O R I G I N A L A R T I C L E
Risk assessment of inhalation exposure to polycyclic aromatic
hydrocarbons in Taiwanese workers at night markets
Ping Zhao•Kuo-Pin Yu•Chi-Chi Lin
Received: 21 January 2010 / Accepted: 17 May 2010 Ó Springer-Verlag 2010
Abstract
Objective To examine the inhalation exposure of cooks at night markets in Taiwan to PAHs and to estimate the corresponding potential human health risks posed by the inhalation of carcinogenic PAHs.
Methods Eight-hour personal air samples collecting par-ticle-bound PAHs and XAD-2 retaining PAHs in the gas phase were taken by personal PM2.5 cyclones with cooks carrying the sampler on the shoulder while cooking at selected food stalls at four night markets in Taipei, and the concentrations of 16 priority PAHs in both particulates and air were measured with GC/MS.
Results The total identified PAHs in both gas and PM2.5 phases exposed by cooks during cook hours ranged from 233,995 to 44,166 ng m-3. Total exposed PAHs in cooks, as well as the percentage of PAHs in PM2.5, were the highest at the barbecue stall F3. The fractions of gaseous PAHs (97%) in the four food stalls were consistently higher than the fractions of particulate PAHs (3%). The diagnostic ratios of PAHs fell within the range of those found in other
studies related to cooking. At all typical food stalls in night markets except for F2, the excess lifetime cancer risk (ELCR) of cooks are beyond the acceptable target risk range of 10-6 to 10-4 for occupational workers set by USEPA.
Conclusion The PAHs measured in the night markets originated from combustion due to food cooking. The control of gaseous PAH emissions would be more impor-tant than the fractions of particulate PAH emissions. Occupational exposure to cooking emissions in Taiwanese workers at night markets is of health concern. Thus, effective protective measures are therefore suggested to minimize cooks’ exposure to such emissions, such as wearing mask of activated carbon, evacuating the exhaust into water tank with bio-surfactant to improve PAH removal, installing effective mechanical exhaust vacuum or building high exhaust fume hood above cooking ovens. Keywords Night markets PAHs Inhalation exposure Cooks Taiwanese
Introduction
Several studies have investigated the relationship between gas stove cooking and potential health effects, including respiratory ailments and lung cancer (Jarvis et al.1996; Ko et al. 2000). Polycyclic aromatic hydrocarbons (PAHs) were found to be generated during food processing or cooking steps such as roasting, grilling, barbecuing, and smoking (Scientific Committee on Foods of EC2002; See et al.2006).
Taiwan, an island republic with a total land area of 36,000 km2and a population of 23 million, is one of the most popular food paradises in the world. In Taiwan, there P. Zhao
Department of Marine Environmental Engineering, National Kaohsiung Marine University, 142 Haijhuan Road, Nan-Tzu District, Kaohsiung 81157, Taiwan, ROC K.-P. Yu
Institute of Environmental and Occupational Health Sciences & Department of Environmental and Occupational Medicine, National Yang-Ming University, No. 155, Sec. 2, Linong Street, Taipei, Taiwan, ROC
C.-C. Lin (&)
Department of Civil and Environmental Engineering, National University of Kaohsiung, No. 700, Kaohsiung University Rd., Kaohsiung, Taiwan, ROC e-mail: chichilin@nuk.edu.tw
are more than 300 night markets that are popular and famous for offering a wide range of local delicacies and traditional snacks. Night market is a very dense outdoor cooking environment. When the concentrations of cooking contaminants are high, the cooking fumes can be very harmful to both the cooks and the tourists present in the night markets.
Personal inhalation exposures to airborne PAHs have been consistently shown to be dominated by indoor source contributions, since individuals spend most of their time indoors (Li et al. 2003; Zhu and Wang 2003; He et al.
2004; See et al. 2006). However, the impact of outdoor sources on personal exposures, and the potential effects on health, may be especially significant in night markets where ambient (i.e., outdoor) air pollution levels are higher than those typically observed in the cities of the more developed countries. Nevertheless, there have been no field investigations conducted at night markets in Taiwan. Consequently, this study aimed at measuring the exposure of cooks in night markets to PAHs and estimating the potential human health risk posed by the inhalation of carcinogenic PAHs by workers in night markets.
Materials and methods Description of night market
A study of four major night markets in Taipei with high visitor densities was conducted from August 2009 to November 2009. No vehicles or motorcycles were allowed inside the night markets. At N1, there are 25% hotpot (Table1), 30% barbecue, 15% grilling, 10% deep fry, 10% stir fry, and 10% others. They all use LPG except that half of hotpot uses alcohol. At N2, there are 30% hotpot, 25% barbecue, 15% grilling, 15% deep fry, 10% stir fry, and 5% others. They all use LPG. At N3, there are 28% hotpot, 21% barbecue, 20% grilling, 15% deep fry, 11% stir fry, and 5% others. They all use LPG except that about one-third of hotpot uses alcohol (50% ethanol and 50% meth-anol). At N4, there are 33% hotpot, 27% barbecue, 22% grilling, 4% deep fry, 6% stir fry, and 8% others. They all use LPG except that three-fourth of hotpot uses alcohol. The selected night markets have land areas of 5,000– 20,000 m2 with 700–2,300 cooks and service workers. Most cooks (70%) are self-employed and do cooking for their whole life. The rest of cooks (30%) are employed and do cooking as their job. It was estimated that the number of people who patronize these night markets range from hundreds to tens of thousands depending upon weekdays or non-weekdays and holiday or non-holiday seasons.
One food stall was chosen in each night market, which was named as N1–N4, as the sampling site based on
availability investigation of voluntary cooks. These food stalls were labeled as F1, F2, F3, and F4. The character-istics of the four food sites are described in Table1. Because food stalls of hotpot and barbecue are the most common stalls at the selected night markets, F1, F3, and F4 are typical cases at night markets, while F2 is a rare case. All four food stalls had no air-conditioning, nor is any mechanical ventilation employed. The stalls are small and open courted. They all use a movable kitchen with no exhaust fume extractor above stoves. Customer seats and tables are facing or are near to the kitchen. Thus, they experience almost natural ventilation.
Sampling and analytical methods
According to questionnaire survey before our sampling, night markets usually open from 5 p.m. to 1 a.m., so does each food stall. Sixteen PAHs that are regarded as priority pollutants by the USEPA were analyzed, namely naph-thalene (Nap), acenaphthene (Ace), acenaphthylene (Acy), fluorene (Flu), phenanthrene (Phe), anthracene (Anth), fluoranthene (Flt), pyrene (Pyr), benz[a]anthracene (BaA), chrysene (Chr), benzo[b]fluoranthene (BbF), benzo[k]flu-oranthene (BkF), benzo[a]pyrene (BaP), indeno[1,2,3-cd]pyrene (Ind), dibenz[a,h]anthracene (DBahA), and benzo[g,h,i]perylene (BghiP). Small battery-powered pumps (Gilian 5000, Sensidyne Inc., Clearwater, FL, USA) were used to pump air through a personal PM2.5 cyclone (GK2.05, BGI Inc, Waltham, MA, USA) operated at 4 l/min equipped with a Pall Corporation PTFE filter (PTFE, 37 mm, 2.0 lm pore size, Krackeler Scientific Inc., Albany, NY, USA) collecting particle-bound PAHs and XAD-2 retaining PAHs in the gas phase, respectively, and PAHs concentrations in air were the sum concentrations in two phases. The cooks carried the sampler on their shoul-der to simulate the breathing zone as the personal sampling while cooking. And each sample was taken for 8 h (1,920 l/sample) during cooking. PTFE filters and XAD-2s were protected against light during and after sampling by wrapping them in aluminum foil. The samples were taken to the laboratory in a black plastic bag and stored at 0°C before the analyses.
All samples were analyzed within 24 h. Each sample was Soxhelt-extracted in a mixed solvent (n-hexane and dicholoromethane V:V = 1:1, 500 ml each) for 24 h. The extract was concentrated by purging with ultrapure nitro-gen to 2 ml. The collected eluate was further concentrated to 1 ml with ultrapure nitrogen. PAHs contents were determined by using a gas chromatograph (GC) (HP6890, Agilent Technologies Inc. Wilmington, DE, USA) with a mass selective detector (MSD) (HP5973, Agilent Technologies Inc. Wilmington, DE, USA). This GC/MS was equipped with a DB-5MS capillary column
(30 m 9 0.25 mm; 0.25-lm film thickness). The running conditions were splitless injection of 2 ll, split opening after 30 s, and injector temperature of 280°C; the oven temperature program was 50°C (hold 2 min); 50°C to 200°C at 10°C/min (hold 1 min); 200–300°C at 5°C/min (hold 8 min). The detector was run in electron impact mode with electron energy of 70 eV and ion source tem-perature of 230°C. Helium at a constant flow rate of 1.0 ml/ min was used as carrier gas. PAHs were monitored using selected ion-monitoring mode (SIM). The standard of the 16 PAHs was purchased as a mixture of solution (Mix 610-M) from Supelco, USA. The mass of PAHs was quantified using a minimum six-point external calibration curve with minimum correlation coefficients of greater than 0.995 over the course of experiments.
Risk estimation
The hazards identified in this study were PAHs, specifically Nap, BaA, Chr, BbF, BkF, BaP, Ind, and DBahA, which are probable or possible human carcinogens as per Inter-national Agency for Research on Cancer (IARC). IARC Class 3 compounds were not included in the calculations as they are not classifiable according to human carcinoge-nicity (Table2). In this study, it was assumed that exposure to PAHs occurred through inhalation only. Thus, the total carcinogenic risk is estimated by excess lifetime cancer risk (ELCR) and is the sum of excess lifetime cancer risks posed by each and every single PAH 1 to n (ELCRi) (USDOE1999): Ci¼ 8 Cc;iþ 16 Cnc;i 24 ð1Þ ELCR¼X n i¼1 ðCi IURiÞ ð2Þ
where Ci= the mean concentration of each PAH breathed in over the whole day (mg m-3); Cc,i= the concentration of that personal PAH during cooking hours(mg m-3); Cnc,i= the concentration of that personal PAH during non-cooking hours(mg m-3), here Cnc,I= 0 assuming personal exposed PAH concentrations in cooks equals to zero when they are not cooking; IURi= inhalation slope factor
(USDOE1999) (mg m-3)-1. According to the USEPA, a lifetime risk of one in a thousand or greater is considered serious and is a high priority for attention (USEPA1992).
Quality assurance
The same sequential processing steps were also applied to the clean XAD-2 adsorbents in order to measure the background content of native PAHs in adsorbents. All of the background PAH concentrations in the blank tests were below detection limit and deemed as zero. To obtain a general idea of the extent of PAH loss during the pro-cessing steps, an aliquot of l.00 ml of PAH standard mix-ture was spiked into the Soxhelt extractor, processed, and analyzed. The standard mixture contained three compo-nents as follows: naphthalene (2-ring), acenaphthene (3-ring), and pyrene (4-ring). The average recovery per-centages, obtained in triplicate, were 82 ± 4, 89 ± 3, and 95 ± 2 (AM ± ASD, n = 3) for naphthalene, acenaph-thene, and pyrene, respectively.
Results and discussion PAH concentrations
The concentrations of PAHs in gaseous and particulate phases exposed to cooks during cooking hours at four food stalls are reported in Table 3, as well as geometric mean and geometric standard deviation, assuming that the values in food stall distribute log-normally. As can be seen from the table, total summation of 16 identified PAHs levels ranged from 23,399 to 44,166 ng m-3 during cooking hours. Total exposed PAHs in cooks, as well as the per-centage of PAHs in PM2.5, were the highest at the barbecue stall F3 (PM2.5= 287.5 lg m-3, PAHs = 1,021 ng m-3, PAHs/PM2.5= 0.36%), followed by two hotpot food stalls F4 and F1 (PM2.5= 252.3 and 241.6 lg m-3, PAHs = 793 and 741 ng m-3, PAHs/PM2.5= 0.31 and 0.31%), and then food stall F3 (PM2.5= 214.1 lg m-3, PAHs = 480 ng m-3, PAHs/PM2.5= 0.22%). The results of PM2.5are consistent with the study conducted at major Table 1 Features of four food stalls
Fixed sites Types Cooking fuel Way of cooking
F1 Hotpot Liquid petroleum gas Boiling food in soup inside a hotpot F2 Bacon burg Liquid petroleum gas Heating by common gas stove F3 Barbecue Liquid petroleum gas Frying food in oil on a hot frying pan F4 Hotpot Alcohol (50% methanol ? 50% ethanol) Boiling food in soup inside a hotpot F1 to F4: Four food stalls at four night markets
night markets in Kaohisung city (Zhao and Lin 2010) in which barbecue stall was also the worst case among four selected food stalls. Theoretically, the fuel with 50% methanol and 50% ethanol does not generate as much PAHs as that of liquid petroleum gas due to higher and more complicated organic chemical components of liquid petroleum gas. Thus, the little difference in PAH concen-trations measured at two hotpot food stalls was less likely from the cooking fuel. Comparing the food stalls F1, F2, and F3, which use only liquid petroleum gas for cooking, the differences in PAH concentrations were probably from different cooking methods. The barbecue cooking method generally involves higher temperature and uses more oil than the other two methods. This suggests that cooks at barbecue stalls should be paid more attention.
PAH contents were further sorted into five categories according to their chemical structure: two-ringed, three-ringed, four-three-ringed, five-three-ringed, and six-ringed PAHs with their respective vapor pressure (Table2). In general, PAHs with five or more rings have vapor pressure of less than 10-6mm Hg, so that they tend to adsorb to particulates in diameters less than 10 lm (Richter and Howard, 2000). Due to higher vapor pressure than PAHs with five rings, PAHs with two rings mainly stay in gaseous phase, while PAHs containing three to four rings exist in both gaseous and particulate phases. The results show the consistency of
vapor pressure of PAHs and the respective PAH distribu-tions between gaseous and particulate phases (Table3). Of the total analyzed PAHs, 99.9% of the low molecular weight PAHs (2 rings) were in the gaseous phase, 99.6% of PAHs with three rings were in the gaseous phase, 97.9% of PAHs with four rings were in the gaseous phase, while 86.1% of low vapor pressure PAHs (5 rings or more) were in the particulate phases.
It was found that the fractions of gaseous PAHs (97%) in the four food stalls were consistently higher than the fractions of particulate PAHs (3%). Hart and Pankow (1994) reported that the XAD filters would collect both gas and aerosol components efficiently although the PAH concentrations are reported as ‘‘gas phase’’. That is to say that the actual gaseous PAHs would be higher than the reported results in this study. The above result is significant since these lighter PAHs, the most abundant type in the atmosphere at night markets, can react with other pollu-tants to form more toxic derivatives, despite having weaker carcinogenic/mutagenic properties on their own (Tuominen et al.1988; Park et al.2002; Ho et al.2002). For example, the hydroxyl (OH) radical–initiated reactions and nitrate (NO3) radical–initiated reactions often lead to the forma-tion of mutagenic nitro-PAH and other nitropolycyclic aromatic compounds, indicating that health risk assess-ments of combustion emissions should include atmospheric Table 2 Toxicity profiles of PAHs
PAHs IARC groups TEFa IURb/mg-1m3 MW Number of rings Vapor pressure (mm Hg)
Nap 2B 0.001 3.4 9 10-2 128 2 7.80 9 10-2 Acy NR 0.001 NR 152 3 6.70 9 10-3 Ace NR 0.001 NR 154 3 2.15 9 10-3 Flu 3 0.001 NR 165 3 6.00 9 10-4 Phe 3 0.001 NR 178 3 1.20 9 10-4 Anth 3 0.01 NR 178 3 6.00 9 10-6 FLt 3 0.001 NR 202 4 9.20 9 10-6 Pyr 3 0.001 NR 202 4 4.50 9 10-6 BaA 2A 0.1 8.8 9 10-2 228 4 2.10 9 10-7 Chr 3 0.01 8.8 9 10-4 228 4 6.40 9 10-9 BaF 2B 0.1 8.8 9 10-2 252 5 NR BkF 2B 0.1 8.8 9 10-3 252 5 NR BaP 2A 1 8.8 9 10-1 252 5 5.60 9 10-9 DBahA 2A 1 8.8 9 10-1 278 6 NR BghiP 3 0.01 NR 276 6 NR Ind 2B 0.1 8.8 9 10-2 276 6 NR
MW molecular weight, NR non-reported
IARC group 2A probable human carcinogens (IARC1987) IARC group 2B possible human carcinogens (IARC1987)
IARC group 3 not classifiable as to human carcinogenicity (IARC1987)
a Nisbet and LaGoy (1992) b USDOE (1999)
transformation products which were not considered here. Thus, it is suggested that in night markets, control of gaseous PAH emissions would be more important than the fractions of particulate PAH emissions.
Table4 provides information on diagnostic ratios for PAHs, including Phe/Phe ? Ant, Flt/Flt ? Pyr, BaA/ BaA ? Chr, and Ind/Ind ? BghiP, which can be used to investigate their origin or the age of the air samples (Co-tham and Bidleman1995; Lohmann et al.2000; See et al.
2006). This data can help to fully estimate the contribution of anthropogenic emissions. All the diagnostic ratios fall within the range of those found in other studies (Li et al.
2003; He et al.2004; See et al.2006), confirming that the
PAHs measured in the night markets originated from combustion due to food cooking.
Risk assessment
Risk is defined as the probability of injury, disease, or death under specific circumstances. In quantitative terms, risk is expressed in values ranging from zero (representing the certainty that harm will not occur) to one (representing the certainty that harm will occur) (USEPA 1989). To estimate the health risks of PAHs in stall workers at night market, the concentrations of PAHs were compared to the present regulatory standards which aimed at protecting peoples’ health. Exposure to total PAHs is regulated by the National Institute for Occupational Safety and Health (NIOSH) at a recommended exposure limit (REL) of 0.1 mg m-3 for an 8-h time-weighted average (TWA) exposure and by the Occupational Safety and Health Administration (OSHA) at a permissible exposure limit (PEL) of 0.2 mg m-3for a 10-h TWA exposure (USDOL
2007). However, to further understand the associated health Table 3 Concentrations of 16 identified gaseous and particulate PAHs at night markets
PAHs (ngm-3) F1 F2 F3 F4 Gas Particulates PM2.5= 241.6 lg m-3 PM2.5= 214.1 lg m-3 PM2.5= 287.5 lg m-3 PM2.5= 252.3 lg m-3
Gas Particulates Gas Particulates Gas Particulates Gas Particulates GMa GSD GMb GSD Nap 5,360.5 3.6 5,608.3 1.9 5,484.4 10.1 5,546.4 2.3 5,499.1 1.02 3.6 2.10 Acy 4,522.4 2.7 3,076.7 1.0 3,799.5 8.4 2,664.6 2.4 3,445.1 1.26 2.7 2.39 Ace 2,567.4 6.1 2,047.3 4.5 2,307.4 7.6 1,697.6 6.9 2,130.2 1.19 6.2 1.26 Flu 1,371.6 7.8 819.8 5.3 1,095.7 6.3 957.7 8.5 1,042.2 1.24 6.9 1.24 Phe 887.3 14.2 1,137.4 11.9 1,012.4 22.6 1,074.9 17.0 1,023.7 1.11 16.0 1.31 Anth 549.2 4.3 962.3 3.0 755.7 6.7 859.0 4.7 765.3 1.27 4.5 1.39 FLt 1,155.2 36.9 965.0 10.9 6,973.5 59.9 11,395 31.1 3,067.9 3.49 29.4 2.05 Pyr 8,231.7 47.2 8,208.3 29.7 21,614 63.5 3,271.9 50.0 8,314.2 2.16 45.9 1.37 BaA 20.2 103.9 15.9 79.6 18.0 185.2 16.9 119.3 17.7 1.11 116.3 1.42 Chr 19.7 53.3 16.4 39.7 18.3 69.3 16.9 60.5 17.8 1.09 54.6 1.27 BaF 21.0 173.6 15.5 100.8 17.7 200.5 17.1 178.4 17.7 1.14 158.2 1.36 BkF 10.9 57.7 7.9 37.6 7.6 90.1 8.7 61.9 8.7 1.18 59.0 1.43 BaP 6.3 38.7 3.0 26.5 1.6 66.3 4.3 42.4 3.4 1.79 41.2 1.46 DBahA 17.1 23.9 9.2 17.3 10.4 31.4 12.3 26.8 11.9 1.31 24.3 1.29 BghiP 14.9 11.5 11.9 8.8 12.6 15.7 12.5 13.2 12.9 1.11 12.0 1.28 Ind 20.9 155.7 13.7 101.8 15.9 177.6 16.2 167.4 16.5 1.19 147.3 1.29 Total 24,776 741 22,919 480 43,145 1,021 27,572 793 28,668 1.33 733 1.37 Total SIP 25,518 23,399 44,166 28,364 29,409c 1.33d
SIP sum of identified PAHs
a Geometric mean of gaseous PAH concentrations b Geometric mean of particulate PAH concentrations c GM for four total SIP values
d GSD for four total SIP values
Table 4 Molecular diagnostic ratios of PAHs
Diagnostic ratios F1 F2 F3 F4 Mean Phe/Phe ? Ant 0.62 0.54 0.58 0.56 0.57 Flt/Flt ? Pyr 0.13 0.11 0.24 0.77 0.31 BaA/BaA ? Chr 0.63 0.63 0.70 0.64 0.65 Ind/Ind ? BghiP 0.87 0.85 0.87 0.88 0.87
risks with cooking at night market, values of excess life-time cancer risk (ELCR) were calculated according to Eqs.1and2. The food stall F3 (barbecue) had the highest ELCR of 1.13 9 10-4, followed by F4 and F1 (hotpot) of 1.03 9 10-4and 1.01 9 10-4, while F2 (bacon burg) had the lowest ELCR of 0.90 9 10-4, and with a geometric mean of 1.01 9 10-4for four food stalls. According to the PAH standards that we know of, there is no standard related to PAH exposures developed in Taiwan. However, the values of cumulative ELCR except one at food stall F2 are beyond the acceptable target risk range of 10-6to 10-4 for occupational workers set by USEPA (USEPA 1992). Meantime, Menichini (2009) reviewed 16 published stud-ies, which showed mean BaP losses were typically in the 20–55% range, causing underestimates of mean BaP con-centrations in ambient air possibly in the order of 100% during field sampling. As a result, actual risk combining the effects of sampling loss and formation of mutagenic nitro-PAH and other nitropolycyclic aromatic compounds caused by gaseous PAHs may be even higher. Thus, the exposure to PAH in cooks at night market due to cooking is of health concern.
Conclusions
For the first time, emissions of PAHs from selected food stalls in four major Taiwanese night markets were quanti-tatively measured. The average concentrations of PAHs were the highest (SIP = 44,166 ng m-3) at the barbecue food stall showing that effective protection should be used to minimize human exposure to such emissions when barbecue stall is operating. Much higher gaseous PAHs concentrations suggest that the control of gaseous PAH emissions would be more important than the fractions of particulate PAH emissions. The diagnostic ratios of PAHs indicate that the PAHs measured in this study originated from combustion due to food cooking. The excess lifetime cancer risk analysis demonstrates that the occupational exposure to cooking emissions in night markets is of health concern. Thus, there is a need for a comprehensive epi-demiological study to be performed in these workers in order to further quantify the cooking impact on their health. More research efforts are thus needed in order to facilitate formulation of a control strategy and regulations for night markets in Taiwan. Effective protective measures are therefore suggested to minimize cooks’ exposure to such emissions, such as wearing mask of activated carbon, evacuating the exhaust into water tank with bio-surfactant to improve PAH removal, installing effective mechanical exhaust vacuum or building high exhaust fume hood above cooking ovens.
Acknowledgments The authors would like to thank all staff and students for providing assistance in sample collection and instru-mental analysis at night markets. We also gratefully acknowledge the participating cooks at night markets who fully supported this research. Conflict of interest statement The authors have no conflicts of interest.
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