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Paraquat Poisoning in Southern Mexico: A Report of 25CasesRoberto Tinoco a , Rolando Tinoco a b , Julie Parsonnet c & David Halperin M.D. a b ca Hospital General “J” , Comitan, Chiapas, Mexicob Comitan Health Research Center , Comitan, Chiapas, Mexicoc Division of Geographic Medicine , Stanford University Medical School , Stanford, California,USAPublished online: 03 Aug 2010.

To cite this article: Roberto Tinoco , Rolando Tinoco , Julie Parsonnet & David Halperin M.D. (1993) Paraquat Poisoning inSouthern Mexico: A Report of 25 Cases, Archives of Environmental Health: An International Journal, 48:2, 78-80

To link to this article: http://dx.doi.org/10.1080/00039896.1993.9938398

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Paraquat Poisoning in Southern Mexico: A Report of 25 Cases

ROBERTO TINOCO Hospital General “J” Comitan, Chiapas, Mexico ROLAND0 TINOCO Hospital General “J” Comitan, Chiapas, Mexico

Comitan Health Research Center Comitan, Chiapas, Mexico JULIE PARSONNET Division of Geographic Medicine Stanford University Medical School Stanford, California

and

DAVID HALPERIN Hospital General “J” Comitan, Chiapas, Mexico

and Comitan Health Research Center Comitan, Chiapas, Mexico

Division of Geographic Medicine Stanford University Medical School Stanford, California

and

ABSTRACT. Paraquat is a bipyridyl herbicide used world-wide. Although accidental and de- liberate ingestions of lethal doses have been reported from many countries, no case has ever been described in Mexico. The authors report on 25 cases of Paraquat poisoning in the state of Chiapas, Mexico, that occurred between 1988 and 1990. Eighty percent of the cases were men, and 64% of the cases died. Alcohol intoxication or suicidal intent were factors at the time of Paraquat ingestion in 75% of the cases. The majority of cases had learned to use Paraquat from a friend; none had been instructed by a professional. Eighty percent of cases did not know the dilution for the proper use of the herbicide, and none kept the herbicide in its original container. Attention to the law, redesign of the Paraquat packaging, and educa- tional efforts directed at populations at risk might reduce the occurrence of poisoning in this region.

PARAQUAT, a bypyridyl herbicide, is used widely throughout the world. Its development was considered to be a major advance in herbicide safety because the chemical decomposed rapidly into harmless com- pounds when it contacted soil and left no toxic residue. Despite its theoretical safety, however, poisonings have been described virtually everywhere Paraquat has been used.

Fulminant Paraquat poisoning occurs following inges- tion of more than 15 ml of a 20% solution. Victims who survive the severe neurologic, renal, and hepatic com- plications that occur during the first hours to days follow- ing ingestion often die several weeks later from pro-

found pulmonary fibrosis. Persons may also suffer from ulceration of the oropharynx and esophagus. Death can occur as soon as 24 h and as long as 3 wk after Paraquat ingestion.’ Moderate to severe Paraquat poisoning re- sults from the ingestion of 20 to 40 mg/kg body weight or, for the average adult, less than 15 ml of a 20% solu- tion. Survivors of even this smaller dose can develop fatal pulmonary disease.

The mechanism of Paraquat poisoning is related to its function as a redox agent and the production of oxygen free radicals. Paraquat reduction is coupled with the re- duction of molecular oxygen, which results in the pro- duction of highly toxic superoxide anion, single oxygen

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and possibly hydroxyl radicals.' Experimental antioxi- dant therapies with vitamins E and C have been tried, but they have not been shown to alter the final out- come."

The prevalence of Paraquat poisoning is difficult to as- sess because of the lack of morbidity and mortality data from countries where the herbicide is used routinely. The World Health Organization (WHO) does not main- tain separate statistics for Paraquat poisonings; rather, it groups agricultural chemical poisonings together. A re- view of the reported incidence of Paraquat poisoning shows high rates in Fiji and Japan (47.0 and 11 .O deaths per million population per year, respectively). Much lower rates are seen in Ireland (2.7 per million popula- tion per year), Great Britain (0.66 per million population per year), and the United States (0.004 per million popu- lation per year).5 To date, only one clinical report of Paraquat ingestion has appeared from Latin America, al- though Paraquat is among the best known and most commonly used agrochemicak6

In 1989, several cases of Paraquat ingestion at the Hos- pital General "J" in Comitan and the Comitan Health Research Center prompted investigation of herbicide poisoning and the circumstances surrounding toxic in- gestions. We report in this article the first case series of Paraquat poisonings from Latin America and describe risk factors for Paraquat ingestion.

Materials and methods The study area included the municipalities of Comi-

tan, Trinitaria, Amatenango, Margaritas, Comalapa, and Chicomuselo in Chiapas, Mexico (population 315 OOO; Fig. 1). Cases of Paraquat ingestion were identified through a review of all hospital inpatient records at Comitan Regional Hospital, the principal referral hospi- tal in the region, between January 1988 and April 1990.

Mortality data from the 1989 civil registries were also re- viewed; these registries are incomplete sources of mor- tality data, especially from rural communities. Cases were also solicited from rural health promoters.

A case was defined as either a person with a clinical ill- ness consistent with Paraquat ingestion who was identi- fied as having ingested Paraquat or as a registry death in which Paraquat was identified as the cause of death.

Age, sex, residence, and clinical outcome were re- corded for all cases. Clinical course of illness and treat- ment were documented inconsistently and were, there- fore, not analyzed. A detailed questionnaire was admin- istered to survivors or household relatives of nonsurviv- ors. The questionnaire addressed issues of socioeco- nomic status and agricultural exposure of the victim. Other questions included location of purchase of the herbicide, the victim's knowledge of its use, and storage methods of the herbicide in or about the victim's home. Information about suicidal intent and coincident alcohol intoxication in the victim was also elicited.

Results Twenty-five cases of Paraquat ingestion were identi-

fied; of these, 16 died and 9 survived. Twenty (80%) of the cases were men. There were 16 cases for whom ques- tionnaire information was available (interview cases); sex and age of interview cases were similar to those of non- interview cases. Eleven of the 12 male interview cases were agricultural workers, and 1 described himself as a day laborer. The 4 female interview cases were described as housewives who were married to agricultural workers. All interview cases were literate.

Eleven of the 16 interview cases lived in one-room houses. Approximately one-half of those interviewed re- ported that the herbicide was stored in the"patio" of the house; the remaining one-half indicated that Paraquat

Fig. 1. The state of Chiapas, Mexico, and municipalities of residence of 16 interview cases: (1) Com- itan (3 cases); (2) Margaritas (1 case); (3) Trinitaria (4 cases); (4) Chicomusdo (2 cases); (5) Comalapa (5 cases); and (6) Amatenango (1 case).

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was either kept inside the house or they were unable to recall where the herbicide was stored. Three interview cases kept the herbicide under the bed. None kept Para- quat in its original container, and several kept the chemi- cal in soft drink containers. Eight (50%) of the interview cases bought Paraquat at a store that specialized in sell- ing agrochemicals, but 14 (87%) of the interview cases stated that instruction for its use came from a friend; none had learned from a professional. Only 4 (25%) in- terview cases knew the proper dilution for use of the commercial preparation.

In 9 (56%) of the 16 interview cases, suicide was the mgtive for Paraquat ingestion; 7 (78%) of these cases died. Two additional interview cases were described as being chronically depressed, but suicidal intent was un- certain. Nine (56%) of the interview cases were de- scribed as intoxicated with alcohol at the time of the in- gestion; 5 of these also had suicidal ideation. Only 1 case was totally accidental, i.e., neither suicidal intent nor alcohol ingestion. This case had siphoned the herbicide when he mistook it for diesel fuel. Most (56%) of the in- terview cases were alone at the time of the ingestion; 31 o/o were in the company of another person; 2 (1 3%) in- terview cases did not provide this information.

Discussion

This is the first series of Paraquat poisonings reported from Latin America. Southern Chiapas now ranks among those regions of the world with the highest known mor- tality rates from Paraquat ingestion. If no other cases oc- curred in the region during the period of study, the mor- tality rate from Paraquat would exceed 20 per million population per year. It is our impression, however, that the 25 cases described here represent only a fraction of the Paraquat intoxications in southern Chiapas. Episodes that occurred in remote rural communities, where ac- cess to hospital care i s minimal, were likely to have been unrecognized.

The case-fatality rate from Paraquat ingestion in Chia- pas is similar to that reported in other parts of the world.@ Deaths are a function almost exclusively of the amount of Paraquat inge~ted,~ and therapy of any kind has very little if any effect on the final o~tcome.’,~*~ Be- cause of the retrospective nature of this study, the amount of Paraquat ingested by the subjects could not be ascertained.

As has been seen in studies from other regions, the in- tent to commit suicide was the most commonly expressed motive for Paraquat In more than half of the attempted or successful suicides, the patients were also intoxicated with alcohol. The herbicide, which was often stored in an unlabeled bottle within the house- hold, provided a convenient method for impulsive, sui- cidal behavior. Unfortunately, the outcome of even a small, gestural ingestion is often fatal. Once a lethal dose is taken, the inevitable, grim outcome cannot be countered.

Intervention to prevent poisoning should be directed toward prevention of impulsive action. For example, Paraquat could be distributed in “child-proof’’ contain- ers, making it difficult for an inebriated adult to open. In

*

addition, the concentration of marketed solution could be lowered so that a lethal dose would require a larger volume. Paraquat could also be sold in a solid, rather than liquid, form. A substance that is foul smelling or has to be mixed with water to be ingested might be less at- tractive for an impulsive action, although such altera- tions in formulation of the chemical in Japan have not re- duced the number of Paraquat-related deaths.

In Mexico, Paraquat is sold as a 20% solution that is di- luted and sprayed from plastic, back-pack tanks. By law, vendors must be certified to sell Paraquat, and all in- juries must be reported.13 Agricultural extension experts are available in the communities to explain the use of herbicides. Yet, this study found that victims of poison- ing did not know the proper dilution for Paraquat use; they learned to use Paraquat from friends, rather than from qualified authorities, and they stored the chemical in a suboptimal manner. Although these victims of poi- soning may not represent the population of Paraquat users in the state, it seems likely that educational efforts directed at populations at risk would enhance under- standing of the toxicity of this agent and foster improved management of hazardous agrochemicals. Some might claim, however, that only banning the chemical can reduce the rates of fatal ingestion of this highly lethal agent.

* * * * * * * * * * Submitted for publication March 5, 1991; revised; accepted March 2,

1992. Requests for reprints should be sent to: David Halperin, M.D., do

Julie Parsonnet, HRP Building, Room 109A, Stanford University School of Medicine, Stanford, CA 94305-5425.

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