Article pubs.acs.org/est
Relationships of Pyrethroid Exposure with Gonadotropin Levels and Pubertal Development in Chinese Boys Xiaoqing Ye,† Wuye Pan,† Shilin Zhao,† Yuehao Zhao,‡ Yimin Zhu,§ Jing Liu,*,† and Weiping Liu‡ †
MOE Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Research Center for Air Pollution and Health, College of Environmental and Resource Sciences, and §School of Public Health, Zhejiang University, Hangzhou 310058, China ‡
S Supporting Information *
ABSTRACT: Although an acceleration of male pubertal development has been observed, precisely which endocrinedisrupting chemicals (EDCs) might contribute to the advancing onset of puberty in boys remains unclear. Here, pyrethroids, a class of widely used insecticides that have been considered as EDCs, are proposed as new environmental risk factors. In this study, 463 boys at the age of 9−16 years old were recruited in Hangzhou, Zhejiang, China. The common metabolites of pyrethroids, 3-phenoxybenzoic acid (3-PBA), and 4-fluoro-3-phenoxybenzoic acid (4-F-3-PBA), as well as gonadotropins, including luteinizing hormone (LH) and follicle-stimulating hormone (FSH), were analyzed in urine samples. Pubertal development was assessed based on Tanner stages and testicular volume (TV). A positive association between 3-PBA and gonadotropins was found (p < 0.001), in which a 10% increase in 3-PBA was associated with a 2.4% and 2.9% increase in LH and FSH, respectively. Higher urinary levels of 3-PBA in boys were associated with 275% and 280% increase in the risk of being genitalia stage 3 (G3) and G4, respectively (p < 0.05). There was a significant (132%) induction in odd of being TV 12−19 mL with increasing 3-PBA concentration compared to being in TV < 4 mL (p < 0.05). For the first time to our knowledge, this work reports on an association of increased pyrethroid exposure with elevated gonadotropins levels and earlier pubertal development in boys.
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INTRODUCTION Puberty is a transient period from childhood to adulthood during which a child undergoes dramatic developmental changes that are essential for the achievement of reproductive capacity. Pubertal maturation begins with the increasing pulsatile release of gonadotrophin releasing hormone (GnRH) from the hypothalamus that stimulates the pituitary release of gonadotropins, including luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Gonadotropins subsequently activate the production of gonadal sex steroids and the progression of secondary sexual characteristics.1,2 In addition to consistent observations of a secular trend toward earlier pubertal onset in girls since the 20th century, an acceleration of male pubertal development also has been reported in more recent epidemiological studies. For example, observed mean ages of pubertal development in the boys in the United States investigated between 2005 and 2010 were 6 months to 2 years earlier than in past studies.3 The age of pubertal maturation in Chinese urban boys investigated between 2003 and 2005 was 2 years earlier than in 1979.4 A one-year acceleration in the age of sexual development was observed in Bulgarian boys from the end of the 20th century compared with data from the 1970s.5 Environmental factors, specifically endocrine-disrupting chemicals (EDCs), have been © XXXX American Chemical Society
shown complex influences on pubertal timing. For example, bisphenol A (BPA) and DDE exposure are positively associated with an earlier age at pubertal onset in girls.6,7 High urinary phthalate metabolite levels were associated with delayed pubertal development in boys and advanced pubertal development in girls.8 Perfluorocarbons have been found to be correlated with a later age of puberty both in girls and boys.9 Many chemicals that have been identified as EDCs are pesticides. Pyrethroids are a class of widely used pesticides placed on the list of the U.S. Environmental Protection Agency (EPA) as potential EDCs given their hormone-like effects.10 Pyrethroids are one of the top 10 classes of pesticides and are extensively used in agriculture, forestry, horticulture, public health, and homes.11 Current annual production of pyrethroids in China reaches around 6 600 000 pounds.12 Because of their large-scale use, the residues of pyrethroids have been frequently detected in residential homes and agricultural products. Therefore, the increased human exposure to pyrethroids through the household environment and diets is expected.13,14 Received: Revised: Accepted: Published: A
November 27, 2016 April 28, 2017 May 8, 2017 May 8, 2017 DOI: 10.1021/acs.est.6b05984 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
Article
Environmental Science & Technology
into four stages, as shown in Table 6 and as described in a previous study.8 Boys were asked to choose one category that contains the value of their self-measured TV. Prior validation studies have compared such self-report procedures with Tanner staging conducted by a physician and found that correlations between physician ratings and self-reported ratings ranged from 0.58 to 0.83, confirming that Tanner self-assessment questionnaire with line drawings and explanatory Chinese text can reliably estimate sexual maturation status in Chinese children.22 The parents completed nurse-administered health, lifestyle, and dietary questionnaires. Information regarding the frequency of household pesticides usage and organic food intake were selfreported by both child and parents, and they provided only one questionnaire. The question about the frequency of organic food intake in the questionnaire was “How often do you have organic food?” The answers included A, never; B, sometimes; C, always; and D, totally. The question about the household pesticides use in the questionnaire was “How often do you use insecticides in your house?” The answers included A, always; B, sometimes; and C, never. Urine Collection and Urinalysis of Pyrethroid Metabolites. Spot urine samples were collected at the time of the interview. Specimens were aliquoted into precleaned and coded glass containers with Teflon-lined caps and stored at −20 °C until chemical analysis. Urinary pyrethroids metabolite levels were measured using a modified method as previously described.13 Briefly, 5 mL of urine was spiked with an internal standard mixture consisting of isotopically labeled 3-PBA and 4F-3-PBA and incubated with β-glucuronidase to liberate conjugated metabolites. The hydrolysates were extracted with hexane three times. The extracts were concentrated and analyzed using an ultraperformance liquid chromatography− triple quadrupole mass spectrometry system (Xevo TQ-S, Waters, Milford, MA). A Waters BEH C18 column (2.1 mm × 50 mm, 1.7 μm) was used for chromatographic separation. Water and acetonitrile (50:50, v/v), both containing 0.1% ammonium solution with a constant flow rate of 0.1 mL/min were used as the mobile phase. All target compounds were analyzed in their negative polarity. The limits of detection (LOD) for 3-PBA and 4-F-3-PBA were 0.005 μg/L and 0.007 μg/L, respectively. The mean recoveries for two metabolites in the interassay and intra-assay ranged from 74.5% to 120.5% at three quality control levels. Pyrethroids metabolites were not detected in the fortified artificial urine prepared as a blank matrix. The pyrethroids metabolite levels were divided by creatinine levels to adjust for variable urine dilutions in the spot urine samples. The creatinine levels in urine were assessed using a commercially available diagnostic enzyme kit (Oxford Biomedical Research, Rochester Hills, MI). Samples with a creatinine level of
