Is paraquat highly toxic? Does banning paraquat harm farmers' interests and affect agricultural production?

The ban on the herbicide paraquat has been discussed in Taiwan, China for many years, and it is a continuation of the policy of successive governments to phase out highly toxic pesticides and switch to alternative agents. Referring to empirical research results at home and abroad, the best way to prevent casualties caused by highly toxic paraquat should be banning it and using alternative drugs.

This article discusses the possible ways and reasons for preventing paraquat harm, cites relevant evidence, considers the overall interests, and organizes the content in a question-and-answer format, hoping to promote rational policy discussion.

1. Is paraquat highly toxic? Is the problem all about suicide?

Paraquat has special toxicity to the human body. Even a small amount absorbed by the body may trigger severe systemic reactions after a few days, including pulmonary fibrosis, respiratory failure, and a painful death. Because there is no antidote, the mortality rate is high. The late Dr. Lin Chieh-liang once reported that the mortality rate of paraquat poisoning treated with traditional methods was as high as 92%; he tried to improve the treatment, but the mortality rate was still as high as 66%[1].

By comparison, according to a report by the Taipei Veterans General Hospital team, glyphosate and glufosinate, which are also broad-spectrum herbicides, have mortality rates of only 7%[2] and 6%[3] respectively, much lower than paraquat's 66-92%. This also means that if other pesticides replace paraquat, many unfortunate deaths can be avoided.

In the past six years in Taiwan, China (2013-2018), 1,253 people died from paraquat poisoning, equivalent to an average of 200 people per year, with one person dying from paraquat poisoning every two days. Suicide accounted for the majority (90%), but in the past six years, 67 people were determined by prosecutors to be accidental poisoning (5% of all paraquat deaths). Therefore, deaths caused by paraquat are not only suicides; there are also cases of accidental death. Banning paraquat can not only reduce suicides but also reduce unfortunate accidental deaths, protecting the overall safety of the community.

2. Is skin contact with paraquat harmless? Is long-term exposure safe?

Paraquat can enter the body through multiple routes, including the skin. When the skin is intact, only a small amount of paraquat is absorbed. However, paraquat may first cause skin burns and damage, and then be absorbed through the damaged areas into the human body, causing systemic poisoning. There have been fatal cases abroad[4]. In Taiwan, China, Dr. Lin Chieh-liang's team once reported a case of skin burns and severe systemic paraquat poisoning[5]. Therefore, if there is extensive skin contact, or if the contacted skin already has multiple wounds, it is necessary to rinse as soon as possible and seek medical attention.

In addition to acute harm, long-term exposure to paraquat can also cause nerve damage and Parkinson's disease. In 2007, all countries in the European Union banned paraquat on the grounds that the suspicion that paraquat may cause Parkinson's disease could not be ruled out. Research by National Taiwan University Hospital found that compared with people who did not use paraquat, those who used paraquat for more than 20 years had a sixfold increased risk of Parkinson's disease[6], and international research shows that long-term users have a twofold increased risk of developing Parkinson's disease[7].

3. Does banning paraquat harm farmers' interests? Does it affect agricultural production?

Banning paraquat and using alternative pesticides involves changing old habits and using new drugs, and may indeed cause inconvenience to users, requiring relevant units to actively provide information and guidance on the use of alternative agents. However, if the gains and losses of using paraquat are considered comprehensively, especially when the loss of life is included, the cost of using paraquat in rural areas is extremely high.

Some people argue that paraquat is cheap. For herbicidal use, the average ex-factory price per liter of paraquat in 2005-2014 was 98 yuan, glyphosate was 109 yuan, and glufosinate was 248 yuan[8]. Compared with glyphosate, paraquat does not necessarily have an absolute price advantage, and the price of glufosinate has also dropped significantly in recent years. Since many years ago, paraquat has no longer been the best-selling herbicide on the Taiwan market[8]. In actual application, the dilution ratio and number of applications must also be considered. Because paraquat is a contact herbicide that "kills the weed but not the root," it may need to be used more times and does not necessarily have an advantage in terms of use cost.

More importantly, if the deaths caused by paraquat are included in the estimate, the overall social loss it causes absolutely far exceeds the price benefit. We once estimated that the deaths caused by paraquat each year (more than 160 people) and the loss of income exceed 1.3 billion yuan[9], all borne entirely by families and society as a whole, and this does not yet include the intangible loss of grief among relatives and friends. At the same time, these losses mainly occur in agricultural areas. If paraquat is banned, agricultural areas will benefit the most.

Does banning highly toxic pesticides affect agricultural production? Research shows that in Sri Lanka[10], South Korea[11], and Bangladesh[12], after banning pesticides (including paraquat), sales of agricultural products did not decline.

4. Can banning paraquat reduce deaths? Will suicides shift to other methods?

Among the deaths caused by paraquat, although a small number are accidental deaths, the vast majority are suicides. In countries around the world that have banned paraquat, a decline in the pesticide suicide mortality rate has indeed been observed, and the overall suicide mortality rate has also declined.

Our previous research cooperation with scholars from South Korea and Sri Lanka showed that after these two countries banned paraquat, the pesticide suicide mortality rate fell by 40-50%, with 850-950 fewer deaths per year, while the suicide mortality rate by other methods did not increase. Therefore, the overall suicide mortality rate fell by 13-21%[11,13].

As can be seen from Figure 1, Sri Lanka gradually banned three highly toxic pesticides, including paraquat, between 2008 and 2011, and in the subsequent period from 2011 to 2015, the pesticide suicide mortality rate fell by 50%. More importantly, the overall suicide mortality rate also fell by 21%, while the suicide mortality rate by other methods increased only slightly by 2%, with no obvious phenomenon of "shifting" to other methods. In 2015 alone, 937 suicides were reduced[13].

After Sri Lanka banned three highly toxic pesticides (including paraquat), the suicide rate declined

The main reason banning highly toxic pesticides can reduce suicide deaths is that it lowers the lethality of poisoning, giving many impulsive suicidal acts a second chance and turning a crisis into a turning point[14]. Research shows that for 24-74% of suicidal behaviors, less than 10 minutes pass from thought to action[15]. Drinking paraquat during interpersonal arguments, low mood, acute stress, or even temporary intoxication will lead to irreversible consequences. Banning paraquat provides an opportunity to avert danger.

Research in Taiwan, China[16] and abroad[17] found that among people taken to hospital because of suicidal behavior, only 2% died by suicide again one year later, while the other 98% did not die by suicide. This indicates that if the first suicide attempt can be saved, the vast majority of people will not die by suicide again.

The phenomenon of "impulse" can explain that removing the most highly toxic pesticides can save lives, and most attempters will not try again, nor will they switch to other methods. Many people think that "people who want to commit suicide will always want to commit suicide," but the World Health Organization publicizes that this is a misunderstanding that makes us miss opportunities to save lives[18].

Restricting lethal tools to reduce suicide is a strategy recognized by the World Health Organization as effective and evidence-supported[18]. Several conditions are required to achieve the effect, including that the restricted tool is common, highly lethal, easily accessible, can be restricted, and is not easily shifted to other methods. In Taiwan, China, banning highly toxic pesticides best meets these conditions, while other tools such as hanging are harder to restrict[14]. Restricting tools cannot prevent all suicides, but it is an important part of a multifaceted suicide prevention strategy and is targeted. Some people mistakenly think that all potential tools must be restricted, but that is actually not the case.

In fact, improving the safety of tools and environments is not only used to prevent suicide deaths but also to prevent accidents such as car crashes. For many years, the medical field has also gradually replaced low-safety drugs, such as barbiturates with high lethality, with safer sleeping medications. Banning the most highly toxic pesticides and replacing them with safer drugs is based on the same principle and is not difficult to understand.

5. What is the situation of other countries banning paraquat? What is China's policy on banning paraquat?

More and more countries around the world are banning paraquat. According to a statistic from seven years ago (2012), 36 countries had banned paraquat[19], but the latest statistics from the Council of Agriculture show that 64 countries have now banned it. Neighboring countries in Asia with situations similar to Taiwan, China have also gradually banned paraquat in recent years, including South Korea (banned in 2012), Vietnam (banned in 2017), Malaysia (banned in 2020), and China (liquid formulations banned in 2016, soluble gel formulations banned in September 2020).

Taking China as an example, on October 17 of last year (2018), the Ministry of Agriculture and Rural Affairs announced, "To safeguard people's lives and safety, further strengthen the supervision and management of paraquat" (paraquat is the Chinese translation of paraquat), adopting four measures[20], namely:

1. "Strictly implement paraquat management regulations": prohibit the sale and use of paraquat, but do not prohibit production and export;
2. "Comprehensively monitor paraquat production dynamics": monitor production, export, and inventory, and strictly prevent export from being diverted to domestic sales;
3. "Thoroughly investigate and handle the remaining problems of paraquat liquid formulations": comprehensively investigate and recover stocked paraquat, with disposal costs borne by production enterprises, operating units, or local governments;
4. "Severely crack down on illegal production and operation of paraquat": strictly investigate the addition of paraquat to other pesticides, or the substitution and counterfeiting of paraquat.

China's complete policy on banning paraquat is worth referencing, especially because after the ban, it also carries out recovery, accelerating the effect of reducing deaths. At the same time, if Taiwan, China continues to use paraquat and imports raw materials from China, it will become an absurd situation in which China bans it but exports paraquat to Taiwan, China, where it continues to cause tragedy.

Some people mention that certain major countries such as the United States and Japan have not banned paraquat. However, the United States has agriculture dominated by large farms, which differs from Taiwan, China, where small farmers mainly purchase, store, and use pesticides themselves. In the United States, paraquat is classified as "restricted use," and only licensed operators can use it. However, some scholars also point out that the U.S. policy on banning harmful pesticides (including paraquat) lags far behind other major pesticide-using countries, including the European Union (banned paraquat in 2007), China (banned paraquat solvent in 2016), and Brazil (plans to ban paraquat in 2020)[21]. The U.S. experience should not apply to Taiwan, China.

In Japan, in view of the harm of paraquat, as early as 1986, paraquat was changed from a 24% solvent to a 5% solvent (Taiwan, China still uses a 24% solvent), sales channels were also regulated, and local production of paraquat in Japan was prohibited in 1999[22]. Overall usage dropped to a very low level, and the number of deaths caused by paraquat also decreased[23]. However, the lethality of paraquat is still as high as 80%, showing that highly toxic paraquat remains highly toxic even at lower concentrations[23].

6. Besides banning, are other management methods effective?

Research shows that most other methods of restricting highly toxic pesticides are ineffective, and only banning has the clearest effect[24]. The following summarizes six methods of managing paraquat and their possible effects:

1. Adding emetics, warning colors, and adsorbents to reduce absorption: Taiwan, China has required paraquat to include emetics and warning colors since 1997, but the number of paraquat deaths rose from 118 that year to 200 in recent years, showing poor effectiveness, because paraquat is simply too toxic and even a small amount absorbed can be fatal. Foreign research has also been conducted on adding emetics, laxatives, and alginate adsorbents, and the result was that the mortality rate fell only slightly from 73% to 63%, with limited effect and still far higher than other pesticides[25].
2. Lowering the concentration: As mentioned above, Japan is one of the few countries that limited paraquat by changing it from a 24% solvent to a 5% solvent. However, the mortality rate of paraquat poisoning is still as high as 80%[23]. If farm households still commonly store paraquat, it may still lead to many poisoning deaths.
3. Changing the formulation: For example, changing paraquat into tablets to reduce suicidal poisoning. However, it still needs to be dissolved into a solvent before use and may be stored at home, so it cannot change the situation in which the solvent is readily available.
4. Restricting use: Ireland once implemented a restricted sales system for paraquat (only licensed or relevant operators could purchase it), provided safety education, and used pesticide safety labels, etc.[26], while South Korea tried a purchaser registration system[11]. As a result, these measures could not reduce the number of suicide deaths from paraquat, and both countries ultimately banned paraquat. The Taiwan Suicide Prevention Center once collected data on paraquat poisoning victims and found that 60% used paraquat stored at home rather than buying it on the spot. Therefore, restricting sales has limited effect.
5. Distributing pesticide storage boxes: Encourage farm households to store pesticides in locked boxes to reduce poisoning incidents among themselves or family members under momentary impulse. According to a study with as many as 220,000 people, this method had no expected effect at all. Comparing areas that distributed boxes with areas that did not, the incidence of suicidal pesticide poisoning was almost the same[27]. Relying on farm households to continuously store pesticides safely may be difficult to implement. Three years after the study began, only half of the farm households used safety boxes and locked them.
6. Professional contract spraying system: Restrict the purchase and storage of paraquat to pesticide contract spraying operators only. If this can be thoroughly implemented, and the paraquat previously stored in farm households is gradually used up, it may achieve an effect similar to a ban. However, Taiwan, China currently has no complete and rigorous contract spraying system, and ordinary farm households may also be unwilling to purchase this service. At the same time, paraquat may still spread to ordinary farm households through contract spraying operators, reducing the effectiveness of control.

For a ban policy to be implemented smoothly, complete supporting measures and alternative drug plans are needed. The Council of Agriculture has proposed multiple alternative agents for herbicidal use, but for defoliation use, because the alternative agents have only been launched in recent years, relevant units urgently need to continue optimizing the effects, provide farm households with clear guidance and incentives for use, and strive to promote them.

In the author's interviews, farm households mostly pointed out that the key is to have alternatives or agents, and they do not insist on using a specific drug. After all, everyone also values the safety of pesticide use. It is hoped that all sectors will refer to the evidence and focus on helping farm households switch to alternative drugs, or use other weed management or defoliation plans, so that highly toxic pesticides can be phased out. Only then can a win-win-win situation be created!