PCDD / F Levels in the Stacks and Food of Fast Food Restaurants

Trace amounts of polychlorinated dibenzodioxins and dibenzofurans (PCDD/Fs) are ubiquitous in the environment. This study determined the levels of PCDD/Fs in the stacks and food of fast food restaurants. The results indicate that the dominant contribution of PCDD/Fs concentration in the stacks of fast food restaurants is PCDFs. 2,3,7,8-TeCDF concentration measured in the stacks of fast food restaurants is the highest among the seventeen investigated PCDD/F congeners, accounting for about 17.9% of the total concentration. For the PCDD/F content in food before and after frying, the OCDD concentration was the highest among the seventeen investigated PCDD/F congeners, accounting for 22.3–93.3% of the total concentration before frying and 82.6–91.8% of the total concentration after frying. The total PCDD/F concentration in the food of fast food restaurants decreases significantly after frying. The mean emission factor and emission rate for total PCDD/Fs from the stacks of fast food restaurants are 208 pg/L and 12400 pg/min, respectively.


INTRODUCTION
Polychlorinated dibenzodioxins and dibenzofurans (PCDD/Fs) are ubiquitous environmental contaminants.PCDDs and PCDFs are unwanted by-products in a variety of industrial and thermal processes.Human exposure to these compounds has been associated with adverse health outcomes (Wang et al., 2009;Hu et al., 2009;Chuang et al., 2010a, b;Lin et al., 2010;Wang et al., 2010;Wu et al., 2010a, b;Chen et al., 2011;Chiu et al., 2011;Offenberg et al., 2011;Stone et al., 2011;Yeh et al., 2011).For the general population, food ingestion is the main route of exposure (WHO/ICPS, 1989).PCDD/PCDFs are persistent and bioaccumulate through the food chain.Many matrices contain PCDD/Fs, such as milk, eggs, meat, fishes, and animal feedstuff, have been investigated.The background levels of polychlorinated dibenzo-p-dioxins (PCDDs), p o ly c h lo r in a t e d d i b e n z o f u r a n s ( P C D F s ) , a n d polychlorinated biphenyls (PCBs) in these matrices can be used to estimate the typical dietary intakes for the general population (Focant et al., 2002).It is important to note that in these surveys, as well as in most reported investigations on the dietary intake of chemicals, food analyses were performed on uncooked/raw products.In an earlier study, the effect of broiling on the levels of PCDD/PCDFs and co-PCBs in ground beef (hamburger), bacon, and catfish were investigated (Schecter et al., 1998).The PCDD/PCDF and co-PCB TEQ values decreased by approximately 50% for each portion after broiling.
To assess toxicologically relevant information on PCDD/Fs, the International Toxicity Equivalent (I-TEQ) values for PCDD/Fs were calculated using 17 2,3,7,8-chlorinated congeners and their International Toxicity Equivalency Factors (I-TEFs) (Kutz et al., 1990).More recently, the World Health Organization (WHO) suggested modified TEFs in 1994 (TEFWHO-94), 1998 (TEFWHO-98), and 2005 (TEFWHO-05) (Ahlborg et al., 1994;Van den Berg et al., 1998, 2006).Although PCDD/F concentrations in many locations have been surveyed, few studies have focused on assessing the effects of PCDD/F pollutants found in homes and restaurants.In Taiwan, there are numerous fast food restaurants that cook fry food.This study determined the levels of PCDD/Fs in the stacks and food of fast food restaurants.Foods included small chicken nuggets, chicken nuggets, french fries, fish fillets, apple pies, and chicken fillets.The I-TEQ concentrations from the stacks and WHO-TEQ in the food are investigated in detail.The PCDD/F emission factor and emission rate from the stacks of fast food restaurants are also studied.

Sampling Strategy
Three fast food restaurants in Taiwan were randomly selected for the study.The main cooking methods were deep frying and stewing.Types of cooking oil were vegetable oil, butter, and corn oil.Food oil usage rates (liters per lunch or dinner period) ranged from 11.2-16.3,with a mean of 13.4.The cooking time for lunch (or dinner) period ranged from 97-121 minutes, with a mean of 109 minutes.The mean of stack diameters (m) was 1.194.The mean stack outlet velocity was 4.12 m/s, and the mean stack inlet and outlet temperatures were 44°C and 36°C, respectively.The mean exhaust flow rate was 136.45 Nm 3 /min.

Analyses of PCDD/Fs
Analyses of ambient air samples followed U.S. EPA modified Method 23 and U.S. EPA Reference Method T09A, respectively.All chemical analyses were carried out at the Super Micro Mass Research and Technology Center in Cheng Shiu University.Each collected sample was spiked with a known amount of the internal standard.After 24 h of extraction, the extract was concentrated, treated with concentrated sulfuric acid, and then subjected to a series of sample cleanup and fractionation procedures.The eluate was concentrated to ~1 mL, transferred to a vial, and then further concentrated to nearly dryness using a nitrogen stream.Prior to PCDD/F analysis, the standard solution was added to the sample to ensure recovery during the analysis process.A high-resolution gas chromatograph (HRGC) and a high-resolution mass spectrometer (HRMS) were used for analyzing 17 PCDD/F species.The HRGC (Hewlett Packard 6970 Series gas, CA, USA) was equipped with a DB-5MS fused silica capillary column (L = 60 m, ID = 0.25 mm, film thickness = 0.25 μm) (J&W Scientific, CA, USA) and splitless injection.Helium was employed as the carrier gas.The HRMS (Micromass Autospec Ultima, Manchester, UK) was equipped with a positive electron impact (EI+) source.The analyzer mode of selected ion monitoring (SIM) had a resolving power of 10000.The Electron energy and source temperature were 35 eV and 250°C, respectively.The toxic equivalent quantity of PCDD/Fs is given by I-TEQ = ΣXi × Ii, where I-TEQ denotes the international toxic equivalent quantity, Xi represents the concentration of PCDD/F congeners, and Ii is the international toxic equivalent factor of each PCDD/F congener (I-TEF) (NATO/CCMS, 1988).

Concentrations of PCDD/Fs Obtained from the Stacks of Fast Food Restaurants
The individual concentrations of the 17 most toxic congeners of PCDD/PCDFs from the stacks of fast food restaurants are summarized in Table 1.The sum of PCDDs and PCDFs, the ratio PCDDs/ PCDFs, and the TEQ for the stacks are also shown.The total PCDD/F concentrations from the stacks of fast food restaurants ranged from 87.4-94.2pg/Nm 3 , with an average of 90.8 pg/Nm 3 .The total PCDDs/PCDFs ratios were 0.368-0.399,indicating that the main PCDD/F contribution from the stacks of fast food restaurants was PCDFs.The total I-TEQ concentrations from the stacks of fast food restaurants ranged from 8.16-8.75pg I-TEQ/Nm 3 , with an average of 8.48 pg I-TEQ/Nm 3 .The mean total I-TEQ concentration of fast food restaurants is smaller than that of municipal solid waste incinerators (72.5 pg I-TEQ/Nm 3 ) (Wang et al., 2007), sinter plants (995-2060 pg I-TEQ/Nm 3 with selective catalytic reduction (SCR) and 3100 pg I-TEQ/Nm 3 without SCR) (Wang et al., 2003b), electric arc furnaces (172 pg I-TEQ/Nm 3 ) (Wang et al., 2010), aluminum smelter plants (9020 pg I-TEQ/Nm 3 ) (Chen et al., 2004), crematories (322-2360 pg I-TEQ/Nm 3 ) (Wang et al., 2003a), and power plants (17 pg I-TEQ/Nm 3 ) (Lin et al., 2007).However, restaurants are close to daily human activity.We should thus pay more attention to PCDD/F emissions from restaurants.The TEQ PCDDs/PCDFs ratios of fast food restaurants are 0.227-0.238,indicating that the main toxicity source of PCDD/Fs was PCDFs.

PCDD/F Content in the Food of Fast Food Restaurants before Frying
The individual content of the 17 most toxic congeners of PCDD/PCDFs from the food of fast food restaurants before frying is summarized in Table 2.The total PCDD/F concentrations in the food of fast food restaurants before frying were 13.91, 7.11, 25.29, 27.00, 11.74, and 14.95 pg/g-l.w.(lipid) for small chicken nuggets, chicken nuggets, french fries, fish fillets, apple pies, and chicken fillets, respectively.Fish fillets had the highest PCDD/F content, and chicken nuggets had the lowest.The ratios of PCDDs/PCDFs were 5.34-23.45for small chicken nuggets, chicken nuggets, french fries, apple pies, and chicken fillets, indicating that the main contribution of their PCDD/F content before frying was PCDDs.However, the ratio of PCDDs/PCDFs concentrations was 0.85 for fish fillets, indicating that the main contribution of PCDD/Fs for fish fillets before frying was PCDFs.
The total WHO-TEQ in the food of fast food restaurants before frying were 0.1184-2.4940pg WHO/g-l.w.(lipid).The WHO PCDDs/PCDFs ratios for small chicken nuggets, french fries, and apple pie were 1.42, 1.13, and 1.096, respectively, indicating that their main toxicity source of WHO-TEQ before frying was PCDDs.However, the WHO PCDDs/PCDFs ratio for chicken fillets was 0.775, indicating that its main toxicity source of WHO-TEQ before frying was PCDFs.

Congener Profiles of PCDD/Fs in the Food of Fast Food Restaurants before Frying
Fig. 2 shows the congener profiles of 17 PCDD/F species from various raw food at fast food restaurants.For all of the food before frying, the OCDD concentration was the highest among the seventeen investigated PCDD/F congeners, accounting for about 88.4, 78.3, 93.3, 22.3, 76.9, and 88% of the total content for small chicken nuggets, chicken nuggets, french fries, fish fillets, apple pies, and chicken fillets, respectively.1,2,3,4,6,7,8-HpCDD was the second dominant among the seventeen investigated PCDD/F  congeners, accounting for about 5.0, 7.3, 1.6, 10.9, 3.4, and 4.9% of the total content for small chicken nuggets, chicken nuggets, french fries, fish fillets, apple pies, and chicken fillets, respectively.OCDF was the third dominant among the seventeen investigated PCDD/F congeners, accounting for about 1.8, 2.8, 1.0, 10.6, 2.9, and 2.2% of the total content for small chicken nuggets, chicken nuggets, french fries, fish fillets, apple pies, and chicken fillets, respectively.

PCDD/F Content in the Food of Fast Food Restaurants after Frying
Table 3 summarizes the individual concentrations of the 17 most toxic congeners of PCDD/PCDFs, the sum of PCDDs and PCDFs, the ratio of PCDDs/PCDFs, the total I-TEQ (given in pg I-TEQ/Nm 3 ), and the total WHO-TEQ (given in pg WHO-TEQ/Nm 3 ) in samples of cooked food.The total PCDD/F concentrations in the food of fast food restaurants after frying were 11.68, 6.20, 12.36, 11.54, 10.16, and 11.43 pg/g-l.w.(lipid) for small chicken nuggets, chicken nuggets, french fries, fish fillets, apple pies, and chicken fillets, respectively.French fries had the highest PCDD/F content, and chicken nuggets had the lowest.The ratios of PCDDs/PCDFs were 10.58-23.71for all the food after frying, indicating that the main contribution of PCDD/Fs for all the food after frying was PCDDs.
The total WHO-TEQ in the food of fast food restaurants after frying were 0.0704-0.1473pg WHO/g-l.w.(lipid).The WHO PCDDs/PCDFs ratios for small chicken nuggets, chicken nuggets, french fries, fish fillets, apple pies, and chicken fillets were 1.274, 1.176, 1.206, 1.148, 1.228, and 1.100, respectively, indicating that their main toxicity source of WHO-TEQ after frying was PCDDs.

Congener Profiles of PCDD/Fs in the Food of Fast Food Restaurants after Frying
Fig. 3 shows the congener profiles of 17 PCDD/F species from various cooked food at fast food restaurants.Similar to food at fast food restaurants before frying, the OCDD concentration was the highest among the seventeen investigated PCDD/F congeners for all food after frying, accounting for about 89.9, 82.6, 91.8, 86.1, 91.4, and 88.2% of the total content for small chicken nuggets, chicken nuggets, french fries, fish fillets, apple pies, and chicken fillets, respectively.1,2,3,4,6,7,8-HpCDD was the second dominant among the seventeen investigated PCDD/F congeners, accounting for about 5.1, 6.1, 2.9, 4.6, 2.9, and 4.6% of the total content for small chicken nuggets, chicken nuggets, french fries, fish fillets, apple pies, and chicken fillets, respectively.OCDF was the third dominant among the seventeen investigated PCDD/F congeners, accounting for about 0.8, 2.2, 1.1, 1.8, 1.5, and 1.7% of the total content for small chicken nuggets, chicken nuggets, french fries, fish fillets, apple pies, and chicken fillets, respectively.

Comparison of PCDD/F Content and Congener Profiles of PCDD/Fs before and after Frying in the Food of Fast Food Restaurants
From Table 2 and Table 3, all six types of food have smaller total PCDD/F concentrations after frying.The total PCDD/F concentrations for small chicken nuggets, chicken nuggets, french fries, fish fillets, apple pies, and chicken fillets, respectively, after frying were 84.0, 87.1, 48.9, 42.8, 86.5, and 76.5% of those before frying.It is likely that a certain amount of fat became attached to the food after frying, significantly decreasing the PCDD/F content.Moreover, the total WHO-TEQ PCDD/F concentrations for small chicken nuggets, chicken nuggets, french fries, fish fillets, apple pies, and chicken fillets, respectively, after frying were 69.2, 67.8, 49.3, 5.90, 21.3, and 83.1% of those before frying.
Few studies investigated 17 kinds of PCDD/F congener before and after frying at fast food restaurants.In our study, OCDD, 1,2,3,4,6,7,8-HpCDD, and OCDF were the three dominant congeners before and after frying (Fig. 2 and Fig. 3).The OCDD congeners for small chicken nuggets, chicken nuggets, french fries, fish fillets, apple pies, and chicken fillets, respectively, after frying were 85.4, 92, 48, 165, 103, and 76.7% of those before frying; the 1,2,3,4,6,7,8-HpCDD congeners for small chicken nuggets, chicken nuggets, french fries, fish fillets, apple pies, and chicken fillets, respectively, after frying were 84.3, 72.1, 86.9, 17.9, 74.5, and 72.4% of those before frying; the OCDF congeners for small chicken nuggets, chicken nuggets, french fries, fish fillets, apple pies, and chicken fillets, respectively, after frying were 39.2, 68.1, 56.5, 7.10, 44.2, and 59.8% of those before frying.Although the OCDD congeners for fish fillets after frying were 1.65 times larger than those before frying, the other 16 congeners for fish fillet after frying were 3.6-17.9% of those before frying.Although the OCDD congeners for apple pies after frying were 1.028 times larger than those before frying, the other 16 congeners for apple pies after frying were 19.9-74.5% of those before frying.Accordingly, the sum of 17 PCDD/F species from six kinds of cooked food at fast food restaurants is smaller than that of raw food.
Table 4 summarizes the fat content and WHO-TEF of the six types of food before and after frying in fast food restaurants.All six types of food exhibit larger fat content after frying, indicating that some cooking oil is present in the food after frying.Small chicken nuggets, chicken nuggets, apple pies, and chicken fillets exhibit smaller WHO-TEF values after frying.The WHO-TEF values of small chicken nuggets and chicken fillets meet the criterion of the Department of Health (DOH) in Taiwan (Taiwan DOH, 2009).

PCDD/Fs Emission Factor and Emission Rate
PCDD/F samples collected from the stacks of fast food restaurants were associated with different food oil consumption rates, cooking times, stack outlet velocities, and stack diameters.Thus, the PCDD/Fs emission factor was calculated according to the following equation (Li et al., 2003): where d, v, t, and CR food-oil are, respectively, the stack diameter (in meters), stack outlet velocity (in meters per second), cooking time (in minutes per lunch period or dinner period), and food oil consumption rate (in liters of food oil per lunch or dinner period).the stacks of fast food restaurants ranged from 3208-3669 pg/min and 8715-9186 pg/min, with an average of 3434 pg/min and 8957 pg/min.The emission rate for total PCDD/Fs from the stacks of fast food restaurants ranged from 11900-12900 pg/min, with an average of 12400 pg/min.Fig. 4 summarizes the profiles of 17 PCDD/Fs species of the emission rate for fast food restaurants and other various sources (Kao et al., 2007).The PCDD/F emission rates (pg/min) at various resources are summarized in  total emission rates, respectively.OCDD was the highest among the seventeen investigated PCDD/F congeners in municipal solid waste incinerators (MSWI), accounting for 35.8% of the total emission rate.

CONCLUSIONS
In this study, we determined the PCDD/F levels in the stacks and food of fast food restaurants.The results indicate that the total I-TEQ concentrations from the stacks of fast food restaurants ranged from 8.16-8.75pg I-TEQ/Nm 3 , with an average of 8.483 pg I-TEQ/Nm 3 .The 2,3,7,8-TeCDF concentration was the highest among the seventeen investigated PCDD/F congeners, accounting for about 17.3-17.8% of the total concentration.The total PCDD/F concentrations for small chicken nuggets, chicken nuggets, french fries, fish fillets, apple pies, and chicken fillets, respectively, after frying were 84.0, 87.1, 48.9, 42.8, 86.5, and 76.5% of those before frying, indicating that frying significantly decreases PCDD/F content.For all food before and after frying, the OCDD concentration was the highest among the seventeen investigated PCDD/F congeners.The PCDD/Fs emission factor was evaluated using food oil consumption rates, cooking times, stack outlet velocities, and stack diameters.The PCDD/F emission rate was estimated from the exhaust flow rate.The main emission factor and emission rate of PCDD/Fs from the stacks of fast food restaurants was PCDFs.This study provides essential information for conducting health and environmental impact studies of stacks and food at fast food restaurants.

Fig. 1 .
Fig. 1.Congener profiles of 17 PCDD/F species from the stacks of fast food restaurants and other sources.

Fig. 2 .
Fig. 2. Congener profiles of 17 PCDD/F species from various types of raw food at fast food restaurants.

Fig. 3 .
Fig. 3. Congener profiles of 17 PCDD/F species from various types of cooked food at fast food restaurants.

Fig. 4 .
Fig. 4. Congener profiles of 17 PCDD/F species of the emission rate for various sources.

Table 1 .
Mean concentrations of PCDD/Fs from the stacks of fast food restaurants.

Table 4 .
Fat content and WHO-TEF of raw and cooked food in fast food restaurants.
aThe regulated standard of Taiwan Department of Health (DOH).

Table 5 .
PCDD/F emission factor (pg per liter of used cooking oil) at fast food restaurants.

Table 6 .
PCDD/F emission rate (pg/min) at fast food restaurants.