Pesticide residue limits relaxed 24-fold: Are leeks still safe to eat?

Since 11 May this year, a new national food safety standard has officially come into effect. The maximum residue limit for flumioxazin in chives has been increased from 0.2 mg/kg to 5 mg/kg, a 24-fold increase.

● Relevant regulations for flumioxazin in GB 2763.1—2022, “National Food Safety Standard: Maximum Residue Limits for 112 Pesticides in Food, including Sodium 2,4-DB”.

While Fomephon is classified as a low-toxicity pesticide, long-term consumption may still pose certain health risks. Experiments on rabbits and rats have confirmed that Fomephon possesses reproductive toxicity. Prolonged exposure in mothers may result in malformations of the offspring’s reproductive organs or impair their skeletal and neurological development. Furthermore, long-term intake may also adversely affect the eyes, the thyroid, and the pancreas. On 29 March, the National Pesticide Residue Standard Review Committee issued a specific response regarding the rationale behind the increase in the Fomephon residue limit. The notice stated that this revision adhered to the “most rigorous standards” and cited risk assessment results suggesting that not only is 5mg/kg acceptable, but raising the limit to 30mg/kg would still pose no safety risk.

But is this actually the case?

1. An excessively high Acceptable Daily Intake

First, we must determine the daily intake level of Fomephon that would pose a safety risk. China’s Acceptable Daily Intake (ADI) for Fomephon is set at 0.1mg/kg bw/d—that is, 0.1mg per kilogram of body weight per day. This standard is based on those established by the Joint FAO/WHO Meeting on Pesticide Residues (JMPR) in 2007. In reality, however, China’s standard is among the more lenient globally.

As the EU does not permit the use of Fomephon products, its ADI is a mere 0.0028mg per kilogram of body weight per day—only 2.8% of the Chinese limit.

Even in countries where Fomephon is permitted for agricultural use, the ADI remains significantly lower than that of the new Chinese national standard. For instance, Australia’s ADI for Fomephon is 0.05mg per kilogram of body weight per day, half the Chinese limit, while Japan’s ADI is 0.038mg, just 38% of China’s.

ADIs are generally formulated based on animal study results, where the dose proven to be harmful is divided by a fixed safety factor to ensure the level is safe for the general population. The standards in the aforementioned countries have largely been revised to incorporate more recent toxicological research. The higher ADI value in China may be due to a failure to incorporate the latest toxicological findings, unlike the other nations mentioned.

II. The Ubiquity of Fomephon

Even if we accept the current domestic maximum allowable daily intake of 0.1 mg/kg bw/d, the issue extends far beyond chives. Under existing standards, a person weighing 50 kg would have a maximum allowable daily intake of 5 mg. If they were to eat only chives, and given the residue limit of 5 mg/kg, they would have to consume 1 kg of chives a day to potentially exceed this stipulated daily limit. Naturally, it is unlikely that an average person would eat that many chives in a single day. The decision to raise the national standard for Fluoxastrobin residues in chives to 30 mg/kg may have been based on this reasoning.

But is it logically sound to relax the limits on pesticide residues simply because the volume of chives consumed is small?

As a broad-spectrum fungicide, Fluoxastrobin is currently widely used for disease control in various fruits and vegetables. According to national standards, the residue limits for Fluoxastrobin in different produce range from 2 to 10 mg/kg. Therefore, we must consider the cumulative intake of Fluoxastrobin from all these combined sources.

● GB 2763-2021 stipulates the maximum residue limits for Fluoxastrobin in certain vegetables.

In a paper published in 2019 titled ‘Residue Detection and Long-term Dietary Exposure Assessment of Flumyzin in Chives’, Zhou Yong et al. calculated that the National Estimated Daily Intake (NEDI) of Flumyzin is 2.5562 mg, based on residue levels across various food types and the average daily intake of the Chinese population.

This means that an adult with an average weight of approximately 63kg, consuming an average of 275g of vegetables and 45g of fruit, would have a potential intake equivalent to 40.6% of the maximum daily intake. However, as living standards rise, the total daily intake of vegetables and fruit for many people likely already exceeds these figures.

The ‘Dietary Guidelines for Chinese Residents (2022)’ recommend a daily intake of 300–500g of vegetables (half of which should be dark-coloured) and 200–350g of fruit. Assuming an average-weight person eats at the upper limit suggested by the Guidelines—500g of vegetables and 350g of fruit—the calculated intake would rise to 7.089mg, representing 113% of the maximum daily intake. This is a significantly concerning figure.

● Daily intake recommended by the 2022 Dietary Guidelines.

If adults are at risk, toddlers with lower body weights are even more vulnerable to the risks associated with boscalid. Liu Yuhong and colleagues pointed out in a 2020 paper that children aged 2 to 7 may face a higher risk due to their relatively higher intake of vegetables. If it is considered a fallacy to discuss toxicity without considering the dose, then discussing the safety of chives in isolation, while ignoring the widespread use of boscalid, is surely equally problematic. From the analysis above, it is evident that regardless of whether the national residue standards for chives are revised, the risk of excessive boscalid levels persists.

III. Boscalid and Grey Mould in Chives

Earlier this year, when the standards were published, some media outlets questioned whether this was a move to reduce the incidence of failed spot checks, thereby boosting the compliance rate of agricultural products and effectively ‘erasing’ the problem of non-compliance. According to incomplete statistics from the Ministry of Agriculture and Rural Affairs’ Department of Agricultural Product Quality and Safety Supervision, 3,799 out of 14,295 batches of edible agricultural products sampled in 2020 were found to be non-compliant, a proportion of 26.57%. Boscalid residue violations accounted for 352 of these batches, ranking first among all pesticide residue excesses; notably, every single one was found in chives.

According to data from the non-profit organisation Ziran Tian, even if the boscalid limit were raised to 5mg/kg, a significant number of samples would still exceed the threshold.

Their investigation of regulatory records from 15 provinces and cities in 2022 revealed 223 instances where boscalid levels in chives exceeded the previous standard. With the limit raised to 5mg/kg, 31 instances remained non-compliant, with the highest recorded residue reaching 35.5mg/kg—seven times the new national standard.

● Ziran Tian also pointed out that this trend of raising limit standards has appeared in other agricultural products as well. For instance, in the revised 2022 edition of the ‘National Food Safety Standard for Contaminants in Food’, the cadmium limit for sea crabs and mantis shrimp was relaxed from 0.5 mg/kg in the 2017 edition to 3 mg/kg in the 2022 edition. Similar to the situation with chives, this is linked to the high frequency of cadmium levels exceeding limits found during the testing of swimming crabs.

Why do flutolanil residue levels in chives remain so high? To understand this, we must look back at the production side.

Flutolanil is applied in chive production primarily to prevent and control grey mould. In 1985, Li Mingyuan and Liu Jie from the Beijing Plant Protection Station first identified the pathogen causing grey mould in chives within China. They also discovered that this fungus thrives in temperatures between 15-20°C and high humidity. When grey mould strikes, chive leaves often develop dry tips or white spots; in severe cases, grey mycelium grows, and entire leaves may wither and die.

● Grey mould in chives is a fungal infection caused by *Botrytis squamosa*.

A technical supervisor at a farm in North China told Foodthink that chives are susceptible to disease during cold, rainy weather. Consequently, spring—with its lower temperatures—is a peak period for grey mould in the North. Even if the infection is not severe, the appearance of white spots on the leaves strips the chives of their commercial value, making them impossible to sell. Furthermore, changes in cultivation methods can alter the growth environment and trigger outbreaks of grey mould.

Li Mingyuan and others discovered as early as 1985 that grey mould is the primary disease affecting chives grown under plastic mulch for warmth during winter and spring. As greenhouses and solar greenhouses became more prevalent, these facilities—often characterised by poor ventilation and high humidity—became hotspots for the disease.

Following a five-year investigation, a local technician in Henan found that grey mould is more severe in solar greenhouses than in plastic sheds; among the plastic sheds, the disease is more prevalent in small hoop houses than in large ones, whereas open-air chives have a relatively lower infection rate.

IV. How to prevent and control grey mould?

Yang Jingyong, head of the Wuhan Little Farmer Ecological Farm and a former plant protection specialist, suggests based on his experience that those growing chives in greenhouses should ventilate them before 9 am to reduce humidity. He believes other measures are also effective in disease prevention, such as spreading sawdust and wood ash, using beneficial bacteria like Bacillus subtilis to compete with pathogens for space, and increasing soil organic matter while balancing nitrogen and phosphorus fertiliser ratios. Additionally, chives should be rotated every two to three years to prevent disease from worsening.

While these methods may enhance plant resilience or improve the growing environment, the current trend toward larger-scale monoculture and an increase in agricultural facilities makes a rise in grey mould outbreaks inevitable unless active steps are taken to promote plant health. For many ordinary farmers, applying chemical treatments after an outbreak has occurred has become the standard practice.

● Similar “ten-thousand-mu chive cultivation bases” are being established in many regions across the country. Such large-scale monoculture makes crop rotation difficult and allows diseases to spread more easily.

Most laboratory experiments on pesticides aim to demonstrate that when applied using standard methods, residues can be kept within acceptable limits. Research conducted by Zhou Yong and colleagues noted that applying Botryticide to chives can limit residues to between 0.04 and 1.06 mg/kg after 30 days. In practice, however, many farmers do not follow these standard operating procedures when applying chemicals.

The pre-harvest interval for the most common Botryticide formulations—smoke agents and wettable powders—is 30 days, which mirrors the standard procedure used in experiments. However, as a typical crop of chives takes roughly 30 days to grow, this implies that chemicals can only be applied once per crop, and must be administered immediately after the previous harvest.

Such a regimen is impractical for growers. For instance, when using Botryticide smoke agents in greenhouses during winter and spring, the common practice is often to spray preventatively every seven days. This is because once an outbreak occurs, the disease becomes extremely difficult to contain. However, farmers rarely wait for the pre-harvest interval to lapse before harvesting; if they do, the chives become too tough and lose their market value.

Decades of continuous Botryticide application have led to *Botrytis cinerea* (grey mould) gradually developing resistance. As the effectiveness of the chemical waned, producers were forced to further increase the dosages.

In 2022, Hu Bin and colleagues tested nine different fungicides against grey mould strains found in chives from a region in Shandong. Their results revealed that these strains were most resistant to Botryticide, rendering it far less effective than the other fungicides tested.

V. From ‘Strictest Supervision’ to ‘Most Rigorous Standards’?

In 2019, the implementing regulations for the new Food Safety Law were released, outlining the ‘four strictest’ principles: the most rigorous standards, the strictest supervision, the most severe penalties, and the most serious accountability. It is the focus on ‘strictest supervision’ and ‘most severe penalties’ that explains why we have periodically seen shocking headlines over the last few years, such as sellers of ‘toxic’ chives being fined thousands or even tens of thousands of yuan. In most of these cases, the fines were triggered by Botryticide levels exceeding the legal limit.

● Under the constraints of the so-called ‘strictest food safety law in history’, the starting point for fines was abruptly raised to 50,000 yuan. Consequently, the past few years have seen a flood of ‘bizarre’ rulings from market regulators. However, relying on fines to tackle the issue of exceeding residue limits is merely scratching the surface. Within the standard food distribution chain, chives pass through multiple intermediaries; vendors often have no inkling of where their produce originates or why it exceeds the permitted limits. Regulators are even less likely to reach the producers, leaving them with no choice but to penalise the vendors.

● Many vegetable markets are now equipped with these pesticide residue testing rooms; however, rapid tests are generally not very accurate and cannot serve as the definitive basis for determining whether residue limits have been exceeded. Photo taken by the author at a vegetable market in Guangzhou.

Now that the maximum residue limit for flutolanil in chives has been relaxed twenty-fourfold, such news reports will likely become rarer. However, the actual safety of the chives remains unchanged; the long-term overuse of low-toxicity pesticides like flutolanil continues to pose uncertain risks.

From a macro perspective, chemical usage has reduced production difficulties, enabling greenhouse farming to provide a year-round supply and helping large-scale operations combat disease. While these year-round, industrial production models are better suited to market demands, they have also created a detrimental dependency on chemicals. This is why, despite China’s two-thousand-year history of growing chives, some farmers now claim that ‘without chemicals, nothing will grow’.

We fear that with pesticides acting as a safety net, fewer and fewer producers will focus on eco-friendly cultivation methods that promote plant health. Ultimately, faced with the threat of pesticide resistance, they will be forced to continuously increase dosages until the chemicals simply cease to work.

Ultimately, the crux of the pesticide residue problem remains the issue of over-application during production—and this is not limited to chives. Because regulation often fails to reach the actual producers, a long-standing contradiction has emerged between regulatory logic and the reality of chemical-dependent production. The reason ‘toxic chives’ became such a well-known term is simply that the chronic issue of exceeding residue limits was particularly prominent, became exposed, and was subsequently amplified by severe penalties, bringing it to public attention.

While the revision of these ‘most rigorous standards’ may ease this tension, it will not change the fundamental state of agriculture. It serves as a reminder to the public that ensuring food safety is not primarily about strict market regulation, but about fundamentally transforming unsustainable agricultural production methods.

● A ‘Blockchain + Chives’ project promoted in one region in 2021 was initially designed to tackle the issue of excessive pesticide residues in chives. However, this may have been just another failed attempt at pesticide regulation.

References

GB 2763.1—2022 “National Food Safety Standard: Maximum Residue Limits for 112 Pesticides in Foods, including Sodium 2,4-dibutylphenyl acetate”. Scientific Rigour in Standard Revision Ensures Food Safety — Relevant officials from the National Pesticide Residue Standard Review Committee answer reporters’ questions regarding the revision of the maximum residue limit (MRL) for procymidone in chives

http://www.moa.gov.cn/gbzwfwqjd/xxdt/202303/t20230329_6424229.htm?eqid=b5fb2f2a001793490000000364263d50

Zhou Yong, Pu Xiuying, Liao Xianjun, Liu Jia, Zhu Hang, Ma Haihao, Zhou Xiaomao, Li Fugen. Detection of procymidone residues in chives and assessment of long-term dietary exposure [J]. Acta Pesticidologica Sinica, 2021, 23(2): 373-379.

[Agricultural Product Quality and Safety Work Bulletin Issue 5] Analysis and summary of failed sampling tests of edible agricultural products by market supervision departments in 2020 http://www.jgs.moa.gov.cn/gzjb/202102/t20210218_6361714.htm

Detection of procymidone residues in chives and assessment of long-term dietary exposure, Liu Yuhong

Hu Bin, Huang Zhongqiao, Liu Xili, et al. Control effects of nine fungicides on Botrytis cinerea in chives [J]. Chinese Agricultural Bulletin, 2014, 30(4):6.

Liu S, Che Z, Chen G. Multiple-fungicide resistance to carbendazim, diethofencarb, procymidone, and pyrimethanil in field isolates of Botrytis cinerea from tomato in Henan Province, China[J]. Crop Protection, 2016, 84: 56-61.

Xing Yanwei. Occurrence and comprehensive control of Botrytis cinerea in chives [J]. Farmers’ Friend for Prosperity, 2014, No. 495(22):95.

Reconsideration of Procymidone: Human health risk assessment report (including Toxicology and Work Health Safety), Australian Pesticides and Veterinary Medicines Authority, 2017

GHS Classification Results by the Japanese Government

https://www.nite.go.jp/chem/english/ghs/20-meti-0055e.html

Foodthink Author

Wang Hao

Foodthink editor and an observer of food and agricultural issues with a background in science and engineering; he is also an avid lover of chive dumplings.

Editor: Ze En

II. The Ubiquity of Fomephon

Published by Foodthink