The situation of chlorpyrifos in Mexico: a case study in environmental samples and aquatic organisms.

Chlorpyrifos (CPF) is one of the most commonly used organophosphate pesticides. Because CPF was described as a toxic compound without safe levels of exposure for children, certain countries in Latin America and the European Union have banned or restricted its use; however, in Mexico it is used very frequently. The aim of this study was to describe the current situation of CPF in Mexico, as well as its use, commercialization, and presence in soil, water, and aquatic organisms in an agricultural region of Mexico. Structured questionnaires were applied to pesticide retailers to determine the sales pattern of CPF (ethyl and methyl); in addition, monthly censuses were conducted with empty pesticide containers to assess the CPF pattern of use. Furthermore, samples of soil (48 samples), water (51 samples), and fish (31 samples) were collected, which were analyzed chromatographically. Descriptive statistics were performed. The results indicate that CPF was one of the most sold (3.82%) and employed OP (14.74%) during 2021. Only one soil sample was found above the CPF limit of quantification (LOQ); in contrast, all water samples had CPF levels above the LOQ (x̄ = 4614.2 ng/L of CPF). In the case of fish samples, 6.45% demonstrated the presence of methyl-CPF. In conclusion, the information obtained in this study indicates the need for constant monitoring in the area, since the presence of CPF in soil, water, and fish constitutes a threat to the health of wildlife and humans. Therefore, CPF should be banned in Mexico to avoid a serious neurocognitive health problem.

Toxicokinetics of temephos after oral administration to adult male rats.

Temephos (Tem) is the larvicide of choice to control mosquito transmission of dengue, Zika, and chikungunya. The toxicokinetic and toxicological information of temephos is very limited. The aim of this work was to determine the toxicokinetics and dosimetry of temephos and its metabolites. Male Wistar rats were orally administered temephos (300 mg/kg) emulsified with saline solution and sacrificed over time after dosing. Temephos and its metabolites were analyzed in blood and tissues by high performance liquid chromatography-diode array detector. At least eleven metabolites were detected, including temephos-sulfoxide (Tem-SO), temephos-oxon (Tem-oxon), temephos-oxon-sulfoxide (Tem-oxon-SO), temephos-oxon-SO-monohydrolyzed (Tem-oxon-SO-OH), 4,4´-thiodiphenol, 4,4´-sulfinyldiphenol, and 4,4´-sulfonyldiphenol or bisphenol S (BPS). The mean blood concentrations of temephos were fitted to a one-compartment model for kinetic analysis. At 2 h, the peak was reached (t1/2 abs = 0.38 h), and only trace levels were detected at 36 h (t1/2 elim = 8.6 h). Temephos was detected in all tissues and preferentially accumulated in fat. Temephos-sulfone-monohydrolyzed (Tem-SO2-OH) blood levels remained constant until 36 h and gradually accumulated in the kidney. Tem-oxon was detected in the brain, liver, kidney, and fat. Clearance from the liver and kidney were 7.59 and 5.52 ml/min, respectively. These results indicate that temephos is well absorbed, extensively metabolized, widely distributed and preferentially stored in adipose tissue. It is biotransformed into reactive metabolites such as Tem-oxons, Tem-dioxons, and BPS. Tem-SO2-OH, the most abundant metabolite of temephos, could be used as an exposure biomarker for toxicokinetic modeling. These results could provide critical insight into the dosimetry and toxicity of temephos and its metabolites.

Hematological indices as indicators of inflammation induced by exposure to pesticides.

Pesticide toxicity, both acute and chronic, is a global public health concern. Pesticides are involved in abnormal inflammatory responses by interfering with the normal physiology and metabolic status of cells. In this regard, inflammatory indices aggregate index of systemic inflammation (AISI), monocyte-to-high-density lipoprotein ratio, monocyte-to-lymphocyte ratio (MLR), neutrophil-to-lymphocyte platelet ratio (NLPR), neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, systemic immune inflammation index, and systemic inflammation response index (SIRI) have been used as predictive markers of inflammatory status in several diseases and also in acute poisoning events. This study aimed to determine systemic inflammation indices and their relationship with pesticide exposure from urban sprayers in 302 individuals categorized into three groups (reference group and moderate and high exposure groups). The data suggest that the AISI, MLR, NLPR, and SIRI indices were significantly higher in the exposed groups compared with the reference group. In conclusion, this study proposes that inflammation indices warrant further attention in order to assess their value as early biomarkers of acute and chronic pesticide intoxication.

Methylation patterns of the CDKN2B and CDKN2A genes in an indigenous population exposed to pesticides.

The INK4-ARF locus includes the CDKN2B and CDKN2A genes and is functionally relevant in the regulation of both cell proliferation and senescence. Studies have reported modifications of DNA methylation in this locus by exposure to environmental contaminants including pesticides; however, until now, specific methylation profiles have not been reported in genetically conserved populations exposed to occupational pesticides. The aim of this study was to determine the methylation profiles of the CDKN2B and CDKN2A genes in a genetically conserved population exposed to pesticides. A cross-sectional and analytical study was carried out in 190 Huichol indigenous persons. Information related to pesticide exposure, diet and other variables were obtained through the use of a structured questionnaire. Blood and urine samples were collected for methylation test and dialkylphosphates (DAP) determination, respectively. DNA methylation was measured by the pyrosequencing of bisulfite-treated DNA and DAP concentrations by gas chromatography-tandem mass spectrometry (GC/MS). The most frequent metabolite in the population was dimethylthiophosphate. The farmer group presented a higher methylation percentage of CDKN2B than the non-farmer group, but no differences in CDKN2A were observed between groups. A positive correlation between methylation of CpG site 3 of CDKN2B and time working in the field was observed in the farmer group. An association between methylation percentage of CDKN2B and age was also observed in the non-farmer group. These results suggest that pesticide exposure and exposure time in Huichol indigenous individuals could modify the methylation pattern of the CDKN2B gene.

Environmental and socio-cultural impacts on global DNA methylation in the indigenous Huichol population of Nayarit, Mexico.

Alterations of global DNA methylation have been evaluated in several studies worldwide; however, Long Interspersed Nuclear Elements-1 (LINE-1) methylation in genetically conserved populations such as indigenous communities have not, to our knowledge, been reported. The aim of this study was to evaluate the relationship between LINE-1 methylation patterns and factors such as pesticide exposure and socio-cultural characteristics in the Indigenous Huichol Population of Nayarit, Mexico. A cross-sectional study was conducted in 140 Huichol indigenous individuals. A structured questionnaire was used to determine general and anthropometric characteristics, diet, harmful habits, and pesticide exposure. DNA methylation was determined by pyrosequencing of bisulfite-treated DNA. A lower level of LINE-1 methylation was found in the indigenous population when compared to a Mestizo population previously studied by our group. This difference might be due to the influence of the genetic admixture and differing dietary and lifestyle habits. The males in the indigenous population exhibited increased LINE-1 methylation in comparison to the females. Sex and alcohol consumption showed positive associations with LINE-1 methylation, while weight, current work in the field, current pesticide usage, and folate intake exhibited negative associations with LINE-1 methylation. The results suggest that ethnicity, as well as other internal and environmental factors, might influence LINE-1 methylation.

Organophosphorus pesticide exposure biomarkers in a Mexican population.

The organophosphate (OP) pesticides are neurotoxic compounds widely used around the world. Evaluation of OP exposure in human studies is important for enabling adequate data analyses and drawing accurate conclusions. The aim of this study was to analyze OP exposure biomarkers and their relationships in a Mexican population with different exposure levels. Dialkylphosphates (DAP) were determined through gas chromatography-mass spectrometry (GC-MSD); acetylcholinesterase (AChE), butyrylcholinesterase (BuChE), arylesterase (AREase), basal paraoxonase 1 (PONase), and ß-glucuronidase activities were detected using spectrophotometric methods. The albumin content was determined in a certified clinical laboratory. The DMTP metabolite was found in the highest concentration, and a negative and significant correlation between DAP and cholinesterase activity was observed. Our results suggested that BuChE is a considerably more sensitive biomarker than AChE. In addition, ß-glucuronidase was positively correlated with albumin, BuChE, and PONase. In conclusion, our data strongly support the use of two or more biomarkers of exposure in human monitoring and the application of a strong and validated questionnaire.

Relationship between butyrylcholinesterase activity and lipid parameters in workers occupationally exposed to pesticides.

Exposure to organophosphate pesticides (OP) has been associated with the inhibition of cholinesterase enzymatic activity, such as butyrylcholinesterase (BuChE). Changes in BuChE activity have been associated with obesity, diabetes, hyperthyroidism, and metabolic syndrome. However, few studies have evaluated the effects of pesticides on both BuChE and lipid parameters. The aim of this study was to evaluate lipid parameters in urban sprayers and their association with BuChE activity. An analytical cross-sectional study was conducted in workers exposed to pesticides. The pesticide exposures were evaluated by the measurement of urinary dialkylphosphates. BuChE activity was determined spectrophotometrically in serum, and biochemical parameters were determined at a certified laboratory. Information regarding general characteristics, lifestyle, and other aspects was obtained from a structured questionnaire. The results showed variations in glucose, cholesterol, albumin, atherogenic index, creatinine, LDL, VLDL, triglycerides, and total lipids according to the level of exposure to pesticides in individuals with overweight and obesity. Furthermore, positive correlations between BuChE activity and lipid parameters were observed; these effects were associated with the body mass index. More studies are needed in human population to better elucidate the role of BuChE in lipid metabolism.

In vitro inhibition of human red blood cell acetylcholinesterase (AChE) by temephos-oxidized products.

Temephos (Tem) is an organophosphorus pesticide widely used to kill and prevent the growth of the main vectors for the transmission of dengue, zika, and chikungunya viruses. In chlorinated water, Tem is oxidized to its dioxon-sulfoxide (Tem-dox-SO), dioxon-sulfone (Tem-dox-SO2), and sulfoxide (Tem-SO) derivatives; however, these compounds are not commercially available to be used as standards and in toxicological studies. In the present study, we synthesized and characterized the Tem-oxidation products and the compound 4,4'-sulfinyldiphenol. These compounds were obtained by a simple reaction between Tem or 4,4'-thiodiphenol with sodium hypochlorite or potassium periodate, and were characterized by IR, NMR, and UPLC-HRESIMS. The in vitro evaluation of inhibitory potency of Tem-oxidized products on human red blood cell acetylcholinesterase (RBC AChE) showed that Tem-dox-SO2 was the most potent inhibitor of human RBC AChE, and its effect was more pronounced than that observed for ethyl-paraoxon, a potent typical inhibitor of AChE. An HPLC-DAD method for the analysis of metabolic products of Tem was developed, which may be useful for monitoring in biological and environmental samples. The ability of Tem-oxidized metabolites to inhibit human RBC AChE suggests that the addition of Tem to chlorinated drinking water could result in an increase in the risk of RBC AChE inhibition after exposure.

Relationship between internal and external factors and the activity of PON1.

Paraoxonase 1 (PON1) is an A-esterase calcium-dependent enzyme that is associated with high-density lipoprotein (HDL) and capable of hydrolyzing a wide variety of substrates, including organophosphate (OP) pesticides. The PON1 phenotype can be modulated by multiple internal and external factors, thereby affecting the catalytic capacity of the enzyme. The aim of this study was to evaluate factors that could modulate PON1 activity in a sample occupationally exposed to pesticides. A cross-sectional, descriptive, and analytical study was carried out with 240 workers. The participants were stratified according to their level of pesticide exposure as reference, moderate-exposure, and high-exposure groups. PON1 activities (arylesterase/AREase, CMPAase, and ssPONase (salt-stimulated)) were determined by spectrophotometry, and the Q192R and L55MPON1 genotypes by real-time PCR. The most frequent genotypes were heterozygous (QR) and homozygous (LL) for PON1Q192R and PON1L55M polymorphisms, respectively. The internal factors associated with the activity of PON1 were the PON1 genotypes (55 and 192) and biochemical parameters related to the lipid profile, in contrast, various external factors related to diet and harmful habits as well as with exposure to pesticides were associated with the activity of PON1. However, using a multivariate mixed ordinal regression model, we found a significant reduction of ssPONase activity in the high-exposure group compared with the reference group only in haplotypes QQLL and RRLL.

Modified CDKN2B (p15) and CDKN2A (p16) DNA methylation profiles in urban pesticide applicators.

Gene-specific changes in DNA methylation by pesticides in occupationally exposed populations have not been studied extensively. Of particular concern are changes in the methylation profile of tumor-suppressor, such as CDKN2B and CDKN2A, genes involved in oncogenesis. The aim of this study was to evaluate the methylation profiles of CDKN2B and CDKN2A genes in urban pesticide applicators and their relationship with occupational exposure to pesticides. A cross-sectional study was conducted in 186 urban pesticide applicators (categorized as high or moderate exposures) and 102 participants without documented occupational exposures to pesticides. Acute and chronic pesticide exposures were evaluated by direct measurement of urinary dialkylphosphates, organophosphate metabolites, and a structured questionnaire, respectively. Anthropometric characteristics, diet, clinical histories, and other variables were estimated through a validated self-reported survey. DNA methylation was determined by pyrosequencing of bisulfite-treated DNA. Decreased DNA methylation of the CDKN2B gene was observed in pesticide-exposed groups compared to the non-exposed group. In addition, increased methylation of the CDKN2A promoter was observed in the moderate-exposure group compared to the non-exposed group. Bivariate analysis showed an association between CDKN2B methylation and pesticide exposure, general characteristics, smoking status, and micronutrients, while changes in CDKN2A methylation were associated with pesticide exposure, sex, educational level, body mass index, smoking status, supplement intake, clinical parameters, and caffeine consumption. These data suggest that pesticide exposure modifies the methylation pattern of CDKN2B and CDKN2A genes and raise important questions about the role that these changes may play in the regulation of cell cycle activities, senescence, and aging.

ß-Glucuronidase and Its Relationship With Clinical Parameters and Biomarkers of Pesticide Exposure.

OBJECTIVE: This study determined ß-glucuronidase activity and its relationship with clinical, biochemical, and pesticide-exposure biomarkers in workers occupationally exposed mainly to OP insecticides. METHODS: A cross-sectional study was conducted in pesticide applicators. Three study groups were established: reference group, moderate-exposure group, and high-exposure group. Blood samples were obtained to determine the activity of ß-glucuronidase. Clinical analysis was conducted in a certified laboratory. RESULTS: The activity of ß-glucuronidase was associated with clinical variables such as glucose, cholesterol, triglycerides, LDL, VLDL, HDL, atherogenic index, transaminases, and BuChE activity, but not with AChE activity. The activity of this enzyme exhibited a significant increase in the group of moderate exposure to pesticides but not in the group of high exposure. CONCLUSION: ß-Glucuronidase activity is a sensitive biomarker under certain scenarios of OP exposure.

Micronucleus frequency is correlated with antioxidant enzyme levels in workers occupationally exposed to pesticides.

Oxidative stress can cause DNA damage leading to nuclear anomalies such as micronuclei (MN). Antioxidant enzymes involved in protection against intracellular oxidative stress include glutathione peroxidase (GPx), glutathione reductase (GR), superoxide dismutase (SOD), and catalase (CAT). Pesticide exposure induces oxidative stress and alters antioxidant defense mechanisms, including detoxification and scavenger enzymes. The aim of this study was to evaluate MN frequency in workers occupationally exposed to pesticides and their relationship with antioxidant enzyme activities. A cross-sectional study was conducted in 201 individuals, some of whom were dedicated to the spraying of pesticides. The cytokinesis-block micronucleus (CBMN) assay was conducted, and the activities of GPx, GR, SOD, and CAT were determined. The geometric mean (GM) of MN was 5.4 (1-26 MN). The GM for the antioxidant enzymes was 198.68 U/mL for GPx, 38.96 U/g Hb for GR, 94.78 U/mL for SOD, and 69.77 U/g Hb for CAT. There was a lower MN frequency in males than that in females, and a higher nuclear index. In addition, age affected MN frequency. There was a negative correlation between MN frequency and GPx activity, but a positive one between MN frequency and GR activity. These findings suggest the involvement of GPx in MN frequency.

Relationship between LINE-1 methylation pattern and pesticide exposure in urban sprayers.

Recently a relationship has been reported between pesticide exposure and changes in global DNA methylation patterns. Urban sprayers are a particularly vulnerable population because of the high risk of pesticide exposure that their work implies. Therefore, the aim of this study was to estimate the changes in the Long Interspersed Nucleotide Element (LINE-1) in urban sprayers and its relationship with pesticide exposure. The study population consisted of 190 individuals stratified into three study groups: no occupational pesticide exposure; moderate exposure, and high exposure. Pesticide exposure and other external factors such as diet, lifestyle, and others were evaluated through a validated questionnaire, and the butyrylcholinesterase enzyme activity was evaluated spectrophotometrically and used as exposure biomarker. DNA methylation was evaluated by pyrosequencing on bisulfite-treated DNA. The results showed a significant decrease of %5mC in both the moderate- and high-exposure groups with respect to the non-exposed group (p < 0.05). In addition, alcohol intake was associated with a higher percentage of LINE- 1 methylation. In conclusion, our results suggest that occupational pesticide exposure and external factors appears to modify the DNA methylation pattern measured through LINE-1.

Paraoxonase 1 and its relationship with pesticide biomarkers in indigenous Mexican farmworkers.

OBJECTIVE: Biomarkers of pesticide toxicity and paraoxonase 1 (PON1) phenotype and genotypes were evaluated in indigenous Mexican farmworkers exposed mainly to organophosphate (OP) pesticides. METHODS: Acetylcholinesterase, butyrylcholinesterase, and PON1 activities--arylesterase and CMPAase activities--were evaluated spectrophotometrically. PON1 55 and 192 polymorphisms were determined by real-time polymerase chain reaction. Hematological parameters were evaluated using a cytometer. RESULTS: Butyrylcholinesterase and arylesterase activities were lower in farmworkers, who also showed lower levels of leukocytes but higher percentages of lymphocytes when compared with the nonexposed group. Our results showed a high frequency of OP, high hydrolysis-related PON1 alleles (LL/QR and LL/RR) in the study population. An association was observed between CMPAase activity and PON1Q192R polymorphism. CONCLUSIONS: Our results suggest that pesticide exposure modifies biochemical and hematological biomarkers in the study population, and that the phenotype of PON1 (CMPAase) is a sensible susceptibility biomarker of OP pesticide toxicity.