Exposición a pesticidas no persistentes y otros disruptores endocrinos, desarrollo puberal y susceptibilidad genética en niños y niñas de la cohorte infancia y medio ambiente (INMA)

Abstract

Numerous non-persistent pesticides, such as organophosphate and pyrethroid insecticides, fungicides or herbicides, and other chemical compounds such as phthalates, widely present in household items, have shown pro-estrogenic and anti-androgenic effects, being classified as endocrine disruptors chemicals (EDCs). The processes involved in pubertal timing are potentially vulnerable to EDCs, and exposure at critical windows of development could be implicated in the secular trend of puberty observed in boys and girls in recent decades. Interindividual genetic variations could confer greater susceptibility to potential adverse health effects of hormonally active compounds. The first specific objective of this doctoral thesis was to conduct a systematic review of epidemiological studies assessing the association between early exposure to non-persistent pesticides and pubertal development (age at the onset and/or state of sexual maturation). A systematic search was carried out using MEDLINE and SCOPUS databases, including original articles published up to November 2020. The PRISMA guidelines were used, and the quality of the evidence was assessed using the GRADE scale. Thirteen studies were selected after excluding non-original and non-human studies. Exposure to different types of pesticides has been associated with altered puberty timing in girls and/or boys in eight studies. In utero exposure to atrazine has been related to earlier age of menarche in girls; exposure to organophosphate (OP) pesticides has been related to delayed sexual development in boys and girls in one study; childhood pyrethroid exposure has been associated with pubertal delay in girls and pubertal advancement in boys in two studies, respectively; prenatal/ exposure to multiple pesticides has been linked to earlier puberty onset in girls and pubertal delay in boys childhood, in two studies respectively, while living in rural area during childhood was associated to a greater age at menarche in one study and to an earlier puberty onset in boys in other study. The second objective was to evaluate the association between exposure to nonpersistent pesticides and pubertal development in 7-11-years-old boys and girls. A crosssectional study was carried out. Four insecticide metabolites (TCPy, chlorpyrifos metabolite; IMPy, diazinon metabolite; DETP, non-specific organophosphate metabolite and 3-PBA, pyrethroid metabolite) and the fungicide metabolite ethylene-bisdithiocarbamate (ETU) were quantified in urinary samples of 939 boys and 606 girls from the Childhood and Environment (INMA) cohort study carried out in Asturias, Gipuzkoa Numerous non-persistent pesticides, such as organophosphate and pyrethroid insecticides, fungicides or herbicides, and other chemical compounds such as phthalates, widely present in household items, have shown pro-estrogenic and anti-androgenic effects, being classified as endocrine disruptors chemicals (EDCs). The processes involved in pubertal timing are potentially vulnerable to EDCs, and exposure at critical windows of development could be implicated in the secular trend of puberty observed in boys and girls in recent decades. Interindividual genetic variations could confer greater susceptibility to potential adverse health effects of hormonally active compounds. The first specific objective of this doctoral thesis was to conduct a systematic review of epidemiological studies assessing the association between early exposure to non-persistent pesticides and pubertal development (age at the onset and/or state of sexual maturation). A systematic search was carried out using MEDLINE and SCOPUS databases, including original articles published up to November 2020. The PRISMA guidelines were used, and the quality of the evidence was assessed using the GRADE scale. Thirteen studies were selected after excluding non-original and non-human studies. Exposure to different types of pesticides has been associated with altered puberty timing in girls and/or boys in eight studies. In utero exposure to atrazine has been related to earlier age of menarche in girls; exposure to organophosphate (OP) pesticides has been related to delayed sexual development in boys and girls in one study; childhood pyrethroid exposure has been associated with pubertal delay in girls and pubertal advancement in boys in two studies, respectively; prenatal/ exposure to multiple pesticides has been linked to earlier puberty onset in girls and pubertal delay in boys childhood, in two studies respectively, while living in rural area during childhood was associated to a greater age at menarche in one study and to an earlier puberty onset in boys in other study. The second objective was to evaluate the association between exposure to nonpersistent pesticides and pubertal development in 7-11-years-old boys and girls. A crosssectional study was carried out. Four insecticide metabolites (TCPy, chlorpyrifos metabolite; IMPy, diazinon metabolite; DETP, non-specific organophosphate metabolite and 3-PBA, pyrethroid metabolite) and the fungicide metabolite ethylene-bisdithiocarbamate (ETU) were quantified in urinary samples of 939 boys and 606 girls from the Childhood and Environment (INMA) cohort study carried out in Asturias, Gipuzkoa Granada, Sabadell and Valencia. As pubertal assessment, the Tanner scale and the Pubertal Development Scale (PDS) were used. The association between each metabolite and the probability of being stage ≥2 for each pubertal milestone was examined using multivariate logistic regression. Effect modification by BMI was explored by interaction terms and stratified analysis. In girls, DETP and ETU exposure was associated with higher odds of overall pubertal development on the PDS, and ETU was also associated with higher odds of breast development in non-overweight girls. In boys, detection of TCPy, ETU, and 3-PBA were associated with higher odds of genital development, and the association for ETU and 3-PBA were significant only in normal/underweight and overweight/obese children, respectively. In contrast, DETP was associated with delayed puberty in overweight/obese children. The third objective was to evaluate the effect of prenatal exposure to phthalates on the pubertal development of boys and girls from Gipuzkoa, Sabadell and Valencia INMA cohorts. Urinary metabolites of six different phthalate diesters (DEP, DiBP, DnBP, BBzP, DEHP, and DiNP) and non-phthalate plasticizer DINCH® were quantified in two urine samples collected during pregnancy from mothers participating in the INMA Spanish cohort study. Pubertal assessment of their children at age 7-10 years (409 boys, 379 girls) was conducted using the parent-reported PDS. Modified Poisson and Weighted Quantile Sum (WQS) regression was employed to examine associations between prenatal phthalates and risk of puberty onset, adrenarche, and gonadarche. Effect modification by child weight status was explored by stratified analysis. Prenatal exposure to DEHP, DEP, and DnBP was associated with a higher risk of puberty onset in boys, and DEHP with a higher risk of adrenarche in girls. In contrast, exposure to BBzP and DINCH® was associated with a lower risk of adrenarche in overweight/obese boys. In overweight girls, DiBP, DnBP, and DINCH® were associated with a slightly increased risk of gonadarchia. Exposure to phthalate mixture, assessed by quantile sum regression, was not associated with puberty in boys or girls. The fourth objective was to examine the association between urinary biomarkers of non-persistent pesticides and sexual maturation in 14 to 17 years old boys from the INMA cohorts of Granada and Menorca. Urinary metabolites were measured in single spot urine samples, including: TCPy, IMPy, DETP and diacid malathion (MDA), malathion metabolite; the non-specific pyrethroid metabolites 3-PBA and dimethylcyclopropane carboxylic acid (DCCA); the 1-naphthol (1-N), carbaryl metabolite and ETU. Sexual maturation was assessed using Tanner stages, self-reported Pubertal Development Scale, and testicular volume (TV). Multivariate logistic regression was employed to examine associations between urinary pesticide metabolites and the odds of being in Tanner stage 5 of genital development (G5) and pubic hair growth; stage ≥4 of overall pubertal development, gonadarche, and adrenarche; or having mature TV (≥25 mL). Exposure to DETP, TCPy, and MDA was associated with a decrease in pubertal maturation (gonadal for DETP and TCPy and adrenal for MDA), while 1-N was associated with an increase in adrenal maturation and decreased testicular volume. Exposure to 3-PBA was associated with smaller testicular size. The fifth objective was to evaluate the relationship between exposure to pesticides and serum concentrations of sex hormones in male adolescents and the possible interaction with polymorphisms in genes involved in pesticide metabolism. For this purpose, two cross-sectional studies were carried out in 16 to 17 years old boys from the INMA Granada cohort. In the first study, urinary concentrations of organophosphate metabolites: TCPy, IMPy, DETP and DEDTP were measured in the urine sample of 134 boys, and in the second study, the urinary metabolites ETU, 3-PBA and 1-N were quantified in 117 boys. For both studies, the serum concentrations of the main sex and thyroid hormones were measured and alterations in the PON1, CYP2C19 and CYP2D6 genes were examined. Exposure to TCPy was associated with increased level of dehydroepiandrosterone (DHEA-S) and decreased oestradiol (E2), FSH, and antimullerian hormone (AMH); the detection of IMPy with increased E2, DHEA-S, FSH, AMH and prolactin and with lower levels of SHBG and LH; DETP detection was marginally associated with elevations in testosterone and triiodothyronine (T3) and decreases in FSH, AMH, and prolactin levels. The effect of IMPy and DETP on DHEAS and TT levels, respectively, was higher in subjects that carried the PON1 55MM genotype, while the effect of TCPy, IMPy, and DETP on thyroid hormone levels was higher in PON1 192QR/RR or 55MM genotype carriers. In the second study, exposure to 3-PBA was associated with elevated T3, while 1-N with elevated DHEA-S and decreased E2 and FSH. Poor CYP2C19 and CYP2D6 metabolizers (GA and AA genotype carriers) showed a greater increase in DHEA-S for detected versus undetected 1-N compared with GG genotype carriers. Poor CYP2D6 metabolizers (1846GA and AA genotypes) evidenced increased cortisol for detected versus undetected ETU. The magnitude of some of the associations was stronger for the carriers of the mutations in the analysed genes. In conclusion, the results of this doctoral thesis suggest that exposure to different classes of non-persistent pesticides and other endocrine disruptors, during critical window such as childhood and pregnancy, could be associated with variations in the concentrations of sexual hormones, in pubertal development and sexual maturation of boys and girls and that nutritional status and individual genetic susceptibility can modify these associations.