* Departamento de Ciências Fisiológicas, Faculdade de Biociências, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Porto Alegre, Brazil; and
Instituto de Ciências Básicas da Saúde, Departamento de Bioquímica, Universidade Federal do Rio Grande do Sul, 90035003 Porto Alegre, RS, Brazil
Received November 12, 2002; accepted January 6, 2003
![]() |
ABSTRACT |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Key Words: organophosphate pesticides; parkinsonism; occupational exposure; acetylcholinesterase; psychiatry.
![]() |
INTRODUCTION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
The clinical syndromes regarding organophophorus toxicity are:
Chronic organophosphate-induced neuropsychiatric disorders (COPIND) are a less well-characterized syndrome in chronic OP poisoning. COPIND may be caused by chronic low-level exposure to OP, without cholinergic symptoms (Ray and Richards, 2001). The underlying mechanisms are not established, but are not dependent on inhibition of esterases (Levin et al., 1976
; Prendergast et al., 1998
). The most common clinical symptoms include impairment in memory, concentration, and learning; anxiety, depression, psychotic symptoms, chronic fatigue, peripheral neuropathy, autonomic dysfunction and extrapyramidal symptoms such as dystonia, resting tremor, bradikynesia, postural instability and rigidity of face muscles; and nonresponsiveness to levodopa treatment. Regarding psychiatric symptoms, Amr et al. (1997)
found that, compared to controls, subjects heavily exposed to pesticides (40 h/week, 9 months/year) had a significant increase in the frequency of psychiatric disorders, especially depressive neurosis and dysthymic disorder (DSM-III-R). These results left unresolved the issue of reversibility of psychiatric symptoms after a pesticide-free period and the occurrence of the syndrome in subjects not so heavily exposed to OP compounds. Another confounding factor in these studies has been the exposure to several types of pesticides, including pyridine compounds, which have been shown to reproduce features of Parkinsons disease (Betarbet et al., 2000
).
Among OP commonly used in our population, chlorpyriphos has been reported to induce these syndromes, including anxiety, depression, and transient parkinsonism (Aiuto et al., 1993; Guadarrama-Naveda et al., 2001
; Kaplan et al., 1993
; Moretto and Lotti, 1998
; Richardson, 1995
; Steenland et al., 1994
; Stokes et al., 1995
). Other pesticides currently used (glyphosate, clomazone, flumetralin, iprodione, and imidacloprid) have not been related to neurotoxicity. The present study was undertaken at two different moments (under current use of OP for 3 months, and after 3 months without OP exposure) to evaluate clinical, psychiatric, and extrapyramidal symptoms, as well as plasma acetylcholinesterase activity, in a sample of workers chronically exposed to these OP.
![]() |
MATERIALS AND METHODS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
The first clinical and laboratory evaluation was conducted in a sample of 37 workers from southern Brazil involved in family agriculture of tobacco in December 2001, when they had been working with OP for 3 months. At the time of evaluation, all subjects had been exposed to OP within the last day. The second evaluation was conducted in 25 workers from the initial sample who returned in March 2002, when they had been off exposure for 3 months.
Clinical evaluation.
Demographic features, alcohol and tobacco use, OP exposure (time and type of exposure, use of protective equipment, and history of acute toxicity) were evaluated using a structured questionnaire by RMS. Two trained psychiatrists (D.R.L. and E.S.G.) assessed the presence of:
Cholinesterase monitoring.
Acetylcholinesterase activity was measured in a blood sample (10 ml) collected in tubes containing EDTA. The activity was determined in plasma by using a colorimetric technique previously described by Ellman et al. (1961) and Kolf-Clauw et al. (2000)
.
Statistical analysis.
Comparisons between the two evaluations were performed with ANOVA for symmetric variables and the Wilcoxon test for asymmetric variables such as the scales scores. Statistical significance was defined as p < 0.05.
![]() |
RESULTS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
|
Plasma acetylcholinesterase activity levels of all subjects were within the normal range according to Brazilian policies (3.2 to 9.0 U/l) and were not different between on- and off-exposure periods (4.7 ± 0.9 and 4.5 ± 1.1 U/l, respectively), although the time off exposure had been sufficient (more than 60 days) to normalize the enzyme activity if it had been inhibited (Cocker et al., 2002).
Clinically significant extrapyramidal symptoms were present in 12 subjects (Fig. 1), as evidenced by a total score of parkinsonism of 5 or more in the ESRS, which can be considered above the normal range, especially in a population of this age. As can be seen in Table 2
and Figure 1
, although there was a considerable and statistically significant reduction of extrapyramidal symptoms after 3 months without exposure to OP, 9 subjects still had clinically significant symptoms as evidenced by a total score of 5 or more in the ESRS. Unlike what is observed with antipsychotic treatment, which also induces parkinsonism, significant akathisia was not observed and did not change after washout of OP. Tremor was the predominant symptom in 6 and absent in 3 of these 12 subjects with clinically significant parkinsonism. Facial mask and reduced pendular arm movement were commonly observed. Improvement in the second evaluation was quite uniform for all symptoms. Mini-mental and word span scores were within the expected range for this population and were not influenced by exposure to OP (Table 2
).
|
|
|
![]() |
DISCUSSION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Descriptions of enduring parkinsonism following chronic OP occupational exposure are scarce. Despite the reduction in extrapyramidal symptoms seen in the second examination, parkinsonism remained clearly higher than expected for a healthy population of this age, which included mostly subjects under the age of 60, when primary Parkinsons disease is rare. The pathophysiological mechanisms for this condition are unclear, but Bhatt et al. (1999) suggested that the absent response to levodopa might indicate striatal dopamine receptor dysfunction. Our results indicate that whatever the mechanism involved, alterations are likely to be permanent. Moreover, although parkinsonism was found in this sample, cognition was not clearly affected and was unchanged after washout of OP, suggesting at least some degree of specificity towards the motor system.
The present results reinforce the previous observations from Stallones and Beseler (2002) of behavioral changes, such as anxiety and depression, as sequelae of OP poisoning in a population exposed to OP agents. Another case-control study (79 subjects) conducted by Jamal et al. (2002)
found that increasing severity of neuropathy induced by OP was accompanied by anxiety and depression as measured with neuropsychological tests. Finally, the study conducted by Sánchez-Amate et al. (2001)
in rats showed clear behavioral changes as an acute effect of chlorpyriphos poisoning in the absence of any classic sign of cholinergic syndrome.
Certain methodological issues of our study must be considered. First, this series consisted only of chronically exposed workers, so these findings must be recognized as being limited to a special group of subjects. Second, the study investigators were actively looking for psychiatric and neurologic morbidity; therefore, the inclusion of an unexposed group keeping the interviewers blind to history of pesticide exposure could be useful; on the other hand, the use of structured interview and physical examination attenuated this bias and there was no a priori hypothesis regarding the persistence of symptoms in the follow-up examination. Third, affected subjects might have enrolled at a higher rate in the study because of their awareness of potential health problems produced by pesticides. Moreover, the lack of a healthy comparison group without OP exposure in this study precludes more definite conclusions, and it also should be taken into account that subjects in our study frequently used two or more compounds, possibly resulting in drug interactions among these compounds, their metabolites, and also with organic solvents often present in commercial formulations. Finally, subjects may have been exposed to a residual level of OP in clothes, equipment, and food, even after occupational use was halted; and other uncontrolled factors present in only one of the examined subjects might have influenced the results.
In conclusion, this study reinforces the need for parameters other than acetylcholinesterase activity to monitor for chronic consequences of low-dose OP exposure and suggests that subjects have not only transient motor and psychiatric consequences while exposed, but may also present enduring extrapyramidal symptoms. We also emphasize that pesticides other than pyridine-like compounds and rotenone, such as those evaluated in this study, may induce significant neurological and psychiatric symptoms, warranting further investigation and prompting further educational and safety measures for exposed subjects.
![]() |
ACKNOWLEDGMENTS |
---|
![]() |
NOTES |
---|
2 To whom correspondence should be addressed. Fax: (55 51) 33165540. E-mail: diogo{at}ufrgs.br.
![]() |
REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Almeida-Filho, N., Mari J. de J., Coutinho, E., Franca, J. F., Fernandes, J., Andreoli, S. B., and Busnello, E. D. (1997). Brazilian multicentric study of psychiatric morbidity. Methodological features and prevalence estimates. Br. J. Psychiatry 171, 524529.[Abstract]
Amr, M. M., Halim, Z. S., and Moussa, S. S. (1997). Psychiatric disorders among Egyptian pesticide applicators and formulators. Environ. Res. 73, 193199.[CrossRef][ISI][Medline]
Betarbet, R., Sherer, T. B., Mackenzie, G., Garcia-Osuna, M., Panov, A. V., and Greenamyre, J. (2000). Chronic systemic pesticide exposure reproduces features of Parkinsons disease. Nat. Neurosci. 3, 13011306.[CrossRef][ISI][Medline]
Bhatt, M. H., Elias, M. A., and Mankodi, A. K. (1999). Acute and reversible parkinsonism due to organophosphate pesticide intoxication: Five cases. Neurology 52, 14671471.
Brown, M. A., and Brix, K. A. (1998). Review of health consequences from high-, intermediate-, and low-level exposure to organophosphorus nerve agents. J. Appl. Toxicol. 18, 393408.[CrossRef][ISI][Medline]
Chouinard, G., Ross-Canard, A., Annable, L., and Jones, B. D. (1980). Extrapyramidal Symptom Rating Scale. Can. J. Neurol. Sci. 7, 233.
Cocker, J., Mason, H. J., Garfitt, S. J., and Jones, K. (2002). Biological monitoring of exposure to organophosphate pesticides. Toxicol. Lett. 134, 97103.[CrossRef][ISI][Medline]
Ellman, G., Courtney, D., and Andres, V. (1961). A new and rapid colorimetric determination of acetylcholinesterase activity. Biochem. Pharmacol. 7, 8895.[CrossRef][ISI][Medline]
Folstein, M. F., Folstein S. E., and Mchugh P. R. (1975). Mini-Mental-State: A practical method for grading the cognitive state of patients for the clinician. J. Psychiatr. Res. 12, 189-198.
Guadarrama-Naveda, M., de Cabrera, L. C., and Matos-Bastidas, S. (2001). Intermediate syndrome secondary to ingestion of chlorpiriphos. Vet. Hum. Toxicol. 4, 34.
Jamal, G. A. (1997). Neurological syndromes of organophosphorus compounds. Adverse Drug React. Toxicol. Rev. 16, 133170.[ISI][Medline]
Jamal, G. A., Hansen, S., Pilkington, A., Buchanan, D., Gillham, R. A., Abdel-Azis, M., Julu, P. O., Al-Rawas, S. F., Hurley, F., and Ballantyne, J. P. (2002). A clinical neurological, neurophysiological, and neuropsychological study of sheep farmers and dippers exposed to organophosphate pesticides. Occup. Environ. Med. 59, 434441.
Kaplan, J. G., Kessler, J., Rosenberg, N., Pack, D., and Schaumburg, H. H. (1993). Sensory neuropathy associated with Dursban (chlorpyriphos) exposure. Neurology 43, 21932196.[Abstract]
Kolf-Clauw, M., Jez, S., Ponsart, C., and Delamanche, I. S. (2000). Acetyl- and pseudo-cholinesterase activities of plasma, erythrocytes, and whole blood in male beagle dogs using the Ellman assay. Vet. Hum. Toxicol. 42, 216219.[ISI][Medline]
Lessenger, J., and Reese, B. E. (1999). Rational use of cholinesterase activity testing in pesticide poisoning. J. Am. Board. Fam. Pract. 12, 307334.[Abstract]
Levin, H. S., Rodnitky, R. L., and Mick, D. L. (1976). Anxiety associated with exposure to organophosphate compounds. Arch. Gen. Psych. 33, 225228.[Abstract]
Mileson, B. E., Chambers, J. E., Chen, W. L., Dettbarn, W., Ehrich, M., Eldefrawi, A. T., Gaylor, D. W., Hamernik, K., Hodgson, E., Karczmar, A. G., Padilla, S., Pope, C. N., Richardson, R. J., Saunders, D. R., Sheets, L. P., Sultatos, L. G., and Wallace, K. B. (1998). Common mechanism of toxicity: A case study of organophosphorus pesticides. Toxicol. Sci. 41, 820.[Abstract]
Moretto, A., and Lotti, M. (1998). Poisoning by organophosphorus and sensory neuropathy. J. Neurol. Neurosurg. Psychiatr. 64, 463468.
Müller-Vahl, K. R., Kolbe, H., and Dengler, R. (1999). Transient severe parkinsonism after acute organophosphate poisoning. J. Neurol. Neurosurg. Psychiatry 66, 253254.
Nava, M. E., Román, P. P., Robles, S. H., and Alvarado, L. M. (1999). Sintomatología persistente en trabajadores industrialmente expuestos a plaguicidas organofosforados. Salud Publica Mex. 41, 5561.[ISI][Medline]
Peter, J. V., and Cherian, A. M. (2000). Organic insecticides. Anaesth. Intensive Care 28, 1121.[ISI][Medline]
Prendergast, M. A., Terry, A. V., Jr., and Buccafusco, J. J. (1998). Effects of chronic, low-level organophosphate exposure on delayed recall, discrimination, and spatial learning in monkeys and rats. Neurotoxicol. Teratol. 20, 115122.[CrossRef][ISI][Medline]
Ray, D. E., and Richards, P. G. (2001). The potential for toxic effects of chronic, low-dose exposure to organophosphates. Toxicol. Teratol. 120, 343351.
Richardson, R. J. (1995). Assessment of the neurotoxic potential of chlorpyrifos relative to other organophosphorus compounds: A critical review of the literature. J. Toxicol. Environ. Health 44, 135165.[ISI][Medline]
Sánchez-Amate, M. C., Flores, P., and Sánchez-Santed, F. (2001). Effects of chlorpyriphos in the plus-maze model of anxiety. Behav. Pharmacol. 12, 285292.[ISI][Medline]
Senanayake, N., and Johnson, M. K. (1982). Acute polyneuropathy after poisoning by a new organophosphate insecticide. N. Eng. J. Med. 306, 155157.[ISI][Medline]
Shahar, E., and Andraws, J. (2001). Extra-pyramidal parkinsonism complicating organophosphate insecticide poisoning. Eur. J. Paediatr. Neurol. 5, 261264.[CrossRef][Medline]
Sheehan, D. V., Lecrubier, Y., Sheehan K. H., Amorim, P., Janavs, J., Weiller, E., Hergueta, T., Baker, R., and Dunbar, G. C. (1998). The Mini-International Neuropsychiatric Interview (M.I.N.I.): the development and validation of a structured diagnostic psychiatric interview for DSM-IV and ICD-10. J. Clin. Psychiatry 59(Suppl. 20), 2233.[ISI][Medline]
Stallones, L., and Beseler, C. (2002). Pesticide poisoning and depressive symptoms among farm residents. Ann. Epidemiol. 12, 389394.[CrossRef][ISI][Medline]
Steenland, K., Jenkins, B., Ames, R. G., OMalley, M., Chrislip, D., and Russo J. (1994). Chronic neurological sequelae to organophosphate pesticide poisoning. Am. J. Public. Health 84, 731736.[Abstract]
Stokes, L., Stark, A., Marshall, E., and Narang, A. (1995) Neurotoxicity among pesticide applicators exposed to organophosphates. Occup. Environ. Med. 52, 648653.[Abstract]
Sudakin, D. L., Mullins, M. E., Horowitz, B. Z., Abshier, V., and Letzig, L. (2000). Intermediate syndrome after malathion ingestion despite continuous infusion of pralidoxime. J. Toxicol. Clin. Toxicol. 38, 4750.[CrossRef][ISI][Medline]