Human exposure assessment of pesticide use in developing countries

Summary Problem. Pesticides play an important role in the
agricultural production but their misuse affect the health of
farmers and workers who manipulate such toxic substances. In the
field of occupational hygiene, researches have been working in
finding out the most appropriate method to estimate the human
exposure in order to assess the risk and therefore to take the due
decisions to improve the processes in the pesticide management and
to reduce the health risk. Goals. The goal of this research was
focused in creating a model for human exposure assessment specially
for farming systems in developing countries by (i) evaluating the
available models for human exposure assessment developed in
industrialized countries, (ii) measuring the exposure in the study
areas of potato and flower farming systems in Colombia, and (iii)
proposing a pesticide flow model to estimate quantitatively the
human exposure. Methods. The research was organized in three phases
by using different methods, namely (i) evaluation of previous
models of human exposure assessment (by means of a Multi-Criteria
and Sensitivity Analysis); (ii) quantification of dermal exposures
in Vereda La Hoya (by applying the Whole Body Dosimetry,
Luminiscence Spectrometry and Tracer Method); and (iii) the
development of a pesticide flow model for the human exposure
assessment (by applying the Material Flow Analysis method). This
model was built with dermal exposure measurements obtained in the
study area of greenhouse flower crops in Sabana de Bogotá,
Colombia. Results. DERM, DREAM, PHED and RISKOFDERM were selected
as the most appropriate models to be applied in farming systems in
developing countries as their determinants are relevant for the
assessment of pesticide use and all the processes involved during
the pesticide management. Afterwards these four models were applied
to assess the dermal exposure in the case study of Vereda La Hoya
and their determinants were compared with the characteristics of
the study area, DREAM and DERM were found as the most appropriate
models to assess the dermal exposure in these study areas. However,
because some relevant determinants are still absent, the accuracy
of these models could be improved if these are included. When
comparing the final model assessment of dermal exposure in the
study area, DREAM was found as the model that assesses more
accurately the dermal exposure in this study area. In the study
area of Vereda La Hoya, Colombia was found that the application was
the activity with the highest PDE. Even though lower body parts
(thighs and legs) were the most exposed, these body parts also
showed the highest level of protection because of the work
clothing. The ADE was high for arms and upper back due to the lack
of adequate work clothing covering the complete arm and the direct
contact of the upper back with the spills on the sprayer tank.
Furthermore, it was found that Metamidophos is the most toxic
pesticide used in Vereda La Hoya. Farmers may reduce significantly
the health risk by using adequate work clothing made of appropriate
fabrics that covers the whole body including the arms, cleaning
properly all the pesticide residues left on the sprayer before each
application, and avoiding the modification of nozzles using only
nozzles with the standard discharge. The proposed pesticide flow
model helps to identify the patterns of pesticide distribution on
the body, the level of protection given by personal protective
equipment and the estimates of potential and actual dermal and
inhalation exposure. This information can be used to determine the
health risk level by comparing the model estimates with the AEOL
reference values for each pesticide. In addition, the model makes
it possible to easily identify the activities or body parts that
have high levels of exposure. This is useful in identifying
improvements that will decrease the exposure during pesticide
management. Because it is not feasible to measure directly the
dermal exposure in all study areas, this model might help to obtain
a quick estimation which could help stakeholders and authorities to
make further decisions. Conclusions. This research evaluated in
depth the available models for human exposure assessment, so
assessors can decide which model is the most appropriate according
to the characteristics of the study area in which the model is
going to be applied and furthermore this research suggested
improvements in the models in order to increase the estimation
accuracy. This research also contributes in the proposal of a new
model for human exposure based on the material flow analysis
methodology studying the pesticide fractioning during the pesticide
management in a certain interval of time. With this model
quantitative estimations of human exposure are obtained which
facilitate the risk assessment and the implementation of measures
to improve the safety during the pesticide management and to
decrease the risk. The proposed model also demonstrates the
feasibility of applying the material flow analysis methodology in
the field of human exposure, obtaining a tool that helps to
understand the mechanisms of distribution of the pesticide in the
farming system based on the processes involved and the flows
between these processes.