International Journal of Hygiene and Environmental Health
Comparison of polycyclic aromatic hydrocarbon levels in placental tissues of Indian women with full- and preterm deliveries
Introduction
Polycyclic aromatic hydrocarbons (PAHs), a number of which closely resemble steroid hormones, are ubiquitous environmental contaminants produced from combustion products of fossil fuels, cigarette smoking and during cooking grilled and smoked foods (Santodonato, 1997). Human exposure to PAHs is chiefly through inhalation and diet (Van Rooij et al., 1994). These compounds are lipophilic in nature, and, therefore, after exposure they can be stored in human tissues like blood, placenta and milk (Madhavan and Naidu, 1995). The ability of PAHs to reach placental tissue and cord blood has been reported in few studies (Huel et al., 1993; Gladen et al., 2000). Such compounds are suggested to be endocrine disrupters and capable of altering the hormonal equilibrium by their antiandrogenic and estrogenic activities (Santodonato, 1997). A direct effect of PAHs on receptors for epidermal growth factor (EGF) and insulin-like growth factors (IGF) I and II in placental cells was found by Guyda (1991). Further, Zhang et al. (1995) showed benzo(a)pyrene mediated loss of EGF receptors and alters trophoblast proliferation as well as its endocrine function. These changes tended to influence placental growth. During animal experimental studies, a variety of outcomes, including decreased fertility, fetal death, malformations and transplacental carcinogenesis, have been observed (MacKenzie and Angevine, 1981; Ridgon and Rennels, 1964). Huel et al. (1993) also reported an association between the PAHs-induced human placental aryl hydrocarbon hydroxylase (AHH) inductions, which threatened with preterm delivery.
Preterm delivery remains the leading cause of perinatal mortality and occurs in approximately 4–10% of pregnancies (Leem et al., 2002; Reagan and Salsberry, 2005). Risk factors coupled with preterm birth and low birth weight include socioeconomic status, race/ethnicity, smoking and environmental contaminants (Farhang et al., 2005). Throughout the pregnancy period, women are exposed to a wide variety of foreign chemicals including PAHs through lifestyle factors (smoking, drug abuse and alcohol consumption), maternal medication and also from occupational and environmental exposure (Nan et al., 2001; Myllynen et al., 2005). It has been already reported that environmental levels of PAHs in India are much higher than the standard limits prescribed by government regulatory agencies (Singh et al., 2007). So there are chances of getting exposed to high PAHs through environment. In addition, there is no barrier to prevent inward movement of these chemicals and they are circulated between mother and fetus by simple diffusion. It has been speculated that chronic exposure to high pollution levels of PAHs here in Indian environment (Sharma et al., 2007) may influence placental functions and length of pregnancy in pregnant women, as previously observed by Huel et al. (1993). An Indian study (Madhavan and Naidu, 1995) reported placental PAHs levels (viz. chrysene, benzo(a)pyrene and benz(a,h)anthracene concentrations) of healthy non-smoking pregnant women from the general population but there is still lack of information about placental PAHs levels among women who did not undergo normal pregnancy, i.e. preterm delivery. Bearing in mind the adverse effects of PAHs on normal placental functions, it may be a topic of interest to see if there is any association between placental PAHs exposure and gestation age of pregnant women. In the current study, we sought to determine the placental tissue PAHs exposure in pregnant women who suffered preterm deliveries, to examine if PAHs expose pregnant women to the risk of preterm delivery. So, the present study was designed to compare placental PAHs levels detected in preterm delivery group of pregnant women with the same found in control group of pregnant women who underwent normal delivery (selected from Lucknow, India).
Section snippets
Selection of subjects
Sixty pregnant women from Lucknow city and nearby areas, after 28 weeks of gestational age, attending the antenatal clinic of a local nursing home during the period August 2005–February 2006 were included in the present study. Lucknow is the capital of the most populous state (Uttar Pradesh) of India. Previous studies conducted in this region show high PAHs levels in environment (Malik et al., 2004); also women population of this area are found exposed to high levels of PAHs during cooking (
Excitation and emission wavelength program
PAH detected Excitation (nm) Emission (nm) Naphthalene, fluorene 275 330 Phenanthrene 250 366 Anthracene 250 400 Fluoranthene 270 460 Pyrene, Benzo(a)anthracene 270 390 Benzo(k)fluoranthene, Benzo(b)fluoranthene, Benzo(a)pyrene 255 410 Dibenzo(a,h)anthracene, Benzo(g,h,i)perylene 290 410
Solvents that constituted the mobile phase were acetonitrile (A) and water (B). The elution conditions were: 0–10 min, 50% A isocratic; 10–24 min, linear gradient 50% A–100% A; 24–35 min, 100% A isocratic; and, finally, back to the
Results
A total of 60 pregnant women (20–35 yr) were involved in the study. Two groups of women were enrolled, based on pregnancy outcome. The first group included pregnancies with full-term delivery (n=31) considered as control group, and second group was formed of pregnancies with preterm delivery (n=29) of women, considered as study group. The socio-demographic and reproductive characteristics of the subjects in both study and control groups are depicted in Table 1. Characteristics such as age,
Discussion
In several environmental health studies, PAHs have received much interest because a number of them are not only carcinogenic, but also associated with reproductive and developmental abnormalities (IARC, 1983; ATSDR, 1995). Toxic effects of PAHs in placental tissues have been demonstrated to be due to their metabolites, epoxides, which interact with DNA and could interfere with the normal course of the pregnancy and might be aborticides, teratogens or carcinogens (Huel et al., 1993). Madhavan
Acknowledgments
The authors express their sincere thanks to the nurses and staff of Safia Clinic and Nursing Home, Lucknow (UP) for their help during collection of placental samples. Thanks are also due to Mohammed Fareed for his assistance during sample collection and processing. One of the authors (Vipul K. Singh) expresses his sincere thanks to the University Grants Commission, Government of India, for awarding him the Senior Research Fellowship.
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