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Scientific studies on paraquat

Studies on

Studies on cases of acute poisoning due to Paraquat

(2014) Chemicals of public health concern in the African Region and their management (PDF, 5.4 MB)

“…pesticide-related poisoning events continue to occur countrywide in Kenya, with a total of 1 479 cases and 579 fatalities reported in 2012. In Uganda, pesticide poisoning incidents that occurred in 2012 in Wakiso and in 2013 in Pallisa caused a total of 87 fatalities. In Nigeria, pesticide poisoning in Kaduna State in 2012 resulted in an unconfirmed number hospitalized. […] Ghana, for example, reported that application of various hazardous pesticides such as paraquat (WHO class II) and aluminum phosphide (a toxic fumigant) by farm workers without adequate protective clothing was a key cause of pesticide poisoning in the country.” [pp. 31-5]  

WHO (2014): Chemicals of public health concern in the African Region and their management.
(PDF, 5.4 MB)

(2014) Agricultural pesticide usage and prioritization in South Korea

“A total of 24 active ingredients were selected for prioritization in South Korea based on toxicity and quantity of use between 2007 and 2011 (Table 3). They account for 39.8% of the total volume of pesticides used and include 14 insecticides, 5 herbicides, 4 fungicides, and 1 fumigant. Among the selected 24 pesticides, paraquat was canceled to reregistration by the Korean government, and a few pesticides (i.e., endosulfan, EPN, methidathion, methomyl, and trichlorfon) have been voluntarily withdrawal by pesticide companies in 2011. [...] Although some pesticides such as paraquat, pendimethalin, benomyl, and chlorpyrifos were not categorized into a specific toxicity classification, they have been reported in epidemiological studies to be related to cancer or neurologic diseases. In particular, paraquat was the most used herbicide in South Korea in both frequency and volume and has been a major causative agent leading to acute poisoning death [Lee et al 2013]. Related long-term health effects such as depressive symptoms [Kim et al 2013] and restrictive ventilatory defects [Cha et al 2012] have also been reported among farmers who applied paraquat in South Korea.” [pp. 283-4, 290-1]

Cha ES, Jeong M, Lee WJ (2014): Agricultural pesticide usage and prioritization in South Korea. Journal of Agromedicine; 19(3): 281-293.

(2013) Paraquat poisoning by skin absorption: Two case reports and a literature review [external Link]

“The present report describes two cases of paraquat poisoning by skin absorption. The cases involved contractual workers who were spraying paraquat in an orchard. Whilst spraying, some solution adhered to their skin. The skin developed erythema followed by blistering and hemorrhaging hemorrhagic diabrosis. Six days later the patients were admitted to the Department of Poisoning and Occupational Disease, Qilu Hospital of Shandong University (Jinan, China) with 3 and 2% total body surface area (TBSA) burns, respectively.”

Zhou Q et al (2013): Paraquat poisoning by skin absorption: Two case reports and a literature review. Experimental and Therapeutical Medicine 2013 Dec; 6(6): 1504–1506.

(2013) Acute kidney injury following paraquat poisoning in India

Paraquat is a widely used contact herbicide in India. Paraquat poisoning is associated with high mortality varying from 35% to 50%. Six cases of paraquat poisoning were treated in a center in India. Acute kidney injury developed in all the cases and mortality was 66%. Respiratory and multi-organ failures are the main causes for mortality. Five of the patients had taken paraquat to self-harm. One was exposed accidentally. Four of the patients died. The authors concluded: “Paraquat consumption is a common agent of suicidal poisoning in this part of India, resulting in very high morbidity and mortality. There is no specific antidote for paraquat poisoning and the mainstay of treatment is supportive. Acute kidney injury is the common complication of paraquat poisoning and needs to be recognized and treated promptly.”  

Pavan M. (2013): Acute kidney injury following paraquat poisoning in India. Iranian Journal of Kidney Diseases, 7(1): 64-66.

(2013) Paraquat poisoning: experience in hospital Taiping (year 2008 – October 2011)

“According to National Poison Centre, the number of paraquat poisoning cases has been rising in recent years. The sale of paraquat was banned from the year 2002 to 2006. Since 2006 when the ban was lifted, the number of paraquat poisoning cases reported has more than doubled up till the year 2008 where there was 7 times the number of cases reported compared to the years when it was banned(18). In a study conducted by National Poison Centre, suicide attempts were the most common circumstances of exposure with percentage as high as 73.8% (18). This shows that over the last few decades, suicide remains the leading cause for paraquat poisoning and the lifting of its sales ban is not addressing the issue but facilitating it. Even though the majority of paraquat poisoning in Taiping are intentional exposures, we must not neglect the other 26.6% of the cases which are accidental exposures. These exposures may be prevented if paraquat was not easily available as pesticides. Among the accidental exposures, unfortunately, 5 deaths were reported.” Reference (18): Sazaroni et al 2012 [see above]  

Tan JT, Letchuman Ramanathan G, Choy MP, Leela R, Lim BK (2013): Paraquat poisoning: experience in hospital Taiping (year 2008 – October 2011). Medical Journal of Malaysia; 68: 384-388.

(2012) Review on paraquat poisoning in Malaysia after lifting of ban

“A total of 278 calls involving paraquat were received during the period of the study [2005-2009]. The cases mainly involved adult males (68.4 %) and common among Indians (32.1 %) compared to Chinese (22 %) and Malay (22 %). Suicide attempts were the most common (73.8 %) circumstances of exposure. Accidental paraquat poisoning mostly involved exposure through ingestion (80.6 %), followed by inhalation (12.3 %) and cutaneous (7.1 %). The number of calls relating to paraquat exposure when it was banned was 67 (36 and 31 in 2005 and 2006 respectively). After its re-introduction, there was a marked increase in the number of cases: 39, 79 and 101 for 2007, 2008 and 2009, respectively.”  

Sazaroni MR, Awang R, Zyoud SH, Haslina H, Adilah MA, Asdariah M (2012): Review on paraquat poisoning in Malaysia after lifting of ban. 10th Annual Congress of the Asia-Pacific Association of Medical Toxicology, Penang, Malaysia, 12-14 Nov. 2011. Journal of Medical Toxicology; 8(2): abstract 93, p. 229.

(2012) Incidence of Acute Occupational Pesticide Poisoning Among Male Farmers in South Korea [external Link]

“The incidence rate of acute occupational pesticide poisoning was 24.7 (95% CI 22.1–27.2) per 100 male farmers, which corresponds to 209,512 cases across South Korea in 2010.[…] The most frequently reported agents related with acute occupational pesticide poisoning were cartap hydrochloride (n = 105) followed by paraquat dichloride (n = 78) [responsible for 14% of all poisonings] and fenobucarb (n = 69). […] Paraquat is a nonselective herbicide that has been most extensively used for weed control and is a major cause of self-poisoning deaths in South Korea [Lee et al., 2009]. Acute occupational paraquat poisoning mostly occurred during paraquat application and produced symptoms of irritation. Agricultural work conditions including backpack application, low tendency to use personal protective equipment, and a hot and humid work environment may aggregate paraquat exposure and poisoning in South Korea. Therefore, to prevent both occupational and non-occupational paraquat poisoning, restricting its availability, including through an outright ban, is an important undertaking required in South Korea.”

Lee WJ et al (2012): Incidence of Acute Occupational Pesticide Poisoning Among Male Farmers in South Korea. American Journal of Industrial Medicine 55:799–807 (2012).

(2011) Poisonings reported in Ecuador between 2008 and 2010 by Toxicology Information Centers

“Experts made a review of statistics generated from Toxicology Information Centers (TICs) in Ecuador from 2008 to 2010, in order to know their contribution to knowledge about performance of intoxications. This review was based on some publications made by many TICs in the world, and on the guidelines set by World Health Organization (WHO) and International Chemical Security Program (ICSP). Pesticide poisoning is a major public health problem in Ecuador, increasing at the rate of 15% up to 35% yearly.” Extract from Spanish text [translated by Stephanie Williamson, PAN UK]: “56% of 1,961 poisoning cases were due to pesticides. Organophosphates, rodenticides and carbamates were the three most frequent groups of all chemicals, including pesticides reported as causing acute poisoning. Paraquat was the eighth most common cause, with around 50 cases. The author noted that most of the reported pesticide poisonings were intentional [but did not give a breakdown by pesticide group] and highlighted that very toxic agents including trichlorfon (an OP), illegal rodenticide products, and paraquat accounted for more than one third of all poisonings reported to the TICs in Ecuador. Easy access via uncontrolled sales of household products is a major problem.”  

Meneses C. (2011): Las intoxicaciones en el Ecuador: Rol del Centro de Información Toxicológica en el período 2008 – 2010. EIDOS; 4: 58-68.

(2010) Pilot study on agricultural pesticide poisoning in Burkina Faso (PDF, 1.8 MB)

“Pesticide formulations containing paraquat (Gramoxone, Calloxone, Gramoquat super, Benaxone) have alone caused 59 incidents, accounting for 20% of the incidents […] With regard to incident frequency rate, GRAMOXONE alone (paraquat 200 g/l) has been implicated in 54 intoxication cases and is the product which has caused the most health problems among agricultural producers. 296 intoxication cases which occurred during pesticide treatments were reported among agricultural producers. Paraquat, which has been implicated in 59 poisoning incidents has been identified as the most hazardous active ingredient found in pesticide formulations. […] In view of their severe adverse effects on farmers, and in order to protect human health and the environment, special attention should be brought to active ingredients such as paraquat or endosulfan to effectively ban them and propose them for inclusion in Annex III of the Rotterdam Convention.”  

Secretariat of the Rotterdam Convention, FAO (2010): Pilot study on agricultural pesticide poisoning in Burkina Faso. (PDF, 1.8 MB)

(2009) Prognosis of paraquat-induced ocular surface injury: therapeutic effect of amniotic membrane transplantation [external Link]

Yoon et al. (2009) report 20 cases (26 eyes) in South Korea injured by splashing with Gramoxone (containing paraquat dichloride) that were irrigated with water immediately: "The grade of ocular surface injury was mild in 19 eyes (73.1%), moderate in 5 eyes (19.2%), and severe in 2 eyes (7.7%), and the mean epithelial defect area was 63.34 ±26.67 mm2 (range, 13.00–105.14 mm2). However, twelve patients (14 eyes) had to undergo an amniotic membrane transplantation combined with medical treatment and 8 patients (12 eyes) received medical treatment."

Yoon KC et al (2009): Prognosis of paraquat-induced ocular surface injury: therapeutic effect of amniotic membrane transplantation. Cornea 28(5):520-3.

(2009) Overview of Pesticide Poisoning in South Korea (PDF, 258 KB)

"The purpose of the article is to provide an overview of pesticide poisoning in South Korea and the relevant epidemiologic characteristics. During the period of 1996.2005, an approximate average of twenty-five hundred fatalities occurred per year due to pesticide poisoning. [...] Paraquat was the leading causative agent for pesticide poisoning, followed by organophosphate insecticides.

Paraquat was the principle causative agent in pesticide poisoning cases, and a variety of factors, including work-related, sociodemographic and seasonal factors were significantly related with pesticide poisoning.

Won Jin Lee and Eun Shil Cha (2009): Department of Preventive Medicine, College of Medicine, Graduate School of Public Health, Korea University, Seoul, South Korea. J Rural Med 2009; 4(2): 53.58.

(2008) Deaths from pesticide poisoning in Japan

“We analyzed the number of deaths due to poisoning by pesticides over 38 years through vital statistics published annually by the Ministry of Health, Labour and Welfare of the Japanese government, from 1968 through 2005. [...] Deaths from pesticide poisoning increased rapidly beginning in 1982, reached a peak in 1986 (death rate per 100,000 population: 2.6 in males and 1.7 in females) and declined gradually thereafter. In the most recent several years, these figures have declined to levels previously unseen (death rate per 100,000 population: 0.4 in males and 0.3 in females). [...] Deaths from pesticide poisoning were extremely well correlated to the history of paraquat. Through the 1985 Advisory Resolution on Paraquat Regulations by the Japanese Association of Rural Medicine and other public health-oriented efforts, the concentration of highly fatal paraquat formulations was reduced, leading to discontinuation of its production, customer identification was strictly enforced when purchasing pesticides, and people's safety consciousness regarding pesticides improved. We regard these developments as having had the greatest contribution to the reduction in deaths from pesticide poisoning. [...] Deaths from pesticide poisoning, observed quite frequently in the three prefectures of northern Kanto and Kagoshima Prefecture in 1986, continue to evidence a regional clustering properly termed ‘rural poisoning’.” [pp. 5, 9]    

Ito T, Nakamura Y (2008): Deaths from pesticide poisoning in Japan, 1968-2005: Data from vital statistics. Journal of Rural Medicine; 3(1): 5-9.  

(2007) A Fatal Case of Paraquat Poisoning Following Minimal Dermal Exposure [external link]

"Paraquat is a pesticide widely used in agriculture. Numerous cases of paraquat intoxication have been reported either accidentally or intentionally as a suicidal attempt. The most severe cases of paraquat poisoning refer to oral ingestion. Complications include respiratory, hepatic, and renal failure, and are usually fatal. Dermal exposure is less frequent and rarely fatal.

This article reports a case of an 81-year-old man with minimal skin burn after accidental paraquat exposure. The patient developed acute renal and respiratory failure and, despite aggressive treatment with hemodialysis, hemoperfusion, and mechanical ventilation, died two days later."

Soloukides A et al (2007): A Fatal Case of Paraquat Poisoning Following Minimal Dermal Exposure. Renal Failure 29(3):375-377.

(2007) Human poisoning in Thailand: The Ramathibodi Poison Center's experience (2001-2004) [external Link]

The study aimed at identifying poisoning and toxic exposure pattern, severity, and clinical outcome in Thailand during 2001 to 2004.

It found that "the death rate of all exposure was 5.5%. Pesticides cause more severe clinical course and the highest death rate (10.0%)."

Conclusion: "Features of poisoning in Thailand were different from those in Western countries. Pesticide poisoning was the major problem in Thailand. Intentional suicide was the major circumstance of poison exposure in adults, but accidental exposure was the major reason of exposure in children. Among the substances most frequently implicated as causes of death ranks Paraquat on the second position (376 poisoning cases, 150 deaths)."

Wananukul W et al (2007): Human poisoning in Thailand: The Ramathibodi Poison Center's experience (2001-2004). Clinical Toxicology 45(5):582 - 588.

(2007) Presentations of patients of poisoning and predictors of poisoning-related fatality: Findings from a hospital-based prospective study [external Link]

"Poisoning is a significant public health problem worldwide and is one of the most common reasons for visiting emergency departments (EDs), but factors that help to predict overall poisoning-related fatality have rarely been lucidated. Using 1'512 subjects from a hospital-based study, they sought to describe the demographic and clinical characteristics of poisoning patients and to identify predictors for poisoning-related fatality.


Paraquat exposure caused the highest fatality rate (31 of 43 [72.1%] exposed) and was the major agent involved in fatalities (46.3%).


Paraquat (24% w/v) is one of the most commonly used herbicides in Taiwan and has been the most common lethal agent of poisoning for a long time [2,24,44,45]. "

Lee HL et al (2008) Presentations of patients of poisoning and predictors of poisoning-related fatality: Findings from a hospital-based prospective study. BMC Public Health 8:7

(2007) Hepatotoxicity Related to Paraquat and Diquat Absorption Through Intact Skin [external Link]

"The patient, a 69-year-old man, a farmer, applied a toxic mix of paraquat/diquat by knapsack sprayers, under a high-temperature and -humidity environment (35–40◦C), wearing light clothing and no appropriate protection (no gloves, rubber aprons, or goggles were used). He was admitted because of continuous right-sided and central abdominal pain. The clinical course was compatible with some previously reported patterns of hepatoxicity as described in experimental models and humans. The case was classified as a probable bipyridyl-induced adverse reaction, according to the Naranjo probability scale (score=7). Bipyridyl herbicides generate superoxide anions and subsequently other redox products that can induce lipid peroxidation.
Both the high lipid peroxide levels observed in the patient and the development of macrocitic anemia are compatible with diquat/paraquat poisoning as previously reported.

Furthermore, the pathological findings are compatible with those observed in severe hepatotoxicity and, conversely, do not suggest alternative causes, such as alcohol, autonimmnunity, and virus.

This case is relevant, because to the knowledge of the scientists it is the first time that a severe liver injury by paraquat/diquat is presented without coexisting lung and kidney toxicity and as a consequence of environmental intact skin exposure— in contrast to a previous case of human hepatotoxicity, which required damaged skin for paraquat absorption."

Peiró AM et al (2007): Hepatotoxicity Related to Paraquat and Diquat Absorption Through Intact Skin. Digestive Diseases and Sciences. Volume 52, Number 11. November 2007.

(2005) Hospital-based survey of pesticide poisoning in Japan [external Link]

Among 65 work-related pesticide poisonings registered in Japanese hospitals during 1998-2000, 13 cases or 20% were caused by diquat and paraquat. 53% of the cases were acute or subacute poisonings, followed by acute dermatitis (24%), chemical burns (15%) and eye injury (6%). In 11% of the cases patients did not recover.

The author states that it would be appropriate to assign paraquat to class I.

Nagami H et al (2005) Hospital-based survey of pesticide poisoning in Japan, 1998-2002. International Journal of Occupational and Environmental Health 11(2), 180-184, 2005.

(2004) Agricultural pesticide-related poisonings in Italy: cases reported to the Poison Control Centre of Milan in 2000-2001 [external Link]

Paraquat was among six pesticides most frequently associated with non-fatal poisonings, which were referred to the main poison center in Itlaly in 2000-2001. 46 poisonings out of a total of 872 were due to paraquat.

Davanzo F et al (2004) Agricultural pesticide-related poisonings in Italy: cases reported to the Poison Control Centre of Milan in 2000-2001 [Article in Italian], Epidemiologia e Prevenzione 28(6), 330-337, 2004.

(2004) Review of clinical and toxicological features of acute pesticide poisonings in Crete (Greece) during the period 1991-2001 [external Link]

"In Crete (Grece) pesticide poisonings have increased during 1991-2001 to 1700 cases (fatal and non-fatal) per year and compounds causing concern were organosphates and paraquat; 45% of the cases were accidental, 40% occupational and 12% suicidal. In a non-fatal case a worker was acutely poisoned with paraquat by skin absorption during spraying. Four case were caused by accidental ingestion of paraquat."

Bertsias GK et al (2004) Review of clinical and toxicological features of acute pesticide poisonings in Crete (Greece) during the period 1991-2001. Medical Science Monitor 10(11), CR 622-627, 2004.

(2003) Did you take your poison today? [external Link]

In Thailand a worker who had sprayed paraquat during three months developed skin burns. When he sought medical care because of skin burns and cough the cause of these effects was not recognised. After three more months of spraying he was too ill to work and died later on.

Danish International Development Assistance - IPM DANIDA (2003) Did you take your poison today? Bangkok 2003, 10.

(2002) Poisoned and silenced: a study of pesticide poisoning in the plantations (PDF, 3.1 MB)

"The current study , though not entirely conclusive is a pioneering attempt to document the health related problems of women sprayers on plantations in Malaysia. The findings raise critical issues regarding the safety and health of workers on plantations that need further in-depth scrutiny and exploration."

Tenaganita and the Pesticide Action Network Malaysia and the Pacific (2002) A study of pesticide poisoning in the plantations. March 2002. (PDF, 3.1 MB)

(2001) Paraquat in developing countries (PDF, 172 KB)

"In developing countries the factors that determine exposure to paraquat continue to be the same today as thirty years ago. High rates of acute poisoning with paraquat, both suicidal and unintentional, have been documented in many countries and in recent years. Local-ised skin damage (including dermatoses and burns), eye injuries, nail damage and nose-bleed occur in a high proportion of exposed workers. Damage to the lungs may be delayed after the absorption of paraquat and long-term exposure may lead to Parkinsons’ disease. There is also evidence that paraquat may cause skin cancer. Regulatory agencies have not fully recognised either the inherent toxicity of paraquat for humans or the particular risks derived from exposures in developing countries. In developing countries there is a need for indepent risk assessment and for a precautionary approach to prevent harm from dangerous pesticides such as paraquat."

Wesseling C et al (2001) Paraquat in developing countries (PDF, 172 KB), International Journal of Occupational Health 7(4), 275-286.

(1995) Risk factors for occupational illnesses associated with the use of paraquat (1,1’-dimethyl-4,4’-bipyridylium dichloride) in California [external Link]

"Between 1971 and 1985 in California 231 cases of illness due to paraquat were reported, corresponding to c. 14 per year (median value, range 1-33; exposure included other pesticides besides paraquat in 23.8% of cases). The majority of illness cases (38.5%) associated with paraquat were systemic (with symptoms of acute poisoning and respiratory symptoms), eye and skin illnesses occurred in 32% and 26% of cases, respectively, and local respiratory symptoms accounted for 3.5% of cases. Most illness cases (39.1%) occurred during handling of spray equipment (by cleaning, due to a malfunction such as leakage or splashes during loading). One third of illnesses were due to various factors including 12.4 % environmental causes (e.g. change of wind, spray drift), 11% accidents and 7.1% accidental contact with paraquat during the spraying or handling. 55 of the 231 cases were associated with loss of workdays (median number 2 days, range 1-30 d), 11 cases were hospitalised and ten of these were systemic (median duration of hospitalisation was 7 days, range 1-17 d). Between 1981 and 1985 the rate of paraquat-related illness cases associated with manual spraying was 18 times higher than with general ground application, while other factors with a higher risk of illness were the crop type (cotton and fruit trees especially) and season. Higher illness rates in summer may arise from less protective clothing worn, different physiological response at higher temperatures or increased paraquat absorption."

Weinbaum Z, Samuels SJ, and Schenker MB (1995) Risk factors for occupational illnesses associated with the use of paraquat (1,1’-dimethyl-4,4’-bipyridylium dichloride) in California. Archives of Environmental Health 50(5), 341-348, 1995.

(1993) Pesticide poisonings in Costa Rica (PDF, 6.5 MB)

It has been estimated that in Costa Rica the proportion of agricultural workers treated in hospital and by other medical personnel for occupational systemic poisoning (all types of pesticides) each year was about 1.5%, while this figure could be about three times higher if also non-treated poisonings were accounted for. By matching the figures of the hospital registry with those of the forensic department the under-registration of fatalities was esti-mated at about 52% and was more pronounced in remote areas. In the banana-growing region of Costa Rica after matching of figures the already high average mortality rate dou-bled from 2.4 to 4.8 per 100'000 inhabitants per year and paraquat was the causal agent that was identified most frequently. Among agricultural workers the average annual rate of hospitalisations due to pesticide poisoning was between 115 and 130 per 100’000 work-ers, more than 13 times higher than for the general population. The relative risk for hospi-talisation was 1.7 higher for wage-earning workers than for independent farmers. Between 1980 and 1986 the hospital discharge registry listed 3’330 cases of pesticide poisoning. About 50% of the 2’566 poisonings where the cause could be identified were occupational. In the year 1986 paraquat caused 21% of 1’800 occupational accidents (acute poisonings, skin and eye injuries).

Wesseling C, Castillo L, and Elinder C-G (1993) Pesticide poisonings in Costa Rica. Scandinavian Journal of Work, Environment and Health 19, 227-235, 1993. (PDF, 6.5 MB)

Studies on Paraquat's long-term effects on the lungs

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(2012) Paraquat application and respiratory health effects among South Korean farmers [external Link]

In June 2012, the international peer-reviewed journal Occupational & Environmental Medicine published an article about the association between paraquat application and adverse respiratory health effects among farmers. We cite from the study: 

"The risks of self-reported physician-diagnosed asthma, chronic obstructive pulmonary disease and allergic rhinitis were non-significantly increased among paraquat-applying farmers compared with non-paraquat-applying farmers. Although the results of a pulmonary function test fell within normal limits, a decline in forced vital capacity and forced expiratory volume in one second was apparent among paraquat-applying farmers compared with non-paraquat-applying farmers. Forced vital capacity and forced expiratory volume in one second significantly decreased with each unit increase in years of paraquat application.

Paraquat-applying farmers showed a significant exposure–response relationship between restrictive ventilatory defects and paraquat application years (p trend=0.015) or lifetime days of application (p trend=0.007).

The findings suggest a possible association between paraquat application and adverse respiratory health effects among farmers."

Cha ES et al. (2012). Paraquat application and respiratory health effects among South Korean farmers. Occup Environ Med. 2012 Jun;69(6):398-403.

(2004) Pulmonary function and exercise-associated changes with chronic low-level paraquat exposure [external Link]

A study with 338 workers from plantations in Costa Rica found that paraquat exposure was associated with an increase in oxygen desaturation and ventilatory equivalent for CO2: "Ventilatory equivalent for CO2 (respired air volume for uptake of certain amount of oxy-gen), arterial oxygen desaturation (difference between oxygen saturation of blood at rest and maximum exercise) and carbon monoxide diffusion capacity were measured, the lung function was tested and cumulative exposure to paraquat was estimated for individual workers. The diffusion capacity and lung function in spirometric tests did not differ between paraquat handlers and non-handlers.

No clinically significant increases in restrictive lung disease or interstitial thickening were observed, and the association with chronic bronchi-tis, wheeze or ever having a diagnosis of asthma was not statistically significant. The index for cumulative exposure to paraquat was associated with an increased relative risk for chronic cough of 1.8 (95% confidence interval: 1.0-3.1) and with an increased relative risk for shortness of breath accompanied by wheeze of 2.3 (95% CI: 1.2-5.1). Paraquat expo-sure was associated with an increase in the ventilatory equivalent for CO2 in a statistically significant manner (this factor accounted for a small portion of total variance); the paraquat exposure index was associated with oxygen desaturation (5% or more) with a relative risk of 1.7 (95% CI: 0.9-3.0). The two latter findings suggested that among the workers in this study exposure to paraquat may be associated with subclinical abnormalities in gas exchange of the lung."

Schenker MB et al. (2004). Pulmonary function and exercise-associated changes with chronic low-level paraquat exposure. American Journal of Respiratory and Critical Care Medicine 170(7), 773-779, 2004.

(2002) Chemical predictors of wheeze [external Link]

In a study of over 20’000 certified pesticide applicators in Iowa and North Carolina, the as-sociation between wheeze (whistling in the chest) and pesticide use was examined. It was found that applicators who used paraquat had elevated odds ratios (OR) for wheeze: "For paraquat, a chemical not associated with animal exposure, the OR for wheeze among nonasthmatics was 3.3 (95% confidence interval [CI] = 1.4, 7.6)". The adjusted OR for wheeze among farmers who used paraquat was 1.27 (95% CI = 1.04, 1.56; p < 0.01).

The authors pointed out: "Paraquat exposure at high doses causes pulmonary fibrosis in hu-mans and animals independent of exposure route (27). A variety of respiratory effects have been observed among occupationally exposed subjects. (...) Among our subjects, paraquat was significantly associated with wheeze in a dose-dependent fashion. Although the mechanism of action of paraquat for less severe respiratory symptoms, such as cough and wheeze, is not known, paraquat is a known skin irritant and may also irritate the mucosal surface of the lung (21)."

Hoppin JA, et al. (2002). Chemical predictors of wheeze among farmer pesticide applicators in the Agricultural Health Study, American Journal of Respiratory and Critical Care Medicine 165(5), 683-689, 2002.

(1999) Long term respiratory health effects of the herbicide, paraquat, among workers in the Western Cape [external Link]

A study in South Africa was carried out with 62 herbicide sprayers (fruit farmers) who had different levels of previous exposure to paraquat. For the individual workers the cumulative paraquat exposure was assessed in interviews and from expert knowledge, and data on respiratory symptoms was collected with the aid of a standard questionnaire followed by a medical examination. The lung function (forced expiratory volume in 1 second, forced vital capacity) and transfer of carbon monoxide (CO) were measured and compared with reference values of the European Community of Coal and Steel (ECCS). Radiographs of the chest were taken to exclude cases of tuberculosis.

Lung capacities were found to be 10-15% lower than EECS reference values. Respiratory symptoms (regular coughing, expectoration, breathlessness) were not significantly related to exposure to paraquat, while desaturation of arterial oxygen during exercise (difference during resting and maximum exercise level) was significantly related to long-term paraquat exposure. Although they contributed to a small proportion of variance, weight, intensity of exposure to paraquat (days per year) and the cumulative exposure to paraquat (total of days) were signignificant factors for oxygen desaturation (p< 0.05) in a regression model. Excluding workers from the sample who reported the use of other herbicides besides paraquat did not weaken the dose-dependent association. This effect was independent of recent paraquat exposure and in 18.8% of workers the level of desaturation was over 5%, which is regarded as clinically notable.

Dalvie MA et al. (1999). Long term respiratory health effects of the herbicide, paraquat, among workers in the Western Cape. Occupational and Environmental Medicine 56(6), 391-396, 1999.

(1997) Respiratory symptoms, spirometry and chronic occupational paraquat exposure [external Link]

In Nicaragua 134 plantation workers who had been exposed to paraquat (0.1-0.2%) over more than 2 years during spraying were questioned and their lung function was examined (forced expiratory volume in 1 second, forced vital capacity). More than half of the workers (53%) had experienced a skin rash or burn from paraquat exposure, 25% had nosebleeds, 58% had nail damage, 42% had splashed their eyes and in several workers this lead to a continued blurred vision, in one case to an opacified cornea.

A group of more intensely exposed workers included those who previously experienced rash or skin burn that was attributed to paraquat. Abnormal results for the lung function were not significantly related to paraquat exposure, except for slightly increased relative risk of 1.3 (not statistically significant) for having an obstructive defect among the more intensely exposed workers. Among the exposed workers there was an increased prevalence of breathlessness (dyspnea) during exertion and this effect was related to intensity of paraquat exposure in a dose-dependent way (adjusted for smoking, age and gender). For grade 3 dyspnea in the more intensely exposed workers the relative risk was largest with 4.6 (95% confidence interval: 2.4-9.0). Among the more intensely exposed workers the prevalence of chronic bronchitis was increased with a relative risk of 2.0 (not statistically significant), and the prevalence of episodic shortness of breath accompanied by wheezing was increased with a relative risk of 2.9 (95% CI: 1.4-6.3). These results suggested that there was an effect of long-term paraquat exposure on respiratory health.

It was presumed that subacute paraquat exposure (over a longer period of time and to relatively low doses) may lead to a decreased diffusing capacity, often with normal forced vital capacity, and does not cause lung fibrosis except in cases where exposure is acute and substantial (Levin et al 1979).

Castro-Gutierrez N et al. (1997). Respiratory symptoms, spirometry and chronic occupational paraquat exposure. Scandinavian Journal of Work Environment and Health 23, 421-427, 1997.

(1993) An epidemiological study of the health of Sri Lankan tea plantation workers associated with long term exposure to paraquat [external Link]

In Sri Lanka a study was carried out with 85 plantation workers who had been spraying paraquat (usually at concentrations of 0.2-0.08%) over an average period of 12 years. To assess the potential risks from long-term exposures workers’ lungs were tested by meas-uring lung functions (forced vital capacity, maximum expiratory flow volume, peak expira-tory flow, transfer of CO), and the function of liver and kidneys was monitored (blood levels of urea, creatinine, certain enzymes). A larger proportion of spray men (23.6%) had skin damages than unexposed factory workers (11.8%) or general workers (15.2%). The incidence of eye damage was similar in spray men and general workers but not reported by factory workers. Nosebleeds occurred in three spray men, one factory worker but not among general workers.

It was found there were no statistically significant or clinically important differences between the groups of workers for any measured parameter except for a certain enzyme. Aspartate transferase activities in blood were positively associated with the total number of spraying days and number of spraying days during the past five years (statistically significant). The increase in aspartate transferase levels was considered to be not clinically significant; this enzyme is used to monitor liver function.

Signs of bronchial obstruction were seen with chest radiography in 9 general and 6 factory workers and in 3 spray men, while respiratory symptoms (mainly cough) were reported by six out of those 9 general workers, by four out of the 6 general workers and by none of the spray men.

Senanayake N et al. (1993). An epidemiological study of the health of Sri Lankan tea plantation workers associated with long term exposure to paraquat. British Journal of Industrial Medicine 50(3), 257-263, 1993.

(1990) Pulmonary obstructive disease in a population using paraquat in Colombia

In Antioquia, Colombia, 11% of 5'483 people interviewed in 1986 used paraquat (15.2% of the rural and 4.4% of urban population) and practically only knapsack sprayers were used. 17% reported having experienced illness during the 2 weeks before the study and 7.2% of the health problems were related to the respiratory system (mostly coughing, runny nose, expectoration, dyspnea or shortness of breathing). 62.5% of participants had the problems for less than 15 days, 22.7% between 2 and 12 weeks and 10.1% for at least 1 year. A subsample of 896 people was medically examined and a physician made the following diagnosis: chronic bronchitis accounted for 12.8% of the responses, asthma for 2.7% and tuberculosis for 0.2%. In the subsample the relative risk for chronic obstructive pulmonary disease in paraquat users was three times higher than in non-users and the association was strongly significant for smokers, indicating a synergic effect. Chronic bronchitis was more prevalent among paraquat users than non-users in smokers and non-smokers. The attributable risk of chronic bronchitis to paraquat use was 84 cases per 1'000 people. Among paraquat users with a high level of exposure the prevalence of colds affecting the chest was increased.

A follow-up study was carried out in the same area as an earlier study by Arroyave (1990). It included 1’157 children who had a family member who used paraquat. The exposure to paraquat was associated with the incidence of chest cold and the relative risk was almost three times higher in the group of children with a high level of paraquat expo-sure, and was increased by a factor two or more for the groups with a low and moderate level of exposure, even after confounding factors were taken into account. The odds ratios for chest cold (and 95% confidence levels) were 2.01 (1.10, 3.67) at the low level, 2.2 (1.13, 4.27) at the moderate level, and 2.85 (1.41, 5.75) (high level of exposure). International Development Research Center (IDRC), Paraquat intoxication (Colombia). Ottawa, Canada 2003.

Arroyave ME (1990). Pulmonary obstructive disease in a population using paraquat in Colombia. In: Forget G, Goodman T, and de Villiers A (eds), Impact of pesticide use on health in developing countries. Proceedings of a symposium held in Ottawa, Canada, 17-20 September 1990, 85-93, Ottawa, Canada: Intl. Development Research Centre 1990.

Studies on Paraquat's long term effect on the brain

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(2011) Rotenone, Paraquat and Parkinson's Disease [external Link]

"We assessed lifetime use of pesticides selected by mechanism in a case-control study nested in the Agricultural Health Study (AHS). Parkinson's Disease was diagnosed by movement disorders specialists. Controls were a stratified random sample of all AHS participants frequency-matched to cases by age, gender, and state at approximately 3 controls: 1 case.

In 110 Parkinson's Disease cases and 358 controls, Parkinson's Disease (PD) was associated with use of a group of pesticides that inhibit mitochondrial Complex I (odds ratio (OD): 1.7, 95% convidence intervall (CI) 1.0, 2.8) including rotenone (OR 2.5, 95% CI 1.3, 4.7), and with use of a group of pesticides that cause oxidative stress (OR 2.0, 95% CI 1.2, 3.6) including paraquat (OR 2.5, 95% CI 1.4, 4.7). Conclusions: Parkinson's Disease was positively associated with two groups of pesticides defined by mechanisms implicated experimentally: those which impair mitochondrial function and those which increase oxidative stress, supporting a role for these mechanisms in PD pathophysiology."

Tanner CM et al. (2011): Rotenone, Paraquat and Parkinson's Disease. Environmental Health Perspective 2011 Jan 26.

(2010) The toxic influence of paraquat on hippocampus of mice: Involvement of oxidative stress [external Link]

"Environmental paraquat (PQ) exposure has been suggested to be a potential risk factor for neurodegenerative disorders such as Parkinson’s disease (PD). The hippocampus plays an important role in the learning and memory abilities of the brain. This study aims to demonstrate the effect and mechanism of paraquat toxicity on the hippocampus of mice.

Paraquat was given orally, once a day and for 28 consecutive days. After treatment with paraquat, the hippocampus cells were found to be irregular and the cytoplasm was found to be condensed. The nissl bodies were reduced and apoptotic or necrotic neuron was observed. Morris water maze tests showed that the response latency increased significantly in animals that were administered paraquat. The level of malondialdehyde (MDA) and generation of reactive oxygen species (ROS) in the hippocampus of mice increased significantly. The activities of total superoxide dismutase (SOD) in the hippocampus of mice decreased significantly after treatment with paraquat. An analysis of the energy metabolism of hippocampus showed that the concentration of adenosine-triphosphate (ATP) decreased significantly in the hippocampus after treatment with paraquat, which implied that the energy synthesis of mitochondria with hippocampal neurocytes declined. The level of 8-OHdG in mitochondrial DNA (mtDNA) increased significantly after treatment with paraquat, which indicated that the oxidative damage of mtDNA increased.

This suggests that paraquat had a toxic influence on the hippocampus of mice, and that the mechanism of toxicity might be associated with the mitochondrial injury of hippocampal neurocytes induced by oxidative stress."

Chen Q et al. (2010): The toxic influence of paraquat on hippocampus of mice: Involvement of oxidative stress. Neurotoxicology 31:310–316.

(2009) Parkinson’s Disease and Residential Exposure to Maneb and Paraquat From Agricultural Applications in the Central Valley of California [external Link]

"The authors developed and validated an exposure assessment tool based on geographic information systems (GIS) that integrated information from California Pesticide Use Reports and land-use maps to estimate historical exposure to agricultural pesticides in the residential environment.

In 1998–2007, the authors enrolled 368 incident Parkinson's Disease (PD) cases and 341 population controls from the Central Valley of California in a case-control study. They generated estimates for maneb and paraquat exposures incurred between 1974 and 1999. Exposure to both pesticides within 500 m of the home increased PD risk by 75% (95% confidence interval (CI): 1.13, 2.73). Persons aged ± 60 years at the time of diagnosis were at much higher risk when exposed to either maneb or paraquat alone (odds ratio = 2.27, 95% CI: 0.91, 5.70) or to both pesticides in combination (odds ratio = 4.17, 95% CI: 1.15, 15.16) in 1974–1989.

This study provides evidence that exposure to a combination of maneb and paraquat increases PD risk, particularly in younger subjects and/or when exposure occurs at younger ages."

Costello S et al. (2009): Parkinson’s Disease and Residential Exposure to Maneb and Paraquat From Agricultural Applications in the Central Valley of California. American Journal of Epidemiology Vol. 169, No. 8.

(2009) Occupation and Risk of Parkinsonism (PDF, 113 KB)

"Occupational use of pesticides was associated with an almost 80% greater risk of parkinsonism. Growing evidence suggests a causal association between pesticide use and parkinsonism. However, the term 'pesticide' is broad and includes chemicals with varied mechanisms.

Because few investigations have identified specific pesticides, we studied 8 pesticides with high neurotoxic plausibility based on laboratory findings. Use of these pesticides was associated with higher risk of parkinsonism, more than double that in those not exposed.

Three individual compounds, the organochlorine 2,4- dichlorophenoxyacetic acid, the herbicide paraquat, and the insecticide and acaricide permethrin, were associated with more than a 3-fold increased risk of disease, although precision was poor for paraquat and permethrin."

Tanner CM et al. (2009): Occupation and Risk of Parkinsonism. A Multicenter Case-Control Study. Archives of Neurology 66 (9):1106-1113 (PDF, 113 KB)

(2009) Pesticides plus genetics increase risk of Parkinson's disease [external Link]

"The investigators enrolled 324 people with newly diagnosed Parkinson’s disease and 334 healthy people, as controls, living in California’s agricultural Central Valley.

The authors were able to identify people who had lived within 500 yards of fields where the pesticides maneb and paraquat had been used at any time during the previous 35 years. Individuals were also interviewed to determine whether they had ever been exposed to pesticides through their jobs. DNA samples were extracted from blood samples or cheek swabs to detect genetic variability in the dopamine transporter gene.

  • People with one susceptible allele who lived near fields where maneb and paraquat were used had a three-fold increased risk of developing Parkinson’s disease.
  • People who had two or more susceptible genetic variants (alleles) had almost a 5-fold increase in risk.
  • Importantly, people who were genetically susceptible but had no pesticide exposure showed no increased risk.
  • Parkinson’s disease, like many diseases, appears to be caused by a complex interaction of genetic and environmental factors."

Ritz BR et al. (2009): Dopamine Transporter Genetic Variants and Pesticides in Parkinson’s Disease. Environmental Health Perspectives Volume 117. Number 6. June 2009

(2007) Pesticide Exposure and Self-reported Parkinson’s Disease in the Agricultural Health Study (PDF, 148 KB)

"Exposure to specific chemicals Considering only chemicals for which there were four or more exposed cases, odds ratios for prevalent PD were elevated
(>=1.4) for the herbicides pendimethalin, paraquat, and cyanazine and the fumigants carbon disulfide/carbon tetrachloride and ethylene dibromide (table 4)."

Kamel F et al. (2007): Pesticide Exposure and Self-reported Parkinson’s Disease in the Agricultural Health Study. American Journal of Epidemiology 165:364–374. (PDF, 148 KB)

(2005) Pesticides and risk of Parkinson disease: a population-based case-control study [external Link]

A study in the US on factors influencing Parkinson’s disease reported relative risks of 1.41 and 1.67 (not statistically significant) for herbicide and paraquat exposure, respectively (Firestone et al 2005). Workers in these studies were exposed to different pesticides and this makes it more difficult to establish a significant association for individual pesticides.

Firestone JA et al. (2005) Pesticides and risk of Parkinson disease: a population-based case-control study. Archives of Neurology 62(1), 91-95, 2005.

(2003) Paraquat exposure and Parkinson's disease [external Link]

This fact sheet summarises findings from several studies on the potential link between paraquat and the development of Parkinsons’ disease in users.

Pesticide Action Network (PAN) Germany (2003). Paraquat exposure and Parkinson's disease - a Factsheet.

(1997) Environmental risk factors and Parkinson's disease: a case-control study in Taiwan [external Link]

The risk for Parkinson’s disease (PD) was greater among farmers in Taiwan who had used paraquat and other herbicides than among farmers who had used herbicides other than paraquat.

Liou HH et al. (1997). Environmental risk factors and Parkinson's disease: a case-control study in Taiwan. Neurology 48(6), 1583-1588, 1997.

Studies on Suicide by ingesting Paraquat

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(2014) Manifestation, complications and clinical outcome in paraquat poison? A hospital based study in a rural area of Karnataka (India) [external Link]

“Paraquat is a broad spectrum liquid herbicide, leading to severe and often fatal toxicity. Most cases of intoxication, especially in third world countries are due to suicidal attempts rather than homicidal or accidental exposure, because of its widespread availability and relative low cost. Diagnosis is often difficult in the absence of proper history, nonspecific clinical features, and lack of diagnostic tests. […] Out of eight cases six patients died despite intensive treatment. Most deaths occurred within in two weeks. […] Paraquat poison is [a] highly lethal or deadly poison with [a] very high mortality rate of around 70 to 80%. Also [the] presentation may be variable and sometimes patient[s] may present […] mild symptoms with normal vitals or may remain asymptomatic for [the] first few days. Although even in such cases morbidity and mortality of poison may be very high.”

Banday TH et al (2014): Manifestation, complications and clinical outcome in paraquat poison? A hospital based study in a rural area of Karnataka. Journal of Environmental and Occupational Science 2014; 3(1):21-24.

(2010) Fatality in paraquat poisoning (PDF, 384 KB)

Introduction: "Acute paraquat (PQ) poisoning continues to be a major public health concern in many developing countries. This study was designed to evaluate the data on cases of acute PQ poisoning and compare the different variables between survivors and non-survivors.Methods: All patients of PQ poisoning who were admitted to the poisoning emergency department during the past five years were retrospectively evaluated. The different variables that were compared between survivors and non-survivors included age and gender, the time from ingestion of PQ to hospital admission, the amount of PQ ingested, occurrence of vomiting after ingestion, the time from hospital admission to initiation of haemodialysis, the length of hospital stay and the outcomes."

Results: "A total of 29 patients were evaluated. The in-hospital fatality rate was 55.2 percent. No significant differences were observed between survivors and non-survivors with regard to the patient characteristics. Most of the patients who died had ingested more than 40 mg/kg of 20 percent PQ (62.5 percent). There was a correlation between the outcome of patients and vomiting (p-value is 0.05; correlation coefficient is 0.45) and age (p-value is 0.013; correlation coefficient is 0.56)."

Conclusion: "A large amount of ingested PQ, vomiting and age may be important variables to consider in association with the high fatality rate of PQ poisoning."

Sabzghabaee A M, Eizadi-Mood N, Montazeri K, Yaraghi A, Golabi M (2010): Fatality in paraquat poisoning. Singapore Medical Journal

(2010) Acute Human Lethal Toxicity of Agricultural Pesticides: A Prospective Cohort Study [external Link]

"Agricultural pesticide poisoning is a major public health problem in the developing world, killing at least 250,000–370,000 people each year. Targeted pesticide restrictions in Sri Lanka over the last 20 years have reduced pesticide deaths by 50% without decreasing agricultural output. We examined the case fatality of different agricultural pesticides in a prospective cohort of patients. Identification of the pesticide ingested was based on history or positive identification of the container. There was a large variation in case fatality between pesticides—from 0% to 42% (paraquat dichloride). Anti-Cholinesterase insecticides and the herbicides paraquat, MCPA, propanil, and glyphosate accounted for 94% of admissions and 98% of deaths. For those ingesting an identified pesticide, just three compounds with relatively high case fatality (paraquat, dimethoate, fenthion) were responsible for 17.6% of total admissions but 47% of the total deaths.Basing regulation on human toxicity will make pesticide poisoning less hazardous, preventing hundreds of thousands of deaths globally without compromising agricultural needs."

Dawson AH, Eddleston M, Senarathna L, Mohamed F, Gawarammana I, Bowe SJ, Manuweera G, Buckley NA (2010): Acute Human Lethal Toxicity of Agricultural Pesticides: A Prospective Cohort Study. PLoS Medicine 7(10): e1000357.

(2010) An Urgent Need to Restrict Access to Pesticides Based on Human Lethality [external Link]

"Over the past two decades, a series of targeted legislative initiatives in Sri Lanka culminated in the withdrawal of World Health Organization (WHO) class I pesticides and, eventually, endosulfan, resulting in a fall in the incidence of suicide by 50%. This decline in suicide by pesticides occurred without a compensatory increase in suicide by other methods. Other notable examples of large-scale population level reductions in suicide incidence due to decreased access to and/or availability of highly lethal and commonly used suicide methods (an approach known as means restriction) have occurred in Samoa and the United Kingdom. In Western Samoa the rise and fall of suicides, but not suicide attempts, closely tracked the introduction and later banning of paraquat on the island. In the UK during the 1960s, a shift in the source of household heating away from coal-gas (capable of producing lethal levels of carbon monoxide) to detoxified natural gas was followed by a30% decline in national suicide rates. As in Sri Lanka, the dramatic decline in overall suicide incidence in the UK was driven by a decline in method-specific suicides (i.e., in carbon monoxide suicides) without compensatory increases in suicide by other (i.e., non-carbon monoxide related) methods. This natural experiment in the UK is known as the ‘‘Coal Gas Story’’, and is perhaps the most famous example of means restriction at the population level."

Miller M & Bhalle K (2010): An Urgent Need to Restrict Access to Pesticides Based on Human Lethality. PLoS Medicine 7(10): e1000358.

(2009) Paraquat Intoxication in Subjects Who Attempt Suicide: Why They Chose Paraquat [external Link]

Background/Aims: "Paraquat (PQ) has been used in suicide attempts; an estimated 2,000 toxic ingestions occur annually, with 60-70% mortality. We sought to determine why PQ is such a common agent for suicide attempts in Korea."

Methods: "We analyzed 250 cases (143 males, 107 females) of attempted suicide by PQ ingestion from January to December 2007. The procurement of the PQ was divided into two categories: purchased and preexisting."

Results: "Men were more likely to have purchased PQ than women (66% vs. 22%, p=0.042). Additionally, men were more likely to be unmarried (n=34, 23.9% vs. n=10, 9.3%) or divorced or separated (n=16, 11.3% vs. n=5, 4.6%) than the women (p<0.001). The group who intentionally selected PQ (38.4%) consisted of 96 cases (54 males, 42 females) and the group who did not intentionally select PQ (61.6%) included 154 cases (89 males, 65 females). The incidence of PQ purchase was higher in the intentional selection PQ group (46.9% vs. 18.2%, p<0.01)."

Conclusions: "Only 38% of patients who attempted suicide with PQ intentionally selected PQ. Thus, greater control of PQ availability is needed, especially in patients at risk."

Seok S-J, Gil H-W, Jeong D-S, Yang J-O, Lee E-Y & Hong S-Y (2009): Paraquat Intoxication in Subjects Who Attempt Suicide: Why They Chose Paraquat. The Korean Journal of Internal Medicine 3(24):247-251.

(2007) Global distribution of fatal pesticide self-poisoning (PDF, 702 KB)

Results: "We conservatively estimate that there are 258,234 (plausible range 233,997 to 325,907) deaths from pesticide self-poisoning worldwide each year, accounting for 30% (range 27% to 37%) of suicides globally. Official data from India probably underestimate the incidence of suicides; applying evidence-based corrections to India's official data, our estimate for world suicides using pesticides increases to 371,594 (range 347,357 to 439,267). The proportion of all suicides using pesticides varies from 4% in the European Region to over 50% in the Western Pacific Region but this proportion is not concordant with the volume of pesticides sold in each region; it is the pattern of pesticide use and the toxicity of the products, not the quantity used, that influences the likelihood they will be used in acts of fatal self-harm."

Conclusion: "Pesticide self-poisoning accounts for about one-third of the world's suicides. Epidemiological and toxicological data suggest that many of these deaths might be prevented if (a) the use of pesticides most toxic to humans was restricted, (b) pesticides could be safely stored in rural communities, and (c) the accessibility and quality of care for poisoning could be improved."

Gunnell D, Eddleston M, Phillips MR, Konradsen F (2007): The global distribution of fatal pesticide self-poisoning: Systematic review. BMC Public Health 7:357

(2006) Deaths from Pesticide Poisoning: a Global Response (PDF, 295 KB)

"Self-poisoning with pesticides accounts for about a third of all suicides worldwide.To tackle this problem, the World Health Organization announced a global public health initiative in the second half of 2005.Planned approaches were to range from government regulatory action to the development of new treatments for pesticide poisoning.With broad-based support, this strategy should have a major impact on the global burden of suicide."

Bertolote JM, Fleischmann A, Eddleston M, Gunnel D (2006): Deaths from pesticide poisoning: a global response. British Journal of Psychiatry

(2005) Hospital-based survey of pesticide poisoning in Japan [external Link]

"Out of 346 pesticide poisonings recorded between 1998 and 2002 in Japanese hospitals, 70% were suicidal, while 65 poisonings (or 18.8%) occurred during spraying, preparation, settlement, or reentry, and 8% were due to accidental ingestion. Organophosphates accounted for 36% of poisonings and bipyridylium herbicides (paraquat and diquat) for 20%. Paraquat products were the main cause of deaths. Patients recovered in 69% of the cases and in 25% of cases they died, while in 6% the outcome appears to be unknown. In Japan the mortality from paraquat poisoning is extremely high and physicians in intensive care units are hoping for a ban on paraquat. It was stated that it would be appropriate to assign paraquat to WHO class Ia or Ib. The hospital-based survey was estimated to cover 1.5-2.5% of all acute poisonings caused by pesticides."

Nagami H, Nishigaki Y, Matsushima S, Matsushita T, Asanuma S, Yajima N, Usuda M, and Hirosawa M, Hospital-based survey of pesticide poisoning in Japan, 1998-2002, International Journal of Occupational and Environmental Health 11(2), 180-184, 2005

(2002) Paraquat intoxication in Korea [external Link]

"Paraquat has been used for 3 decades in Korea. It has caused an estimated 2,000 intoxications annually, and the annual mortality among those intoxicated is 40-50%. One hundred seventy-five patients, poisoned by pesticides, were admitted to the Institute of Pesticide Poisoning (IPP), from January through December 1999. Of those 175 patients, 154 (88.8%) were intoxicated by paraquat. Out of the154 recorded paraquat poisonings 73.4% were intentional, and it represented a significantly higher fatality rate (53.2%) than accidental poisoning (19.1%). Pesticide poisonings also occurred due to lacking safety measures. Among 54 farmers who were treated, 32 of the cases were intentional, 17 accidental and 5 occupational (by paraquat aerosol). Suicidal attempts were associated significantly with fatality in crude analysis, but the significance disappeared after the adjustment for the ingested amount. No significant relationships between critical therapeutic modalities and outcomes were observed. The risk of a fatal outcome increased significantly with the amount of paraquat ingested and absorbed. A positive urine test for paraquat was associated significantly with fatality in a dose-dependent manner."

Hwang K-Y, Lee E-Y, and Hong S-Y, Paraquat intoxication in Korea, Archives of Environmental Health 57(2), 162-166, 2002

Studies on exposition to Paraquat in Agriculture

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(2005) Determinants of dermal exposure [external Link]

A study on factors influencing skin exposure of workers (based on videotaped observation and tracing with fluorescent dye) found that the following factors were associated with an increased visual score of exposure: temperature, using a hand-pressurised sprayer, volume of sprayed diluted solution, spraying with the nozzle directed in front, splashing on the feet and gross contamination of hands. In statistical analysis factors related to working practices explained 52% of variability of the total visual score (exposure). Factors related to equipment and working environment explained 33% and 25% of the score, respectively. Several factors were strongly associated with an increased score (exposure): sprayed area, spraying on wet/muddy terrain, use of a manual backpack sprayer and direct contact with spray solution. The main factor with a preventive effect was wearing long pants. A suitable education programme for the farmers in this study should emphasise maintenance of the equipment, the correct spraying technique when using manual backpacks and the type of clothes to wear during applications, in particular the use of gloves.

Blanco LE et al. (2005). Determinants of dermal exposure among Nicaraguan subsistence farmers during pesticide applications with backpack sprayers. Annals of Occupational Hygiene 49(1), 17-24, 2005.

(2005) Pesticide use and dermal exposures and effects in developing countries: data from Central America [external Link]

"Paraquat is another frequent agent of systemic poisoning, mostly after ingestion but severe and fatal occupational and accidental poisonings have been documented also after skin absorption, in adults and children. (…) Total actual dermal exposure to paraquat in applicators of banana plantation in Costa Rica, assessed by skin pads in 1995, varied between 35 - 1130 mg/kg or 2 - 57 mg/hr, comparable to earlier studies in Asia performed in the eighties and about a factor 100 higher than a study performed in the US in 1975. Wrists, legs and back were the most exposed body areas. Protective clothing did not effectively control dermal exposure with the herbicide getting under the clothing and gloves and into the boots, possibly increasing the penetration through the covered skin. Although it was not clear if the measured levels would lead to adverse health effects, observations showed the continuous presence of hazardous situations potentially leading to very high exposures. A second study evaluating the effectiveness of protective clothing measured lower levels of paraquat but still considerable amounts of skin residues, especially on the hands. (…) Dermal exposures in developing countries are often so gross that no measurements seem to be needed to understand where and how the exposures occur and to intervene, e.g. spraying bare handed, in shorts and without shoes as occurred in the Nicaragua study (…) measurements may contribute to improvement of working practices, e.g. in the case of plantation workers with inefficient protective equipment."

Wesseling C et al. (2005). Pesticide use and dermal exposures and effects in developing countries: data from Central America. Occupational and Environmental Exposure of Skin to Chemicals - abstract 52, 2005.

(2004) Pesticides – health survey: data of 123 farmers in Chainat [external Link]

A survey of 123 farmers in Thailand found that practically all wore a long-sleeved shirt and long pants, 48% wore a mask made of cloth, 17% a sponge mask and 35% wore no mask. 105 of these farmers also used paraquat. The signs and symptoms of poisoning that farmers reported were moderate in 63.4% of farmers (nausea, blurred vision, tremor, muscle cramps, chest pain or vomiting), mild in 34.1% (dry throat, dizziness, exhaustion, headache, shaky heart, itchy skin, weakness of muscles, skin rashes or sore throat), severe in 1.6% (convulsions or loss of consciousness), while 0.8% of farmers had no symptoms.

Danish International Development Assistance (IPM DANIDA) (2004). Pesticides – health survey: data of 123 farmers in Chainat, Thailand. August-September 2004.

(2004) Use of personal protective equipment and exposure to herbicide among handlers in Costa Rica [external Link]

"The use of personal protective equipment (PPE) by workers who sprayed paraquat was studied and the protective effect was assessed by measuring urinary levels in 119 workers and by interviewing workers on symptoms previously experienced. Use of PPE was not significantly associated with self-reported health symptoms, while the measured levels of paraquat showed a slight protective effect from the use of coveralls. No similar association was found for other types of PPE."

Lee K et al. (2004). Use of personal protective equipment and exposure to herbicide among handlers in Costa Rica. Proceedings of the American Industrial Health Conference, 2004.

(1997) Reregistration Eligibility Decision (RED): Paraquat Dichloride [external Link]

The US Environmental Protection Agency found that margins of exposure to paraquat for workers using low-pressure sprayers or backpack sprayers were ‘unacceptable’. It was concerned about the ‘practicality’ of adding another layer of personal protective equipment due to heat stress and comfort. Even with the addition of gloves the margin of exposure was not satisfactory. To reduce the health risks the concentration of the spray solution for backpack sprayers was limited at 0.23% for spot application1) and at 0.37% for non-spot application.

US Environmental Protection Agency - EPA (1997). Reregistration Eligibility Decision (RED): Paraquat Dichloride. pp. 56 & 111-112, Washington D.C. 1997.

(1996) Paraquat exposure of knapsack applicators on banana plantations in Costa Rica (PDF, 3.9 MB)

A study on banana plantations measured the exposures of 11 spray applicators to diluted paraquat (0.1-0.2%): direct skin exposure was measured with the aid of skin pads and the respiratory exposure was measured with personal air samplers. Total dermal exposures (a sum of certain body areas) measured were 0.2-5.7 mg paraquat per hour (equivalent to doses of 3.5-113.0 mg/kg). Urinary levels (detected in 2 of 28 samples) were 0.24 mg/l and <0.03 mg/l; respiratory exposure was 0-0.043 mg/l, corresponding to 0.3% of the total dermal exposure. This is on the same order as the proportion of paraquat absorbed through intact skin (0.23-0.29%). It was not clear whether the measured levels of exposure would lead to acute or chronic health effects, however, it was found that the risk of a high and therefore hazardous exposure was continually present, due to poor working conditions. Health problems recorded were: blistering and burns of the hands, thighs, back, testicles and legs (due to defetive equipment or contact with sprayed leaves); two eye splashes causing redness and burning sensation. Three workers had nosebleeds (in one case frequently); nonspecific symptoms were headache, stomachache, nausea and blurred vision. No different exposures of wrists and legs were found in workers wearing gloves or overalls. When an apron was worn exposure on the back was relatively low (but not significantly lower), while wearing trousers resulted in significantly lower exposure of the legs. This study indicated that use of protective clothing does not necessary result in adequate protection as spray solution may get under clothing or soak into it and can get into gloves or boots.

Van Wendel de Joode BN, de Graaf IA, Wesseling C, and Kromhout H (1996). Paraquat exposure of knapsack applicators on banana plantations in Costa Rica. (PDF, 3.9 MB) International Journal of Occupational and Environmental Health 2, 294-304, 1996.