Congener specific distribution of polychlorinated dibenzo-p-dioxins and dibenzo-p-furans in ambient air particulates (less than PM10) in Delhi, India

Abstract

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzo-p-furans (PCDFs) are unintentionally formed during inefficient combustions and as a by-product. Due to their resistance to degradation and their toxic effect on health, PCDD/Fs are listed by the Stockholm Convention as persistent organic pollutants (POPs). Once released into the atmosphere, most of them are adsorbed to air particles and transported away from sources in atmosphere. India signed the Stockholm Convention India agreeing thereby to reduce and eliminate the use of POPs. The German agency for Technical Cooperation helped develop facilities for monitoring POPs at a national level in Delhi. This paper presents the data generated during a training assignment for Central Pollution Control Board officials at the German laboratory. Air borne particulate matter (<PM 10 ) was collected from 6 different locations in Delhi, India and analyzed in a German laboratory for 17 congeners of PCDD/Fs. The concentrations of ∑PCDD/Fs ranged between 1720-9010 fg m -3 (mean 5559 fg m -3 ) and their toxic equivalency values ranged from 67 to 460 fg I-toxic equivalent quantities (TEQ) m -3 , with an average of 239 fg I-TEQ m -3 which was lower than the ambient air standards. The dominant congeners were octachlorinated dibenzo-p-dioxin (OCDD), octachlorinated dibenzo-p-furans (OCDF), 1,2,3,4,6,7,8-heptachlorinated dibenzo-p-furans, and 1,2,3,4,6,7,8-heptachlorinated dibenzo-p-dioxin. The contributions of individual homologs for ∑PCDDs/Fs I-TEQ was in the order of OCDD (31%)>HCDF (21%)>hexa-chlorodibenzofurans (13%)=OCDF (13%)> HCDF (12%) and other individual congeners contribute less than 5%. High chlorinated congeners contributed with more than 80% for ∑PCDD/Fs I-TEQ. Rough estimates of tolerable daily intake (TDI) shows low health risk of exposure to ∑PCDD/Fs with inhalation of 0.098 pg I-TEQ kg -1 day -1 for adult and 0.152 pg TEQ kg -1 day -1 for children, which is much lower than World Health Organization recommended TDI for dioxins.