Doutoramento em BiologiaThe present research concerns the environmental impact of
pesticides used in the Fluvio Lagoon Palizada River Subasin
(FLPRS) in Campeche, Mexico on environmental health using
biomarkers in wild mosquitofishes (Gambusia yucatana) and
whistling ducks (Dendrocygna autumnalis), likewise in
campesinos (peasants).
Mosquitofishes (G. yucatana) and black-bellied whistling
duck (D. autumnalis) were chosen as bioindicators as they
are abundant species, the fishes in small streams of the
region; and the whistling ducks (D. autumnalis) in wetlands,
being most abundant in flooded savannahs and irrigated rice
fields. In this work were included human been because they
applied the pesticide and are exposed at the first time.
The biomarkers used to asses the environmental
exposures to pesticides were acetylcholinesterase (AChE, EC
3.1.1.7), glutathione-S-transferases (GST, EC 2.5.1.18) and
lactate dehydrogenase (LDH, EC 1.1.1.28).
In this research was evaluated the environmental impact of
pesticide use in the FLPRS in order to 1) know the
environmental conditions of PRS in relation to water quality
and land use, 2) evaluate in laboratory the use of biomarkers
such as AChE, GST and LDH in wildlife exposed to
pesticides, 3) estimate with biomarkers the environmental
pesticide effects on organisms from aquatic (mosquitofish, G.
yucatana) and terrestrial (whistling ducks, D. autumnalis)
compartments, and 4) evaluate the adverse effects of
pesticides used by fieldworkers from El Juncal, Palizada using
symptoms related to pesticide exposure and a biomarker.
The assessing of environmental impact of pesticide was
carry out with the biomarkers mentioned with a test battery in
situ through a biomonitoring study and toxicity test chambers
in aquatic organisms, and with a survey on brain
cholinesterase biomarker in terrestrial organisms.
The results of this study indicated that during the last 20
years, in the Palizada River Subasin (PRS) the land use
change has been drastic mainly in agriculture cover because
this increase in more than 1,000 %, and the total amount of
pesticide used is parallel to this increase in agricultural
hectares. The use of an index of water quality (WQI) identified
that from the nine sampling sites studied in the PSR, sites
with cattle ranching (WQI= 0.58) and agricultural (WQI= 0.65)
activity were the sites with a significant average of WQI worse
than the others sites (WQI = 0.68 – 0.73).
In mosquitofish (G. yucatana), the characterization of
cholinesterases seems that the main form present in both
muscle and head is AChE. The ranking of in vivo toxicity
(LC50) of the tested pesticides to G. yucatana was
chlorpyrifos > carbofuran > glyphoste. ChE activities of
muscle and head of mosquitofish were significantly inhibited
by furadan after 24 hrs of exposure with an inhibition of 60%
at 0.06 mg/L. The mixture chlorpyrifos/glyphosate is 34%
more toxic than the chlorpyrifos tested alone. In the test with
6
chlorpyrifos, fish that survived after an exposure of 96h to
concentrations between 0.006 and 0.012 mg/L showed a ChE
inhibition near to 80%. Muscle and head AChE activity was
inhibited by chlorpyrifos and carbofuran; gill GST was
inhibited by carbofuran; and muscle LDH activity was not
altered by any of pesticides tested.
In the case of whistling duck (D. autumnalis), the forebrain
ChE seems to be AChE. The carbofuran-chlorpyrifos mixture
was the most potent in vitro inhibitor of D. autumnalis brain
ChE tested. This is important because in real conditions the
exposure is with a mixture of pollutants which can cause
possible synergistic effects.
The field study in the PRS was focused to three different
sampling sites, one with cattle ranching activity, other with
agricultural activity, and the last one was the Palizada River.
The first phase of the in situ study demonstrated the
possibility of a link between the water quality index (WQI) and
the variation of abiotic conditions that may cause effects on
survival, growth, and biomarkers on fishes exposed not
related with direct effects of pollutants.
In the biomonitoring studies using enzymatic biomarkers in
wild fish present the advantage of diagnosing the real
exposure and/or effects of environmental contaminants but
they may underestimate the actual contamination of the
water, since organisms with a reasonable degree of mobility
may avoid the exposure. The results obtained in this study
indicate that some water variables can influence directly or
indirectly on enzymatic activity, and consider it as a natural
variability of activity.
The integration of information generated in situ toxicity test
and wild fishes reflected a concordance between percentages
of AChE activity in wild fishes and exposed in situ in the
Palizada River during February, July and November. The
results of the study with whistling duck (D. autumnalis)
suggest that ducks are exposed to pesticides (inhibition above
30% of ChE activity), at least during the season of intensive
application.
The evaluation of the adverse effects of pesticides in
fieldworkers from El Juncal, Palizada using AChE as a
biomarker showed no conclusive results from the regression
analysis of symptoms and AChE inhibition activity. Some
symptoms are probably compatible with acute
organophosphate and carbamate poisoning such as
headache, weakness, nausea, sweating and tiredness. No
differences were observed with respect to use of protective
clothing.
It is recommended the use of pesticide less aggressive to
environment and human health, also further field studies
incorporating a systematic monitoring of wild populations and
investigating also population parameters are particularly
important for local pesticide management