Clemente Aguilar-Garduño

Cadmium exposure and neuropsychological development in school children in southwestern Spain

This study assessed the association between cadmium exposure and neuropsychological development in children from a region with high industrial and mining activities in southwestern Spain. We conducted a cross-sectional study with 261 children aged 6-9 years between January and March 2012. Cadmium exposure was measured in urine and hair of children, and neuropsychological development was assessed with the Wechsler Intelligence Scale for Children-Fourth Edition (WISC-IV) and with three computerized tests from the Behavioral Assessment and Research System (BARS): Reaction Time Test (RTT), Continuous Performance Test (CPT) and Selective Attention Test (SAT). Multivariate linear regression models, adjusted for potential confounders, were used to estimate the association between neuropsychological development and cadmium exposure measured in urine and hair samples. Geometric means of urine and hair cadmium levels were 0.75 μg/g creatinine and 0.01 μg/g, respectively. We observed that doubling of levels of cadmium in urine was associated with a reduction of two points (95% CI: -3.8 to -0.4) in the Full-Scale intelligence quotient (IQ) in boys. By domains, association was statistically significant for Verbal Comprehension (β=-2.0; p=0.04) and close to the significance level for Perceptual Reasoning (β=-1.8; p=0.06). Among girls, only Verbal Comprehension showed suggestive associations with cadmium exposure (β=-1.7; p=0.06). Cadmium exposure is associated with cognitive delays in boys in our region. Our results provide additional evidence of the neurotoxic effect of low-level postnatal cadmium exposure among children, and support the hypothesis of differences between sexes in the neurotoxic effect of metals on children.

Assessment of the total effective xenoestrogen burden in extracts of human placentas.

We have standardized a method to assess the total effective xenoestrogen burden (TEXB) in human placentas by the extraction and separation by high-performance liquid chromatography of two fractions containing lipophilic xenoestrogens (alpha) and endogenous hormones (beta), followed by assessing their estrogenicity in MCF-7 breast cancer cell-based E-Screen and Yeast Estrogen Screen (YES) bioassays. The means of TEXB alpha concentrations (in estradiol equivalent (Eeq) units) were 1.32 and 0.77 Eeq pM g−1 placenta in the E-Screen and YES, respectively; TEXB beta concentrations were 6.97 and 11.56 Eeq pM g−1 placenta, respectively. The interclass correlation coefficient was low and a fair level of agreement was observed after kappa test correction. According to the E-Screen and YES, TEXB alpha was ≥LOD in 70.0 and 55.0% of the placentas and 92.5 and 82.5% in beta, respectively. Although both bioassays can be recommended for assessing TEXB, there is greater experience with the use of the E-Screen for estrogenic assessment after extensive extraction of complex human matrices.

Pre- and postnatal exposures to pesticides and neurodevelopmental effects in children living in agricultural communities from South-Eastern Spain

BACKGROUNDnChildrens exposure to neurotoxic compounds poses a major problem to public health because oftheir actively developing brain that makes them highly vulnerable. However, limited information is available on neuropsychological effects in children associated with pre- and postnatal exposures to pesticides.nnnOBJECTIVEnTo evaluate the association between current and pre- and postnatal exposures to pesticides and their effects on neurodevelopment in children aged 6–11 years living in agricultural communities from South-Eastern Spain.nnnMETHODSnAn ambispective study was conducted on 305 children aged 6–11 years randomly selected from public schools of the study area. Current exposure to organophosphate pesticides was assessed measuring childrens urinary levels of dialkylphosphates (DAPs). Both prenatal and postnatal residential exposure to pesticides was estimated by developing a geographical information system (GIS) technology-based index that integrated distance-weighted measure of agricultural surface, time-series of crop areas per municipality and year, and land-use maps. Neuropsychological performance was evaluated with the Wechsler Intelligence Scale for Children-Fourth Edition (WISC-IV). The association of pre- and postnatal and current pesticide exposure with WISC-IV scale scores was assessed using multivariate linear regression models and generalized estimating equation (GEE) models, respectively.nnnRESULTSnGreater urinary DAP levels were associated with a poorer performance on intelligence quotient and verbal comprehension domain, with effects being more prominent in boys than in girls. The influence of an increase in 10 ha per year in crop surface around the childs residence during the postnatal period was associated with decreased intelligence quotient, processing speed and verbal comprehension scores. As regards prenatal exposure to pesticides, a poor processing speed performance was observed. These effects were also more prominent in boys than in girls.nnnCONCLUSIONSnOur results suggest that postnatal exposure to pesticides can negatively affect childrens neuropsychological performance. Prenatal exposure was weakly associated to neurodevelopment impairment.

Effect on risk of anencephaly of gene-nutrient interactions between methylenetetrahydrofolate reductase C677T polymorphism and maternal folate, vitamin B12 and homocysteine profile.

OBJECTIVEnTo evaluate the effects on anencephaly risk of the interaction between the maternal profile of folate, vitamin B12 and homocysteine and the 677C→T polymorphism in the gene encoding methylenetetrahydrofolate reductase (MTHFR).nnnDESIGNnCase-control study paired (1:1) on maternity clinic, date of birth and state of residence. Cases of anencephaly were identified using the Registry of the Mexican Neural Tube Defect Epidemiological Surveillance System. Case and control mothers were selected from the same maternity departments. All mothers completed a structured questionnaire and blood samples were obtained to determine the MTHFR 677C→T polymorphism and biochemical profile.nnnSETTINGnMexico, Puebla and Guerrero states, Mexico.nnnSUBJECTSnA total of 151 mothers of cases and controls were enrolled from March 2000 to February 2001. We had complete information on biochemical profile and MTHFR C677T polymorphism for ninety-eight mothers of cases and ninety-one mothers of controls.nnnRESULTSnThe adjusted models show that the risk of anencephaly in mothers with 677TT genotype was reduced by 18 % (OR = 0·82; 95 % CI 0·72, 0·94) for each 1 ng/ml increment in serum folate. In terms of tertiles, mothers with 677TT genotype with serum folate levels in the upper tertile (>14·1 ng/ml) had a 95 % lower risk to have a child with anencephaly than mothers with serum folate levels in the first and second tertiles (P trend = 0·012).nnnCONCLUSIONSnOur data agree with the hypothesis of a gene-nutrient interaction between MTHFR 677C→T polymorphism and folate status. We observed a protective effect on anencephaly risk only in mothers with 677TT genotype as serum folate levels increased.

Effect of exposure to p,p'-DDE on male hormone profile in Mexican flower growers

Objectives p,p-Dichlorodiphenyldichloroethene (p,p-DDE) acts as an androgen receptor antagonist, however data regarding its hormonal effects in men are limited. The objective of this study was to evaluate the association between serum levels of p,p-DDE and reproductive hormone profile in Mexican male flower growers. Methods A longitudinal study was carried out in a population of men working in the production of flowers and ornamental plants in two Mexican states during July–October 2004 (rainy season) and December 2004–May 2005 (dry season). A questionnaire including information on socioeconomic characteristics, tobacco and alcohol use, presence of chronic and acute diseases, occupational history and anthropometry was used and blood and urine samples were obtained. Serum levels of p,p-DDE were analysed by gas chromatography; FSH, LH, testosterone, oestradiol, inhibin B and prolactin levels were measured by enzymatic immunoassay. Urinary levels of dialkylphosphates (DAPs) were analysed by gas chromatography. Associations between serum levels of p,p-DDE and male reproductive hormones (both transformed to their natural logarithm) were evaluated using multivariate generalised estimating equation (GEE) models. Results Median p,p-DDE levels were 677.2u2005ng/g lipid (range 9.4–12 696.5) during the rainy season and 626.7u2005ng/g lipid (range 9.4–13 668.1) during the dry season. After adjusting for potential confounders (age, body mass index, state of residence and DAPs), p,p-DDE levels were negatively associated with prolactin (β=−0.04; 95% CI −0.07 to −0.008) and testosterone (β=0.04; 95% CI −0.08 to 0.005) and positively with inhibin B (β=0.11; 95% CI 0.02 to 0.21). Conclusion These results indicate that p,p-DDE can affect hypothalamic–pituitary–gonadal axis function in humans.

Effect of current tobacco consumption on the male reproductive hormone profile.

The knowledge about the effect of cigarette smoking on the male reproductive function is still limited. The objective of this study was to evaluate the association between active exposure to tobacco smoke and the male reproductive hormone profile in a group of 136 Mexican flower growers. Serum levels of FSH, LH, prolactin, total testosterone, Inhibin B and estradiol were measured using enzyme-linked immunoabsorbent assay. Weight and height were also measured and a structured questionnaire was applied to get information on sociodemographic characteristics, clinical and work history and alcohol and tobacco consumption (current smoking habit and number of cigarettes smoked per day). Based on this information tobacco consumption was divided into four categories: never-smokers, ex-smokers, current smokers under five cigarettes/day and current smokers over or equal to five cigarettes/day. Using the group of never-smokers as reference and after adjusting for potential confounders, current smokers of five or more cigarettes/day showed significantly higher levels of LH (β=0.33, p=0.01), prolactin (β=0.18, p=0.03) and testosterone (β=0.21, p=0.02). Current smokers of less than five cigarettes/day also showed higher levels of prolactin (β=0.12, p=0.03) and testosterone (β=0.18, p<0.01). Hormone levels of ex-smokers were similar to those of never-smokers. Our results are compatible with the hypothesis that tobacco consumption may act as an endocrine disruptor on the male hormone profile.

Polymorphisms of pesticide-metabolizing genes in children living in intensive farming communities.

Polymorphisms in genes encoding xenobiotic-metabolizing enzymes (XME) are important parameters accounting for the wide inter-individual variability to environmental exposures. Paraoxonase-1 (PON1), butyrylcholinesterase (BChE) and Cytochrome-P450 constitute major classes of XME involved in the detoxification of pesticide chemicals, in particular organophosphates. This study explored the allelic frequency, linkage disequilibrium and haplotype analysis of ten common polymorphic variants of seven key genes involved in organophosphate metabolism (BCHE-K, BCHE-A, PON1 Q192R, PON1 L55M, PON1 -108C/T, CYP2C19 G681A, CYP2D6 G1846A, CYP3AP1 -44G/A, GSTM1∗0 and GSTT1∗0) in a children population living near an intensive agriculture area in Spain. It was hypothesized that individuals with unfavorable combinations of gene variants will be more susceptible to adverse effects from organophosphate exposure. Genomic DNA from 496 healthy children was isolated and amplified by PCR. Hydrolysis probes were used for the detection of eight specific SNPs and two copy number variants (CNVs) by using TaqMan® Assay-based real-time PCR. Frequencies of SNPs and CNVs in the target genes were in Hardy-Weinberg equilibrium and broadly consistent with European populations. Linkage disequilibrium was found between the three PON1 genetic polymorphisms studied and between BCHE-K and BCHE-A. The adverse genotype combination (unusual BCHE variants, PON1 55MM/-108TT and null genotype for both GSTM1 and GSTT1) potentially conferring a greater genetic risk from exposure to organophosphates was observed in 0.2% of our study population. This information allows broadening our knowledge about differential susceptibility toward environmental toxicants and may be helpful for further research to understand the inter-individual toxicokinetic variability in response to organophosphate pesticides exposure.

Association between PON1 genetic polymorphisms and miscarriage in Mexican women exposed to pesticides.

BACKGROUNDnPlacental oxidative stress has been involved in the pathogenesis of certain reproductive adverse effects, including miscarriage. Paraxonase 1 (PON1) is a high-density lipoprotein(HDL)-linked enzyme that prevents oxidation of low-density lipoproteins (LDL) and is involved in detoxification from organophosphate pesticides.nnnOBJECTIVEnTo assess the association between maternal PON1 polymorphisms (PON1192Q/R, PON155 L/M y PON1-108C/T) and the risk of miscarriage in women chronically exposed to organophosphate pesticides in Mexico.nnnMETHODSnIn a cross-sectional study, socio-demographic data, reproductive history data, environmental exposures, and other variables of concern were collected by means of a questionnaire from 264 women (floriculturists and wives of floriculturists) who had been pregnant sometime during the 10 years preceding the study. Blood samples were also collected from them. PON1192 and PON155 genotypes were determined by PCR amplification, and PON1-108 genotypes, by a TaqMan real-time polymerase chain reaction assay. Complete information regarding the results of pregnancy and maternal genotype tests was obtained for 514 pregnancies (35 miscarriages and 479 controls). The association between PON1 genotypes and miscarriage was evaluate through GEE models.nnnRESULTSnThe risk of miscarriage by mothers with PON1192RR genotype was 2.2 higher than by mothers with PON1192QR/PON1192QQ genotype (95% CI 0.93-5.17). The risk was close to 4 times higher in mothers with PON155MM/PON155LM genotype than in mothers with PON155LL genotype (OR=3.9; 95% CI 1.38-11.0). No significant differences were found in risk of miscarriage based on the maternal PON1-108C/T genotype. No evidence was found of an interaction between the various PON1 genotypes and the mothers floricultural activity during pregnancy.nnnCONCLUSIONSnThis study suggests that there is an effect of genetic maternal PON1 polymorphisms on miscarriage and provides additional evidence that combines with the growing information about the ways in which certain PON1 genotypes can affect the development of the fetus in utero.

Association between organochlorine pesticide exposure and thyroid hormones in floriculture workers.

Several studies have suggested that exposure to DDT may be related to changes in thyroid hormone levels in animals and humans, even though results across studies are inconsistent. The aim of this study was to assess the association between exposure to p,p-DDE (a stable metabolite of DDT) and serum levels of thyroid hormones in floriculture workers. A longitudinal study was conducted on 136 male subjects from the States of Mexico and Morelos, Mexico, who were occupationally exposed to pesticides, during agricultural periods of high (rainy season) and low (dry season) levels of pesticide application. Using a structured questionnaire, a survey was carried out on socio-demographic characteristics, anthropometry, clinical history, alcohol and tobacco consumption, residential chemical exposure, and occupational history. Blood and urine samples were collected to determine serum levels of TSH, total T3, total T4, and p,p-DDE, and metabolites of organophosphate pesticides (OP), respectively. The analysis of the associations between p,p-DDE levels and thyroid hormone profile adjusting by potential confounding variables including urinary OP metabolites was carried out using multivariate generalized estimating equation (GEE) models. Our results showed that the geometric means of p,p-DDE levels were 6.17 ng/ml and 4.71 ng/ml in the rainy and dry seasons, respectively. We observed positive associations between the serum levels of p,p-DDE and those of total T3 (β=0.01, 95% CI: -0.009, 0.03), and total T4 (β=0.08, 95% CI:0.03, 0.14) and negative but no significant changes in TSH in male floricultural workers, supporting the hypothesis that acts as thyroid disruptor in humans.

Occupational predictors of urinary dialkyl phosphate concentrations in Mexican flower growers

Abstract Background: Flower growers have high potential for exposures to pesticides. Occupational factors, such as tasks performed, the production method (organic or conventional), the use of personal protective equipment (PPE), and workplace characteristics influence the intensity of pesticide exposure. Objective: To evaluate occupational characteristics affecting urinary concentration of dialkylphosphate (DAP) metabolites of organophosphate pesticides among a group of Mexican floricultural workers. Methods: A questionnaire was administered to 117 workers who also provided a first morning urine sample. According to tasks performed and the production methods, pesticide contact was defined as low, medium, or high. PPE use was categorized as acceptable, fairly acceptable, and unacceptable. Urinary concentration of DAP metabolites were determined using gas–liquid chromatography. Association between occupational characteristics and DAP urinary concentrations was assessed by means of linear regression models. Results: After adjusting for potential confounders, the workers in the medium and high contact categories had significantly higher DAP concentrations than those in the low contact category (β: 0.3, CI 95%: 0.1–0.5). Greenhouse workers had greater DAP concentrations than outdoors workers (β: 0.3, CI 95%: 0.1–0.5). Compared with non-acceptable use of PPE, acceptable use of PPE was associated with lower DAP concentrations (β: −0.4, CI 95% −0.6 to −0.1). Conclusion: Improved safety training is needed for correct PPE usage, especially among flower growers who use conventional pest control methods and who work in a greenhouse environment.