Exposure to atmospheric pollutants in both open and closed environments has an adverse effect upon the early development of the fetus, leading to premature deaths. The most frequently studied pollutants are sulphur dioxide (SO2), nitrogen dioxide (NO2), particulate matter and polycyclic aromatic hydrocarbons (PAHs). The effect of air pollution on placental during pregnancy are not fully understood. The present cross-sectional study was conducted to know the effects of air pollution on placenta during pregnancy and the impact of these effects on the fetus and the nervous system by taking 373 women volunteer participants with normal pregnancy from different regions of Odisha. The effect of air pollutants on the developing fetus was studied by using neonatal anthropometric measures. The tools for the assessment of anthropometric measures include physical examination and maternal questionnaire. Maternal venous blood was  collected prior to and cord blood, placental tissue was collected immediately after delivery. The estimation of homocysteine level in serum was done by clinical analyzer. Serum homocysteine level was measured using Boils 24i automated clinical chemistry analyzer. The present study showed significant decrease in birth weight, body mass index, head circumference and placental weight in heavy traffic congestion areas (Cuttack zone) and industrial areas (Jajpur zone) in comparison to rural non-industrial areas (Nilagiria zone). But percentage of low birth weight (40.90 %, 27.27 %, and 13.63 %), cephalization index (130.33, 112.80, and 101.59) and serum homocysteine level were significantly increased (p< 0.01) in heavy traffic and industrial areas as compared to nonindustrial areas. These findings advocate that the exposure of pregnant women to air adversely affects the growth and development of the fetus in highly polluted areas. 

PAH; Serum; Anthropometric parameter; Homocysteine; Birth weight

Das P, Das L, Patri M (2017) Exposure of Pregnant Women to Air Pollution in Odisha, India: A Case Study. JSM Health Educ Prim Health Care 2(3): 1034.

PAH: Polycyclic Aromatic Hydrocarbon; IUGR: Intrauterine Growth Restriction; SGA: Small-for-gestational age; B[a] P: Benzo[a] pyrene; BPDE: Benzo Pyrene Diol Epoxide; IQ: Intelligence Quotient; CAT: Catalase; SODs: Superoxide Dismutases; ICMR: Indian council of medical research; BMI: Body Mass Index; CI: Cephalization index; LPx: Lipid peroxidation; LDH: Lactate dehydrogenase; tHcy: Total Homocysteine; ATP: Adenosine Triphosphate; SAM: S-Adenosyl methionine; SAH: S-Adenosyl Homocysteine; PD: Preterm Delivery; LBW: Low Birth Weight

Population growth, rapid industrialization and increased vehicular load are the main causes of increasing pollution load in ambient air. Pollutants enter the human body through several routes such as inhalation of contaminated air, consumption of contaminated water and food, exposure to contaminated soil and industrial waste [1]. Exposure to ambient organic air pollutants like sulphur dioxide (SO2 ), nitrogen dioxide (NO2 ), particulate matter and polycyclic aromatic hydrocarbons (PAHs) has been reported to be inducing birth defects and abnormal brain development [2]. PAHs are widespread environmental pollutants and classified under hazardous genotoxic compounds. The transplacental transfer of PAH to the fetus can have a significant impact on fetal development such as inducing an increased risk of intrauterine growth restriction (IUGR), small-for-gestational age (SGA) and preterm delivery [3,4]. Benzo[a]pyrene (B[a] P) is a prototype of PAH and is mainly produced due to incomplete combustion of organic matters. The B[a] P reacts and binds with DNA through its metabolite to form Benzo Pyrene Diol Epoxide (BPDE), which results in mutations, various disorders and diseases [5]. Daily exposure to B[a] P is mainly through air pollution, food, and cigarette smoke. However, the role of this toxin in pregnancy has not been extensively evaluated.

Recent studies have analysed the importance of exposure to air pollutants during intrauterine life and the possible repercussions of the said exposure at birth, during childhood, and during adulthood. Studies also reported that anthropometric parameters of birth, such as birth weight, birth length, head and chest circumference are indicators of the thinness of a newborn baby and cephalization index is the indicator of brain-sparing [6,7]. Both indices have been remarkably correlated with severe intrauterine growth restriction (IUGR) and poor neural development [8]. Recent study demonstrated that the increase in prenatal PAH exposure was associated with an increase in cephalization index [6]. Hence prenatal exposure to PAH may influence the infants’ neurodevelopment, including decreased cognitive and motor functions, a reduced child intelligent quotient (IQ), an increased risk of behavioral problems [9,10], genetic and oxidative damage in newborns [11].

Evidence from our laboratory suggests that B[a] P may result, at least in part. From peroxidase-catalysed bioactivation to reactive free radical intermediates, which, if not detoxified and generate reactive oxygen species (ROS). ROS can cause damage to embryonic or fetal DNA, proteins and lipids potentially leading to premature deaths. Several biomarkers such as lipid peroxidation (LPx), lactate dehydrogenase (LDH), 8-oxo-dG, catalase (CAT), superoxide dismutase (SOD), and homocysteine are indices of oxidative stress of the pregnant women those were exposed to particulate pollutants. Ambient particulate pollutants are mainly associated with an increase in plasma homocysteine concentration which is a well-known predictor of cardiovascular disease [12]. The elevation of total homocysteine level in serum induces endothelial cell injury and oxidative stress [10]. Hyperhomocysteinemia is believed to be a major risk factor for venous thrombosis, atherosclerosis, myocardial infarction, and cardiovascular stroke [9,13].

Existing literature advocates the significant correlation between the increase of homocysteine level in serum and rising pollution load [4]. However, the literature collected so far does not throw much light on the possible correlation between rise of total serum homocysteine level and its impact on fetal development. Understanding each pollutant with respect to its specific chemical mechanism of action on development may be essential in determining its toxic effects on the embryo or the fetus, and what might be the actual cause of these major birth abnormalities. Hence, the present study aims at assessing the impact of ambient air pollution on neonates and the link between particulate matter exposure containing gaseous SO2 , NO2 and particulate pollutants (e.g. PAHs) with development of fetus, possibly due to its ability to increase intracellular oxidative stress by production of superoxide anions.

Ethics statement

The design and procedure of the experiment were approved by the Institutional Ethical Committee on biomedical research on human subjects of SCB Medical College, Cuttack, Odisha, India in compliance with the guidelines of Indian Council of Medical Research (ICMR) (213/29.1.16). Written consents were obtained from all women volunteers’ participants.

Study design

The present cross-sectional study-design includes 373 female volunteers of three distinctly different areas such as Group-1 (Cuttack zone), Group-2 (Jajpur zone) and Group-3 (Nilagirizone) of Odisha, India. The Cuttack zone has reference as a thickly populated and traffic polluted area which includes the urban city of Cuttack, the old capital of Odisha. Kalinganagar, regarded as the steel hub of Asia, is situated in the district of Jajpur, Odisha. Kalinganagar has more than twenty steel plants and other ancillary industries. The non-industrial areas refer to remote tribal-rural areas of Nilagiri in Balasore district of Odisha.

Volunteers belong to almost the same socio-economic classes and they delivered their babies during the period between January 2016 and March 2017.

The questionnaire administered to the participant mothers specifically covers all possible aspects of their exposure to air pollution from the early days of their conception to delivery. The assessments of pregnancy include physical examinations and opinion of the treating physicians. Data were collected by researchers adopting the questionnaire method. The different measurements of new born babies like length, weight, head circumference of babies, weight of placenta etc. were personally taken by the researcher inside the labor room in the presence of the doctors and nurses. The enrolment was restricted to women volunteers in their singleton pregnancy without any complicacy. Women volunteers with pre-medical history of serious chronic diseases were excluded from the study.

Maternal questionnaire

A maternal questionnaire was prepared with slight modifications and administered to the volunteers at the time of delivery to obtain information about maternal characteristics and other aspects relating to the present study [15]. The questionnaire covers sociodemographic characteristics (age, marital status, parity, maternal education and employment), health of parents, environmental exposures (outdoor/indoor), occupational exposures, maternal diets, height, weight, medical treatment, vaccination, duration of sleep during pregnancy. The study also covers reproductive history, family history of allergies, respiratory and hereditary diseases, educational qualifications, place of residence (distance from plants or mines), type and size of residence. The questionnaire also covers whether the expecting mother was exposed to smoke of the cooking fire and burning candles or lamps, passive smoking and alcohol consumption etc.

Neonatal information

Neonatal information like exact time of birth, gestational age at birth (weeks), sex of new born baby, birth weight (grams), birth length (centimeters), birth head circumference (centimeters), chest circumference (centimeters), placental weight (grams), placental diameter (centimeter), placental thickness (centimeter) were properly collected and documented.

Outcome variables

In addition to above data body mass index (BMI) [birth weight (gm)/birth length (cm)] and cephalization index (CI) [head circumference (cm)/birth weight (gm) × 104 ] were also calculated [15].

Sample collection and preparation

Prior to delivery, venous blood (5 ml) was collected from the mother and immediately after delivery umbilical cord arterial blood (5 ml) was collected from neonates, after cord separation. Then the blood samples collected in 4ml gel tube (gel and clot activator, 13x75 mm,) were put in incubation for a period of 15 minutes at the room temperature (RT-37°C). After the expiry of 15 minutes the blood samples were centrifuged at 4000 rpm for 5 minutes and serum collected there from them was stored at -20- °C until taken for clinical analysis [16].

Just after delivery placental tissues were collected from both maternal and fetal side of placenta, and repeatedly washed with 9% saline water and stored at -20°C temperature for further analysis [17].

Quantification of total homocysteine level in serum Serum

Homocysteine level was measured using commercial kits from Euro diagnostics, adapted to Boils 24i automated clinical chemistry analyzer, serial no. 2605780911(Tokyo Boeki medical system, Japan).

Serum Homocysteine level was measured using Boils 24i automated clinical chemistry analyzer.

Clinical significance

Total homocysteine (t Hcy) represents all forms of homocysteine (oxidized, protein bound and free forms). Homocysteine [HSCH2 CH2 CH (NH2 ) COOH] is naturally occurring sulfur containing non-protein amino acid. Amino acids are the building blocks of proteins. When proteins break down, elevated levels of amino acids like homocysteine may be found in the bloodstream. It is synthesized by demethylation of methionine. Methionine accepts one adenosine molecule from one ATP molecule in presence of Methionine adenosyl transferase and forms S-Adenosyl methionine (SAM). SAM releases one methyl group (CH3 ) in the presence of enzyme Methyl transferase and become S-Adenosyl homocysteine (SAH). SAH accepts one H2 O molecule in the presence of Adenosyl homocysteine hydrolase and releases one adenosine molecule and become Homocysteine. Homocysteine accepts one serine molecule in the presence of B6 (CBS cystathionine β-synthase) and is converted to cystathionine with one H2 O molecule. During transulfuration cystathionine in the presence of B6 (CTH cystathionine γ-lyase) accepts one H2 O molecule and splits into NH4 + , cysteine and α-keto-butyrate. Homocysteine and cysteine are isomers. During reduction reaction α-keto-butyrate in presence of COA.SH and NAD+ form NADH and propionyl COA. Homocysteine can be converted in to methionine by remethylation process in the presence of Methionine synthetase (B12) [8]. Low concentration of Vitamin B12 (Methionine synthetase), Vitamin B6 (Pyridoxine), and B9 (Folic acid) reduces demethylation and transulfuration, which prevents conversion of homocysteine to methionine and cysteine respectively [9].

Because of which homocysteine level increases in serum and leads to hyperhomocysteinemia condition. More than 15 µmole/ lit of homocysteine in serum cause hyperhomocysteinemia. Hyperhomocysteinemia is associated with pregnancy complications as preterm delivery (PD), low birth weight (LBW), intrauterine growth retardation (IUGR) [18].

Assay sample (25μl) was taken into a 3ml curette having R1 assay solution (480μl). Then assay mixture was incubated for a period of 5 minutes at 37ºC temperature and R2 assay solution (130μL) was added. After 150 seconds of incubation initial reading (A1) was taken at the absorbance 340 nm. The second reading (A2) was recorded after 150 seconds of A1 reading.

Absorbance calculation (Δ A)

Δ A= A2-A1

Calculations

Homocysteine (μmol/L) = (Δ A) sample/(ΔA) calibrator x Calibrator value

Units

One international unit (IU) is the amount of enzyme that transforms 1 mol of substrate per minute, in standard conditions. The concentration is expressed in units per liter of sample (μmol/L).

Statistical analysis

The volunteers were categorized into three separate groups depending on the collection area as Group-1 (Cuttack zone), Group-2 (Jajpur zone) and Group-3 (Nilagiri zone). Mean, standard deviation (SD) and standard error of mean (SEM) were calculated for each group. Statistical analysis was performed using one-way ANOVA analysis Statistical Package for the Social Science (SPSS) version 20.0. Post-hoc tests were applied to perform all pair wise comparisons between group means (p< 0.05). Relations between variables were analyzed by calculating the Pearson correlation coefficients were significant (p< 0.01).

Level of air pollutants

In the present study, the levels of ambient air pollutants for the year (2016-17) in different study areas of Odisha were collected from ‘The Odisha State Pollution Board’ (OSPC), Bhubaneswar. Air pollution level of three different study zones and their sources of pollution were shown (Table 4).

Table 4: Different study areas in Odisha.

The major components of air pollution and the air quality index of three different study zones were shown (Fig-1i,Table-5).

Figure 1(i) : Air pollution level: Histogram represents air pollution level of Cuttack zone, Jajpur zone and Nilagiri zone. The level of air pollutant PM10 and PM2.5is remarkably high in Cuttack zone (95µgm/m3 ), Jajpur zone (71µgm/m3 ) than Nilagiri zone (53µgm/m3 ). No significant difference was recorded in the level of SO2 and NOX in three different study zones.

Table 5: Types of air pollutants measured during January 2016 to March 2017 in different areas.

Newborn anthropometric measures

Birth weight: Just after delivery birth weight of neonates from different community health centers of three zones were measured and recorded in questionnaire. Neonatal birth weight (BW) in Cuttack (2.47 ± 0.08) and Jajpur zone (2.99 ± 0.11) in comparison to that of Nilagiri zone (3.40 ± 0.12) (F2,371=16.39, P < 0.05) were found to be significantly less after the exposure of pregnant women to ambient air particulate pollutants. The most significant weight loss was observed in neonates of Cuttack zone in comparison to that of other zones (Figure1a & Table 1).

Figure 1(a): Measurement of Birth weight: Histogram represents birth weight of neonates of different areas. Values were expressed as mean ± SEM (n=3 groups) “a” denotes p < 0.05 when compared to Cuttack zone “b” denotes p < 0.05 when compared with Jajpur zone.

Table 1: Neonatal growth Characteristics and maternal blood index

The birth weight of male children of Cuttack zone (2.54 ± 0.09), Jajpur zone (3.12 ± 0.19) and Nilagiri zone (3.50 ± 0.20) is higher than female children of Cuttack zone (2.41 ± 0.14), Jajpur zone (2.92 ± 0.13) and Nilagiri zone (3.31 ± 0.16) respectively. No remarkable difference was observed between the birth weight of male children and female children of different regions. But significant difference was recorded among male children of different zones. Similar observations were also found in female children (F2,371=17.04, P< 0.0001) (Figure 1f & Table. 2).

Figure 1f: Comparison between birth weight of male child and female child: Histogram represents weight of male child (a) and weight of female child (#) of participants of different area. Values were expressed as mean ± SEM (n=3 groups). “a” denotes p < 0.01 when compared to birth weight of male child of Cuttack zone, and “#” denotes birth weight of female child of Cuttack zone p< 0.01 when compared to other zones.

Table 2: Maternal and neonatal status of anthropometric measures.

Low birth weight: The increase in percentage of low birth weight recorded in Cuttack zone (40.909) was found to be significantly more than in Jajpur zone (27.273). Nilagiri zone (13.636) had the lowest percentage of low birth weight (F2,371=3.245, P < 0.05), (Figure1 c).

Figure 1(c): Percentage of Low birth weight: Histogram represents low birth length of neonates of different area. Values were expressed as mean ± SEM (n=3 groups) “a” denotes p < 0.05 when compared to Cuttack zone “b” denotes p < 0.05 when compared to Jajpur zone.

Birth length: The body length of the neonates was measured and recorded in questionnaire immediately after delivery. Neonatal birth length (BL) of Cuttack zone (46.12 ± 0.44) and Jajpur zone (47.26 ± 0.39) was found to be decreased in comparison to that of the Nilagiri zone (49.32 ± 0.49) (F2,371=6.843, P < 0.05). Both Cuttack zone and Jajpur zone showed a comparatively remarkable decrease in birth length than that of Nilagiri zone (Figure 1b).

Figure 1(b): Birth length: Histogram represents birth length of neonates of different area. Values were expressed as mean ± SEM (n=3 groups). “a” denotes p < 0.05 when compared to Cuttack zone “b” denotes p < 0.05 when compared to Jajpur zone.

Placental weight: Placental weight (PW) of Cuttack zone (344.13 ± 17.20) is found to be the lowest whereas Nilagiri zone (518.14 ± 20.32) has the highest placental weight in the mother in comparison to pregnant mothers of Jajpur zone (425.79); (F2,371=1.092, p < 0.05) (Figure 1e). Birth weight of neonates of different zone showed positive correlation with their placental weight at significant level p< 0.01 (Figure 1e).

Figure 1(e): Placental weight: Histogram represents placental weight of neonates of different area. Values were expressed as mean ± SEM (n=3 groups). “a” denotes p < 0.05 when compared to Cuttack zone “b” denotes p < 0.05 when compared with Jajpur zone.

Head circumference: The finding of the present study showed that the neonatal head circumference (HC) in Cuttack zone (30.89 ± 0.25) showed to be the lowest as compared to Jajpur zone (32.66 ± 0.30) and with increased HC in Nilagiri zone (34.58 ± 0.22) in comparison to other zones (F2,371=3.094, p< 0.05) (Figure 1g & Table 1).

Figure 1(g): Head circumference: Histogram represents head circumference of neonates of different area. Values were expressed as mean ± SEM (n=3 groups).”a” denotes p < 0.05 when compared to Cuttack zone and “b ” denotes p < 0.05 when compared to Jajpur zone.

Chest circumference: The lowest chest circumference was observed in Cuttack zone (30.89 ± 0.25) where as Nilagiri zone (34.58 ± 0.22) has the highest chest circumference with Jajpur zone (32.66 ± 0.30) placed in the middle (F2,371=7.236, p <0.001). A noted difference was recorded between the chest circumference of the neonates of Cuttack and Nilagiri zones at p < 0.05 (Table 3).

Table 3: New born anthropometric measure.

Body mass index: Body mass index (BMI) is the ratio between birth weight (kg) and birth length (m2 ). Significantly decreased Body mass index (BMI) was recorded in Cuttack zone (11.62 ± 0.31) in comparision to that of Jajpur (13.35 ± 0.41) and Nilagiri zones (14.07 ± 0.56) (F2,371=6.949, p< 0.05). The significantly decreased BMI of neonates in Jajpur zone was less in comparision to Nilagiri zone (Figure 1d & Table 1).

Figure 1(d) Body mass index: The graphical representation of body mass index of neonates of Cuttack zone, Jajpur zone, Nilagiri zone. Values were expressed as mean ± SEM (n=3 groups). “a” denotes p < 0.05 when compared with Cuttack zone.

Cephalization index: Cephalization index is the ratio of head circumference (cm) with birth weight (g) multiplied by104 . Our present study showed that cephalization index (CI) increased noticeably in Cuttack zone (130.33 ± 2.97) followed by Jajpur zone (112.80 ± 2.97) and Nilagiri zone (101.59 ± 4.37) (F2,371= 3.094. p < 0.05), (Figure 1h & Table 3).

Figure 1(h): Cephalization index: Histogram represents cephalization index of neonates of different area. Values were expressed as mean ± SEM (n=3 groups). “a” denotes p < 0.05 when compared to Cuttack zone and “b” denotes p < 0.05 when compared to Jajpur zone.

Serum homocysteine level: Serum homocysteine level of maternal blood (MB) and cord blood (CB) of Cuttack zone, Jajpur zone and Nilagiri zone showed positive correlation at the level p <0.01. Serum homocysteine level of both maternal and cord blood significantly increased in heavy traffic area (MB was 14.25 ± 0.17 & CB was 17.04 ± 0.30) and industrial areas (MB, 13.61 ± 0.17 & CB, 16.85 ± 0.19) in comparison to non-industrial areas like Nilgiri (MB, 11.23 ± 0.46 & CB, 14.20 ± 0.36). A positive correlation was observed between ambient air particulate pollutants and augmented serum homocysteine level of maternal blood before delivery and umbilical cord blood of Cuttack zone, Jajpur zone and Nilagiri zone at the level (p < 0.01) (Figure 2).

Figure 2: Measurement of serum Homocysteine level: Histogram represents homocysteine level of mother serum (a) and cord serum (#) of participants of different area. Values were expressed as mean ± SEM (n=3 groups). “a” denotes p < 0.01 when compare to homocysteine level of mother blood of Cuttack zone,” #” denotes p< 0.01 when compared to homocysteine level of cord blood of Cuttack zone.

Exposure of pregnant women to ambient air pollution is causally related to adverse pregnancy outcomes, that would be considerably increased through understanding of biological mechanisms by which such effects could occur. Air pollutants may be absorbed into the maternal bloodstream, cross the placental barrier and have direct toxic effects on the fetus. The particulate pollutants seem to be the most important pollutant exposure for infant deaths, and the effect on IUGR seems linked to polycyclic aromatic hydrocarbons, whereas the neonatal birth outcome is a multi-factorial dependent parameter. It depends on age, height, health, genetic constituent, food habit, economic status and antenatal care services of the mother. Mostly the urban population shows more adverse birth outcomes than rural areas.

Exposure of pregnant women to ambient air pollution was associated with a greatly reduced birth weight in Krakow Caucasians and in NYC African Americans [19,20]. Exposure of environmental tobacco smoke during pregnancy is associated with earlier delivery and reduced birth weight [21]. Ambient air pollution induces oxidative stress. Oxidative stress adversely affects placental mitochondria which reduces the ability of the placenta to support the growing fetus [22-24]. The consequence of low placental ability leads to low birth weight. Low birth weight is associated with both short and long-term health complications [25]. An increased risk of preterm delivery and low birth weight of neonates were reported from women residing in traffic congestion areas [26]. Our study showed significantly reduced birth weight (p< 0.05) and an increased percentage of low birth weight in heavy traffic urban and industrially polluted areas than remote rural non- industrial areas.

The Combined exposure to high environmental tobacco smoke (ETS) and high benzo-a-pyrene-DNA (BaP-DNA) adducts had a significant effect on birth weight and head circumference [27]. Head circumference was associated with the length of gestation period [28]. In our present study, a reduced head circumference was observed in heavy traffic area and industrial areas than rural non-industrial areas. It was reported that PAH exposure had impact on the cephalization index, the ratio of head size (cm) to birth weight (gm) [6]. Increased cephalization index suggests intrauterine growth restriction (IUGR). The growth restriction might induce a “brain-sparing” process during embryogenesis. Increased cephalization index is a sign of retarded prenatal growth. Thus, cephalization index indicates a strong correlation between neonatal growth and exposure to particulate pollutants during pregnancy [29]. In the present study, higher cephalization index was recorded in heavy traffic and industrially polluted areas in comparison to non-industrial or remote rural area.

Ambient air pollution is associated with higher homocysteine concentrations and with lower placental weight, lowers birth weight [30]. Elevated homocysteine concentrations (16-24 lmol/l) may induce cytotoxic and oxidative stress, leading to endothelial cell impairment [31]. Evidence collected from experiments showed that homocysteine induced the death of trophoblast cells through the release of cytochrome c. It might also increase cellular apoptosis and lead to inhibition of the function of trophoblastic cells [31]. The present study showed less placental weight in high traffic areas and industrial areas in comparison to the non-industrial areas. PM2.5, an ambient air particulate is composed of nitrates, BC (Black Carbon), OC (Organic Carbon), soot of sulfate, and transition metals. Black carbons are generated directly from vehicular combustion. Organic carbons are emitted both from primary and secondary chemical reactions of gaseous organic precursors (e.g. PAH) [32]. Recent studies have demonstrated that vehicular emission particles were more strongly associated with cardiovascular problems than secondary coal-burning particles [33,34]. Both active and passive cigarette smoking is related to oxidative stress and inflammation in human body.

Oxidative stress may play an important role in raising homocysteine metabolism [35]. Several possible physiological mechanisms may explain the link between particle exposure from ambient air and increased homocysteine concentration. Homocysteine is produced intracellular by demethylation of methionine and transulfuration pathway. Transition metals bound to particles may directly inactivate the enzyme methionine synthetase which is involved in homocysteine demethylation [36]. Ambient air particle pollutants generate reactive oxygen species (ROS) which may lead to oxidative stress [37] and results in the rising level of plasma homocysteine. This finding suggests that ambient particle pollutants may elevate the homocysteine concentration due to interruption of the demethylation pathway

Homocysteine is naturally occurring sulphur containing non-protein α-amino acid. It is synthesized by demethylation of methionine (amino acid that is found in meat, fish, and dairy products). Vitamins B6 (pyridoxine), B12 (methylcobalamin) and B9 (folic acid) are needed for this demethylation reaction. Exposure to air pollution is known to be associated with an increased risk of cardiovascular dysfunction in human beings [38,39], and acceleration of atherosclerosis and vascular inflammation has been shown in mice after 6 months of exposure to concentrated air pollutants [40]. Ambient particulate pollutants were found associated with an increase in plasma homocysteine concentration in blood. Homocysteine concentration is a well-known predictor of cardiovascular disease [41,42]. Existing literature advocates the possible role of exposure to environmental toxicants on prenatal growth and brain development. However, our present study was conducted on pregnant women to elucidate the correlation of toxicant exposure with altered serum homocysteine level.

Age, sex and race of human beings are important determinants of plasma homocysteine concentration. Another study found an association between inflammatory state and homocysteine concentration among subjects aged 65 or older [43]. It can be concluded that exposure to vehicular emission related particles were associated with an increase in plasma homocysteine concentration. Higher concentrations of plasma folate and vitamin B12 do not allow the plasma homocysteine concentration to increase in heavy traffic areas [14]. We have recorded the duration of time spent by participants at home, at work place and outside to know the duration of their exposure to particulate pollutants. We also considered other factors including age, birth weight, head circumference, body mass index (BMI), smoking status, alcohol consumption, and histories of diabetes, hypertension, and heart disease.

Elevated level of homocysteine level has emerged as an important risk factor in the assessment of cardiovascular disease [44,45]. Excess homocysteine concentration in the blood stream may cause injuries to arterial vessels due to its irritant nature which results in inflammation and plaque formation. Plaque formation may cause blockage of blood flow to the heart. Elevated levels of homocysteine are also linked with Alzheimer’s disease [8,46-48]. Serum homocysteine level determination has been recently established in clinical laboratories. An area having higher concentration of PM2.5 shows more homocysteine concentration in maternal blood serum and in cord blood serum. In the present study, it was also observed that cord blood serum contains more homocysteine concentration than maternal blood serum [49,50]. The results of this study suggested a possible mechanism by which particulate exposure may lead to adverse cardiovascular problems through increased serum homocysteine concentration. The focus of the present study is limited to assessing the harmful effects of exposure to air particulate pollutants alone on the fetus due to synergistic effects of exposure to both gaseous and particulate pollutant. It needs the analysis of types of ambient air pollutants [50-54].

The present study provides evidence that the exposure of pregnant women to ambient air particulate pollutants adversely affects the growth and development of fetus. Exposure to particulate pollutants like PAH may induce oxidative stress in the pregnant mother, reduced birth weight or low birth weight. It also showed reduced body mass index, placental weight and head circumference of the new born baby, which may be due to significantly increased lipid peroxidation by production of reactive oxygen species. Ambient air exposure is associated with an increased serum homocysteine concentration in maternal and cord blood as a biomarker of exposure effects. Thus, exposure of air pollutants during pregnancy should be avoided for substantial health benefits of newborns and their subsequent neural development.

he authors acknowledge the Directorate of Higher Education for the grant of State Government Study Leave vides DHE office order no. 27205 dated 28.07.16. The authors would like to thank all the volunteer participants (pregnant mothers), who participated in this study and all the staff involved in the project realization. This study was conducted in community health centers of three different areas of Odisha. We gratefully acknowledge the contribution of doctors, midwives and pharmacies of community health centers of Cuttack, Jajpur and Nilagiri of Balasore districts of Odisha.

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