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Sistema de Información Científica
Red de Revistas Científicas de América Latina y el Caribe, España y Portugal
Centro de Ciencias de la Atmósfera, Universidad Nacional Autónoma de México, Ciudad Universitaria, Co-
yoacán 04510 D.F., México
Instituto de Investigación en Ambiente y
Salud y Departamento de Ciencias Biológicas, Universidad de
Occidente, Boulevard Macario Gaxiola y Carretera Internacional, Los Mochis, Sinaloa, México
Instituto de Medicina Forense, Universidad Veracruzana, Veracruz, Ver. México
* Corresponding author:
(Recibido junio 2012, aceptado noviembre 2012)
Key words: micronuclei, exfoliated cells, child risk, pesticides, cytogenetic biomarkers
Pesticide ambient exposure is a potential risk when children live in or near a feld
aerial sprayed with such chemicals as is the case in Sinaloa state in the northwest of
Mexico. In this study the possible genotoxic risk assessment was evaluated in two
groups: 125 children (52 females and 73 males) living in residential proximity to ar-
eas of intensive agriculture and exposed to agricultural activity of pesticide mixtures,
in addition to 125 control youngsters (57 females and 68 males) living in the city of
Los Mochis, Sinaloa. The risk assessment was done through the use of micronuclei
(MN) in exfoliated buccal cells as biomarkers. The age range in both groups was 1 to
13 years. Microscopic analysis was performed in 3000 buccal epithelial cells for each
sample. Signifcant increment oF MN Frequencies was observed when the odds ratios
(OR) values were calculated (3.11 and 95 % CI 2.70 and 3.50), indicating high health
risk to the exposed children. Other nuclear abnormalities associated to cytotoxicity or
genotoxicity as binucleate cells, nuclear buds, karyorrhesis and karyolysis were detected;
in all cases the diFFerences were signifcant in relation with the control group. The MN
assay in exfoliated cells was useful, and a minimally invasive method was followed
for monitoring cytogenetic damage in the children who live in residential proximity to
areas of intensive agriculture treated with large amounts of pesticide mixtures.
Palabras clave: micronúcleos, células exfoliadas, riesgo infantil, plaguicidas, biomarcadores citogenéticos
La exposición ambiental a plaguicidas constituye un riesgo potencial para los niños que
viven en o cerca de campos agrícolas asperjados de forma aérea con estas sustancias,
como es el caso en el estado de Sinaloa en el noroeste de México. En este estudio el
posible riesgo genotóxico fue evaluado en dos grupos: 125 niños (52 mujeres y 73
Rev. Int. Contam. Ambie. 29 (3) 217-225, 2013
S. Gómez-Arroyo
et al.
hombres) cuyas casas están cercanas a zonas de intensa actividad agrícola que son
asperjadas con mezclas de plaguicidas y en 125 niños testigos (57 mujeres y 68 hom-
bres) que viven en la ciudad de Los Mochis, Sinaloa, utilizando como biomarcador los
micronúcleos (MN) en células exfoliadas de mucosa bucal. El rango de edad en ambos
grupos fue de 1 a 13 años. El análisis microscópico fue realizado en 3000 células del
epitelio bucal para cada muestra. Se observó incremento signifcativo en la Frecuencia
de MN. También fue calculada la razón de momios (RM) (3.11 y 95 % CI 2.70 y 3.50)
indicando los valores alto riesgo a la salud de los niños expuestos. Otras anormalidades
nucleares asociadas a citotoxicidad o genotoxicidad como células binucleadas, yemas
nucleares, cariorresis y cariolisis fueron detectadas; en todos los casos las diferencias
Fueron signifcativas con relación al grupo testigo. El ensayo de MN en células exFo
liadas resultó un método útil y poco invasor para el monitoreo del daño citogenético
en los niños que viven en o cerca de las áreas agrícolas que son intensamente tratadas
con grandes cantidades de mezclas de plaguicidas.
Pesticides are among the chemical products
most extensively used to control agricultural pests.
The development of agrochemical industries in the
century originated a great number of highly
aggressive and toxic compounds against humans,
and that altered the equilibrium in ecosystems.
To a high or low degree, human populations are
unavoidably exposed to environmental pollutants
in physical, chemical or biological forms through
products presented or degraded in air, water, soil or
food. Environmental exposure to pesticides causes a
potential risk to humans; when children are exposed,
the risk is heightened. Children are more sensitive
to toxic effects because of immature metabolism
and liver functions (National Research Council
1993). There are many associated factors that af-
fect children’s health. Children interact with the
environment in a way unlike adults, they are more
sensitive to physical and biological factors, and
present a different behavior (Faustman
et al
. 2000,
Garry 2004, Neri
et al
. 2006). Children’s health is
at a higher risk than that of adults of being affected
by exposure to pesticides, considering primarily that
the immunological system and the metabolic capac-
ity in children are not mature (National Research
Council 1993). Thus, a fundamental principle of
pediatric medicine to bear in mind is that “children
are not little adults”, a fact which is particularly
important when the discussion is centered on chil-
dren and their exposure to pesticides. Children are
at risk through diverse sources and are vulnerable
to a higher degree than adults under similar condi-
tions of exposure (Neri
et al
. 2006). Furthermore,
the respiratory rate, heart rate, and metabolism of
children are signifcantly diFFerent From those oF
adults (Bearer 1995). Wassels
et al
. (2003) provide
evidence that factors as body surface/body weight
ratio, circulatory ±ow rates, as well as intake oF
water, milk and fruits are greater in children than in
adults. Additionally, consumption oF large quantities
of fresh food (possibly contaminated) and the high
Frequency oF hand-to-mouth habits also increase
the susceptibility of children to pesticide exposures
et al
. 2002).
In the northwest of the Mexican Republic, in
Sinaloa state, agriculture is a predominant activity.
The climatic conditions have favored the develop-
ment of pests and plant diseases, which has given
rise to a preventive practice related with the use of
pesticides. Likewise, children living in or near treated
crop lands can be exposed in the course of agricultural
application (Carozza
et al
. 2008), as in the north of
Sinaloa state where large amounts of pesticides are
aerial sprayed in the felds.
Epidemiological studies have described associa-
tions between childhood cancer and either parental
or child exposure to pesticides (Daniels
et al
. 1997,
Zahm and Ward 1998, Thompson
et al
. 2003, Nas-
terlack 2006). Pesticide spraying by parents has been
associated with acute lymphocytic leukemia, tumors
in the central nervous system and non-Hodgkin’s
lymphoma (Daniels
et al
. 1997, Zahm and Ward
1998, Flower
et al
. 2004).
In Mexico, the mortality caused by leukemia in
individuals younger than 20 years of age represents
a serious health problem, and therefore an early di-
agnosis is important for health prevention (Rizo-Ríos
et al
. 2005). For this purpose the use of biomarkers
such as micronucleus (MN) is appreciated in showing
signs of chromosomal damage and affording a marker
of an early-stage of chronic diseases as cancer; such
markers also reveal an increase in micronuclei fre-
quency predicting cancer risk in humans (Bonassi
. 2005, 2007).
Micronuclei are formed by chromosomal damage
in the basal cells of the epithelium; when these cells
divide, chromosomal fragments or entire chromo-
somes that lack an attachment to the spindle apparatus
are excluded from the main nuclei in the daughter
cells and they appear as Feulgen-specifc bodies in
the cytoplasm called micronuclei. Later, these cells
mature and exfoliate (Rosin 1992).
Nevertheless, cytogenetic biomarkers are known
to be useful as endpoints in the study of subjects
occupationally exposed to genotoxic agents. The
micronucleus (MN) assay in human exfoliated cells
has been widely used to detect the genotoxic effects
of environmental mutagens (Titenko-Holland
. 1994, Bolognesi
et al
. 2011). The MN test in
epithelial cells has several advantages as has been
suggested by Bonassi
et al
. (2009): it is a non-
invasive method (particularly important in studies
which involve children), and the exfoliated epithe-
lial cells from the mouth can be collected easily and
rapidly to make the cytogenetic analysis, among
other benefts. MN assays in buccal epithelial cells
have been used in the biomonitoring of agricultural
workers exposed to pesticides, and the data reported
indicate both positive (Gómez-Arroyo
et al
. 2000,
et al
. 2007, Bortoli
et al
. 2009, Martínez-
et al
. 2009, Remor
et al
. 2009) and
negative correlations (Lucero
et al
. 2000, Pastor
. 2001a, b, 2002).
The aim of the present study was to assess the
genotoxic risk in children who live in residential
proximity to areas of intensive agriculture treated
with pesticide mixtures in the north of Sinaloa; this
was done through the use of micronuclei (MN) in
exfoliated buccal cells as biomarkers.
Study population
Sinaloa state is situated in the northwest of the
Mexican Republic. At the beginning of the study, all
of the children’s parents were informed of the pur-
pose of the work; the parents consented and signed a
document in which they agreed to participate in the
study and to complete a standardized questionnaire
that contained personal data with a history of recent
illness, medical treatment and food habits, as well as
to inform about the pesticides used in these agricul-
tural areas (
Table I
). The parents interviewed said
that the area is continually aerial sprayed during at
least two annual periods. This study was performed
in accordance with the principles of the Declaration
of Helsinki. The study protocol and sample collec-
tion procedure were reviewed and approved by the
local Pediatric Committee. The MN test was carried
out on the buccal epithelial cells. The samples were
obtained from March to November 2008 of 125 chil-
dren (52 females and 73 males) whose parents were
agricultural workers living and working in the north
of Sinaloa, in addition to 125 control youngsters (57
females and 68 males) who lived in the city of Los
Mochis, Sinaloa. The age range in both groups was 1
to 13 years. At the moment of the sampling none of
the children were under medical treatment or exposed
to radiation, none had infectious diseases, and none
had had recent vaccines.
The houses of the children involved in the re-
search were in all cases located near the agricultural
felds where mango, corn, sorghum, beans, among
other products, are cultivated almost all year long;
thus, when the pesticides were aerial sprayed on the
felds, the houses were also sprayed with the applied
pesticides and the substances dripped on the sheet
of the metal roofs. The children that participated
in this study as well as the control group did not
live in the vicinity of busy roads, waste sites, nor
of industrial emissions, and in most of the cases
the children’s parents mentioned that they did not
smoke inside their houses, which suggested that they
are not passive smokers. All of them corresponded
to the same socioeconomic status. Two important
±actors involve the pesticide behavior: frst, the
area studied is a valley without barriers that pre-
vent the movement of volatilized pesticides whose
molecules can go several kilometers; secondly, the
climate exhibits mainly high temperatures during
the summer up to 48
C and relative humidity of
85% (INEGI 2005). For this reason children wear
minimal clothing, and often walk or play outside
the house, thereby increasing the pesticide contact
and dermal absorption; also, given the fact that
these communities lack recreational activities, the
children spend many hours playing in the open space
behind their house.
With respect to the general dietary habits, all of the
children were found to be omnivores. They consumed
meat, fsh and ±ruit at least once a week and they ate
vegetables daily, including the corn “tortilla” which
is the basis of the Mexican diet.
procedure in buccal exfoliated cells
After the children had rinsed their mouth with
water, sample cells were obtained from the buccal
S. Gómez-Arroyo
et al.
mucosa with a wooden spatula. The sample was then
applied to a clean microscope slide. Smears were air
dried and fxed in methanol-acetic acid (3:1). The
cell smears were stained using the Feulgen technique
described by Stich and Rosin (1984) and modifed as
follows: the cell smears were pretreated with 1 N HCl
for 10 min at room temperature, placed in 1 N HCl
for 10 min at 60 ºC, rinsed in distilled water, put in
Schiff’s reagent for 90 min and washed with running
tap water. The ±requency o± micronucleated cells was
estimated according to the criteria of Stich and Rosin
(1984), and Livingston
et al
. (1990). For each child
3000 epithelial cells were scored to determine the MN
±requency and other nuclear anomalies as nuclear buds
also known as “broken eggs” (nuclei appear cinched
with a Feulgen-negative band), karyolysis (nuclear
dissolution, in which a Feulgen-negative, ghost-like
image of the nucleus remains), karyorrhexis (disinte-
grated nuclei) and binucleate cells (presence of two
nuclei within a cell), which were classifed according
to Tolbert
et al
. (1992) and Holland
et al
. (2008).
the slides were coded before scoring to avoid bias.
Statistical analysis
The U of Mann-Whitney
test was applied to the
results of MN and the other nuclear anomalies. The
correlation between different parameters was estab-
lished by means of the Spearman correlation test.
For evaluating and determining the risk factors for
children exposed to environmental conditions, prob-
ability distribution of two binary random variables
using logistic regression was applied and the odds
ratios (OR) values were calculated (Wassertheil-
Smoller 2003). The odds higher than 1.5 and the
confdence interval (CI) higher than 1.5 indicated
risk for the studied children.
Table II
shows the mean of MN per 1000 cells
in the children living in the areas of high agricultural
activity and the mean of the control group; in this
table we observe that the mean of the cells in the
former group is six times higher than in the control
group. The range of micronuclei observed is of 0 to
10 % in the former and 0 to 0.4 % in the control. The
di±±erence was signifcant ±or the
U of Mann-Whitney
test p < 0.0001. The calculated OR to evaluate risk
for health of exposed children shows 3.11 with 95 %
CI 2.70 and 3.50, which explains the signifcant risk
for children living in contaminated agricultural areas.
Endosulfan (II, UM)
Parathion methyl (3, Ia,
Aldicarb (Ia)
Fenvalerato (II)
Chlordane (III, 2B)
Azinphos methyl (Ib)
Carbofuran (Ib)
Cypermethrin (III)
Aldrin (3, AIOP)
Gusathion (Ib)
Oxamyl (Ib)
Monocrotophos (Ib)
Lannate (Ib)
Diazinon (II, UM)
Vydate (Ib)
Chlorpyrifos (II)
Propoxur (II)
Malathion (3, III)
Carbaryl (III)
Carbosulfan (III)
Molinate (II)
Paraquat (II)
Butylate (U)
2,4,D (III)
Aminocarb (AIOP)
Glyphosate (U)
Atrazine (U, UE)
Dinoseb (AIOP)
Pentachlorophenol (Ib)
Benomyl (U)
Captan (U)
Mancozeb (U)
Cupravit (U)
Maneb (3, U, UE)
IARC (2012) 2B= possible carcinogenic to humans, 3= not classify as to its carcinogenicity to humans.
WHO (2004) hazard classifcation: Ia= extremely hazardous, Ib= highly hazardous, II= moderately hazardous,
III= slightly hazardous, U= unlikely to present acute hazard in normal use, AIOP= active ingredients believed to
be obsolete or discontinue for use as pesticides.
CICOPLAFEST (2012) UE = possible endocrine effects, UM = probably teratogen effects
When the MN frequencies were compared be
tween female and male as well as with age, in chil-
dren living in the Felds sprayed with pesticides, no
signiFcant differences were found. No correlation
was observed between MN frequency and low or no
consumption of meat, Fsh or fruit.
The analysis of exfoliated cells of the buccal
mucosa also provided evidence of other nuclear
anomalies such as binucleate cells, nuclear buds,
karyorrhesis and karyolysis; in all the cases the differ-
ence was signiFcant in relation with the control group
for the U of Mann-Whitney
test p < 0.0001(
Table II
Table II
presents the OR values for other nuclear
anomalies such as binucleate cell (OR = 4.30, 95 %
CI 3.90, 4.60), karyolysis (OR= 2.63, 95 % CI 2.57,
2.69), nuclear buds (OR= 1.53, 95 % CI 1.45, 1.80)
and the highest karyorrhesis (OR= 17.80 95 % CI
14.80, 20.80).
When MN frequency was compared between the
samples obtained from male and female children
whose residence involved contact with pesticides, no
signiFcant differences were observed. These results
agreed with Ganguly (1993), Barale
et al
. (1998)
and Shi
et al
. (2000) who found that MN frequencies
in male and female children were not signiFcantly
different. However, Bolognesi
et al
. (1993) did Fnd
higher MN frequency in women than in men; in both
cases, individuals had been exposed to pesticides.
No effect of age was observed in the children who
lived in the north of Sinaloa and consequently were
under pesticide exposure. These results agreed with
et al
. (2001) who did not observe an age-
dependant increase in MN in exfoliated buccal cells
of children aged 5-12. However, other studies have
shown an MN increase in lymphocytes (Ganguly
1993) and in urothelial cells (Holland
et al
. 2001).
The MN test in epithelial cells of the buccal mucosa
allowed the conclusion that the exposure to pesticides
signiFcantly increased MN frequencies. This implied
that the tissue was damaged at the chromosomal level,
and that it had undergone chromosome breakage and/
or mitotic spindle alterations, along with other nuclear
abnormalities such as pycnosis, karyolysis, karyor-
rhesis and nuclear buds. According to Tolbert
et al
(1992), pycnosis and karyorrhexis are associated with
both cytotoxicity (necrosis and keratinization) and
genotoxicity, while karyolysis is only related with
cytotoxicity. In contrast, the nuclear bud is perhaps
related to anaphase bridges, which occur as a result of
chromosome aberrations; however, the origin of the
nuclear bud and its signiFcance are even now unknown
et al
. 1994, Holland
et al
. 2008). In
our research, results for the children with residential
proximity to agricultural areas with intense aerial
pesticide applications showed that all the frequencies
of nuclear anomalies were signiFcantly different from
those of the control group, a Fnding that agrees with
other studies in which pesticides caused this kind of
abnormalities in adults (Gómez-Arroyo
et al
. 2000,
et al.
2007, Martínez-Valenzuela
et al
. 2009).
The comparison of exposed and control children
through OR calculations is a basic epidemiological
measure of risk assessment, and a powerful statistical
tool to determine if an exposure is associated with
a prospective condition following two groups, one
exposed and one unexposed. The magnitude of the
difference in the MN frequency between the two
groups is a consequence of the pesticide contact, and
the MN OR value evidences a possible health risk for
exposed children. In all the other nuclear anomalies
analyzed, the OR values were higher than 1.5; that
means that the pesticide exposition probably caused
cytotoxic and genotoxic effects.
The analysis in epithelial cells is relevant because
approximately 92 % of cancer cases are of epithelial
origin (Rosin 1992). The heightened risk of childhood
cancer is associated with residence in agriculturally
intense areas in the United States of America. Chil-
dren living in areas of great agricultural activity may
be exposed to higher levels of pesticides than others
et al
. 2008). Thus, through this simple and
sensitive analysis, the damage in target organs can
be evaluated.
The study of Carozza
et al
. (2008) indicates an in-
creased risk of different types of childhood cancers as
leukemia and central nervous system tumors related
95 %
3.6 ± 0.79* 0.6 ± 0.15
3.11* 2.70, 3.50
1.3 ± 0.56* 0.2 ± 0.32
4.30* 3.90, 4.60
2.8 ± 0.25* 1.2 ± 0.30
2.63* 2.57, 2.69
Karyorrhesis 1.8 ± 0.28* 0.2 ± 0.19 17.80* 14.80, 20.80
Nuclear buds 1.1 ± 0.52* 0.6 ± 0.47
1.53* 1.45, 1.80
In 125 children
n= 3000 cells in each individual
A Exposed
mean + SD per 1000 cells
B Controls means + SD per 1000 cells
SigniFcance p
< 0.001
S. Gómez-Arroyo
et al.
with pesticide exposure, generally related to the resi-
dence of children in places with greater agricultural
pesticide use. In Sinaloa state, parents working in the
felds are exposed to pesticides as well as children liv
ing in places where the crops are aerial sprayed with
pesticides; because of a shorter life period, the young-
sters did not present signs of cancer. The positive MN
test is a warning because other children not included
in the study did show leukemia and because family
members of the children included in the study had
other types of cancer; in fact, several young women
had breast cancer. The questionnaire indicated that
about 40 % of the families of the children living in a
feld sprayed with pesticides had at least one Family
member with cancer, while in the control group about
18 % of the families had a member with cancer. The
MN show signs of chromosomal damage and afford
a marker of an early-stage of chronic diseases as
cancer (Bonassi
et al
. 2005).
In the present study, parents of the children ex-
posed to pesticide mixtures said that in their area
the most Frequently used compounds contained diF
ferent active ingredients, mainly organophosphorus
and carbamates. Some of the mixtures included two
compounds which, according to the WHO (2004)
classifcation, are “extremely hazardous” (parathion
methyl and aldicarb) and eight which are “highly
hazardous” (azinphos methyl, monocrotophos,
gusathion, oxamyl, carbofuran, lannate, vydate and
the fungicide pentachlorophenol). According to the
IARC (2012), chlordane and pentachlorophenol are
considered as possibly being carcinogenic to humans;
as indicated by CICOPLAFEST (2012), endosulfan,
parathion methyl, diazinon, carbofuran, propoxur,
carbaryl, benomyl, 2,4,D, atrazine and captan are clas-
sifed as possibly having teratogen eFFects, and maneb
and atrazine as possibly having endocrine effects.
The possible genotoxic damage caused by each
pesticide in the children is associated with residence
in agriculturally intense areas that are treated with
these compounds in the north of Sinaloa, but this
cannot be determined mainly because the substances
are applied as complex mixtures. Moreover, the geno-
toxicity of some of these pesticides is unknown. The
signifcant increase in the Frequency oF MN could be
due to the accumulative effects of pesticides with
clastogenic activity as is the case of endosulfan,
paraquat, malathion, parathion methyl and 2,4, D
(Titenko-Holland 1997, Zeljezic and Garaj-Vrhovac
2001). Nevertheless, the activity of other pesticides
which have an aneugenic effect, as those associated
to the use of glyphosate and carbofuran (Mladinic
. 2009), can probably be shown.
The pesticide amounts are diFfcult to evaluate
due to the fact that the children live in the proximity
oF the felds that are aerial sprayed almost all year
around. In this way, it is important to mention that
during the 2007 agriculture cycle in the Ahome
place in which children were living, 65 171.29 ha of
corn, 15 979 ha of sugar cane, 15 258 ha of sorghum,
7850.39 ha of bean, 2938 ha of mango, and 2694.56
ha of alfalfa, among others, were sow (INEGI 2008).
A personal communication of the Technical Coordi-
nator of the Agricultural Association of Río Fuerte
Sur, Sinaloa, indicates that only for the mango culture
during the 2007-2008 period, the following were ap-
plied: chlorpyrifos (II) 3 L/ha, chlordane (III, 2B)
3 L/ha, lannate (Ib) ½ kg/ ha, endosulfan (II, UM)
1.5 L/ha, vydate (Ib) 3 L/ha (which is a liquid that
in contact with water forms a gas), atrazine (U, UE)
2 L/ha, 2,4 D (III) 2 L/ha (this herbicide has been
forbidden but it is still applied, despite its high tox-
icity), molinate (II) 3 L/ha, benomyl (U) 3 kg/ha,
captan (U) 1.5 kg/ha, mancozeb (U) 1.5 kg/ha, and
paraquat (II) 1.5 kg/ha. As an example, in 5000 ha
of cultures about of 6500 ton of captan were applied.
Considering this data and the information sup-
plied by the children parents about the time the
youngsters remain outdoors, we can establish that
the exposure should be considered as constant and
that it is highly probably the cause of the observed
cytogenetic effects.
It is well known that pesticide toxicity may be
caused not only by the active ingredients and the
associated impurities, but also by solvents, carriers,
emulsifers, and other constituents oF the Formulated
product (Al-Saleh 1994). This is so, due to the pres-
ence of solvents and surfactants which penetrate the
lipid skin easily as a result of the alterations in cellular
permeability; likewise, the pesticides may contain
impurities such as dioxins, or solvents as naphthalene
and benzene all of which are also carcinogenic.
Another important factor considered in our study
was the dietary intake, given that in child population
vulnerability to the toxic effect of pesticides increases
due to malnutrition (Faustman
et al
. 2000, Lu
et al
2000, Suk
et al
. 2003, Garry 2004, Neri
et al
. 2006).
However, in the children of Sinaloa with residence
in agriculturally intense areas, malnutrition may not
be a conFounding Factor in±uencing the susceptibility
to pesticides; this statement is based on the fact that
no correlation was found between the low intake or
lack oF consumption oF meat, fsh or Fruit and the
MN Frequency.
The results obtained in the present study confrm
the importance of designing strategies to protect
mainly children. The reason is that they are the most
vulnerable sector of the population; children in the
north of Sinaloa state are at risk of harm to their health
when they are living exposed to pesticides associated
with intensive agriculture activities.
It is for this reason that we make the following
recommendations for reducing child exposure:
- The possibility of sending the planned schedule
to spray pesticides to all of the inhabitants in the
vicinity of the agricultural areas (it is important to
circulate the information at least 24 hours before
fumigation) must be considered.
- The person responsible in charge of the fumiga-
tion should be prepared to afford speciFc information
and to avoid the pesticide application in the presence
of pregnant women and of children particularly dur-
ing class hours. Fumigations on Friday nights or
during the end of the week are advisable.
- It is important to restrict the passing of chil-
dren and women into the fumigated areas until the
pesticides dry as well as to follow the instructions
for users.
- It is appropriate to inform all individuals
involved, as parents, children, day laborers, and
farmers, about the risk of exposure to this type of
compounds and how to be better protected, or if
possible advise them to move away.
We thank PROMEP (Programa para el Mejora-
miento del Profesorado) for granting the fellowship
to Dr. Carmen Martínez-Valenzuela, and the Gonzalo
Río Arronte ±oundation for Fnancial support. We also
appreciate the valuable contributions of Dr. Jesús
Kumate Rodríguez to the study, and the important
aid of Claudio Amescua in structuring the article.
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