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Abstract for Plenary Talk 5.2

 

 

Pesticide Use and Dermal Exposures and Effects in Developing Countries: Data from Central America

C. Wesseling, Central American Institute for Studies on Toxic Substances, Universidad Nacional, Heredia, Costa Rica
A. Aragón, Center for Research of Workers Health and the Environment, National Autonomous University of Nicaragua at León, León, Nicaragua
L. Blanco, Center for Research of Workers Health and the Environment, National Autonomous University of Nicaragua at León, León, Nicaragua
H. Penagos, Social Security of Panama, David, Panama
B. van Wendel de Joode, Central American Institute for Studies on Toxic Substances, Universidad Nacional, Heredia, Costa Rica

Agricultural policies in the developing countries of Central America favor pesticide use. The dependence on chemical pest control extends from export plantations to locally consumed crops and small farmers, including the very poor. More than 35 thousand tons of active ingredients per year are sprayed in the Region. Pesticide handling continues to be exceedingly unsafe. Risk assessment and management based on exposure circumstances in developing countries are nonexistent. Acceptable Operator Exposure Levels (AOEL) are not in use. Reentry intervals are short or not respected at all. Assessment of environmental exposures is not yet a policy issue.

The skin is the main route for uptake for most pesticides in the occupational setting, potentially resulting in systemic toxicity. Over the last decade, reports of systemic poisonings increased in all countries due to newly established surveillance systems. However, it was shown in Costa Rica that in the early 1990s interventions aiming at improved handling of highly toxic insecticides and nematocides on banana plantations sharply decreased systemic poisoning (Fig. 1a),[1] which then stabilized at 0.7 poisonings (with medical attention) per 100 banana workers per year.[2] Although not documented, similar trends may have happened in other countries as well. Based on house to house surveys in six of the seven Central American countries, it was estimated in 2000 that grossly 400,000 events with symptoms of poisoning occur yearly in Central America, almost 2% of the population over age 15.[3] A majority are occupational poisonings among agricultural workers with organophosphate and carbamate pesticides which are readily absorbed by the skin. 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.[4] In Honduras, long-term dermal (and possibly respiratory) contact with chlorpyrifos caused decreased cholinesterase levels, increased acute and chronic symptoms, and impairment of central and peripheral nervous system functions among banana workers who place chlorpyrifos treated plastic bags around the fruit, using full protective equipment, as compared to unexposed banana workers.[5]

In Costa Rica, reports of pesticide dermatoses to the workers’ compensation system increased noticeably in the early 1990s associated to exposure to herbicides and fungicides, especially among female agricultural workers (Fig. 1b and c).[1] Among banana workers the incidence of pesticide dermatoses decreased from 33 in 1993 to 19 per 1000 in 1996, with herbicide sprayers at highest risk (34 and 23 per 100) mostly associated with paraquat. The decrease was partially due to underreporting by company doctors and a decrease in paraquat use on plantations. In Panama, the incidence of contact dermatitis has been estimated at 11 per 1000 banana workers.[6] In a recent study, the prevalence of pesticide-related dermatosis among banana workers in Panama was 0.10 (37/366) and the prevalence of allergic contact dermatitis 0.03 (15/366). It was estimated that ≥ 16% of the workers were sensitized to one or more pesticides.[7] Allergic contact dermatitis was associated in Panama with carbaryl, benomyl, ethoprophos, chlorothalonil, imazalil, glyphosate, thiabendazole, chlorpyrifos, oxyfluorfen, propiconazole, tridemorph and aluminium hydroxide.[6, 7] Chlorothalonil has also been associated with ashy dermatitis.[8] Many of the irritant and sensitizing pesticides mentioned have also carcinogenic, reproductive, endocrine disrupting or other long-term health effects.

 

a) Pesticide illness

b) Pesticide topical injuries

c) Pesticide topical injuries

 

Figure 1: Time trends over three one-month time periods in Costa Rica of a) pesticide related illness by type of injuries, b) topical injuries by gender, and c) topical injuries by type of pesticides, rates per 1000 agricultural workers.

 

A number of studies have examined skin exposure in the occupational setting for hazardous pesticides by different methods. In Costa Rica, an icon-calendar-based form was used to assess historical dermal pesticide exposure in a case control study on childhood leukemia a parental pesticide exposure.[9] 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.[10] 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.[11]

In Nicaragua, a study among smallholders spraying chlorpyrifos or methamidophos with manual or motorized backpacks combined qualitative, semi-quantitative and quantitative sampling methods. Fenske’s visual scoring system with a fluorescent tracer was modified and dermal exposure was assessed under Nicaraguan field conditions.[12] Hands were the most frequently contaminated body part and the back contributed most to the scores. The contaminated body surface ranged between 1 and 66%. The highest total visual score was 60 % of the maximum possible. Fluorescent images reflected work practices and contamination mechanisms. A reliability evaluation showed repeatability, conditioned to some improvements in the field and the reading of low contamination images.[13] Skin exposure determinants were collected through observations and videorecordings. Multiple linear regression modeling was used to evaluate the association between factors identified as determinants of exposure by observation and the fluorescent tracer visual score. Sprayed surface, spraying on a wet or slightly muddy terrain, using a manual backpack, and important skin contamination by touching directly the spray solution emerged as the strongest determinants; wearing long pants emerged as the main preventive factor.[14] Skin residues were analyzed from wipes of various parts of the body with different fluorescent intensities and residues increased with increasing fluorescence intensities.[12] Total amount of residues on both hands obtained from skin wipes ranged between 0,01 - 2,45 µg/cm² for methamidophos and 0,03 - 6,02 µg/cm² for chlorpyrifos.[15] Accounting for concentration of pesticide spray solution, the results suggested that chlorpyrifos (lipophilic) has a slower removal rate from the skin than methamidophos (hydrophilic). Statistical analyses relating observation of hand contamination with fluorescent visual scores and residues on the hands and analyses associating total visual scores and urine metabolites are ongoing. The Nicaraguan study illustrates that a combination of sampling methods allows the identification of different dimensions of dermal exposure. Removal techniques quantify pesticides present on the skin at the moment of sampling, a fluorescent tracer technique scores overall extent and intensity of dermal exposure and identifies exposure mechanisms and pathways, and observations allow the pinpointing of specific determinants of skin contact with the pesticide.

Several studies in Central America have analyzed residues in multiple substrates of the domestic (soil, dust) and general environment (air, surface waters, well waters). The results are worrisome and assessment of dermal exposure of children and adults through the environment is important. Although not assessing directly dermal exposure, a recent study in Nicaragua found a significant correlation between exposure of small farmers and exposure of their children to chlorpyrifos, as measured by urinary 3,5,6-trichloro-2-pyridinol on the evening of the application day, suggesting take home pathways of exposure. No relation was found for diazinon.[16] Also in El Salvador, farmers’ pesticide application predicted urinary excretion of organophosphate metabolites in family members.[17]

The importance of dermal exposure assessment in developing countries relates to its potential to contribute to improvement of occupational and environmental pesticide contamination. 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. However, even under those working conditions, some exposure determinants emerged which have hardly or never been discussed in the literature (e.g. spraying on a wet or muddy terrain, hand versus motor pressurized backpack, dew on crops). In addition, dermal exposure measurements may contribute to improvement of working practices, e.g. in the case of plantation workers with inefficient protective equipment. Also, dermal as well as exposure assessment in general is a crucial asset in epidemiologic research in developing countries. However, dermal exposure assessment as a basis for risk evaluation and management must be based on general practice in developing countries and not on best practice as it is now in industrialized countries. Given that decades of safe use strategies have resulted in ever increasing pesticide use and environmental contamination, it is unrealistic to assume that risk evaluations and management based on local use and exposure conditions will be carried out within a reasonable time span. To come to sustainable solutions, pesticide problems must be studied with a multidisciplinary methodology, examining multiple sources, pathways and effects and how these are modulated by and interact with socioeconomic and cultural factors. Dermal exposure assessment can be an important method within such a broad ecosystem approach towards the achievement of efficient interventions.

References

1. Wesseling C; Hogstedt C, Fernandez P, Ahlbom A. Time trends of occupational pesticide-related injuries in Costa Rica, 1982-1992. Int J Occup Environ Health 2001;7:1-6.

2. Wesseling C, van Wendel de Joode B, Monge P. Pesticide-related illness among banana workers in Costa Rica: A comparison between 1993 and 1996. Int J Occup Environ Health 2001;7: 90-97.

3. Murray D, Wesseling C, Keifer M, Corriols M, Henao S. Surveillance of pesticide illness in the developing world: Putting the data to work. Int J Occup Environ Health 2002;8:243-8.

4. Wesseling C, van Wendel de Joode B, Ruepert C, León C, Monge P, Hermosillo H, Partanen T. Paraquat in developing countries. Int J Occup Environ Health 2001;7:275-286.

5. Wesseling C, Aragón A, Rojas M, Blanco L, López L, Soto A, Fúnez A, Ruepert C, Miranda J, López I. Efectos de clorpirifos sobre la salud de trabajadores bananeros de La Lima, Honduras. Informe técnico. Heredia, Costa Rica: SALTRA, IRET-UNA, UNAN-León, 2004.

6. Penagos H, Contact dermatitis among banana plantation workers in panama. Epidemiology 1995;6(Suppl.4):S120.

7. Penagos H, Ruepert C, Partanen T, Wesseling C. Pesticide patch test series for the assessment of allergic contact dermatitis among banana plantation workers in Panama. Dermatitis 2004;15:137-45.

8. Penagos H., Jimenez V, Fallas V, O`Malley M, Maibach H. Chlorothalonil, a possible cause of erythema dyschromicum perstans (ashy dermatitis). Contact Dermatitis 1996;35:214-218.

9. Monge P, Wesseling C, Engel LS, Keifer M, Zuurbier M, Rojas M, Partanen T. An icon-calendar-based form for assessment of parental occupational pesticide exposure to evaluate cancer in the offspring. Int J Occup Environ Health 2004;10:72-8.

10. van Wendel de Joode BN, de Graaf IA, Wesseling C, Kromhout H. Paraquat exposure of knapsack applicators on banana plantations in Costa Rica. Int J Occup Environ Health 1996;2:294-304.

11. Spruit O, van Puijvelde . Evaluation of the protective equipment used during herbicide application on banana plantations. 1998. Internal report 1998-304, Wageningen Agricultural University.

12. Aragón A, Blanco LE, Funez A, Ruepert C, Lidén C, Nise G, Wesseling C. Assessment of dermal pesticide exposure with fluorescent tracer: A Nicaraguan modification of a Visual Scoring System. Submitted. 

13. Aragón A, Blanco L, López L, Lidén C, Nise G, Wesseling C. Reliability of a visual scoring system with fluorescent tracers to assess dermal pesticide exposure. Ann Occup Hyg 2004;48:601-6.

14. Blanco LE, Aragón A, Lundberg I, Lidén C, Wesseling C, Nise G. Determinants of dermal exposure among Nicaraguan subsistence farmers during pesticide applications with backpack sprayers. Ann Occup Hyg 2005;49:17-24.

15. Aragón A, Ruepert C, Blanco LE, Funez A, Lidén C, Nise G, Partanen T, Wesseling C. Hand exposure to organophosphate pesticides among subsistence farmers in Nicaragua, a comparison of three sampling methods: Skin wipe, observation, and visual scoring system. Manuscript. 

16. Rodríguez TR, Lyounglove, Lu C, Fenske R, Irish R, Fúnez A. Organophosphorus pesticide exposures among Nicaraguan farmers and their children. In: Book of Abstracts: III Conference on Occupational and Environmental Health in the Americas 2005. Alajuela, Costa Rica, February 6 – 9, 2005. p 92.

17. Azaroff LS. Biomarkers of exposure to organophosporous insectivdes among farmers’ families in rural el Salvador: Factors associated with exposure. Env Res 1999;Section A 80:138-147.

Content last modified: 10 April 2005

 

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