Effect of dibenzopyrene measurement on assessing air quality in Beijing air and possible implications for human health

Abstract

Size fractionated particulate matter (PM) was collected in summer and winter from Beijing, China for the characterization of an expanded list of PAHs and evaluation of air pollution metrics. Summertime ΣPAHs on PM was 14.6 ± 29(PM 1.5), 0.88 ± 0.49(PM 1.5-7.2) and 0.29 ± 0.076(PM 7.2) ng m(-3) air while wintertime concentrations were 493 ± 206(PM 1.5), 26.7 ± 14(PM 1.5-7.2) and 5.3 ± 2.5(PM 7.2) ng m(-3) air. Greater than 90% of the carcinogenic PAHs were concentrated on PM(1.5). Dibenzopyrene isomers made up a significant portion (∼30%) of the total carcinogenic PAH load during the winter. To our knowledge, this is the first report of dibenzopyrenes in the Beijing atmosphere and among the few studies that report these highly potent PAHs in ambient particulate matter. Lifetime risk calculations indicated that 1 out of 10,000 to over 6 out of 100 Beijing residents may have an increased risk of lung cancer due to PAH concentration. Over half of the lifetime risk was attributed to Σdibenzopyrenes. The World Health Organization and Chinese daily PM(10) standard was exceeded on each day of the study, however, PAH limits were only exceeded during the winter. The outcomes of the air pollution metrics were highly dependent on the individual PAHs measured and seasonal variation.

Fig. 1

Representative chromatograms of m/z 302 from Urban Dust SRM 1649b and Beijing PM_1.5. Gas chromatography-mass spectrometry scans were collected in selected ion monitoring mode. Numbered peaks correspond to PAH isomers that were positively identified using authentic standards. 1 D[a,l]P, 2 D[a,e]P, 3 D[a,h]P, 4 D[a,i]P, 5 D[j,l]F, 6 D[b,k]F and D[a,e]F, and 7 N[2,3-b]F.

Fig. 2

Mean PAH concentrations from Beijing PM_1.5 samples, plotted with standard deviation. Summer 2007 (n = 7) and winter 2008 (n = 8) PAHs are normalized per cubic metre of air sampled. Note the scale difference portraying an order of magnitude higher concentration in the winter. Only known carcinogenic PAHs (International Agency for Research on Cancer14) are bracketed as “carcinogenic”.

Fig. 3

Carcinogenic PAHs from Beijing PM_1.5 samples are plotted after potency adjustment using Toxic Equivalency Factors. Summer 2007 (n = 7) and winter 2008 (n = 8) average concentrations with standard deviation are shown. ΣPAHs represent only PAHs listed in Table 1. The figure highlights the contribution of notable PAHs on air quality assessments based on BaP limit values set by the European Union and China.

Fig. 4

Box plots of excess risk per million people during summer 2007 (top), winter 2008 (middle), and calculated for a lifetime (bottom) from exposure to select PAHs and the sums of carcinogenic PAHs measured on PM_1.5. Boxes represent the 5^th and 95^th percentile; dotted and solid horizontal lines represent mean and median values, respectively.