that glyphosate can cause malignant lymphoma in rats, these studies ignored the fact that mammals themselves already have a very high background rate.
Wu Kun-Yu, a professor at National Taiwan University's College of Public Health, explained that the so-called "background rate" refers to the fact that animals already have a high proportion of malignant lymphoma even when completely unexposed to glyphosate, and added that EFSA believes that the dose given in some animal experiments was as high as 1460 mg per kg of body weight per day, which is too high to prove a relationship between glyphosate and lymphoma.
EFSA believes that, based on the current stage of research evidence, glyphosate is not genotoxic and poses no risk of causing cancer. However, Wu Kun-Yu pointed out that EFSA this time only reviewed the risk assessment of "pure glyphosate," and whether mixtures made from glyphosate and other pesticides could be genotoxic is something that EU peer experts believe needs to be further clarified.
EU relaxes the allowable daily intake of glyphosate from food
Based on a new wave of international animal studies, EFSA this time adjusted the allowable amount of glyphosate that each person may ingest through food per day, from the original 0.3 mg per kg of body weight per day to 0.5 mg, but at the same time EFSA adjusted the acceptable operator exposure level (AOEL) from 0.2 mg per kg of body weight per day to 0.1 mg. "EFSA revised this value in order to respond to the residues of glyphosate in body fluids and urine of South American farmers mentioned in the IARC report after they applied glyphosate." Weng Su-Shen, former head of the Residue Control Division at the Institute of Toxicology said.
In the face of EFSA's determination on glyphosate's carcinogenicity being inconsistent with IARC's, Weng Su-Shen believes that overall the impact on Taiwan is actually not great. After all, Taiwan does not grow genetically modified crops. Compared with countries that allow the planting of glyphosate-resistant GM cotton, GM soybeans and the like, whose crops may raise concerns about glyphosate residues, Taiwan mostly uses it for weed control, so there is no need to worry about crop residue problems.
Weng Su-Shen specifically mentioned that, in addition to adjusting the ADI value, EFSA also set an "acute reference dose (ARfD)" of 0.5 mg per kg of body weight per day. This figure represents the dose at which intake of glyphosate from food within a short period (within one meal or one day) may cause discomfort in humans, and with this value there will be one more layer of constraint on the allowable amount and risk assessment for glyphosate crops.
Wu Kun-Yu said that it is very common for different international organizations to hold differing views on the same pesticide, and now that EFSA's conclusion is opposite to that of IARC, it is bound to spark debate internationally, and IARC is very likely to restart its assessment within a certain period of time.
After IARC released its research report in March of this year stating that glyphosate is probably carcinogenic, there were reports of calls to ban glyphosate in countries including Brazil and the Netherlands, and the president of Sri Lanka even directly announced a ban. In response, Wu Kun-Yu said that if some countries do decide to ban it because of IARC's assessment, then in the future, countries that allow the use of glyphosate, such as the EU, if their exported agricultural products are subject to controls by countries that have banned glyphosate, the EU may file for arbitration with the World Health Organization, and at that point IARC may have to restart its assessment.
As for whether the glyphosate residue limits for imported food in our country will be revised accordingly, Pan Chih-Kuan, head of the Food Division at the Food and Drug Administration, said in an interview regarding the IRAC cancer risk report that if the Council of Agriculture makes no further decision, there will not be much change in the FDA's risk assessment of pesticide residues.