The occurrence of polycyclic aromatic hydrocarbons (PAHs) and nitrated derivatives (NPAHs), as well as their transformation may have significant health impacts on humans. To investigate the level, spatial distribution and the transformation process of PAHs and NPAHs in North China, we performed a gridded field passive air sampling campaign in summer of 2011. The median concentration of 25 PAH congeners and 13 NPAHs was 294 ng m(-3) (or 26.7 mu g sample(-1)) and 203 ng sample(-1), respectively. Relative higher level of PAHs in Shanxi Province and NPAHs in megacities was observed. In North China, coal/biomass combustion and photochemical formation was the predominant source of PAHs and NPAHs, respectively. To investigate the relationship between these pollutants, a model incorporating NPAHs, PAHs and NO2 was established, and the result indicated that NO2 will promote the transformation processes from PAHs to NPAHs, which may increase the total toxicity of PAH-NPAH mixtures. (C) 2014 Elsevier Ltd. All rights reserved.
Eighty-seven soil samples collected from North China were analyzed for Dechlorane Plus (DP). The concentrations of DP ranged from not detectable (ND) to 12.21 ng/g with a mean of 0.55 ng/g. The mean concentrations of total DP and syn-DP in four regions of North China were in the following order: Jingjin (Beijing and Tianjin) > Shandong > Shanxi > Hebei, while the mean concentrations of anti-DP in the four regions were in a different order: Shandong > Jingjin > Shanxi > Hebei. The mean f (syn) values for Jingjin (0.27), Hebei (0.24), and Shanxi (0.24) were close to 0.25, while the mean f (syn) value for Shandong (0.31) was closer to 0.35. In addition, the f (syn) value for Shandong was significantly higher (P < 0.01) than those of the other regions (Jingjin, Heibei, and Shanxi), indicating specific sources of DP. Syn-DP displayed a strong linear relationship with anti-DP (R (2) = 0.74), indicating that no obvious stereoselective process occurred in the soil of North China. Ordinary kriging was undertaken to map the spatial patterns of DP. High concentrations of DP in soils were present in south of Shanxi, central Hebei, south of Tianjin, and the south and northeast of Shandong, which were suggested to be connected with human activities such as e-waste dismantling.
Organochlorine pesticides (OCPs) in placental tissue have been reported to be associated with an increased risk for fetal neural tube defects (NTDs). Our case-control study was performed to explore the association between maternal serum OCP concentration and NTD risk in offspring. Serum samples were collected from 117 mothers who delivered NTD infants (case group) and 121 mothers who delivered healthy infants (control group). Only three of the 25 OCPs were detected in more than half of the maternal serum samples. The median concentration of total OCPs in the case group was significantly higher than that of the control group. However, no dose-response relationships between higher levels of any individual OCPs or total OCPs and the risk of NTDs or subtypes were observed in either the unadjusted binary unconditional logistic regression model or the model adjusted by potential confounders. We conclude that no clear association between maternal serum OCP residues and NTD risk in offspring was observed in this population. Capsule: No clear association between maternal serum levels of organochlorine pesticides and risk of neural tube defects in offspring was observed for a Chinese population. (C) 2014 Elsevier B.V. All rights reserved.
Characteristics and sources of particle-bound polycyclic aromatic hydrocarbons ( PAHs) in PM_(2. 5) in three typical transportation microenvironments were investigated,and the health risks were assessed. Fine particle exposure by pedestrians and commuters taking buses and subways were collected using personal exposure samplers in December 2011 in Beijing. Concentrations of multiple PAHs were measured by gas chromatography-mass spectrometry ( GC-MS) . Sources of PAHs were identified by distribution patterns and ratios of different PAHs. Health risk assessments associated with respiratory exposure to PAHs were conducted based on benzo[a]pyrene ( BaP) equivalent concentrations ( BEQ) ,BaP based equivalent carcinogenic power ( BaPE) and inhalation cancer risk. The results showed that: 1) The average exposure level of PAHs in roadside,buses,and subways were ( 120 119) ,( 101 46. 6) ,and ( 50. 8 25. 6) ng/m~3 , respectively. 2) The similarity of PAHs distribution patterns in the three transportation microenvironments and the ratios of PAHs rho( Flt) / [rho( Flt) + rho( Pyr) ]and rho( IcdP) /[rho( IcdP) + rho( BghiP) ]> 0. 5,rho( BaA) /[rho( BaA) + rho( Chr) ]> 0. 35 suggested common sources in these environments,mainly from vehicle emissions and coal combustion. 3 ) Inhalation cancer risk ( 19. 8 * 10 ~(- 6) , California Environmental Protection Agency( CalEPA) -based method; 15. 6 * 10~( - 4),World Health Organization ( WHO) -based method) was found to be highest in the roadside environment,about 1. 4 and 3. 6 times those for buses and subways,respectively. 4) PAHs were more enriched under the roadside and bus environments. Exposure to PAHs and the health risks obviously increased in the roadside environment during days with elevated PM_(2. 5) concentrations.对北京市3种典型交通环境下PM_(2.5)中PAHs(多环芳烃)的污染水平、来源及其暴露健康风险进行了研究.于2011年12月利用颗粒物个体暴露 采样器采集北京市道路边、公共汽车、地铁等不同交通环境下的PM_(2.5)样品,采用GC-MS测定rho(PAHs),结合PAHs组成特征以及特征 化合物比值等鉴别PAHs来源,根据苯并[a]芘等效毒性(BEQ)、等效致癌浓度(BaPE)及致癌风险等参数评估PAHs呼吸暴露的健康风险.结果显 示:1观测期间,北京市道路边、公共汽车和地铁内rho(PAHs)平均值分别为(120119)、(10146.6)、(50.825.6)ng/m~ 3;23种交通环境下PAHs特征成分谱相似,rho(荧蒽)/[rho(荧蒽)+rho(芘)]、rho(茚并[1,2,3-cd]芘)/[rho(茚 并[1,2,3-cd]芘)+rho(苯并[g,h,i]苝)]均大于0.5,rho(苯并[a]蒽)/[rho(苯并[a]蒽)+rho()]大于0. 35,表明机动车尾气和燃煤排放是北京冬季3种交通环境下PAHs的重要贡献源;3分别采用美国加州环境保护局(California Environment Protection Agency,CalEPA)和世界卫生组织(World Health Organization,WHO)方法计算致癌风险可知,2种方法计算的道路边PAHs的致癌风险(19.8*10~(-6)、15.6*10~(-4 ))最高,约为公共汽车及地铁内的1.4和3.6倍;4道路边与公共汽车内的PAHs在PM_(2.5)中更为富集,道路边PAHs污染水平及健康风险在 高rho(PM_(2.5))环境下增加显著.
Polybrominated diphenyl ethers (PBDEs), a group of persistent organic pollutants (POPs), are caused for concern recently due to their adverse health effects and environmental ubiquity. In this study, atmospheric and soil PBDE levels in Taizhou, one of the largest WEEE dismantling areas in the world, were measured, ranging from 884 to 2791 pg m(-3) with an average of 1968 pg m(-3) for atmosphere and 2.96 to 200 ng g(-1) dry weight (dw) with the mean of 65.2 ng g(-1) dw for farmland soils, respectively. The close connection between soil PBDE accumulation and atmospheric deposition was also revealed by the estimation of the annual PBDE deposition flux (3.1 +/- 0.9 mg m(-2) a(-1)) and the similarity between deposited congener pattern and soil congener profile. Positive matrix factorization (PMF) was conducted to extract possible sources of farmland soil PBDEs and to calculate their contributions. Based on the measured source profiles of PBDE-related activities, five sources were identified representing WEEE dumping, WEEE dismantling, WEEE open burning, residential waste dismantling, and residential waste open burning. WEEE-related recycling activities contributed primary percentage (52%) to farmland soil PBDE concentration, and open burning was an important pathway for PBDEs entering the environment. (C) 2013 Elsevier B.V. All rights reserved.
Objective To explore the relationship between persistent organic pollutants exposure and DNA damage repair in the residents in electronic waste disposing area (e-waste area). Methods Peripheral blood persistent organic pollutants contents of the residents (n=23) in e-waste area and control area(n=25) were determined in a region of north China. The expression of 126 genes of DNA damage repair pathway in the blood samples of two groups was determined by RNA-seq in November, 2011. Results Various POPs showed significantly higher concentration in the exposed group than those in non-exposed group. A total of 17 genes showed differential expression,four (NEIL3, EXO1,MA PK12 and TP73) of which showed significant differential expression between the two groups. A total of nine genes were up-regulated and eight genes were down -regulated among 17 differential expression genes. Interestingly,the expression of certain genes,i.e., MA PK12, EXO1, NTHL1, GADD45G, RA D51, RAD51B appeared to be more significantly different merely among the females of the exposed and non-exposed group,while the expression of RA D54L, DMC1, BBC3, UNG, XRCC6BP1, TP73 merely occurred differential among the males. Conclusion POPs contents in peripheral blood of residents in e -waste area increased significantly, DNA damage repair -related genes expression condition has changed. The differential expression of genes in DNA damage repair system participates in various DNA damage repair pathway and has an effect on it. Gender difference may exist in response to POPs-mediated DNA damage.目的了解电子垃圾处理区域人群中持久性有机污染物(POPs)暴露与DNA损伤修复的关系。方法于2011年11月,检测某电子垃圾处理区域居民(暴露组 ,n=23)及非暴露地区居民(非暴露组,n=25)外周血POPs含量。以RNA测序比较两组血样中DNA损伤修复通路中126个基因的表达情况。结果 暴露组人群外周血多氯联苯(PCBs)、多溴联苯醚(BDEs)、得克隆(DP)的含量高于非暴露组;17个基因出现差异表达,其中NEIL3、EXO1 、MAPK12、TP73表达出现统计学差异。17个差异表达基因中9个基因下调,8个基因上调。MAPK12、EXO1、NTHL1、GADD45G、 RAD51、RAD51B仅在女性暴露组和非暴露组间出现差异;而RAD54L、DMC1、BBC3、UNG、XRCC6BP1、TP73仅在男性出现差 异表达。结论本次调查的电子垃圾处理区域人群外周血POPs含量高于非暴露组,DNA损伤修复相关基因表达量存在一定差异。机体对POPs所致DNA损伤 的应答机制可能存在性别差异。
Electronic waste (e-waste) disposal is a growing problem in China, and its effects on human health are a concern. To determine the concentrations of pollutants in peripheral blood and genetic aberrations near an e-waste disposal area in Jinghai, China, blood samples were collected from 30 (age: 41 +/- 11.01 years) and 28 (age: 33 +/- 2.14 years) individuals residing within 5 and 40 km of e-waste disposal facilities in Jinghai (China), respectively, during the week of October 21-28, 2011. Levels of inorganic pollutants (calcium, copper, iron, lead, magnesium, selenium, and zinc) and malondialdehyde (MDA), identities of persistent organic pollutants (POPs), micronucleus rates, and lymphocyte subsets were analyzed in individuals. Total RNA expression profiles were analyzed by group and gender. The population group living in proximity to the e-waste site displayed significantly higher mean levels of copper, zinc, lead, MDAs, POPs (B4-6DE, B7-9DE, total polychlorinated biphenyls, and BB-153). In addition, micronucleus rates of close-proximity group were higher compared with the remote group (18.27% vs. 7.32%). RNA expression of genes involved in metal ion binding and transport, oxidation/reduction, immune defense, and tumorigenesis varied between groups, with men most detrimentally affected (p<0.05). CD4(+) / CD8(+)T cell ratios, CD4(+)CD25(nt/hi)CD127(lo)regulatory T cell percentages, and CD95 expression were greater in the e-waste group (p < 0.05). Residing in close proximity to e-waste disposal facilities ( 5 km) may be associated with the accumulation of potentially harmful inorganic/organic compounds and gender-preferential genetic aberrations. (C) 2014 Elsevier Inc. All rights reserved.
Characterizing pseudo equilibrium-status soil/vegetation partition coefficient K-sv, the quotient of respective concentrations in soil and vegetation of a certain substance at remote background areas, is essential in ecological risk assessment, however few previous attempts have been made for field determination and developing validated and reproducible structure-based estimates. In this study, K-SV was calculated based on measurements of seventeen 2,3,7,8-substituted PCDD/F congeners in soil and moss (Dicranum angustum), and rouzi grass (Thylacospermum caespitosum) of two background sites, Ny-Alesund of the Arctic and Zhangmu-Nyalam region of the Tibet Plateau, respectively. By both fugacity modeling and stepwise regression of field data, the air-water partition coefficient (K-AW) and aqueous solubility (S-W) were identified as the influential physicochemical properties. Furthermore, validated quantitative structure-property relationship (QSPR) model was developed to extrapolate the K-SV prediction to all 210 PCDD/F congeners. Molecular polarizability, molecular size and molecular energy demonstrated leading effects on K-SV. (C) 2014 Elsevier B.V. All rights reserved.
Polybrominated diphenyl ethers (PBDEs) were measured in 87 soil samples collected from North China. Eleven PBDE congeners (BDE28, 47, 49, 66, 99, 100, 119, 183, 196, 203, and 209) were identified with a high frequency of detection (84-100 %) in soil samples, and their frequencies were used for statistical analysis in the present study. PBDE concentrations ranged from 0.08 to 8260 ng/g with a mean of 202 ng/g, thus indicating severe pollution at these sample sites. BDE209 was the predominant congener with concentrations of 0.08-8140 ng/g (mean 188). Analysis of the spatial distribution of PBDEs in North China soils indicated that relatively high concentrations of both lower- and higher-brominated BDEs were present in Shandong Province, and a decreasing trend in PBDE concentrations from the east toward the west of North China was observed. Source identification analysis suggested that Jinghai County in Tianjin and the coastal area of Laizhou Bay, Shandong province, were the major sources in North China. The sources in Jinghai County were connected with the dismantling of electronic waste, whereas the sources in the coastal area of Laizhou Bay were connected with the production of PBDEs. Modeling results showed that the distance between the sampling sites and these point sources had a large influence on the transfer of PBDEs.
Human exposure to pollutants from e-waste is an important scientific issue for their health effects. In this study, organohalogen pollutants in human serum sample from an e-waste dismantling site (n = 35) and a control site (n = 21), both located in Tianjin, Northern China, were analyzed using GC-ECNI-MS. Geometric mean concentrations of tetra- through hexa-BDEs, hepta- through nona-BDEs, PCBs, PBB-153, and DP in the exposure group were 2.77, 12.2, 44.1, 0.52, and 7.64 ng g(-1) lipid, respectively, which ranged from 1.5 to 7.4-fold higher than those in the control group through multivariate regression analysis, indicating that working and/or living in the e-waste site was associated with elevated body concentrations of these pollutants. Pollutants with low vapor pressures (i.e., hepta- through nona-BDEs and DP) were at significantly higher levels for e-waste dismantling workers than for local residents living around the e-waste site, suggesting higher exposure to these pollutants might exist for the occupational workers. (C) 2012 Elsevier Ltd. All rights reserved.
Brominated flame retardants (BFRs) such as polybrominated diphenyl ethers (PBDEs) are important pollutants, yet few data on ambient BFRs levels have been available for North China, one of the most developed regions of the country. In this study, we investigated levels and spatial distributions of BFRs based on gridded field observations coupled with passive air sampling in the aforementioned region. A model incorporating both point and nonpoint sources was developed to simulate the spatial distribution and to achieve source apportionment. Although high concentration was observed at an electronic-waste (e-waste) recycling site, the median level of the sum of tri-, tetra-, hepta-, hexa-, and hepta-PBDEs (Sigma 10PBDEs) was 0.56 ng/sample, which was lower than those observed previously in mainland China. Source apportionment revealed that nonpoint emissions contributed nearly 78% of Sigma 10PBDEs observed in this study. In contrast, high levels of BDE-209 and DBDPE were observed, with median concentrations of 4.0 and 10.2 ng/sample, respectively. Point sources located in the region around Laizhou Bay, Shandong Province were the major sources, which contributed 31% of BDE-209 and 70% of DBDPE observed in this study, indicating that this manufacturing base was the most important source region for atmospheric deca-BFRs in North China. To our knowledge, this is the first study to report source apportionment of atmospheric BFRs based on gridded field observations.
The health effects of exposure to pollutants from electronic waste (e-waste) pose an important issue. In this study, we explored the association between oxidative stress and blood levels of e-waste-related pollutants. Blood samples were collected from individuals living in the proximity of an e-waste recycling site located in northern China, and pollutants, as well as reactive oxygen species (ROS), were measured in comparison to a reference population. The geometric mean concentrations of PCBs, dechlorane plus, and 2,2',4,4',5,5'-hexabromobiphenyl in plasma from the exposure group were 60.4, 9.0, and 0.55 ng g(-1) lipid, respectively, which were 2.2, 3.2, and 2.2 times higher than the corresponding measurement in the reference group. Correspondingly, ROS levels in white blood cells, including in neutrophil granulocytes, from the exposure group were significantly higher than in those from the reference group, suggesting potential ROS related health effects for residents at the e-waste site. In contrast, fewer ROS were generated in the respiratory burst of neutrophil granulocytes for the exposure group, indicating a depressed innate immune function for the individuals living at the e-waste site. These findings suggest a potential linkage between exposure to pollutants from e-waste recycling and both elevated oxidative stress and altered immune function.
Brominated flame retardants (BFRs) are important persistent organic pollutants. Analysis of BFRs in atmospheric samples in a previous study led us to suspect the presence of unidentified organic bromides, other than polybrominated diphenyl ethers (PBDEs), in the atmosphere. In this study, we identified and quantified polybromobenzenes, a group of organic bromides, in air samples collected through passive sampling in gridded observations in North China. We investigated their concentrations and spatial distribution, and estimated the proportion due to different sources. We detected seven species of polybromobenzenes, including hexabromobenzene (HBB), pentabromotoluene (PBT), pentabromoethylbenzene (PBEB), pentabromobenzene (PeBB), tetrabromobenzenes (TeBBs), and tribromotoluene (TrBT), in all or most of the field samples, indicating widespread occurrence of this class of pollutants. The median concentrations of each pollutant ranged from 20.0 to 144 pg/sample (or from 0.07 to 1.16 pg/m(3)), with relatively high concentrations found near e-waste recycling sites, BFR manufacturing sites, and areas of high population density. Positive matrix factorization (PMF) analysis revealed that similar to 70% of HBB, PBT, PBEB, and PeBB was from commercial products, while similar to 80% of 1,2,3,S-TeBB, 1,2,4,S-TeBB, and 2,4,5-TrBT was linked with BFR manufacturing. This study provides essential information on widespread polybromobenzene pollutants in the atmosphere, particularly TeBBs and TrBT, for which this is the first report of their presence as atmospheric pollutants.
Polychlorinated naphthalenes (PCNs) belong to a group of dioxin-like pollutants; however little information is available on PCNs in North China. In this study, gridded field observations by passive air sampling at 90 sites were undertaken to determine the levels, spatial distributions, and sources of PCNs in the atmosphere of North China. A median concentration of 48 pg m(-3) (range: 10-2460 pg m(-3)) for Sigma(29)PCNs indicated heavy PCN pollution. The compositional profile indicated that nearly 90% of PCNs observed were from thermal processes rather than from commercial mixtures. Regarding the source type, a quantitative apportionment suggested that local non-point emissions contributed two-thirds of the total PCNs observed in the study, whereas a point source of electronic-waste recycling site contributed a quarter of total PCNs. The estimated toxic equivalent quantity for dioxin-like PCNs ranged from 0.97 to 687 fg TEQ m(-3), with the electronic-waste recycling site with the highest risk. (C) 2013 Elsevier Ltd. All rights reserved.
Polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) are persistent organic pollutants suspected to have various toxic effects, including reproductive toxicity. The aim of this study was to determine the concentrations of PCBs and PBDEs in human placentas and to examine the potential association between in utero exposure to these pollutants and the risk of neural tube defects. Subjects were recruited from a birth defects surveillance program in a rural area of Shanxi Province, China, from 2005 to 2007. 80 placental samples from fetuses/neonates with neural tube defects and 50 samples from healthy newborn infants were analyzed for PCBs and PBDEs using electron-capture negative-ionization gas chromatographic mass spectrometry. The median concentrations were 0.89 and 0.54 ng/g lipid for the eight PCB congeners and six PBDE congeners detected, respectively. The median concentration of total PCBs was slightly higher in the case samples than in the controls (0.91 vs. 0.89 ng/g lipid), but the difference was not significant (P=0.46), as also found for the median concentration of total PBDEs (0.55 vs. 0.54 ng/g lipid, P=0.61). For both PCBs and PBDEs, when their placental concentration was above the median of all samples, it was associated with a non-significantly higher or equal risk of neural tube defects. Low levels of PCBs and PBDEs are not likely risk factors for neural tube defects in this population. (C) 2012 Elsevier Inc. All rights reserved.
Polybrominated diphenyl ethers (PBDEs), extensively used as flame retardants, are ubiquitous environmental contaminants that are found in both abiotic and biotic environmental samples. Sufficient evidence shows that PBDEs have been rapidly accumulating in the environment of China, especially in the Southeast regions. This paper summarizes and critically reviews the published scientific data on PBDEs in China, including the levels of PBDEs in the air, soil, water, sediment, the terrestrial and marine organisms, and human samples in China. The data preliminarily reveal the state of PBDEs in China. (C) 2012 Elsevier Ltd. All rights reserved.
Investigation on PAHs in agricultural soils in Dongguan, South China were conducted. A total of 59 agricultural soil samples were collected from sites representative of the region for analysis of contents of 16 PAHs. Results show that 13 PAHs were detected with detectable ratios above 90%, Fie, Phe, Chr and Bbf were detected in all 59 samples, the detectable ratio of Ant was the lowest (13.56%). Sigma PAHs in soil samples is ranged from 29 to 2184 mug/kg, and 44.07%, 8.47% and 3.39% soil samples were slightly, moderately and heavily polluted by PAHs, respectively. Compared with other regions, Dongguan city is higher in soil PAHs contents, which can be confirmed that the increase of PAHs in agricultural soils is connected with human activities closely. Principal component analvsis demonstrate that the above-said 16 PAHs in agricultural soils may have three major contributors, corresponding to biomass burning, volatilization of oil production, and coal burning respectively. It is found that environmental factors (temperature, humidity), soil characters (pH, organic materials) and other pollutants (heavy metals) can affect environmental behaviors of PAHs. By means of ordinary Kriging interpolation, spatial distribution of 16 PAHs were studied. The results indicate that 16 PAHs vary greatly in spatial distribution between types, PAHs contents in west-north soils are much higher than that in south-east soils, and the highest PAHs contents area is in Wangniudun town, which hint that there are some pollutant sources connected with poisonous wastes combustion.
Ursolic acid(UA,3beta-hydroxy-urs-12-en-28-oic acid),a pentacyclic triterpene compound, exists abundantly in the plant kingdom as the major constituent of medicinal herbs. UA has been reported to display a remarkable spectrum of biochemical activities to influence processes capable of controlling cancer development. The pleuripotent anti-tumor activities of UA have stimulated the experts to research actively in this field. This paper summarizes the modification and pharmacological activity of ursolic acid derivatives according to literature and reports both at home and abroad熊果酸(UA,3beta-羟基-乌苏烷型-12-烯-28-羧酸),五环三萜化合物,作为药草的主要成分,存在于丰富的植物王国中.据报道,UA具有广 谱的生物活性,调控和控制肿瘤细胞形成.UA多效性的抗肿瘤活性激发了专家们在这方面的积极研究,现综合国内外文献报道,对熊果酸结构修饰物及其药理活性 进行综述
Persistent organic pollutants (POPs) have been associated with a wide range of adverse health effects. Our case-control study was performed to explore the association between placental levels of selected POPs and risks for neural tube defects (NTDs) in a Chinese population with a high prevalence of NTDs. Cases included 80 fetuses or newborns with NTDs, whereas the controls were 50 healthy, nonmalformed newborn infants. Placental concentrations of polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides, polychlorinated biphenyls, and polybrominated diphenyl ethers were analyzed by gas chromatography-mass spectrometry. The medians of PAHs, o,p'-isomers of dichlorodiphenyltrichloroethane (DDT) and metabolites, alpha- and gamma-hexachlorocyclohexane (HCH), and alpha-endosulfan were significantly higher in case placentas than in controls. PAH concentrations above the median were associated with a 4.52-fold (95% confidence interval (CI), 2.10-9.74) increased risk for any NTDs, and 5.84-(95% CI, 2.28-14.96) and 3.71-fold (95% CI, 1.57-8.79) increased risks for anencephaly and spina bifida, respectively. A dose-response relationship was observed between PAH levels and the risk of NTDs, with odds ratios for the second, third, and fourth quartiles, compared with the first, of 1.77-(95% CI, 0.66-4.76), 3.83-(95% CI, 1.37-10.75), and 11.67-fold (95% CI, 3.28-41.49), respectively. A dose-response relationship was observed for anencephaly and spina bifida subtypes. Similar results were observed for o,p'-DDT and metabolites, alpha-HCH, gamma-HCH, and alpha-endosulfan, whereas no dose-response relationship was observed for the last two pollutants. Elevated placental concentrations of PAHs, o,p'-DDT and metabolites, and alpha-HCH were associated with increased risks of NTDs in this population.