Links Between Environmental Geochemistry and Rate of Birth Defects: Shanxi Province, China
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Science of the Total Environment 409 (2011) 447–451 Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv Links between environmental geochemistry and rate of birth defects: Shanxi Province, China Hai-ying Yu a,b, Ke-li Zhang a,⁎ a State Key Laboratory of Earth Surface Processes and Resource Ecology, School of Geography, Beijing Normal University, Beijing 100875, PR China b College of Resources and Environmental Sciences, Sichuan Agricultural University, Ya'an, Sichuan 625014, PR China article info abstract Article history: The rate of birth defects in Shanxi Province is among the highest worldwide. In order to identify the impacts of Received 16 July 2010 geochemical and environmental factors on birth defect risk, samples of soil, water and food were collected Received in revised form 10 October 2010 from an area with an unusually high rate of birth defects (study area) and an area with a low rate of birth Accepted 11 October 2010 defects (control area) in Shanxi Province, China. Element contents were determined by ICP-OES, and the Available online 23 November 2010 results were analyzed using a non-parametric test and stepwise regression. Differences in the level and distribution of 14 geochemical elements, namely arsenic (As), selenium (Se), molybdenum (Mo), zinc (Zn), Keywords: strontium (Sr), iron (Fe), tin (Sn), magnesium (Mg), vanadium (V), calcium (Ca), copper (Cu), aluminum (Al), Birth defect Geochemical elements potassium (K) and sulfur (S) were thus compared between the study and control areas. The results reveal that Abnormalities the geochemical element contents in soil, water and food show a significant difference between the study area High birth defect area and control area, and suggest that the study area was characterized by higher S and lower Sr and Al contents. These findings, based on statistical analysis, may be useful in directing further epidemiological investigations identifying the leading causes of birth defects. © 2010 Elsevier B.V. All rights reserved. 1. Introduction and of these defects a hospital study has shown that neural tube defects (NTDs) are the most common birth defect. However, the rate Birth defects (congenital anomalies) are the leading cause of death of NTDs in China varies greatly between different regions. Data from in babies under 1 year of age (Petrini et al., 2002; Detrait et al., 2005). the Chinese Birth Defects Monitoring Program (CBDMP) indicated For the past several decades, epidemiological surveying has been a that NTD rate at birth in the whole of China is 2.7‰, but is 10.6‰ in key approach to identifying the causal factors, and has demonstrated Shanxi Province, which ranks highest and has become known as that causes leading to birth defects are very complex. However, all “Everest” due to its high incidence rate (Chen et al., 2009; Xiao et al., birth defects can be presumed to be caused by a combination or 1990; Li et al., 2006). The rate is so high that a logical first step in interaction of genetic and environmental factors. etiological research is to identify geographic factors associated with Epidemiologists are interested in whether it is genetic or risk. Population and family studies indicate a complex etiology in environmental factors (or both) that distinguish individuals with or NTDs, involving both environmental and genetic factors. Environ- without birth defects. In its widest sense, an environmental cause is mental factors implicated in increasing the risk of birth defects any nongenetic factor that increases the risk of a birth defect for the include geography, epidemic trends, socioeconomic class, maternal exposed individual, generally including nutritional excesses and age, maternal diet, maternal diabetes and obesity. deficiencies, maternal illness and injection, drug use, chemical Early studies of the causes of birth defects were mainly focused on exposures in the workplace or home, exposure to radiation, and genetic factors. However, by the 1960s, influences of environmental chemical contaminants in air, food, water and so on. causes on birth defects had been extensively confirmed. Vinceti et al. Although no direct causal connections have been established (2001) monitored birth defects in the area seriously polluted by lead between the geographic environment and rate of birth defects, the in northern Italy and found that over a period of time, decreasing the fact that regions with a particularly high rate of birth defects do occur environmental lead content reduced the incidence of heart diseases, require that studies must be conducted to investigate the causes of orificial clefts and bone diseases. Irgens et al. (1998) collected data birth defects in terms of geographic and environmental factors. The from all newborn babies between 1970 and 1993 in Norway, and highest rate of birth defects in the world has been reported in China, compared data on fetus defects between those from parents who were likely to have been exposed to lead pollution and those from parents with unlikely lead exposure. They concluded that newborns ⁎ Corresponding author. Tel.: +86 10 58805163; fax: +86 10 58806955. born to mothers exposed to lead pollution had a greater risk of low E-mail address: [email protected] (K. Zhang). weight and NTDs. It has further been shown that the occupations of 0048-9697/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.scitotenv.2010.10.019 448 H. Yu, K. Zhang / Science of the Total Environment 409 (2011) 447–451 pregnant women have a major affect on the health of children, and 2. Materials and methods also that women's exposure to glycol might lead to birth defects (Cordier et al., 1997). More recent research has suggested that women 2.1. Study areas and birth defect surveys with long-term occupational exposure to anesthetic gases, and pregnant women living in areas polluted by nuclear radiation, might Shanxi Province has the highest rate of birth defects in China. The be at higher risk of giving birth to a child with birth defects (Ratzon et province is located in northern China, and is surrounded by the al., 2004). Some researchers have considered that the rate of Luliang mountains in the west and Taihang mountains in the east. nongenetic birth defects is proportional to the level of the economic Epidemiological surveys show that the birth defects rate is highest in poverty (Vrijheid et al., 2000); in particular, the socioeconomic the Luliang mountains. In this study, Zhongyang County and Jiaokou circumstances during a woman's childhood were shown to have more County in the Luliang region were selected as areas with high rates of influence on birth defects than those during pregnancy (Sever and birth defects, at 717.64 per 10,000 births and 917.06 per 10,000 births, Emanuel, 2008). Although the prevalence rate of birth defects has respectively, according to the survey by the Capital Institute of been attributed to numerous environmental factors, the geographic Pediatrics. Pingyao County, located in the middle of Shanxi Province, “gradients” of relatively higher rates compared with other places in was chosen as the control area (Fig. 1). the world reveal that the geographic environment has a significant A population-based retrospective study was conducted in high impact on birth defects (Olney and Mulinare, 1999). Even in China, prevalence areas from Jan. 1, 2002 to Dec. 31, 2004. During these three epidemiological surveys have indicated that there is an obvious years, 542 cases of birth defects were diagnosed among 6420 fetuses. territorial clustering of high prevalence areas, whereby the incidence Types and incidence rate of birth defects are shown in Table 1. in the north of China is higher than that in the south (Cynthia et al., 1998). Also, in general the birth defects rate in rural areas is higher 2.2. Sampling than that in urban areas. Although many environmental factors associated with increased risk In the epidemiological survey, 146 surface soil samples (cropland of birth defects have been discussed in the studies mentioned, the and woodland), 146 drinking water samples (well water and river contribution of environmental factors to birth defects is still inconclu- water) and 170 crop samples (corn) were sampled in the study area sive. Meanwhile, so-called environment factors have generally been and control area from January to May in 2005. Samples were collected limited to secondary environmental factors, such as pollution in water, from both sides of the river, in an area where the population is air and foods, and unusual workplace environments. Few studies have relatively dense, while soil samples were collected in areas far away dealt with causal factors based on comprehensive analysis of raw from residential areas and roads to ensure the samples were geographic information in a high prevalence region of birth defects. We representative. therefore believe that the identification of leading causes of birth defects through their link with abnormal environmental conditions is of great 2.3. Sample preparation and laboratory analysis importance in areas with high rates of birth defects. Here, we statistically analyzed and compared geochemical The samples were immediately processed in the laboratory after anomalies in areas with high and normal rates of birth defects to sampling. Air dried soil samples were sieved with a 100 mesh sieve. elucidate the relationship between incidence rate of birth defects and 0.1 g of each soil sample was then mixed with 3 ml nitric acid, 1 ml geochemical anomalies, and to provide a non-medical basis for perchloride acid and 1 ml hydrofluoric acid. The samples were placed effective prevention and cure of birth defects. in an oven for nitration for 5 h, then removed and heated on an Fig. 1. Location of the study areas. H. Yu, K. Zhang / Science of the Total Environment 409 (2011) 447–451 449 Table 1 Prevalence of various birth defects in the high birth defects area (2002–2004).