Dermal exposure to pesticides in Nicaragua : A qualitative and quantitative approach
Author: Aragón, Aurora
Date: 2005-12-16
Location: Aulan, plan 2, Norrbacka, Karolinska Universitetssjukhuset, Solna
Time: 9.00
Department: Institutionen för folkhälsovetenskap / Department of Public Health Sciences
View/ Open:
thesis.pdf (641.0Kb)
Abstract
Background: Pesticide use continues to be a serious public health problem
in developing countries, despite decades of safe pesticide use
strategies. In Nicaragua, organophosphate insecticides, in particular
chlorpyrifos and methamidophos are responsible for about half of the
acute pesticide poisonings. Contamination of the skin occurs frequently
in the occupational setting. There is extensive research to improve
methods to assess dermal exposure. The applicability and feasibility of
such methods in developing countries is uncertain.
Aim: This thesis aims at increasing the understanding of risk factors
underlying exposure, evaluating dermal exposure among Nicaraguan
subsistence farmers, and proposing more suitable methods for developing
country conditions.
Methods: A group of 29 subsistence farmers were interviewed in four focus
groups and their responses were analyzed using grounded theory. Field
data for semi-quantitative and quantitative exposure measurements of 31
farmers were collected during 33 pesticide applications, using
observation, supplementary video recording, a fluorescent tracer, and
skin wiping. A visual scoring system developed in the US was modified
into a Nicaraguan Visual Scoring System suitable for developing country
conditions. Pesticides were traced during application. Skin fluorescence
was videotaped in a foldaway darkened room which was later measured
through Body Segment Scores (BSS), Contaminated Body Area (CBA) and Total
Visual Score (TVS). TVS was used as a criterion indicator for the
identification of main exposure determinants by observation. Univariate
and multivariate analyses were performed. Hundred and ten potential
exposure determinants were reduced to 27 variables grouped as worksite,
spray equipment, work practices, clothing, and hygiene practices.
Reliability of the visual score was tested with intraclass correlation
coefficients, in a sub-sample of five farmers evaluated by five raters.
Observations of hand exposure events (direct and indirect contacts) were
summarized into a Concentrate Contamination Index (CCI) and a Solution
Contamination Index (SCI). Chemical residues were quantified for the
hands and selected body parts according to fluorescent intensities.
Spearman rank correlation coefficients were computed to compare the
observational indices (CCI+SCI), fluorescent visual scores and
quantitative residues.
Results: Reasons for unsafe practices were connected with poverty,
inadequacy of personal protective equipment, climatic factors, and
limited knowledge influenced by beliefs and traditions. Farmers felt
affection towards their traditional crops and this relationship seemed to
have strong meanings for pest removal and pesticide use, contributing to
dangerous work practices. The observed fluorescent images on the skin of
farmers reflected work practices and contamination mechanisms and
pathways. Novel determinants included spraying on a muddy terrain, dew on
plants, sealing of tank lids with a cloth, and wiping sweat from the
face. The Visual Scoring System was highly consistent (Cronbach alpha =
0.96) and reasonably reliable (0.75; 95% CI: 0.62-0.83), with scoring of
extent being more reliable than scoring of intensity. The highest CBA was
66% and the farmer with the highest TVS scored 60% of the maximum
possible. Hands were most frequently contaminated and the back had the
highest BSS. Hand contact was most frequently indirect, by touching
contaminated surfaces. All farmers had quantifiable pesticide residues on
their hands. Spearman correlation coefficients between the observational
contamination scores, fluorescent visual scores and residues in relation
to the hands ranged from 0.65 to 0.74 for chlorpyrifos and 0.62 to 0.87
for methamidophos. Differences in scores could be explained by
limitations of the different methods.
Conclusions: Poverty and cultural factors contribute to pesticide use and
unsafe use conditions. Education programs should be culturally
appropriate to achieve pesticide exposure reduction. Each method studied
in this thesis can be used independently. However, they can also
complement each other, providing a better understanding of the mechanisms
of skin exposure. With further improvements, a combination of observation
and fluorescent visual scoring techniques, both lowcost and practical,
would become highly accessible methods for surveillance and for
epidemiological studies in developing countries.
List of papers:
I. Aragon A, Aragon C, Thorn A (2001). "Pests, peasants, and pesticides on the Northern Nicaraguan Pacific Plain. " Int J Occup Environ Health 7(4): 295-302
Pubmed
II. Blanco LE, Aragon A, Lundberg I, Liden C, Wesseling C, Nise G (2005). "Determinants of dermal exposure among Nicaraguan subsistence farmers during pesticide applications with backpack sprayers." Ann Occup Hyg 49(1): 17-24. Epub 2004 Dec 15
Pubmed
III. Aragon A, Blanco LE, Funez A, Ruepert C, Liden C, Nise G, Wesseling C (2005). "Assessment of Dermal Pesticide Exposure with Fluorescent Tracer: A Modification of a Visual Scoring System for Developing Countries." Ann Occup Hyg Aug 26: Epub ahead of print
Pubmed
IV. Aragon A, Blanco L, Lopez L, Liden C, Nise G, Wesseling C (2004). "Reliability of a visual scoring system with fluorescent tracers to assess dermal pesticide exposure." Ann Occup Hyg 48(7): 601-6. Epub 2004 Sep 20
Pubmed
V. Aragon A, Ruepert C, Blanco LE, Funez A, Liden C, Nise G, Wesseling C (2005). "Skinexposure of hands to organphosphate pestcides among subsitence farmers in Nicaragua: a comparison of hygiene observation, fluorescent visual scoring and skin wiping." (Manuscript)
I. Aragon A, Aragon C, Thorn A (2001). "Pests, peasants, and pesticides on the Northern Nicaraguan Pacific Plain. " Int J Occup Environ Health 7(4): 295-302
Pubmed
II. Blanco LE, Aragon A, Lundberg I, Liden C, Wesseling C, Nise G (2005). "Determinants of dermal exposure among Nicaraguan subsistence farmers during pesticide applications with backpack sprayers." Ann Occup Hyg 49(1): 17-24. Epub 2004 Dec 15
Pubmed
III. Aragon A, Blanco LE, Funez A, Ruepert C, Liden C, Nise G, Wesseling C (2005). "Assessment of Dermal Pesticide Exposure with Fluorescent Tracer: A Modification of a Visual Scoring System for Developing Countries." Ann Occup Hyg Aug 26: Epub ahead of print
Pubmed
IV. Aragon A, Blanco L, Lopez L, Liden C, Nise G, Wesseling C (2004). "Reliability of a visual scoring system with fluorescent tracers to assess dermal pesticide exposure." Ann Occup Hyg 48(7): 601-6. Epub 2004 Sep 20
Pubmed
V. Aragon A, Ruepert C, Blanco LE, Funez A, Liden C, Nise G, Wesseling C (2005). "Skinexposure of hands to organphosphate pestcides among subsitence farmers in Nicaragua: a comparison of hygiene observation, fluorescent visual scoring and skin wiping." (Manuscript)
Issue date: 2005-11-25
Rights:
Publication year: 2005
ISBN: 91-7140-588-7
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