Exposure profiles, seasonal variation and health risk assessment of BTEX in indoor air of homes at different microenvironments of a terai province of northern India

Chemosphere 176 (2017) 8e17

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Exposure profiles, seasonal variation and health risk assessment of BTEX in indoor air of homes at different microenvironments of a terai province of northern India Amit Masih a, *, Anurag S. Lall a, Ajay Taneja b, Raj Singhvi c a b c

Environmental Research Lab, Department of Chemistry, St. Andrew’s College, Gorakhpur, India Department of Chemistry, Dr. BhimRaoAmbedkar University, Agra, India Environment Response Team, United States Environment Protection Agency, NJ, USA

h i g h l i g h t s
The indoor concentrations of BTEX were measured at four locations in the city of Gorakhpur.
The samples were extracted CS2 and the aromatic fraction was subjected to GC-FID.
Average BTEX were found to be highest at agricultural site during winters.
Integrated lifetime cancer risk value was higher than 106 for benzene at all the sites, while for ethylbenzene, it was only higher at agricultural site.
Cumulative Hazard Index was lower than 1.0 at all the sites.

a r t i c l e i n f o

a b s t r a c t

Article history: Received 9 January 2017 Received in revised form 19 February 2017 Accepted 20 February 2017 Available online 21 February 2017

BTEX are known for their ability to deteriorate human health. A monitoring study was conducted at Gorakhpur, for a span of one year. BTEX were sampled by drawing air through activated charcoal tubes, using a low flow SKC model 220 pump. Samples were extracted with CS2 followed by subjecting the aromatic fraction to GC-FID. The mean concentration of BTEX was highest at agricultural (54.3 mg m3) followed by industrial (18.2 mg m3), roadside (12.3 mg m3) and residential site (6.1 mg m3). Toluene levels were higher than benzene at all the sites except agricultural site, where benzene concentration exceeded toluene. Seasonal variation showed highest BTEX concentration during winters (32.56 mg m3) followed by monsoon (19.90 mg m3) and summers (14.44 mg m3). At each site, BTEX levels increased with decrease in temperature. Benzene and toluene levels were plotted against indoor temperature, which revealed a significant linear correlation (p < 0.001) for each plot. BTEX concentrations were compared between different sites using Student’s t and Mann Whitney U tests. Value of integrated lifetime cancer risk (ILTCR) was higher than 106 for benzene at all the sites, while for ethylbenzene, it was only higher at agricultural site. Cumulative hazard index (HI) was lower than 1.0 at all the sites. © 2017 Elsevier Ltd. All rights reserved.

Handling Editor: R Ebinghaus Keywords: BTEX Indoor air Microenvironments Terai region ILTCR HQ

1. Introduction The impact of air pollution on human health has become a major issue of concern worldwide for various scientific communities. Present human lifestyle has forced us to spend most of our time in enclosed spaces like classrooms, offices and our homes. Thus we are more susceptible to exposure to indoor air. Level of pollutants in the indoor air is far more dangerous than that in outdoor air. According

* Corresponding author. E-mail address: [email protected] (A. Masih). http://dx.doi.org/10.1016/j.chemosphere.2017.02.105 0045-6535/© 2017 Elsevier Ltd. All rights reserved.

to USEPA’s total exposure assessment methodology (TEAM) study, the concentration of contaminants found in indoor environment is significantly higher than that found in outdoors (Wallace L., 1986; Guo et al., 2003). At outdoors, pollutants get diluted in air due to dispersion. However in indoor environment, due to lack of proper ventilation and high humidity, the concentration of pollutants increases exceedingly. Amongst the wide variety of organic and inorganic air pollutants which have been recognized, volatile organic compounds (VOCs) deserve special consideration, because of their ability to affect human health as well as the environment. Many studies have shown that exposure to elevated levels of VOCs

A. Masih et al. / Chemosphere 176 (2017) 8e17

can cause several adverse health effects such as irritation in mucous membrane, physical and mental weakness, difficulty in concentrating, nausea, discomfort and headache (Pouli et al., 2003; Cometto-Muniz et al., 2004; Wolkoff et al., 2006; Bernstein et al., 2008). VOCs which are predominantly found in indoor environment include benzene, toluene, ethylbenzene and isomers of xylene (BTEX) (Ilgen et al., 2001a, 2001b; Guo et al., 2003). Even at very low concentrations of microgram per cubic meter, BTEX can cause serious health problems (Ueno et al., 2001; Badjagbo et al., 2010). Thus, a proper and systematic study of these monoaromatic pollutants is necessary for monitoring the indoor air quality. Contamination of indoor air by BTEX can be attributed to various emission sources. The major sources include the combustion processes like cooking, heating and burning. In most of the religious rituals, burning of scented candles and incense is quite common. Similarly, some of the occupant activities such as smoking, use of air fresheners, deodorants and insect repellants may also release BTEX in indoor air. It can be easily noticed that even a single house contains numerous synthetic chemical products such as cleansers, stain removers, paints, adhesives, solvents, oils and various plastic products. These products continuously emit many harmful VOCs including BTEX in air and hence deteriorate the quality of indoor air. Certain building materials such as furnishings, wood finishings, furniture foam, floorings and carpets also have a major contribution. In addition to these, BTEX from outdoor air may also enter indoor air through various vents present in the building (Batterman et al., 2007). According to USEPA, benzene has been proved to be carcinogenic for both humans as well as other animals (USEPA, 1998). IARC has placed benzene in group 1 carcinogens (IARC, 2002). Toluene is a potent human teratogen (Hersh J.H., 1989; Donald et al., 1991). Ethylbenzene has been categorized as a possible human carcinogen and has been placed in group 2B by IARC (IARC, 2000). BTEX also act as sensitizers and cause irritation in upper respiratory tract. They can even cause lung cancer and leukemia (Rezazadeh et al., 2012). BTEX slows down the brain activity and is toxic at high doses. Among BTEX, benzene and toluene have the highest toxicity (Molhave, 2003). In India, several studies have been conducted on ambient levels of BTEX (Srivastava et al., 2005a, 2005b; Hoquea et al., 2008; Saxena and Ghosh, 2012). However, despite of so many adverse health effects of BTEX, only a limited number of studies have been conducted on indoor levels of BTEX particularly in this part of India. The aim of this study is to investigate the exposure levels of BTEX in indoor microenvironments of different sites as well as estimate the related human health risk. Moreover, the effect of temperature as well as seasonal variation on the indoor concentration of BTEX has also been discussed. 2. Materials and methods 2.1. Description of sampling sites Gorakhpur (26 450 3200 N 83 2201100 E) is located in the terai region of eastern Uttar Pradesh in northern India, near the border of Nepal, in the foothills of the Shiwalik Himalayas. Gorakhpur city is surrounded by the rivers Rapti, Rohini and other small streams from three sides. River Rapti is interconnected through many other small rivers. The present district of Gorakhpur, 265 km east of capital Lucknow, on National Highway (NH-28), covers geographical area of 3483.8 km2 having total population of about 4,440,895 (Masih et al., 2016). Indoor air was sampled within homes located at four different sites of Gorakhpur city, namely residential, roadside, industrial and agricultural (rural) area. Questionnaires

9

concerning the characteristics of the site and prevalent activities within the homes were completed with help of the occupants. Information regarding the building age, dimensions of the homes, building type, indoor sweeping materials, smoking activities, burning of incense/candles/mosquito coils, and use of air fresheners were included. Detailed information regarding the considered homes, namely age and size of building, potential indoor sources, description of each monitoring site and related activities nearby the sampling sites are summarized in Table 1. Limited information concerning ventilation at each site was also included as ventilation rate could not be measured directly. Except agricultural site, all sites had extensive ventilation with most of the windows opened throughout the day as needed by the occupants. Additionally, exhaust fans were also used in kitchen during cooking at residential site. Fig. 1 shows the map of Gorakhpur indicating all the four sites. Taramandal was considered representative of a residential area. Golghar was selected as a representative roadside area. It is situated in the heart of Gorakhpur city, by the side of a road that carries high traffic density resulting in the emission of smoke and total suspended particulate matter from engine exhaust (Masih et al., 2014). GIDA (Gorakhpur Industrial Development Area) was selected as an industrial zone because large numbers of industries are located in this area. A national highway NH-28 also passes through industrial area. Haiderganj to the north, is exclusively agricultural/rural area. 2.2. Sampling & analysis Air sampling was accomplished within homes located at the four previously described sites for a span of one year (Nov. 2014 to Oct. 2015). Indoor air was monitored 20e24 h, once a week in a scheduled manner. Thus 48 samples were collected from each site, and a total of 192 samples were collected from all the sites. BTEX were sampled and analyzed using a methodology based on National Institute for Occupational Safety and Health (NIOSH) method 1501 (USEPA, 1988a, 1988b; NIOSH, 1994; OSHA, 2004; BIS, 2001; BIS, 2006). BTEX were sampled by drawing air through activated coconut shell charcoal tubes (CSC, 8 mm  110 mm, 600 mg) containing two sections (main section 400 mg, second section 200 mg) separated by a 2 mm urethane foam (SKC Inc.), using a low-flow SKC Model 220 sampling pump (SKC, Inc., 84, PA, USA) at the flow rate of 250 ml/min for 20e24 h. The air suction rate was verified every week using calibrated rotameters with an accuracy of ±1%. The sample tubes wrapped in aluminum foil were put into polythene bags that were tightly closed and stored in a box in a deep freezer at -5  C until processed. The second section of tube was analyzed in order to detect breakthrough. Charcoal beds in the sorbent tubes were transferred to 2 ml vials and extracted by adding 1.0 ml of carbon disulphide (CS2) with occasional agitation for 30 min. Sampled air was then analyzed with an HP 6890 gas chromatography/mass spectrometer and gas chromatography/ flame ionization detector. The cold trap operating temperature was initially at 30  C and it was raised to 250  C for 3 min. The analysis was performed using Agilent 19091J-413/E column (30 m  0.32 mm i.d.  0.25 mm) with nitrogen as a carrier gas. The column temperature was maintained for 5 min at 40  C, then it was raised to 100  C for 5 min and finally it was further raised to 200  C for 2 min. One target and one qualifier ion were examined for each compound. The identification of different compounds was carried out on the basis of their relative retention time and ion ratios. The identified compounds were successfully quantified with help of an internal calibration method, using five levels of calibration: 0.1; 1; 5; 25; 100 mg/ml in CS2. Calibration solutions from Supelco were used for this purpose. The correlation coefficients were calculated and 0.99 was assumed to be acceptable. In order to determine the

10 m2 More than 50 years & 15 ft.

LPG: Liquefied petroleum gas, DALDA & GHEE: A polysaturated hydrogenated oils used for cooking, BIDI: thin hand rolled cigarettes (tobacco wrapped in tendu or temburni leaf), DHOOP: extruded form of incense.

Incense, dhoop, Candles/kerosene oil lamp Frequently Wood, charcoal and cow dung cakes Poor ventilation

10-12 m2 12 years & 15 ft.

No traffic, with lot of greenery

Dalda and mustard oil

15-18 m2 17 years & 15 ft.

Cross ventilation with windows

18e20 m2

Residential (Medium population, homes made up of bricks) Roadside (High population, homes made of bricks) Industrial (Low population, homes made of bricks surrounded by various factories of alcohol, textile, mustard oil and pharmaceuticals) Agricultural (Low population, homes made of mud, khaprail, grasses and bamboos)

5 years & 15 ft.

Dalda, Refined and mustard oil

Dalda and mustard oil

Cow dung

Cow dung cakes and stubble/ brushwood

Incense, dhoop & Mosquito coil No LPG /kerosene oil Phenyl

Wood and coal (Angithee)

Incense, dhoop & Mosquito coil Rare LPG Phenyl

Electric room heaters

Incense, dhoop & Mosquito coil Less frequent Electric room heaters LPG Phenyl Ghee, refined and mustard oil

Use of exhaust fan, cross ventilation and windows Cross ventilation with windows

Very less traffic, greenery around, use of invertor Heavy traffic with LMV, no greenery, use of diesel gen-sets Moderate traffic with LMV & HMV, use of diesel gen-sets

Type of fuel used Material used for sweeping Oil used for cooking Ventilation Traffic/Gensets/Invertor Living room area Home age & height Sampling site (condition)

Table 1 Description of monitoring sites and related activities at/nearby sampling sites.

Material used for heating

Other Combustion activities

A. Masih et al. / Chemosphere 176 (2017) 8e17

Smoking Status (Cigarette/Bidi)

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reproducibility of the obtained results, duplicate samples were also analyzed and it was found that the difference was below 10% every time. Moreover, before each sample analysis, blank runs were also performed. With help of the calibration curves, the uncertainties were estimated as: benzene 18%, toluene 10%, ethylbenzene 21%, m, p-xylene 8% and o-xylene 12% (US EPA, 1988a, b). Temperature and humidity in indoors were measured by using Young Environment System (YES-206, 205 Canada) which are IAQ monitors and use non-dispersive infrared (NDIR) method. Table 2 shows the mean temperature, humidity, sample duration and number of samples at each site. 2.3. Statistical analysis (Student’s t test & Mann Whitney U test) In order to identify the significance of differences between average BTEX levels at different sites statistically, Student’s t test and Mann Whitney U test were implemented. 2.3.1. Student’s t test Student’s t test is a statistical method used to compare means of two small sets of data when samples are independent of each other. It is a parametric test and assumes that the two sample sets being tested must have reasonably normal distribution.

sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ðn1  1Þs21 þ ðn2  1Þs22 Pooled Standard Deviation ¼ sp ¼ n1 þ n2  2 Test Statistic ¼ t * ¼

x1  x2 qffiffiffiffiffiffiffiffiffiffiffiffiffiffi sp n11 þ n12

where n1, n2 and s1, s2 are the sample size and standard deviation for the two samples respectively. The test is significant at a level, if the obtained t* > tcrit 2.3.2. Mann-Whitney U test Mann-Whitney U test is the alternative test to the student’s ttest. It is a non-parametric test used to compare the distributions of two independent samples. This test is also used to compare medians of two populations if the distributions for the two populations have almost same shape. The test statistic U ¼ min (U1,U2)

U1 ¼ n1 n2 þ

n1 ðn1 þ 1Þ  R1 2

U2 ¼ n1 n2 þ

n2 ðn2 þ 1Þ  R2 2

where, n1, n2 and R1, R2 are the sample size and sum of adjusted ranks for the two samples respectively. If the observed U < Ucrit then, the test is significant at a level. Moreover, Pearson and Spearman correlation coefficients were also calculated in order to determine linear and monotonous relationship between two variables. 2.4. Cancer and non-cancer risk estimation Risk assessment has become one of the most efficient tools in order to estimate the effect of hazardous materials on human health and to develop effective strategy for handling a particular environmental problem (LaGrega et al., 1994; Zhang et al., 2012). It also informs about the serious effects caused by a chemical and the site of its action. BTEX are often regarded as compounds toxic to humans. Amongst BTEX, benzene and ethylbenzene are considered carcinogenic while toluene, m,p-xylene and o-xylene though noncarcinogenic are desperately unsafe to human health. The average

A. Masih et al. / Chemosphere 176 (2017) 8e17

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Fig. 1. Map of Gorakhpur showing sampling sites.

Table 2 Mean indoor temperature and humidity of selected homes. Area

RES RDS IND AGR



Mean Temperature ( C)

Mean RH (%)

S

M

W

S

M

W

28.0 28.2 27.7 27.5

27.2 27.6 26.8 26.4

19.2 19.4 18.8 18.6

74.7 76.1 84.2 82.4

82.9 83.6 82.9 85.8

61.0 62.8 67.8 65.9

exposure level of each pollutant was used to estimate the contaminant intake for the exposed population variables. The estimated lifetime risk for chronic leukaemia is 4.4e7.6  106 when benzene concentration is just 1 mg m3 (WHO, 2000; Dutta et al., 2009). Also ethylbenzene has been categorized as a group 2B carcinogen (IARC, 2000; Majumdar et al., 2008). The current study calculates the integrated lifetime cancer risk (ILTCR) and the non-cancer hazard risk caused by BTEX at their usual levels. The chronic daily exposure (E), effective lifetime exposure (EL) for carcinogenic substances and exposure concentrations for noncarcinogenic substances of an individual through inhalation only were calculated according to our previous study. The detailed information regarding estimation of cancer and non-cancer risk has been given in our previous paper (Masih et al., 2016).

Sampling Duration (h)

No. of Samples

24 24 24 24

48 48 48 48

Table 3 Mean, median and range for BTEX (mg m3) at Gorakhpur. VOCs

Mean

Median

Range

Benzene Toluene Ethylbenzene Xylene

40.67 ± 9.04 38.06 ± 7.57 5.69 ± 1.09 4.88 ± 0.81

48.12 44.54 7.21 5.57

1.74e181.92 2.97e123.68 0.13e29.50 0.22e18.97

mean value of 5.69 mg m3 whereas xylene had mean concentration of 4.88 mg m3 with a range of 0.22 mg m3 to 18.97 mg m3. Thus the total mean indoor concentration of BTEX at all the sites together was 89.30 mg m3. 3.2. Spatial distribution

3. Results and discussion 3.1. Concentration of BTEX in indoor air The statistical data for BTEX concentrations at Gorakhpur has been represented in Table 3. The concentration of benzene ranged from 1.74 mg m3 to 181.92 mg m3 with mean value of 40.67 mg m3. Concentration of toluene was found in the range 2.97 mg m3 to 123.68 mg m3 with mean value of 38.06 mg m3. Ethylbenzene ranged from 0.13 mg m3 to 29.50 mg m3 with a

Table 4 depicts the mean, standard deviation and range of BTEX at different sites of Gorakhpur. The average benzene, toluene, ethylbenzene and xylene concentrations were highest at agricultural site homes having 124.67, 65.47, 17.00 and 10.20 mg m3 followed by industrial site (16.22, 41.80, 9.33 and 5.60 mg m3), roadside (13.84, 30.0, 2.73 and 2.73 mg m3) and residential (7.97, 14.99, 0.27 and 1.01 mg m3) site homes. Thus the concentration of toluene and benzene were predominantly high at all the sites. Toluene levels were higher than benzene at residential, roadside

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A. Masih et al. / Chemosphere 176 (2017) 8e17

Table 4 Mean concentration of BTEX (mg m3) at different sites of Gorakhpur.

Benzene Toluene Ethylbenzene Xylene

RES

RDS

IND

AGR

7.97 ± 1.20 (1.74, 18.42) 14.99 ± 3.07 (2.97, 41.24) 0.27 ± 0.04 (0.13, 0.48) 1.01 ± 0.13 (0.22, 2.35)

13.84 ± 2.33 (4.42, 35.07) 30.00 ± 5.71 (13.19, 51.68) 2.73 ± 0.36 (0.82, 4.55) 2.73 ± 0.42 (1.06, 5.30)

16.22 ± 2.85 (5.16, 37.52) 41.80 ± 6.94 (10.52, 85.48) 9.33 ± 1.29 (2.84, 18.70) 5.60 ± 0.76 (1.19, 13.35)

124.67 ± 22.54 (75.21, 181.92) 65.47 ± 8.73 (24.29, 123.68) 17.00 ± 2.51 (4.26, 29.50) 10.20 ± 1.81 (3.94, 18.97)

Concentration ¼ Mean ± standard deviation (minimum, maximum).

and industrial site. However at agricultural site, benzene concentration was higher than toluene. At agricultural site, indoor sources were dominant due to improper ventilation, while at residential, roadside and industrial sites the indoor levels possibly caused from indoor sources, building physiognomies as well as permeation of outdoor pollutants indoors (through aeration due to substandard building segregation etc.) as similar observations reported previously (Masih et al., 2010; Amato et al., 2014; Rivas et al., 2015). Highest concentration of BTEX at agricultural site may be explained on account of prevalent use of biomass fuel (Albalak et al., 1999, 2001; Fan et al., 2014) as well as other indoor activities such as smoking within the house (Brajenovi
c et al., 2015; Hazrati et al., 2016) (Table 1). At industrial site, in addition to common household emission sources and indoor activities such as combustion and cooking, high concentration of BTEX may also be attributed to various outdoor sources such as alcohols/chemicals, rubber sleepers/sandals and iron shaft manufacturing plants located in this area. Moreover, a national highway NH-28 also passes through the industrial area. Similarly, concentrations at roadside site may result from the proximity of intense automobile traffic in addition to the

common household sources and indoor activities. At residential site, indoor activities like combustion, cooking and smoking may contribute to the BTEX levels. Inspite of many indoor sources, BTEX levels were minimum at residential site due to appropriate air circulation and ventilation. 3.3. Correlation of BTEX Correlation analysis was performed by using the Spearman rank correlation coefficients for BTEX at different sites as shown in Table 5. The table shows that at agricultural site, benzene and toluene showed strong correlation with each other (r ¼ 0.925) and good correlation (r ¼ 0.762e0.897) with ethylbenzene and xylene. At industrial site, toluene was strongly correlated (r ¼ 0.945e0.966) with ethylbenzene and xylene. Similarly ethylbenzene was strongly correlated with xylene (r ¼ 0.938). Also benzene showed good correlation (r ¼ 0.709e0.751) with toluene and xylene. Roadside site showed good correlation (r ¼ 0.847) between benzene and

Fig. 2. Seasonal Pattern of BTEX at different sites of Gorakhpur.

Table 5 Spearman rank correlation coefficients for BTEX at different sites. Benzene Residential Homes Benzene Toluene Ethylbenzene Xylene Industrial Homes Benzene Toluene Ethylbenzene Xylene

Toluene

Ethylbenzene

1 0.842 0.788 0.814

1 0.864 0.872

1 0.918

1 0.751 0.622 0.709

1 0.945 0.966

1 0.938

Xylene

1

1

Benzene Roadside Homes Benzene 1 Toluene 0.847 Ethylbenzene 0.550 Xylene 0.618 Agricultural Homes Benzene 1 Toluene 0.925 Ethylbenzene 0.884 Xylene 0.897

Toluene

Ethylbenzene

Xylene

1 0.616 0.572

1 0.692

1

1 0.762 0.845

1 0.829

1

Correlations (r > 0.700) significant at the 0.05 level (p < 0.05) have been indicated in bold.

Table 6 Results of student’s t test and Mann-Whitney U test. Variable

Residential Homes n

Mean

Median

n

Mean

Median

Student’s t test

Mann-Whitney U test

Benzene Toluene Ethylbenzene Xylene

48 48 32 48

7.97 14.99 0.27 1.01

6.12 9.37 0.24 0.89

48 48 48 48

13.84 30.00 02.32 02.73

09.15 27.25 02.03 02.79

0.009 0.002 0.000 0.000

0.037 0.023 0.000 0.000

Variable

Roadside Homes

Benzene Toluene Ethylbenzene Xylene

Roadside Homes

P value

Industrial Homes

P value

n

Mean

Median

n

Mean

Median

Student’s t test

Mann-Whitney U test

48 48 48 48

13.84 30 2.32 2.73

9.15 27.25 2.03 2.79

48 48 32 48

16.22 41.80 09.33 05.60

11.23 39.17 07.56 04.62

0.239 0.002 0.000 0.000

0.085 0.009 0.000 0.001

P values indicate the significance of difference between the sites in terms of the pollutant concentration.

A. Masih et al. / Chemosphere 176 (2017) 8e17

toluene. At residential site, ethylbenzene was strongly correlated with xylene (r ¼ 0.918) while all other species showed good correlation (r ¼ 0.788e0.864) with each other. Differences in average BTEX concentrations between different sites were tested using Student’s t test and Mann Whitney U test. These tests were performed between BTEX levels at residential/roadside and roadside/ industrial sets as the differences in concentration at these sets of sites were found minimum. BTEX concentrations tended to differ significantly for residential/roadside set (p < 0.05) as shown by both parametric (Student’s t) and non-parametric (Mann Whitney U) tests (Table 6). Similar trend was found for roadside/industrial set for toluene, ethyl benzene and xylene, while the difference in benzene levels for roadside/industrial set was not statistically significant (p > 0.05).

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3.4. Seasonal variation of BTEX In Gorakhpur region three seasons are observed e Summer Season (March to June), Monsoon Season (July to October) and Winter Season (November to February). The average indoor temperature during sampling was about 27.9  C during summer season, 27.0  C during monsoon season and 19  C during winter season. Fig. 2 displays the seasonal pattern of BTEX concentration. Table 7 shows the mean concentrations of benzene, toluene, ethylbenzene and xylene in the indoor air of different sites during summer, monsoon and winters. It was found that benzene, toluene, ethylbenzene and xylene followed a similar trend of seasonal variation. At each site, the concentrations of each of these pollutants were highest in winter, moderate in monsoon and lowest in summer season. This suggests that the concentration of these

Table 7 Mean indoor concentration of BTEX (mg m3) at different sites observed in summer, monsoon and winters. Site

Residential

Roadside

Industrial

Agriculture

Season

Summer Monsoon Winter Summer Monsoon Winter Summer Monsoon Winter Summer Monsoon Winter

Benzene

Toluene

Ethylbenzene

Xylene

Mean ± SD

Min

Max

Mean ± SD

Min

Max

Mean ± SD

Min

Max

Mean ± SD

Min

Max

3.00 ± 0.61 6.11 ± 0.94 14.80 ± 2.47 5.84 ± 0.90 9.47 ± 1.43 26.20 ± 4.67 7.53 ± 1.41 11.23 ± 1.58 29.90 ± 4.47 105.00 ± 16.03 119.00 ± 19.19 150.00 ± 21.76

1.74 4.51 10.55 4.42 7.11 18.14 5.16 8.42 23.03 75.21 82.66 112.39

3.93 7.60 18.42 7.76 11.55 35.07 10.18 13.76 37.52 131.78 149.31 181.92

5.48 ± 1.29 9.28 ± 1.09 30.20 ± 7.68 25.00 ± 5.49 28.49 ± 6.25 36.50 ± 9.02 21.00 ± 5.47 39.00 ± 8.14 65.40 ± 11.47 41.4 ± 9.06 59.70 ± 10.25 95.30 ± 16.01

2.97 7.02 16.52 13.19 15.57 17.50 10.52 21.02 42.98 24.29 40.11 66.01

8.00 11.38 41.24 34.04 39.86 51.68 30.32 54.13 85.48 59.83 78.09 123.68

BDL 0.19 ± 0.04 0.35 ± 0.07 1.49 ± 0.34 2.00 ± 0.37 3.47 ± 0.64 BDL 4.76 ± 0.90 13.90 ± 2.49 6.90 ± 1.04 11.49 ± 1.99 22.50 ± 4.25

BDL 0.13 0.22 0.82 1.24 2.20 BDL 2.84 8.75 4.26 7.26 13.72

BDL 0.25 0.48 2.08 2.67 4.55 BDL 6.37 18.70 8.64 14.98 29.50

0.30 ± 0.04 0.88 ± 0.07 1.86 ± 0.26 1.35 ± 0.14 2.79 ± 0.42 4.05 ± 0.58 1.40 ± 0.15 4.62 ± 0.66 10.79 ± 1.42 5.42 ± 0.73 9.44 ± 1.23 15.75 ± 1.84

0.22 0.74 1.36 1.06 2.01 2.92 1.19 3.21 7.98 3.94 7.21 12.58

0.38 0.98 2.35 1.60 3.55 5.30 1.70 5.80 13.35 6.87 11.53 18.97

Benzene

Toluene

Ethylbenzene

Xylene 3

Fig. 3. Boxplot of BTEX levels (mg m

) at different sites in summer, monsoon and winter.

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A. Masih et al. / Chemosphere 176 (2017) 8e17

Table 8 Seasonal ratios for BTEX at different sites.

Benzene Toluene Ethylbenzene Xylene

Residential

Roadside

Industrial

Agricultural

M/S

W/S

M/S

W/S

M/S

W/S

M/S

W/S

2.04 1.69

4.93 5.51 1.84 2.11

1.62 1.14 1.34 2.07

4.49 1.46 2.33 3.00

1.49 1.86

3.97 3.11

a

a

3.30

7.71

1.13 1.44 1.66 1.74

1.43 2.30 3.26 2.90

a

2.93

M/S is the ratio between monsoon and summer concentration and W/S is the ratio between winter and summer concentration. a The summer concentration at these sites was below detection limit.

including BTEX are additionally produced due to incomplete combustion of solid fuel used for heating purpose (Wang et al., 2013). Fig. 3 shows the boxplot of BTEX concentration at different sites in summer, monsoon and winter season. The figure clearly indicates that as the concentration increases, the inter-quartile range (IQR) also increases. The ratio of monsoon to summer concentration (M/S) and winter to summer concentration (W/S) for individual benzene, toluene, ethylbenzene and xylene in the indoor air of different sites have been shown in Table 8. From the table, it is evident that W/S ratio for xylene (7.71) was maximum at industrial site followed by toluene (5.51) and benzene (4.93) at residential site homes. The W/S and M/S ratios of benzene (1.43, 1.13) and toluene (1.46, 1.14) were found to be lowest at agricultural and roadside homes respectively. Low W/S and M/S ratios at these sites indicate that indoor concentration of benzene and toluene were not considerably affected by seasonal change at agricultural and roadside area homes respectively. The relative percentage concentration of BTEX during different seasons has been illustrated with help of stacked column graph in Fig. 4. The indoor concentrations of benzene and toluene were plotted as a function of indoor temperature in Fig. 5. In each case a significant linear correlation was observed between concentration and temperature. The observed Pearson’s correlation coefficients for benzene and toluene were r ¼ 0.863, 0.900; p < 0.001 at residential site, r ¼ 0.875, 0.787; p < 0.001 at roadside site, r ¼ 0.892, 0.841; p < 0.001 at industrial site and r ¼ 0.859, 0.880; p < 0.001 at agricultural site.

Fig. 4. Relative concentration (%) of BTEX during different seasons.

pollutants is inversely related with temperature i.e. as the temperature decreases, the concentration of these pollutants increases. During summers, lower BTEX concentrations may be attributed to lesser emission sources and enhanced ventilation. However in winters, the emissions are relatively high (Na et al., 2005). Apart from the common sources, in winter season many of the pollutants

3.5. Health risk assessment Table 9 represents the typical daily exposure, effective life time exposure, cancer risk (ILTCR) and non-cancer risk (HQ) for an individual considering approximately 15 years residing time. Since indoor levels of toluene and benzene were highest, the effective life time exposure for these compounds was maximum followed by

Fig. 5. Concentration of benzene and toluene plotted as a function of indoor temperature.

A. Masih et al. / Chemosphere 176 (2017) 8e17

15

Table 9 Estimate of individual pollutant indoor exposure, related non-cancer and cancer risk. Pollutant

Site

Yearly Average Concentration (mg/m3)

Daily Exposure (mg/kg/day)

Effective Lifetime Exposure (mg/kg/day)

Individual HQ

ILTCR

Benzene

Residential Agricultural Roadside Industrial Residential Agricultural Roadside Industrial Residential Agricultural Roadside Industrial Residential Agricultural Roadside Industrial

7.9E-03 1.2E-01 1.3E-02 1.6E-02 1.4E-02 6.5E-02 3.0E-02 4.2E-02 2.7E-04 1.7E-02 2.7E-03 9.3E-03 1.0E-03 1.0E-02 2.7E-03 5.6E-03

9.4E-04 1.5E-02 1.6E-03 1.9E-03 1.7E-03 7.8E-03 3.6E-03 4.9E-03 3.2E-05 2.0E-03 3.3E-04 1.1E-03 1.2E-04 1.2E-03 3.3E-04 6.7E-04

1.9E-04 2.9E-03 3.3E-04 3.9E-04 3.6E-04 1.6E-03 7.1E-04 9.9E-04 6.4E-06 4.0E-04 6.5E-05 2.2E-04 2.4E-05 2.4E-04 6.5E-05 1.3E-04

2.4E-04 3.7E-03 4.2E-04 4.9E-04 7.5E-02 3.3E-01 1.5E-01 2.1E-01 2.7E-04 1.7E-02 2.7E-03 9.3E-03 1.0E-04 1.0E-03 2.7E-04 5.6E-04

5.2E-06 8.1E-05 8.9E-06 1.0E-05

Toluene

Ethylbenzene

Xylene

2.5E-08 1.6E-06 2.5E-07 8.5E-07

The values exceeding the permissible limits are in BOLD.

xylene and ethylbenzene. At all the sites, benzene had the highest ILTCR followed by ethylbenzene. The predicted cancer risk for benzene was higher than the threshold value 1E-06 at all the four sites. However for ethylbenzene, it only surpassed the threshold value at agricultural site. Assuming that the carcinogenicity from different contaminants can be added, the cumulative ILTCR (benzene and ethylbenzene) was calculated at all the four sites of Gorakhpur. It was found that the cumulative ILTCR was maximum at agricultural area (8.1E-05) followed by industrial (1.1E-05), roadside (9.1E-06) and residential (5.2E-06) areas. Toluene gave the highest non-cancer HQ followed by ethylbenzene, benzene and xylene. The individual HQs for BTEX did not surpass unity anyplace suggesting no severe hazard of chronic non-cancer health effect in contaminant particular target organs for the urban inhabitants (Majumdar et al., 2011). The cumulative non-cancer hazard indices (HI) calculated for BTEX at residential, roadside, industrial and agricultural sites were 0.07, 0.15, 0.22 and 0.35 respectively; indicating no harmful health effects to the hematological, bone marrow and neurological toxicities (USEPA, 2010). 3.6. Worldwide comparison of indoor BTEX levels and related cumulative cancer risk Table 10 shows the comparison of indoor concentrations of BTEX measured in present study, with other studies worldwide.

Average concentration of BTEX at urban site (12.68, 28.93, 4.11 and 3.11 mg m3) was found to be lower than those reported at Dhaka (Bangladesh), Kolkata (India), Rio-de-Janeiro (Brazil) and Guangzhou (China) while it was higher than those reported at Eskis¸ehir (Turkey) and Perth (Australia). However, mean BTEX levels (124.67, 65.47, 17.00 and 10.20 mg m3) at rural (agricultural) site, were higher than that observed at Kowloon (Hong Kong), Los Angeles
al (Canada), Perth (Australia) and (USA), Eskis¸ehir (Turkey), Montre Mumbai (India). Fig. 6 illustrates the cumulative cancer risk due to exposure of BTEX compared with other reported values in different studies worldwide. It is evident from the figure that the cumulative ILTCR value at Gorakhpur was lower than majority of the values reported in other studies, but consistent with that observed at Eskis¸ehir (Turkey) whereas higher than that reported at New Delhi (India). 4. Conclusion The indoor levels of BTEX were measured at homes located at selected sites of the city. The mean concentrations of BTEX at residential, roadside, industrial and agricultural sites were found to be 6.1, 12.3, 18.2 and 54.3 mg m3 respectively. Seasonal variation was also observed in BTEX levels at all the sites. The mean concentration of BTEX was highest in winter season (32.56 mg m3) followed by monsoon (19.90 mg m3) and summer (14.44 mg m3) at all the

Table 10 Comparison of mean concentration of BTEX (mg m3) in indoor air worldwide. Country

Site

B

T

E

X

Reference

Kowloon, Hong Kong Los Angles, USA Eskis¸ehir, Turkey Montreal, Canada Barcelona, Spain Perth, Australia Dhaka, Bangladesh Rio-de-Janeiro, Brazil Guangzhou, China Bangkok, Thailand New Delhi, India Kolkata, India Mumbai, India

Urban Urban Urban Urban Rural Urban Urban Urban Urban Urban Urban Urban Urban

4.99 3.54 0.92 1.8 5.8 1.31 37.3 54.14 18.5 8.08 7.2 42 10.7

59.13 15.26 42.01 7.5 67.0 10.1 31.75 209.24 173.2 110 94.0 69.3 21.6

2.72 2.55 0.39 1.5 e 1.36 e 45.87 e 12.1 10.1 22.8 e

4.58 4.94 0.62 3.2 51.4 2.06 44.5 59.46 49.45 10.9 20.9 73.7 6.2

Guo et al. (2003) Su et al. (2013) Demirel et al. (2014) St-Jean et al. (2012) Gallego et al. (2008) Maisey et al. (2013) Khalequzzaman et al. (2007) de Castro et al. (2015) Du et al. (2014) Ongwandee et al. (2011) Kumar et al. (2013) Majumdar et al. (2012) Srivastava et al. (2000)

Gorakhpur, India Gorakhpur, India

Urban Rural

12.68 124.67

28.93 65.47

4.11 17.00

3.11 10.20

Present study Present study

16

A. Masih et al. / Chemosphere 176 (2017) 8e17

Fig. 6. Cumulative cancer risk due to indoor concentration of BTEX in different countries.

sites. Toluene was found to be dominant at residential, roadside and industrial area homes. However, at agricultural site, benzene levels were higher than toluene. Due to lack of proper ventilation in agricultural/rural area homes, the indoor levels of BTEX were exceedingly high compared to other sites. Industrial area houses were under the influence of both industrial emissions as well as roadside traffic emissions from national highway NH-28. Health risk assessment from the data indicated that benzene exceeded the acceptable value of ILTCR ¼ 106 at all the sites, however ethyl benzene only surpassed the threshold value at agricultural site. The HQ for BTEX was below unity at all the sites, indicating no serious risk for chronic non-cancer health effects. Since it is impossible to desist the use of common household activities as they have become an integral part of our lives, hence we recommend enforcement of proper ventilation norms for buildings in order to improve indoor air quality up to some extent. Additionally, indoor plants may also be used. Acknowledgement Financial support from Department of Science and Technology (DST), New Delhi, India in Project No. SR/FTP/ES-77/2013 is duly acknowledged. Authors gratefully acknowledge Revd. Prof. J. K. Lal (Principal) and Dr. S. D. Sharma (Head) Chemistry Department, St Andrew’s College, Gorakhpur, UP, India, for providing necessary facilities. Authors are also thankful to Mr. Jay Patel, ERT, USEPA for providing technical support during the analysis of samples. References Albalak, R., Bruce, N., McCraken, J.P., Smith, K.R., de Gallardo, T., 2001. Indoor respirable particulate matter concentrations from an open fire, improved cookstove, and LPG/open fire combination in a rural Guatemalan community. Environ. Sci. Technol. 35, 2650e2655. Albalak, R., Keeler, G.J., Frisancho, A.R., Haber, M., 1999. Assessment of PM10 concentrations from domestic biomass fuel combustion in two rural Bolivian highland villages. Environ. Sci. Tecnol. 33, 2505e2509.  Amato, F., Rivas, I., Viana, M., Moreno, T., Bouso, L., Reche, C., Alvarez-Pedrerol, M., Alastuey, A., Sunyer, J., Querol, X., 2014. Sources of indoor and outdoor PM2.5 concentrations in primary schools. Sci. Total Environ. 490, 757e765.
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