Article pubs.acs.org/est
Pyrethroid Pesticide Exposure and Risk of Childhood Acute Lymphocytic Leukemia in Shanghai Guodong Ding,†,‡,# Rong Shi,‡,# Yu Gao,*,‡ Yan Zhang,‡ Michihiro Kamijima,§ Kiyoshi Sakai,∥ Guoquan Wang,⊥ Chao Feng,⊥ and Ying Tian*,‡,† †
MOE and Shanghai Key Laboratory of Children’s Environment Health, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China ‡ Department of Environmental Health, School of Public Health, Shanghai Jiao Tong University School of Medicine, Shanghai, China § Department of Occupational and Environmental Health, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan ∥ Environmental Health Department, Nagoya City Public Health Research Institute, Nagoya, Japan ⊥ Shanghai Municipal Center for Disease Control and Prevention, Shanghai, China ABSTRACT: Significant amounts of pyrethroid pesticides are used throughout China. Previous studies have suggested that exposure to pesticides may increase the risk of childhood cancer; however, few studies have focused on pyrethroid metabolites. We investigated five nonspecific metabolites of pyrethroid pesticides found in children’s urine and examined the correlation with childhood leukemia. We conducted a hospital-based case-control study of childhood acute lymphocytic leukemia (ALL) in Shanghai between 2010 and 2011. The study included 176 children aged 0−14 years and 180 controls matched for age and sex. Compared with those in the lowest quartiles of total and individual metabolites, the highest quartiles were associated with an approximate 2fold increased risk of ALL [total metabolites: odds ratio (OR) = 2.75, 95% confidence interval (CI), 1.43−5.29; cis-DCCA: OR = 2.21, 95% CI, 1.16−4.19; trans-DCCA: OR = 2.33, 95% CI, 1.23−4.41; and 3-PBA: OR = 1.84, 95% CI, 1.00−3.38], and most of the positive trends were significant (p < 0.05). Our findings suggest that urinary levels of pyrethroid metabolites may be associated with an elevated risk of childhood ALL and represent a previously unreported quantitative exposure assessment for childhood leukemia.
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INTRODUCTION Childhood leukemia represents the most common type of childhood cancer, although the etiology of the disease is poorly understood.1 It represents 30% of all cancers diagnosed in children younger than 15 years of age.2 In this population, acute lymphocytic leukemia (ALL) accounts for approximately 80% of all childhood leukemia diagnoses, with incidence peaks at 2− 5 years of age, indicating that exposure early in life is important.3 Over the past several decades, the incidence of childhood ALL has been gradually increasing globally,4−6 suggesting that environmental exposure may have an etiologic function. Epidemiologic studies have implicated residential and parental exposure to pesticides as risk factors for childhood leukemia. However, most of these studies are limited by the use of self-reported pesticide use information, rather than environmental or biological samples to validate reported exposure levels.7−9 Additionally, most of the evidence regarding childhood leukemia and pesticide use is derived from casecontrol studies that lack data on specific chemicals, thus making it difficult to pinpoint risks associated with specific pesticides or classes of chemicals.10−12 In contrast, several large studies © 2012 American Chemical Society
examining pesticide exposure associated with childhood leukemia have produced inconsistent results, as some of these studies have reported a positive relationship and others have shown no association.13,14 Pyrethroid pesticides, a group of synthetic analogues of pyrethrins (natural chemicals found in chrysanthemums), were manufactured in the 1970s after the removal of organochlorine pesticides from the consumer market.15 Pyrethroids not only display the biologic activity (ability to kill insects) of their natural counterpart, but also display enhanced environmental stability. With the phaseout of organophosphate (OP) pesticides use in residential environments and some agricultural applications, pyrethroids have been developed and used extensively.16 Currently, approximately 3000 tons of pyrethroids are produced annually in China and are widely used in agriculture, horticulture, public health (e.g., hospitals), and homes.17 Recent studies have indicated that pyrethroid Received: Revised: Accepted: Published: 13480
August 18, 2012 November 14, 2012 November 15, 2012 November 15, 2012 dx.doi.org/10.1021/es303362a | Environ. Sci. Technol. 2012, 46, 13480−13487
Environmental Science & Technology
Article
(25 cases lacking urinary samples and 12 cases that were lacking important questionnaire data) and 55 controls (31 cases lacking urinary samples and 24 cases that were lacking important questionnaire data). In total, 176 cases and 180 controls were enrolled in the study. All participating parents signed the consent form approved by the Shanghai Jiao Tong University School of Medicine Institutional Review Board. Data Collection. Specially trained interviewers carried out the face-to-face interviews with the mothers of the case and control children using structured questionnaires. The case children’s mothers were interviewed shortly after the diagnosis (with corresponding dates for the controls). The questions addressed the parents’ sociodemographic characteristics, (e.g., age, educational level, household income, occupation, place of residence, and address), the children’s prenatal characteristics (e.g., maternal smoking, alcohol use, X-ray exposure, and viral infection during pregnancy), and the family history of cancer and autoimmune diseases. Information regarding household pesticide use included whether any pest control measures were regularly used by the mother herself or other family members from birth to diagnosis and if so, the types of pesticides were assessed. Different types of pesticides (mosquito repellent, cockroach killer, mothproofing agent, rodenticide, termite control agents, herbicide, and other pesticides) were examined. No study family used either professional pest control or pesticides for garden crops or lawn services; therefore, these items were excluded from our analysis. Urine Collection and Urinalysis. Spot urine samples were collected from each participant at the time of the interview in the hospital. Specimens (5 mL) were aliquoted into precleaned glass containers with Teflon-lined caps, bar coded, and stored at −80 °C until shipment to the Shanghai Municipal Center for Disease Control and Prevention (CDC, Shanghai) for analysis. Urinary pyrethroid metabolite levels were measured using a sensitive and selective capillary gas chromatography−mass spectrometric detection (GC−MS) based on a slightly modified method described by Kühn et al.25 Five analytes were measured in each sample: cis-DCCA, trans-DCCA, 3-PBA, 4F3PBA, and cis-DBCA. The limits of detection (LOD) for all targeted metabolites were defined as a signal-to-noise ratio of three, the LOD for five metabolites was 0.1 μg/L. Individual metabolite levels below the LOD were assigned a value equal to half the LOD, and this value was included in each sum. Intra-assay precision was determined five times with three quality control standards (1.0, 5.0, and 20.0 ng/mL) as mean recoveries and relative standard deviations, and inter-assay precision was also tested with the same quality control standards on five different days. The mean recoveries for five metabolites in the inter-assay and intra-assay ranged from 90.67% to 101.15% at three quality control levels. The mean inter-assay and intra-assay relative standard deviation for the urinary metabolites assessed was between 3.52% and 6.35%.17 For quality control, fortified artificial urine was prepared as a blank matrix, and pyrethroid metabolites were not detected in the blank matrix. The calibrations were prepared by spiking specific amounts of metabolite standards into the blank matrix, which were prepared and analyzed in the same manner as the samples. Each analytical experiment contained several unknown samples, calibration standards, artificial urine samples, and three different levels of quality control materials. A calibration curve was measured and calculated for each analytical run. The quality control samples included three concentration levels (1.0, 5.0, and 20.0 ng/mL) for each target compound. The
pesticide exposure is widespread among some susceptible populations, including pregnant women and children.16,17 Children can be exposed to pyrethroids via multiple sources, and household exposure may represent a major source of exposure in China.18 Furthermore, pyrethroids are considered potential carcinogens and may cause perturbations of the immune system at relatively high exposure levels.19 Exposure to parent pyrethroid pesticides may be linked to multiple sources and multiple routes; the quantification of exposure is not a trivial process.20 As the metabolites of currently used pyrethroids are usually excreted in urine, the biological monitoring of exposure to pesticides has typically involved the quantification of urinary pesticide metabolites in many epidemiologic studies.21 Human dose-excretion studies and occupational exposure studies have confirmed that the five nonspecific metabolites, including cis-3-(2,2-dichlorovinyl)-2,2dimethylcyclopropane carboxylic acid (cis-DCCA), trans-3-(2,2dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (transDCCA), 3-phenoxybenzoic acid (3-PBA), 4-fluoro-3-phenoxybenzoic acid (4F3PBA), and cis-(2,2-dibromovinyl)-2,2dimethylcyclopropane-1-carboxylic acid (cis-DBCA), are important indicators of pyrethroid pesticide exposure in humans.22,23 The most frequently detected pyrethroid metabolite is 3-PBA, a common metabolite for many pyrethroids, such as permethrin, cypermethrin, and deltamethrin, followed by trans- and cis-DCCA, two geometric isomeric metabolites for permethrin, cypermethrin, and cyfluthrin.16 4F3PBA and cisDBCA are specific metabolites for cyfluthrin and deltamethrin, respectively.16 Currently, few published studies have examined the association between pyrethroid metabolites and childhood leukemia. In this report, we investigated the urinary levels of pyrethroid metabolites in Shanghai children in China, and evaluated the association with childhood ALL. We tested the hypothesis that after adjusting for potential confounders, pyrethroid metabolites may be associated with an increased risk of childhood ALL.
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MATERIALS AND METHODS Study Population. From January 2010 to December 2011, we recruited children (0−14 years of age) to participate in this study from the departments of hematology and oncology of four children’s hospitals located in Shanghai (Xinhua Hospital, Shanghai Children’s Medical Center, Shanghai Children’s Hospital, and Children’s Hospital of Fudan University). These individuals had been newly diagnosed (
