Pesticide patch test series for the assessment of allergic contact dermatitis among banana plantation workers in Panama
H. Penagos*1,2, C. Ruepert3, T. Partanen3, C. Wesseling3
1Department of Occupational Dermatology, Social Security Bureau of Panama, David, Panama
2Institute of Environmental Sciences, University of Chiriquí, Panama
3Central American Institute for Studies on Toxic Substances, Universidad Nacional, Costa Rica
Introduction
Pesticides are an extremely heterogeneous group of chemical compounds. Skin is the major route of exposure, particularly in developing countries. Pesticides are increasingly identified as a cause of occupational skin diseases. Irritant contact dermatitis and allergic contact dermatitis (ACD) are frequent among agricultural workers, requiring targeted interventions. For differential diagnosis, patch testing is necessary but still uncommon for pesticides.
This study explores the frequency of allergic contact dermatitis (ACD) and sensitization to pesticides among highly exposed banana workers, by means of a pesticide patch test tray specific for this population.
Methods
Frequently and recently used pesticides on banana plantations in Divalá,
Panama, were documented. A structured interview was administered to 366 participants, followed by a complete skin examination.
A pesticide patch test tray specific for this population was prepared The pesticide patch test (PPT) series,
as well as a Standard Patch Test (SPT) series, were applied on 37 workers with dermatoses likely to be caused by pesticides,
and on 23 control workers without dermatoses.
The pesticide patch test tray was prepared at the laboratory for Pesticide Residue Analysis of the
Central American Institute for Studies on Toxic Substances at the Universidad Nacional in Heredia, Costa Rica, according to standard
international chemical guidelines (see Table ). Most of the pesticide standards used (with a purity of > 94%) obtained from
Dr. E.-M. Ehrenstorfer-Schäfers of Ausburg, Germany, or from Riedek de Haen of Seelze, Germany. Vehicles used were white petrolatum
Laboratorios Zepol, Curridabat, Costa Rica), issoctene (Omnisolve, EM Science, Gibbstown, NJ), water (Milli-Q water purification system,
Millipore Corporation, Bedford, MA), or a 1:1 mixture of water and acetone (Omnisolve, EM Science). For pesticides with test concentrations
published in the literature, we used concentrations of 0.1% weight per weight (w/w) instead of the usually recommended 1.0% w/w because of
possible toxicity considerations.
In accordance with the procedures outlined by Abrahams and colleagues, we applied ethoprophos and tridemorph to
10 consenting subjects from an urban dermatologic clinics who were not exposed to pesticides. We evaluated the responses at 96 hours.
None of these patients developed a positive patch-test reaction at 96 hours.
The pesticide patch test series was applied to the workers at the same time as the SPTS was applied, with
Finn Chambers /Epitest Ltda OY, Tuusula, Finland) and ·3M tape. Readings were made as were made for the SPTS (48 and 96 hours).
The results of the SPTS and the pesticides patch test series were interpreted according to International Contact Dermatitis Research Group (ICDRG).
Results
The pesticide patch tests identified 15 cases (41%) with ACD (20 positive reactions) among the 37 workers
diagnosed with pesticide dermatosis (contact dermatitis, figures 2, 3). The prevalence of ACD was 4% (15 of 366) controls had allergic
reactions to pesticides (4 positive reactions).
The insecticide and nematocide carbaryl triggerd most of the allergic skin reactions (5 cases) and was followed
by the fungicide benomyl (4 cases) and the nematocide ethoprophos (3 cases).
Ethoprophos and tridemorph had not been previously identified as sensitizers.
We estimated that at least 16% of the entire population was sensitized to pesticide.
Discussion
This study developed a pesticide patch test tray to test a specific worker population in Panama that was highly
exposed and found a positive response in 41% of workers diagnosed with a pesticide-associated contact dermatitis and in 13% of control workers
without dermatoses. Although the prevalence of ACD was 3%, at least 16% of the entire workers population was estimated to have been sensitized to pesticides.
A prevalence of 16% of sensitized workers appears high when compared with findings reported for other
agricultural populations, which range from 5 to 10%. However, banana plantation workers are exposed to a large number of pesticides during working hours and
often also at home as they generally live in the middle of the plantations. The fact that packing plant workers mostly had positive test reactions to pesticides
used in the field may be explained by indirect exposure by way of the ambient air in the open packing plant or in the houses nearby.
One limitation of the study is that the correct concentration for patch testing is uncertain with many pesticides because they have
not been widely used. This is particularly the case for ethoprophos and tridemorph because no previous reports exist and because 19 volunteers with negative
patch–test reactions make up a rather small group for confirming that an appropriate concentration has been used. At least 20 to 50 control subject would
have been required for statistical and scientific validity. However, we feel confident that the reactions observed are well interpreted.
Conclusion
Pesticide patch test trays can be successfully developed in Central America and should be used as an instrument
in the assessment of health skin problems in worker groups that are highly exposed to pesticides.
The application of this diagnostic tool showed high prevalence of ACD among workers exposed to pesticides with known
sensitizing properties but also to several pesticides not previously known to be human sensitizers.
The study confirms that when applied to these agricultural worker, standard patch series are not sufficient
to prove an allergic skin reaction because they are not frequently exposed to these allergens. It is therefore necessary to test
agricultural workers with specific pesticide patch test series
Content last modified: 9 June 2005
