Exposure levels and health risk assessment of ambient BTX at urban and rural environments of a terai region of northern India.

Benzene, toluene and xylene (BTX) belong to an important group of aromatic volatile organic compounds (VOCs) that are usually emitted from various sources. BTX play a vital role in the tropospheric chemistry as well as pose health hazard to human beings. Thus, an investigation of ambient benzene, toluene and xylene (BTX) was conducted at urban and rural sites of Gorakhpur for a span of one year in order to ascertain the contamination levels. The sampling of BTX was performed by using a low-flow SKC Model 220 sampling pump equipped with activated coconut shell charcoal tubes with a flow rate of 250 ml/min for 20-24 h. The analysis was in accordance with NIOSH method 1501. The efficiency of pump was checked weekly using regulated rotameters with an accuracy of ±1%. The samples were extracted with CS2 with occasional agitation and analyzed by GC-FID. The total BTX concentration ranged from 3.4 µg m-3 to 45.4 µg m-3 with mean value 30.95 µg m-3 and median 24.8 µg m-3. The mean concentration of total BTX was maximum during winter (39.3 µg m-3), followed by summer (28.4 µg m-3) and monsoon season (25.1 µg m-3). The mean concentration of BTX at urban site (11.8 µg m-3) was higher than that at rural site (8.8 µg m-3). At both the sites, T/B and X/B ratios were highest in monsoon and lowest in winters. Toluene against benzene plot shows R2 value of 0.96 and 0.49 at urban and rural sites respectively. Higher R2 value at urban site clearly indicates similar sources of emission for benzene and toluene. At both the sites, the estimated integrated lifetime cancer risk (ILTCR) for benzene exceeded the threshold value of 1E-06 whereas the individual hazard quotients (HQ) for BTX did not exceed unity at any of the sites.

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.

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 µg m-3) followed by industrial (18.2 µg m-3), roadside (12.3 µg m-3) and residential site (6.1 µg m-3). 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 µg m-3) followed by monsoon (19.90 µg m-3) and summers (14.44 µg m-3). 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 10-6 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.