Suicide by pesticide ingestion in Nepal and the impact of pesticide regulation

Pesticide poisoning affects peoples’ lives and health, particularly in low- and middle-income countries (LMIC) where high proportions of the population are engaged in agriculture and use highly hazardous pesticides (HHPs [1, 2]) on a daily basis. There is a growing international acceptance that rapidly reducing and progressively eliminating exposure to toxic chemicals is essential for the protection of human rights, health, and lives, and for achieving the Sustainable Development Goals (SDGs) [3, 4]. Both the World Health Organization (WHO) and Food and Agriculture Organization of the United Nations (FAO) stress their commitment to pesticide risk reduction, including a progressive ban of HHPs [5].

HHPs have been responsible for an estimated 14 million premature deaths from pesticide suicide since the Green Revolution placed them into rural households completely unable to use or store them safely [6]. Data from Sri Lanka [7‐9], Bangladesh [10], South Korea [11] and Kerala (India) [12] indicate that pesticide regulation to remove HHPs from agriculture results in marked reductions in pesticide suicides without apparent effect on agricultural yield. Means restriction works for highly lethal suicide methods, such as poisoning with HHPs, because it puts space and time between the person and means, allowing the suicide impulse to pass or selection of a less lethal means, increasing the chance of survival [13, 14].

Nepal is a South Asian LMIC with the population of 29 million that is heavily dependent on agriculture. According to the WHO, it has a high suicide rate of around 20/100,000 per year in 2012 [13]. Poisoning is a common cause of suicide [15‐17], with pesticides the most important poison [18, 19]. Pesticides are commonly used in Nepalese agriculture; they are regulated by the Plant Quarantine and Pesticide Management Centre (PQPMC) within the Ministry of Agriculture and Livestock Development (Box 1).

There are no nationwide data on the incidence of acute pesticide poisoning or of the pesticides causing deaths in Nepal [16, 20]. The Ministry of Health and Population collects data on poisoning but groups all poisons and forms (intentional, accidental, or occupational) of poisoning together, limiting the possibility for analysis. The Nepal Police records the numbers of suicides by poisoning, but again does not distinguish the agent. The Government of Nepal’s Heath Management Information System (HMIS) does not include the detailed information on poisoning and suicides that would make comprehensive data collection possible. Record-keeping at hospitals is under-resourced, limiting its usefulness for analysis of the precise poisons involved in cases and deaths [20].

The aim of this work was to identify the pesticide regulation that has been performed in Nepal, to identify pesticides responsible for most poisonings, and to relate these to the incidence of poisoning suicides over the last 40 years in the country.

Nepal’s data on pesticide registration, use, and bans were obtained from the PQPMC website and from PQPMC officials. Suicide data were extracted from the Police and National Statistical Bureau reports for the years 1980 to 2019. The methods used in recording suicides are classified into seven categories: hanging, poisoning, weapon and instruments, drowning, burning, jumping, and electric current. The poisoning classification includes poisoning with substances other than pesticides (i.e. drugs and medicines). We used the World Bank data on the population of Nepal for each year from 1980 to 2019 as the denominator to calculate crude suicide rates.

We reviewed the literature for all papers reporting pesticide poisoning in Nepal from 1980 to 2019. We hand-searched Nepalese language and national journals for studies. We systematically searched PubMed and www.​google.​com for studies on pesticide and poisoning in Nepal using the search terms “Nepal” and “poisoning”. We selected English language papers reporting primary studies with the aim to identify the compounds responsible for pesticide poisoning. There were no publication date restrictions. We reviewed the first 150 hits found on www.​google.​com until no new studies were revealed compared to the PubMed search.

There is no systematic system for suicide surveillance in Nepal [20]. Suicide and attempted suicide cases need to be reported to the police but due to the stigma and perceived (not actual) illegality of the act, many cases are believed to not be reported, leading to under-reporting of national data [16, 20]. In addition, there is misclassification as well as gaps in hospital record-keeping. This is a common situation across South Asia in countries with an uncertain legal status for suicide [75]. A small anomaly in Nepal is that group suicides are recorded by the police as a single suicide, further reducing numbers.

The WHO presents a wide range of competing estimates for suicide in Nepal, both considerably higher and lower than the official statistics. In 2014, the WHO modelled a 2012 predicted suicide rate, ranking Nepal 7th in the world at 24.9 per 100,000, the 3d highest for women (20 per 100,000) and 17th for men (30.1 per 100,000) [13]. In contrast, the WHO Global Health Estimates for 2019 reports 2544 suicides in Nepal (markedly lower than the 5819 reported by the police), of which 1176 (8.0/100,000) occurred in females and 1368 (11.4) occurred in males. This equates to an overall suicide rate of 9.6/1000,000, lower than the mean global rate of 10.5/100,000 population [13]. The discrepancy in numbers shows the importance of developing reliable national data on suicides and pesticide suicides.

Nepal’s hospital staff have difficulties identifying the compounds responsible for poisoning for patients who present to hospitals. In most cases, when the poisoning agent is recorded in hospital records, the patient or their family brought the containers to the hospital. When the compound used is not known, the atropine challenge test is used to determine if the patient ingested an OP chemical [37]. For the non-OP pesticides, the diagnosis is usually based on the container or information from the patient or family. In cases of OP poisoning determined by the atropine challenge test, the exact compound is usually unknown. If there is no container of the ingested compound and the atropine challenge is negative, the name of the agent is not indicated in the medical notes, making it difficult to identify the responsible agent.

We found that the number of suicides in Nepal have increased markedly since 1980, mostly due to a great increase in suicides from hanging. Pesticide suicides have made up about ¼ of suicides during this time but have not increased in number to the same extent. The most important pesticides responsible for pesticide poisonings and deaths in the literature has been OP pesticides. Most frequently used was methyl parathion (Metacid); although banned in 2006, it still appears as widely used poisoning agent, suggesting that the pesticide may have come across the border from India. However, very few patients bring the pesticide bottles with them to hospital and the pesticide is named from memory. Since Metacid is a widely used pesticide, it is possible that the term Metacid is used generally for any pesticides as occurred in Sri Lanka with Folidol (another brand name for methyl-parathion) and then Tamaron (methamidophos). This habit may have led to an overestimation of the importance of methyl parathion as poisoning agent. Our recent data from forensic science laboratories which identify the actual compounds ingested in fatal poisoning suggest that methyl-parathion poisoning is not a significant problem in Nepal anymore (Ghimire et al., submitted).

The other important pesticides for fatal self-poisoning were dichlorvos and aluminum phosphide, which were either banned completely (dichlorvos) or high concentration formulations banned (aluminum phosphide) in 2019.

Other pesticides have become increasingly frequently identified as involved in pesticide poisoning, including cypermethrin, chlorpyrifos, and malathion. Since the historically most important pesticides for suicide (methyl-parathion, dichlorvos and aluminum phosphide tablets) are now banned in Nepal, it will be important to observe for changes in the Nepal’s suicide rate. In this context, implementation of the regulations and elimination of the illegal sales become very important, as well as providing farmers with advice on substitution of banned pesticides. Based on data from elsewhere in Asia [76], these HHPs bans should result in a marked fall in pesticide suicides over the next 2–5 years.

Nepal has been successful at reducing the number of HHPs used in its agriculture, despite the increase in use of pesticides. This likely accounts for the very low number of occupational poisoning cases we have found to be admitted in hospital in Nepal (Ghimire, submitted). There are now only two WHO class Ia (bromadiolon) and Ib (Zinc Phosphide) pesticides left in use in Nepal. The necessity of their use should be reviewed by the PQPMC and removed if they cannot be used safely. As the recent bans are enacted and stockpiles run out, it will be important to see which WHO hazard class II insecticides become problematic for suicide, requiring an analysis of their need in agriculture.

In the last twenty years (2001–2019), Nepal has banned many HHPs, including the ones that were commonly used for pesticide self-poisoning. During this time, the incidence of hanging has risen markedly with a much smaller increase in pesticide suicides, which might be related to the regulation. Research is now needed on the effect of the 2019 ban of eight pesticides, many of which have been key for pesticide suicides over the last 15 years.