Levels and composition of volatile organic compounds from the electric oven during roasting pork activities

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1 Sustain Environ Res, 22(1), 1724 (2012) 17 Levels and composition of volatile organic compounds from the electric oven during roasting pork activities 1, 2, LienTe Hsieh, * HsiHsien Yang, YuanChung Lin and ChengHsien Tsai 1 Department of Environmental Science and Engineering National Pingtung University of Science and Technology Pingtung 912, Taiwan 2 Emerging Compounds Research Center National Pingtung University of Science and Technology Pingtung 912, Taiwan 3 Department of Environmental Engineering and Management Chaoyang University of Technology Taichung 413, Taiwan 4 Institute of Environmental Engineering National Sun YatSen University Kaohsiung 804, Taiwan 5 Department of Chemical and Material Engineering National Kaohsiung University of Applied Sciences Kaohsiung 807, Taiwan Key Words: Oven, indoor air, VOCs, aromatics, cooking ABSTRACT The present study investigated levels and composition of volatile organic compounds (VOCs) from the electric oven pork roasting commonly associated with indoor air quality issues of human activities A series of experiments were conducted to evaluate three heating temperatures of 170, 200, and 230 C to identify the characteristics of the VOCs emitted Fumes were collected in SKC sampling bags and later analyzed by gas chromatography mass spectrometry There were fifteen VOCs identified as follows: nundecane, 3methylheptane, 1butene, propylene, npentane, m diethylbenzene, styrene, isopentane, oethyltoluene, ndodecane, nbutane, 1pentene, nheptane, 1 hexene and nhexane The results indicate that total VOC mean concentrations show clear trend of increasing with heating temperature Also, detailed distribution of alkanes, alkenes and aromatics in the oven emission data is discussed INTRODUCTION In recent years considerable concern has arisen over the investigation of quantitative levels of volatile organic compounds (VOCs) in cooking events [16] Moreover, concern about human exposure to VOC pollutants has historically been focused on ambient air and occupational/industrial environments, which are regulated by the government administrations (such as, EPA or Occupational Safety and Health Administration in the United States) Therefore, the emission of VOCs from cooking behaviour/activity on both air qualities and health issues is of critical importance [711] Heated cooking oils can produce considerable amounts of acrolein, thus cooking is likely an important source of indoor acrolein [6] A series of cooking experiments were conducted by Seaman [6] to determine the emission rates of acrolein and other volatile carbonyls for different types of cooking oils (canola, soybean, corn and olive oils) and deepfrying different food items The oil cooking resulted in high concentrations of acrolein ( ìg m ) which exceed all the chronic regulatory exposure limits and many of the acute exposure limits Their report indicates that indoor acrolein concentrations can persist for considerable time after cooking in poorlyventilated homes Fullana et al [1] investigated emissions of low molecular weight aldehydes (LMWAs) from deepfrying of extra virgin olive oil, olive oil, and canola oil (control) at 180 and 240 C, for 15 and 7 h, respectively They collected the oil fumes in Tedlar bags and analyzed the samples by gas chromatography mass *Corresponding author Lthsieh@mailnpustedutw

2 18 Hsieh et al, Sustain Environ Res, 22(1), 1724 (2012) spectrometry (GCMS) Finally, they found that seven alkanals (C2C 7 and C 9), eight 2alkenals (C3C 10), and 2,4heptadienal were in the fumes of all three cooking oils Fullana et al [2] further investigated LMWAs formed during the heating of frying media (triglycerides) They used Tenax to adsorb LMWAs and analyzed by GCMS after thermal desorption They revealed that six alkanals (C to C ), seven 2alkenals 5 10 (C 5 to C 11) and 3 alkadienals (C 7, C 9 and C 10) were in the fumes of canola oil (control), virgin olive oil, and refined olive oil, heated at 180 and 240 C However, cooking activity emissions can constitute a major share of personal indoor environment concentrations of many VOCs and other air pollutants in public restaurant areas Particularly high concentrations may occur at microenvironment related to using personal or small electric cooking appliances Such levels are not reflected by monitoring at fixed sites As far as particles emitted from cooking is concerned, Buonanno et al [5] investigated particle emission factors during cooking activities They concluded that particle number, surface area and mass concentration all increased at higher temperatures, for both gas and electric stoves Their study showed that all of the emission factors for the electric frying pan were significantly lower than those generated by frying using a gas stove They supposed that the main factor could be the lower frying temperature (ie, at or below 190 C) during electric frying pan that may reduce the emission factors, also taking into account that electric frying leads to fewer emissions than gas frying Additionally, the type of food used did not appear to have a significant impact on the emission factors from frying [5] Up to now, the conventional oven has been a kitchen appliance and been used for roasting and heating Food normally cooked in this manner includes meat, casseroles and baked goods such as bread, cake and other desserts Therefore, with the increasing usage of electric oven cooking, emission levels and compositions of VOCs during such activities have become more critical The present paper is an attempt to supplement the findings of these earlier studies It is similar to the previous studies discussed above, in that the focus is on the measurement of certain target VOCs It differs from previous studies in that levels and composition of certain target VOCs from the usage of the electric oven during roasting pork activities are investigated In light of these concerns, this article has three purposes: (a) to provide the selected levels of VOCs; (b) to provide the compositions of selected VOCs; and (c) to determine the characteristics of selected VOCs from the electric oven during roasting pork activities 1 Sampling Strategy MATERIALS A METHODS To investigate levels and composition of VOCs from the electric oven during roasting pork activities, a labscale system of the electric oven generator was operated at indoor environment The experimental setup for these experiments is shown in Fig 1 Our labscale process operation system consists of (1) oil fume generator, (2) gasflow meter and controller, (3) uniform passing chamber, (4) sampling bags (three selected pathway available), (5) 7100A preconcentrator and 6890 GC/MS system, and (6) PC recording and data storage (1) oil fume generator (2) gasflow meter and controller (3) uniform passing chamber (4) sampling bags (three selected pathway available) (5) 7100A preconcentrator and 6890 GC/MS system (6) PC recording and data storage Fig 1 Schematic diagram of experimental setup This study was carried out during the spring and summer of 2009 in our laboratory in Department of Environmental Science and Engineering, National Pingtung University of Science and Technology In this experiment, the exhaust fume was generated from a smallscale electric oven with rectangular geometries (Fig 1) Only one electric oven in our laboratory was used during the roasting pork experiments The input pork of 300 g was heated and roasted at three heating operational temperatures individually (ie, at 170, 200, and 230 C), a steady gas flow rate, and a batch feeding pork amount (300 g) for each run According to our survey of residents nearby, the amount of pork typically used per meal for a family is approximately at least 300 g (in fact, exceed 300 g) Therefore, the quantity of 300 g is set as the basis quantity in our study In addition, the three heating operational temperatures of 170, 200, and 230 C are based on the design of most ovens sold in supermarkets or stores in Taiwan During the experiments, the exhaust fume gas flow followed the pathway: passing the collected hood, passing the aluminum cylindrical pipe, introducing into gasflow meter and controller, flowing uniform passing chamber, and entering the sampling bags (by adjusting threepathway valve) In this study, our electric oven is a rectangular chamber

3 Hsieh et al, Sustain Environ Res, 22(1), 1724 (2012) 19 with a width of 485 cm, length of 392 cm, and height of 291 cm It is based on the system described by Hsieh et al [12] and has been modified for the use of VOCs Details are described by Hsieh et al [12] Generally speaking, the oven used to cook and heat food in many households can be divided into three conditions as follows: (i) The most common may be to heat the oven from below This method is used for baking and roasting (ii) The oven may be able to heat from the top to provide broiling And (iii) in order to provide both faster heating operation function and enhancing the convection, ovens use a small fan to blow hot air around the cooking chamber Combining above three situations, therefore, we conducted at three heating operational temperatures individually (ie, at 170, 200, and 230 C) In this study, total volume of oven capacity (25 L) was passing into the uniform passing chamber and then partly introducing into the sampling bags In this study, the residence time of the oven is approximately 94 s It is not a completely mixing type of cooking chamber because we tried to simulate the regular cooking process in the kitchen The thermocouple probe is a long wire, and it is easy to attach in the inner wall of oven We used four probes in the oven and placed those probes in the up, bottom, right, and left directions The average of the four measured temperatures in each run was reported in this study 2 Procedure Controls VOC samples were collected using an SKC universal pump and patent Tedlar 1 L sampling bags (CAT#:23201, capacity: 1 L, PATENT# SKC) This method of sampling has been successfully used in a number of gaseous phase sampling of VOCs [1,13 16] Different Tedlar bags (capacity from 1 to 5 L) are commonly accepted sampling containers in breath analysis [17] This is due to their moderate price, inertness, relatively good durability and reusability Therefore, in our experiment, all bags were new and unused According to the producer s recommendations prior to the first use bags were flushed ten times with highpurity nitrogen (type %) In this study, the air sampling and analyzing methods refer to the standard process of Taiwan National Environmental Analysis Methods (A73470B) [18] Our VOC sampling was operated by connecting the 1 L bag sample to the hood collector hanging above an oven Throughout each run, temperatures were measured from the gas in oven and exhaust in the exit with Ktype thermocouples After achieving the designed temperature in oven, the cooking exhaust was introduced into the sampling bags by the SKC pump In order to prevent the sampled exhaust from possible photochemical reactions, all pipes were wrapped with aluminum foil in advance After sampling, all Tedlar bags were stored in black opaque plastic bags to keep them away from light 3 Analysis This study measured the concentrations of fiftytwo selected VOCs from the electric oven during roasting pork activities The exhaust gases were collected in 1 L clear layered Tedlar bags All samples were analyzed within a 12 h period to avoid degradation of the sample During all analytical procedure, the collected gas samples were introduced into the 7100A preconcentrator to process the preconcentration The 7100A preconcentrator is equipped with three trapping devices and is acceptable for Tedlar bags After the preconcentration in 7100A, the preconcentrated samples were introduced into GC by using the transfer line and then analyzed by MS detector The concentrated extract was then transferred into the column A GC (Agilent 6890) with an MS detector (Agilent 5973N) and a computer workstation was used for VOC analysis This GC/MS was equipped with a capillary column (a 60 m x 025 mm diameter DB5MS capillary column, 025 ìm film thickness) GC was operated in splitless mode, at an injector temperature of 300 C 1 and a Helium (carrier gas) flow rate of 10 ml min The compounds were separated using the following temperature program: initial temperature 40 C (held 1 for 8 min) to 240 C (held for 15 min) at 10 C min in the constant flow mode The transfer line temperature was 300 C The GC/MS analysis was performed by electron impact ionization with electron energy of 1 70 ev and the scan was at 296 scans s Products were identified by comparing product mass spectra with mass spectral database (National Institute of Standards and Technology, MD) The average value of all the response factors from these standards was calculated and used to quantify results In this study, it is difficult to separate the two VOC species by our GC column (DB5MS capillary column) Therefore, we use the pxylene + mxylene to present the two VOC species Seven sampling traps spiked with standards were used to determine the method detection limits (MDL) of the system The MDL ranged from 02 to 09 ìg m for the target VOCs 4 Statistical Analyses Data from VOC emissions were examined by analysis of variance using SPSS software (SPSS 801C Standard Version) The value of significance test is used to evaluate the mean effects (namely, different heating temperatures for each level of VOCs produced) Significance was defined at p 005 RESULTS A DISCUSSION 1 Overall Compounds Fiftytwo analyzed VOC mean concentrations (ìg m) emitted from the electric oven during roasting pork

4 20 Hsieh et al, Sustain Environ Res, 22(1), 1724 (2012) cooking at three different heating temperatures are listed in Table 1 Total VOC concentrations at 170, 200, and 230 C were 61, 76, and 154 ìg m, respectively, indicating that higher heating temperatures (such as at both 200 and 230 C) produced more total VOC concentrations The ratios of individual selected compounds emitted at three different temperatures are listed in Table 2 For an overall discussion, the mean concentrations of measured VOCs at three different temperatures are as follows: (i) at 170 C: nundecane > 3methylheptane > 1butene > propylene > npentane > mdiethylbenzene > styrene > isopentane > oethyltoluene > ndodecane > nbutane > 1pentene > nheptane > 2,3 dimethylbutane > pxylene + mxylene > 1hexene > nhexane > trans2pentene > npropylbenzene > ndecane > pdiethylbenzene > isoprene > propane + isobutane The sum of these compounds accounted for 92% of total selected VOC mean concentrations at 170 C (61 ìg m ) (ii) at 200 C: nundecane > npentane > 1butene > propylene > 3methylheptane > styrene > oethyltoluene > mdiethylbenzene > 1pentene > nhexane > nbutane > isopentane > ndodecane > nheptane > pxylene + mxylene > isoprene > noctane > 1,2,4trimethylbenzene > propane+isobutane > 2,2,4trimethylpentane > 1hexene The sum of these compounds accounted for 92% of total selected VOC mean concentrations at 200 C (76 ìg m ) (iii) at 230 C: npentane > 1butene > nundecane > styrene > propylene > 1pentene > 3methylheptane > nbutane > nhexane > noctane > 1hexene > mdiethylbenzene > nheptane > oethyltoluene > 2,2,4trimethylpentane > trans2butene > isopentane > ndodecane > cis2butene > 1,2,4trimethylbenzene The sum of these compounds accounted for 91% of total selected VOC mean concentrations at 230 C (154 ìg m ) There are fifteen compounds emitted at all three temperatures They were: nundecane (1114 ìg m ), 3methylheptane (5461 ìg m ), 1butene (522 ìg m ), propylene (511 ìg m ), npentane (41 ìg m ), mdiethylbenzene (37 ìg m ), styrene (213 ìg m ), isopentane (1619 ìg m ), oethyltoluene (175 ìg m ), ndodecane (1418 ìg m ), nbutane (1355 ìg m ), 1pentene (1271 ìg m ), nheptane (1128 ìg m ), 1hexene (065 ìg m ) and nhexane (0942 ìg m ) These 15 compounds might be useful for determining permissible VOC limits in indoor air quality Additionally this information could be used along with database of VOC inhalation through outdoor sources such as traffic emissions to study human inhalation of harmful VOCs Table 3 shows the selected VOC compositions (%) emitted at three heating temperatures Except for those screened 15 compounds (as mentioned above), others (they are below detection level) including 2,3 dimethylbutane, pxylene + mxylene, trans2pentene, Table 1 Selected VOCs mean concentrations (ìg m ) emitted from the electric oven during roasting pork cooking at three different heating operational temperatures Selected compounds 170 C Ethylene + Acetylene + Ethane Propylene 514 Propane + Isobutane 064 1Butene 539 nbutane 127 Trans2Butene 037 Cis2Butene 040 Isopentane 167 1Pentene 122 npentane 419 Trans2Pentene 082 Isoprene 068 Cis2Pentene 025 2,2Dimethylbutane Cyclopentane 2,3Dimethylbutane 097 2Methylpentane 3Methylpentane 020 1Hexene 092 nhexane 085 2,4Dimethylpentane Methylcyclopentane Benzene 022 Cyclohexane 046 2Methylhexane 2,3Dimethylpentane 3Mehtylhexane 2,2,4Trimethylpentane 034 nheptane 106 Methylcyclohexane 026 2,3,4Trimethylpentane 025 2Methylheptane 3Methylheptane 582 Toluene noctane 028 Ethylbenzene 061 pxylene + mxylene 093 nnonane Styrene 219 oxylene Isopropylbenzene npropylbenzene 082 methyltoluene + pethyltoluene 020 oethyltoluene 165 1,3,5Trimethylbenzene 026 1,2,4Trimethylbenzene 046 ndecane 076 1,2,3Trimethylbenzene 042 mdiethylbenzene 367 pdiethylbenzene 071 nundecane 1343 ndodecane 154 TotalVOCs* 61 Mean concentrations ( ìg m ) 200 C *TotalVOCs = sum of target VOCs in this study : Below the detection level 230 C

5 Hsieh et al, Sustain Environ Res, 22(1), 1724 (2012) 21 Table 2 Comparative mean concentration ratios at three different heating operational temperatures Selected compounds Propylene Propane + Isobutane 1Butene nbutane Trans2Butene Cis2Butene Isopentane 1Pentene npentane Trans2Pentene Isoprene Cis2Pentene 2,3Dimethylbutane 2Methylpentane 3Methylpentane 1Hexene nhexane Benzene Cyclohexane 2,2,4Trimethylpentane nheptane Methylcyclohexane 2,3,4Trimethylpentane 3Methylheptane noctane Ethylbenzene pxylene + mxylene Styrene methyltoluene + pethyltoluene oethyltoluene 1,3,5Trimethylbenzene 1,2,4Trimethylbenzene ndecane 1,2,3Trimethylbenzene mdiethylbenzene pdiethylbenzene nundecane ndodecane TotalVOC ratios Comparative ratios 200 C 170 C C 170 C C 200 C npropylbenzene, ndecane, pdiethylbenzene, isoprene, propane + isobutane accounted for lower than 2% of total VOCs at 170 C Similarly, pxylene + m xylene, isoprene, noctane, 1,2,4trimethylbenzene, propane + isobutane, 2,2,4trimethylpentane, and 1 hexene accounted for less than 15% of total VOCs at 200 C Additionally, noctane, 2,2,4trimethylpentane, trans2butene, cis2butene and 1,2,4 trimethylbenzene were accounted for less than 25% of total VOCs at 230 C Some important information of total VOCs emitted at different temperatures with different aliphatics and aromatics is discussed below 2 Alkanes Excluding the item of ethylene + acetylene + Table 3 Selected VOCs percentage compositions (%) emitted from the electric oven during roasting pork cooking at three different heating operational temperatures VOCs compounds Propylene Propane + Isobutane 1Butene nbutane Trans2Butene Cis2Butene Isopentane 1Pentene npentane Trans2Pentene Isoprene Cis2Pentene 2,3Dimethylbutane 2Methylpentane 3Methylpentane 1Hexene nhexane 2,4Dimethylpentane Benzene Cyclohexane 2,3Dimethylpentane 3Mehtylhexane 2,2,4Trimethylpentane nheptane Methylcyclohexane 2,3,4Trimethylpentane 3Methylheptane noctane Ethylbenzene pxylene + mxylene nnonane Styrene npropylbenzene methyltoluene + pethyltoluene oethyltoluene 1,3,5Trimethylbenzene 1,2,4Trimethylbenzene ndecane 1,2,3Trimethylbenzene mdiethylbenzene pdiethylbenzene nundecane ndodecane Total % Percentage compositions (%) 170 C C C ethane (ie, below detection level as listed in Table 1), the 22 alkanes identified include propane + isobutane, nbutane, isopentane, npentane, 2,3dimethylbutane, 2methylpentane, 3methylpentane, nhexane, cyclohexane, 2,3dimethylpentane, 3mehtylhexane, 2,2,4 trimethylpentane, nheptane, methylcyclohexane, 2,3,4trimethylpentane, 2methylheptane, 3 methylheptane, noctane, nnonane, ndecane, n undecane, and ndodecane Total VOC concentrations measured at 170, 200, and 230 C were contributed

6 22 Hsieh et al, Sustain Environ Res, 22(1), 1724 (2012) mostly by total alkanes (sum of all alkanes), which accounted for 56, 53, and 52% of total VOCs at the three temperatures, respectively (Table 3) High concentrations at three temperatures included nbutane, isopentane, npentane, nhexane, nheptane, 3methylheptane, nundecane and ndodecane The highest level of npentane at 230 C reached 305 ìg m However, nundecane concentration measured at both 170 and 200 C were higher than other alkanes and its levels accounted for 22 and 15% of total VOCs, respectively In order to gain insight into the comparison of the influence of temperatures on the change of emitted VOC levels (ie, 170 vs 200 C, 170 vs 230 C, and 200 vs 230 C), the data were performed by using a paired ttest method We found that among the 27 alkane compounds, several noticeable features are obtained, as follows (i) In the case of 170 vs 200 C, only npentane (p = 00085) and noctane (p = 0035) were significant, hence the change of both compounds at the two temperatures (170 vs 200 C) differ significantly at p < 005 Excluding npentane and noctane, other alkanes showed their insignificant differences (ii) In the case of 170 vs 230 C, seven compounds (among 22 alkanes) were significant, including n butane (p = 0011), npentane (p = 00004), 2,3 dimethylbutane (p = 0042), nhexane (p = 0003), 2,2,4trimethylpentane (p = 0007), nheptane (p = 0049) and noctane (p = 0006) (iii) In the case of 200 vs 230 C, also same seven compounds were significant, including nbutane (p = 0041), npentane (p = 00004), 2,3dimethylbutane (p = 0013), nhexane (p = 0021), 2,2,4trimethylpentane (p = 0018), noctane (p = 0006) and ndecane (p = 0046) The above results clearly implied that the exhaust emitted from higher heating environment had high alkane generation and possible toxicity and the variation of VOC compositions increased with temperatures Such significant changes are attributable to the fact that higher heating operation gives higher chemical reactive energy for VOC generation However, higher heating operation mode could reduce the cooking time Therefore, it is important that there is adequate ventilation in the indoor workplace before using the oven 3 Alkenes The nine alkene compounds identified include propylene, 1butene, trans2butene, cis2butene, 1 pentene, trans2pentene, isoprene, cis2pentene and 1hexene During roasting pork activities, total alkenes measured at 170, 200, and 230 C accounted for 24, 28, and 32% of total VOCs, respectively Based on the levels of alkenes emitted at 170 C, the ratios of alkene levels at 230 and 200 C to those of levels at 170 C (ie, 230 C/170 C and 200 C/ 170 C) are compared in Table 2 It shows that most of the values for 230 C/170 C and 230 C/200 C exceed 10 This trend indicates the increase of heating temperature has an important impact on the formation of alkenes Our result is similar to the report by Buonanno et al [5] They investigated the temperature effect for grilling bacon on a gas stove with average grill temperature 242 ± 52 C for the stove operating at maximum power and 171 ± 17 C for the stove operating at minimum power They concluded that grill temperature had a significant impact on emission factors, with an increase of 70% in the case of particulate number concentration, and a 29fold increase in mass concentration The alkenes with the highest concentrations at all three heating temperatures included propylene, 1 butene, 1pentene and 1hexene However, 1butene concentrations measured at 170, 200, and 230 C (highest at 22 ìg m ) were higher than others alkene and their levels accounted for 9, 13, and 14% of total VOCs, respectively (Table 3) Briefly, aliphatics are the major species in cooking gaseous fumes The selected alkanes and alkenes together comprised 80, 81, 84% of totalvoc levels at 170, 200, and 230 C, respectively (Table 3) To gain some insight into the comparison of the influences of temperatures on the change of alkenes emitted levels (ie, 170 vs 200 C, 170 vs 230 C, and 200 vs 230 C), we found that among the nine alkene compounds, several noticeable characteristics are as follows (i) In the case of 170 vs 200 C, only propylene (p = 0035) and 1butene (p = 0006) were significant, hence the change of both compounds at two temperatures (170 vs 200 C) differ significantly at p < 005 Excluding propylene and 1butene, other alkenes showed their insignificant differences This trend of alkenes resembles that of alkanes (ii) In the case of 170 vs 230 C, all alkene compounds except for trans2pentene and 1hexene were significant at p < 005 Therefore, the variation of all alkenes (excluding trans2pentene and 1hexene) differed significantly (iii) In the case of 200 vs 230 C, all alkene compounds were significant (except for 1hexene) at p < 005 As in the case of 170 vs 230 C, the variation of all alkenes (excluding trans2pentene and 1hexene) at the case of 170 vs 200 C differ significantly Not surprisingly, the findings about alkenes being highly significant are due to the reason that these alkenes have more double bonds in their structures 4 Aromatics Fifteen compounds were identified including benzene, toluene, ethylbenzene, pxylene + mxylene, styrene, oxylene, isopropylbenzene, npropylbenzene, methyltoluene + pethyltoluene, oethyltoluene, 1,3,5

7 Hsieh et al, Sustain Environ Res, 22(1), 1724 (2012) 23 trimethylbenzene, 1,2,4trimethylbenzene, 1,2,3 trimethylbenzene, mdiethylbenzene, and p diethylbenzene Results reveal that aromatics with the highest concentrations at all three heating temperatures included styrene, oethyltoluene, and m diethylbenzene The styrene concentrations measured at both 200 and 230 C were higher than other aromatics and their levels accounted for 5 and 8% of total VOCs, respectively (Table 3) However, the level of m diethylbenzene at 170 C is high than that of styrene Again, for comparison of their significance with temperature, statistical analysis was performed with several characteristics as follows (i) In the case of 170 vs 200 C, none of the fifteen aromatic targets is significant indicating that the variation of aromatic targets at the heating temperature from 170 to 200 C does not differ significantly at p < 005 This fact is different from the variation of alkene or alkene compounds The reason for this difference could be due to higher chemical bond energy in the formation of aromatics compared to alkene or alkene targets (ii) In the case of 170 vs 230 C, only benzene (p = 00017), styrene (p = 00041) and 1,2,4 trimethylbenzene (p = 00299) were significant at p < 005 (iii) In the case of 200 vs 230 C, six aromatics, including benzene (p = 0012), styrene (p = 00028), methyltoluene + pethyltoluene (p = 00093), 1,2,4 trimethylbenzene (p = 00098), and 1,2,3 trimethylbenzene (p = 00322) were significant at p < 005 It is emphasized the importance of different outdoor/indoor environment situations, such as certain changes taking place in the spatial distribution of the cooking fumes During cooking operations, the actual concentration to which persons in kitchen and restaurant workers might be exposed will be lower because certain VOCs may be distributed into an open ambient area Further, reheating of the oil is not recommended as usedoil will contains a higher freefatty acid content and consequently drastically decreases its original smoke point, which results in higher emissions of volatiles at lower temperatures [16] CONCLUSIONS This work reports on measurements of VOCs emitted from the electric oven during roasting pork activities in an indoor environment A total of twelve samples were collected in a research laboratory that simulates a kitchen located in southern Taiwan and analyzed by GCMS for 52 target compounds Total VOC mean concentrations show clear trend of increasing with heating temperature As far as alkane is concerned, the exhaust emitted from higher heating environment had high alkane generation and possible toxicity and the variation of VOC compositions increased with the difference of heating temperatures Such significant changes are attributable to the fact that higher heating operation gives higher chemical reactive energy for VOC generation in the oven As for alkenes, excluding propylene and 1butene, other alkenes in this situation (170 vs 200 C) showed their insignificant differences This trend of alkenes greatly resembles the trend of alkanes in the situation of 170 vs 200 C For aromatics, in the case of 170 vs 200 C, none of the fifteen aromatic compounds is significant Moreover, in the cases of 170 vs 230 C and 200 vs 230 C, benzene, styrene and 1,2,4 trimethylbenzene are significant at p < 005 ACKNOWLEDGEMENTS The authors wish to thank Mr MingCheng Lee, a graduate student from the Department of Environmental Science and Engineering, National Pingtung University of Science and Technology, for helping with the laboratory The authors would like to thank the National Science Council the Republic of China, Taiwan for partially financially supporting this research under Contract No NSC E020006My2 REFERENCES 1 Fullana, A, AA CarbonellBarrachina and S Sidhu, Comparison of volatile aldehydes present in the cooking fumes of extra virgin olive, olive, and canola oils J Agric Food Chem, 52(16), (2004) 2 Fullana, A, AA CarbonellBarrachina and S Sidhu, Volatile aldehyde emissions from heated cooking oils J Sci Food Agric, 84(15), (2004) 3 See, SW and R Balasubramanian, Physical characteristics of ultrafine particles emitted from different gas cooking methods Aerosol Air Qual Res, 6(1), 8292 (2006) 4 See, SW and R Balasubramanian, Chemical characteristics of fine particles emitted from different gas cooking methods Atmos Environ, 42 (39), (2008) 5 Buonanno, G, L Morawska and L Stabile, Particle emission factors during cooking activities Atmos Environ, 43(20), (2009) 6 Seaman, VY, Indoor acrolein emission and decay rates resulting from domestic cooking events Atmos Environ, 43(39), (2009) 7 Dennekamp, M, S Howarth, CA Dick, JW Cherrie, K Donaldson and A Seaton, Ultrafine particles and nitrogen oxides generated by gas and electric cooking Occup Environ Med, 58(8), (2001) 8 Gustafson, P, L Barregard, B Strandberg and G Sallsten, The impact of domestic wood burning on personal, indoor and outdoor levels of 1,3

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