Barbecue Fumes: An Overlooked Source of Health Hazards in

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Barbecue Fumes: An Overlooked Source of Health Hazards in Outdoor Settings? Chen-Chou Wu,†,∥ Lian-Jun Bao,† Ying Guo,‡ Shao-Meng Li,§ and Eddy Y. Zeng*,†,‡ †

State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China ‡ School of Environment and Guangzhou Key Laboratory of Environmental Exposure and Health, Jinan University, Guangzhou 510632, China § Air Quality Research Division, Environment Canada, 4905 Dufferin Street, Toronto, Ontario M3H 5T4, Canada ∥ University of Chinese Academy of Sciences, Beijing 100049, China S Supporting Information *

ABSTRACT: Barbecuing or charcoal-grilling has become part of popular outdoor recreational activities nowadays; however, potential human health hazards through outdoor exposure to barbecue fumes have yet to be adequately quantified. To fill this knowledge gap, atmospheric size-fractioned particle and gaseous samples were collected near an outdoor barbecuing vendor stall (along with charcoal-grilled food items) in Xinjiang of Northwest China with a 10-stage micro-orifice uniform deposit impactor and a polyurethane foam (PUF) sampler and were analyzed for particulate matter and polycyclic aromatic hydrocarbons (PAHs). Exposure to PAHs through inhalation and dermal contact by adult consumers who spent 1 h per day near a charcoal-grilling vendor for a normal meal (lunch or dinner) amounted to a BaP equivalent (BaPeq) dosage of 3.0−77 ng day−1 (inhalation: 2.8−27 ng day−1 of BaPeq; dermal contact: 0.2−50 ng day−1 of BaPeq), comparable to those (22−220 ng day−1 of BaPeq) from consumer exposure through the consumption of charcoal-grilled meat, assumed to be at the upper limit of 50− 150 g. In addition, the potential health risk was in the range of 3.1 × 10−10 to 1.4 × 10−4 for people of different age groups with inhalation and dermal contact exposure to PAHs once a day, with a 95% confidence interval (7.2 × 10−9 to 1.2 × 10−5) comparable to the lower limit of the potential cancer risk range (1 × 10−6 to 1 × 10−4). Sensitivity analyses indicated that the area of dermal contact with gaseous contaminants is a critical parameter for risk assessment. These results indicated that outdoor exposure to barbecue fumes (particularly dermal contact) may have become a significant but largely neglected source of health hazards to the general population and should be well-recognized.

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INTRODUCTION

Eating outside the home increasingly makes up much of diets today for leisure and business. For example, American adults spent approximately 50% of their food expenditures on awayfrom-home foods.12 Street foods, an attractive alternative to home-cooked foods13 that originated in Asia, Latin America, and Africa, have become an integral component of the local food culture in various parts of Europe and North America.14 Apart from street foods, outdoor barbecuing is also a popular event during summer and winter seasons in some parts of Asia, Europe, and North America. A study showed that annually, over 30 000 tons of charcoal are consumed with barbecues in England.15 In North America, propane also has been used as an

There are increased interests worldwide in recognizing the importance of cooking fumes as a source of negative impacts on air quality1 and human health.2,3 Cooking fumes are known to contain substances with mutagenic activity, such as fine particulate matter (PM2.5),4 black carbon, heterocyclic amines,5 and polycyclic aromatic hydrocarbons (PAHs).6 There is ample evidence that cooking fumes are associated with an increased risk of respiratory tract cancer in chefs, bakers, and other foodservice workers.7,8 As of now, many studies have been conducted to assess the significance of personal exposure to airborne particles from indoor sources such as indoor cooking,5,9 which is understandable given that individuals spend the majority of their time in indoor environments. However, only limited information is available about human health risks arising from exposure in outdoor-cooking microenvironments.10,11 © 2015 American Chemical Society

Received: Revised: Accepted: Published: 10607

January 15, 2015 August 2, 2015 August 10, 2015 August 10, 2015 DOI: 10.1021/acs.est.5b01494 Environ. Sci. Technol. 2015, 49, 10607−10615

Article

Environmental Science & Technology important type of fuel.16 Barbecues and street foods are often prepared in residential, commercial, or recreational areas that have insufficient ventilation and poor air circulation.14 Exposure of vendors, consumers, and residents to barbecue-linked pollutants may occur through incidental inhalation or dermal contact with cooking fumes, as well as via ingestion of chemicals absorbed by or deposited onto food. So far, there have been limited measurements of outdoor exposure to barbecue fumes. Particularly, dermal contact is often neglected in assessments of combustion-derived PAHs. To address the above-mentioned knowledge gap, we selected an outdoor barbecuing vendor stall in Urumqi, Xinjiang Uygur Autonomous Region of China as a case study (Figure S1). Such a selection was made on the basis of the fact that charcoal grilling is a prevailing cooking method (Text S1) in this region, and beef and mutton dominate the daily diet for the local ethnic population under Islamic influence.17 Gaseous and particle samples, as well as charcoal-grilled lamb meat samples, were collected and processed. Target pollutants in barbecue fumes and meat include particulate matter (PM) with aerodynamic diameters less than 10 μm (PM10) and less than 2.5 μm (PM2.5) and PAHs, which have been found to occur abundantly in cooking fumes.18 The objectives of the present study were to (1) determine the occurrence of PM2.5, PM10, and PAHs in barbecue fumes; (2) examine the relative importance of inhalation, dermal contact, and food ingestion as the human exposure pathways; and (3) assess the potential human health risk associated with barbecue-fume exposure in outdoor barbecuing settings.

moderately exposed scenarios, and a background site on the rooftop of a five-story building (≈15 m in height) at a horizontal distance of approximately 30 m from the barbecuing stove (Table S1). Samples were collected daily over a three-day period at each site during 12:30−14:30 and 19:30−21:30 (Beijing time) for the exposed sites and 09:30−21:00 (Beijing time) for the background site, which encompassed the lunch and dinner times in Urumqi. Charcoal-grilled lamb-meat samples were also collected from the stall on the last day of the sampling campaign and included kabobs of lamb meat, lamb rib, lamb liver, lamb kidney, lamb intestine, beef back strap, and nan (a specially made bread of local origin). Overall, 88 size-fractioned particle samples, eight gaseous samples, and samples of seven types of stall foods were obtained. Vapor samples (PUFs) were sealed consecutively with plastic zipperclosed bags and lightly vacuumized plastic bags, whereas particle samples were kept in membrane cell holders immediately after sampling. Food samples were first wrapped with aluminum foil and then placed in plastic zipper-closed bags. All samples were cooled with ice during transport to the laboratory and were stored at −20 °C until analysis. Sample Extraction and Instrumental Analysis. Before extraction, the gaseous and particles samples were spiked with the surrogate standards and sonicated twice with 20 mL of hexane, dichloromethane, and acetone mixture (2:2:1 in volume). Each extract was concentrated, solvent-exchanged to hexane, and further concentrated with a Zymark TurboVap 500 (Hopkinton, MA). The concentrated extract was spiked with the internal standards before instrumental analysis. The food sample extracts were purified consecutively with Bio-Beads SX3 and a Florisil column for lipid removal before final concentration. All samples were analyzed with a Shimadzu gas chromatograph coupled to a mass spectrometer (GCMS-2010 Plus). An HP-5MS capillary column (30 m × 0.25 mm i.d. with a 0.25 μm film thickness) was used for chromatographic separation. The column temperature was programmed from 60 °C (initially held for 1 min) and elevated to 200 °C at 10 °C min−1, ramped to 230 °C at 5 °C min−1 (held for 10 min), and further increased to 278 °C at 5 °C min−1 (held for 15 min). All samples were automatically injected (2 μL each) in a programmed temperature vaporizer with an initial temperature of 60 °C and then elevated to 280 °C at 400 °C min−1 (held for 20 min). The carrier gas was ultrahigh-purity helium at a flow rate of 1 mL min−1. The ion source temperature was set at 250 °C. The mass selective detection was conducted in the electron impact mode. Mass spectra were acquired in the full scan mode with an electron impact energy of 70 eV. Quality Assurance and Quality Control. A single procedural blank sample was analyzed for every batch of 20 samples. The recoveries of the surrogate standards, i.e., naphthalene-d8, acenaphthene-d10, phenanthrene-d10, chrysene-d12, and perylene-d12, were 52 ± 8%, 54 ± 6%, 67 ± 12%, 82 ± 8%, and 96 ± 8% in blank samples and 38 ± 12%, 49 ± 11%, 60 ± 10%, 75 ± 13%, and 84 ± 20% in field samples. The average recovery of the target standards in matrix-spiked samples was 78 ± 21%. Concentrations of PAHs in all field samples, except for Nap, Ace, and Acy in particle and food samples that were excluded for further analyses, were corrected (by subtraction) for those detected in the corresponding procedural blanks within the same batch but were not corrected for the surrogate standard recoveries. The lowest calibration concentrations divided by the actual sample volumes were

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MATERIALS AND METHODS Materials. A standard solution including 16 priority PAHs designated by the United States Environmental Protection Agency (USEPA) was purchased from AccuStandard (New Haven, CT); these PAHs are naphthalene (Nap), acenaphthylene (Acy), acenaphthene (Ace), fluorene (Fle), phenanthrene (Phe), anthracene (Ant), fluoranthene (Flu), pyrene (Pyr), benzo[a]anthracene (BaA), chrysene (Chr), benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF), benzo[a]pyrene (BaP), indeno[1,2,3-cd]pyrene (IcdP), dibenzo[a,h]anthrancene (DahA), and benzo[g,h,i]perylene (BghiP), the sum of which is defined as ∑16PAH in the present study. Internal standards (2-fluorobiphenyl, p-terphenyl-d14, and dibenzo[a,h]anthrancene-d14) and surrogate standards (naphthalene-d8, acenaphthene-d10, phenanthrene-d10, chrysene-d12, and perylene-d12) were purchased from Dr. Ehrenstorfer GmbH (Augsburg, Germany). SX-3 Bio-Beads used in gel permeation chromatography were purchased from Bio-Rad Laboratories (Hercules, CA). Sample Collection. Sampling was conducted in August of 2013. Particle samples were collected with a micro-orifice uniform deposit impactor (MOUDI) (MSP Corporation, Shoreview, MN). Each sample was collected on 47 mm diameter glass microfiber filters (Whatman International, Maidstone, England) at a constant flow rate of 30 L min−1 and separated into 11 size fractions: >18, 10−18, 5.6−10, 3.2− 5.6, 1.8−3.2, 1.0−1.8, 0.56−1.0, 0.32−0.56, 0.18−0.32, 0.10− 0.18, and 0.056−0.10 μm. Gaseous samples were collected by a stainless steel unit, which contained polyurethane foam (PUF), connected with the MOUDI.19 Both particle and air samples were collected at two downwind spots approximately 2 and 10 m away from an outdoor-barbecuing stove (≈1.2 m above the ground) at different time points, representative of heavily and 10608

DOI: 10.1021/acs.est.5b01494 Environ. Sci. Technol. 2015, 49, 10607−10615

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Environmental Science & Technology

Table 1. Contents of Particulate Matter (μg m−3), Benzo[a]pyrene (ng m−3), and Airborne Polycyclic Aromatic Hydrocarbons (ng m−3) around a Barbecuing Stove in Urumqi in Summer PM10 background 10 m 2m

80 ± 30 530 ± 180 2600 ± 1700

f

PM2.5

BaP

PAHga

PAHpb

PAHg‑BaPeqc

PAHp‑BaPeqd

PAHg/t‑BaPeqe

50 ± 20 450 ± 170 2400 ± 1700

0.15 ± 0.02 2.2 ± 0.3 8.0 ± 0.8

250 ± 120 1800 ± 830 2900 ± 480

6±2 50 ± 14 320 ± 265

0.4 ± 0.3 2.5 ± 1.4 3.7 ± 1.7

0.2 ± 0.1 2.5 ± 0.5 10 ± 8.7

67% 50% 30%

a

PAHg: gaseous PAHs. bPAHp: particle-bound PAHs. cPAHg‑BaPeq: BaP equivalent (BaPeq) concentration for gaseous PAHs. dPAHp‑BaPeq: BaPeq concentration for particle-bound PAHs. ePAHg/t‑BaPeq: fraction of BaPeq for gaseous PAHs to total of BaPeq for gaseous and particle-bound PAHs. f(A ± B) represents the mean (A) and standard deviation (B).

is the BaPeq concentration of PAHs in food item (ng g−1); IR is the rate of inhalation (IRin, m3 h−1) or daily dietary intake (IRfood, g day−1); tevent is the event time, i.e., the time duration for a day with exposure (h day−1); kp_g is the transdermal permeability coefficient of gaseous compounds (m h−1); SA is the skin surface area (m2); M sa is the exposed dermal fraction; kp_d is the transdermal permeability coefficient of particlebound compounds (m h−1); CSFi is the cancer slope factor of BaP for exposure route i (mg kg−1 day−1)−1 and is agedependent as specified by average body weight; ED is the lifetime exposure duration (year); EF is the exposure frequency, i.e., the number of days with exposure per year (days per year); BW is the average body weight; and AT is the average time for carcinogenic effects (day). Detailed values for these parameters are provided in Tables S2 and S3. Daily exposure was assumed to be 1 h at the charcoal-grilled-barbecue vendor for a normal meal (lunch or dinner), and cancer risk was thus estimated based on an eating-out frequency of once a day. We assessed three exposure scenarios for the age groups of 1−11 years (childhood), 12−17 years (adolescent), and 18−70 years (adulthood). The first scenario was for bystanders, food servers, or local residents who do not consume any charcoalgrilled foods (inhalation and dermal contact only). The second scenario was for people who consume the stalls’ charcoal-grilled foods elsewhere (dietary intake only). The last scenario was for people who consume charcoal-grilled foods at a vendor (inhalation, dermal contact, and dietary intake). Crystal Ball software (version 2000.2, Decisioneering, Denver, CO) was employed to conduct Monte Carlo simulations, each with 10 000 iterations, to generate 2.5 and 97.5 percentiles at a 95% confidence interval for all calculations presented. The procedures of sensitivity analysis are described in Text S2.

defined as the reporting limits for the target compounds, i.e., 50 pg m−3 for MOUDI samples of 4 m3 and 0.2 ng g−1 wet weight for a 10 g food sample. Analyte concentrations below the reporting limits were set to two-thirds of the reporting limits in the assessment of deposition fluxes and health risk. Data Analysis. To estimate the deposition efficiency and flux of inhaled PAHs in the human respiratory tract (HRT), we adopted the International Commission on Radiological Protection (ICRP) model.20 The model calculates the deposition fractions of inhaled particles in four anatomical regions: (1) the extrathoracic region (ET) that includes the nasal passage (ET1), composed of the anterior nose and the posterior nasal passage, and the pharynx (ET2), composed of the larynx and mouth; (2) the bronchial region (BB), combined by the airway from the trachea, main bronchi, and intrapulmonary bronchi; (3) the bronchiolar region (bb), joined by the bronchioles and terminal bronchioles; and (4) the alveolarinterstitial region (AR), the airway from the respiratory bronchioli through the alveolar sacs. The adult breathing rate under light exercise conditions was chosen as 1.5 m3 h−1.20 More details for ICRP-HRT model development and construction are given elsewhere.20,21 Daily intake of PAHs via inhalation (DIig for gaseous PAHs and DIip for particle-bound PAHs) or dietary intake (DIfood) and dermal contact (DIdg for gaseous PAHs and DIdp for particle-bound PAHs) and cancer risk (Risk) were estimated by22−25 DI ig =

∑ (Cg × TEFPAH) × IR in × tevent

(1)

DI ip =

∑ (Cip × TEFPAH) × IR in × tevent

(2)

∑ (Cfood × TEFPAH) × IR food

(3)

DI food = DIdg =

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RESULTS AND DISCUSSION Concentrations of Airborne Particulate Matter and Polycyclic Aromatic Hydrocarbons. Airborne PM and PAHs are the major pollutants generated from cooking processes, with BaP as the individual PAH of greatest health concern.1 As expected, the highest levels of PM10, PM2.5, BaP, and total PAHs were found 2 m from the stove, and the lowest levels at the background site (Table 1 and Tables S3−S5). The concentrations of PM10, PM2.5, and BaP (900−5300 and 700− 4100 μg m−3 and 7.2−8.8 ng m−3, respectively) near the stove exceeded the national ambient air quality standards of China (24 h averages of 150 μg m−3, 75 μg m−3, and 2.5 ng m−3, respectively).26 Furthermore, the concentrations of PM10, PM2.5, and BaP (37−93 μg m−3, 20−60 μg m−3 and 0.13− 0.17 ng m−3, respectively) at the background site were below China’s air quality standards. The concentrations of gaseous and particle-bound PAHs were 2400−3400 and 55−590 ng m−3, 1000−2600 and 40−60 ng m−3, and 130−370 and 4−8 ng m−3, respectively, at distances of 2 and 10 m from the stove and

∑ (Cg × TEFPAH) × k p_g × SA × Msa × tevent (4)

DIdp =

∑ (Cdp × TEFPAH) × k p_d × SA × Msa × tevent (5)

Risk =

∑ (DI i × CSF)i × ED × EF × tevent/(BW × AT) (6)

where TEFPAH is the toxicity equivalency factor of PAH based on BaP; the BaP equivalent (BaPeq) concentration of an individual PAH compound equals the PAH concentration multiplying with its corresponding TEF; Cip is the sum of BaPeq concentrations of size-fractioned particle-bound PAHs distributed in five regions of the human respiratory tract (ng m−3), calculated by the size-fractioned BaPeq concentration of PAHs multiplying the deposition efficiency derived from the ICRPHRT model; Cg and Cdp are the BaPeq concentrations of gaseous and particle-bound PAHs, respectively (ng m−3); Cfood 10609

DOI: 10.1021/acs.est.5b01494 Environ. Sci. Technol. 2015, 49, 10607−10615

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Environmental Science & Technology at background sites. Furthermore, the concentrations of particle-bound PAHs in cooking fumes around the 2 m site were within the same order of magnitude with those inside coal-using houses and in the middle of the range for cooking fuels in indoor environments (Table S6). In general, the data acquired in the present study were consistent with a previous finding that PM emissions from cooking processes were dominated by PM2.5.18 Genotoxicity studies also found that PM1.0−0.56, containing the largest amount of carcinogenic PAHs such as BaP, induced the highest DNAadduct levels.27 Therefore, the relatively high levels of PM and BaP near the charcoal-grill stall stove should be of health concern for vendors and consumers who have regularly cooked or consumed foods near charcoal-grill stoves for extended time durations. Deposition of Particle-Bound Polycyclic Aromatic Hydrocarbons in the Respiratory System. Deposition efficiency (Table S7) and fluxes of particle-bound PAHs in the adult male’s respiratory tract were calculated using measured size-fractioned concentrations of inhaled PAHs and the ICRP model. The deposition fluxes of ∑16PAH were 30−350, 21−44, and 2.5−6.0 ng h−1, respectively, at the 2 m, 10 m, and background sites, with the mean values following the sequence of 2 m (165 ng h−1) > 10 m (41 ng h−1) > background (6.2 ng h−1) (Figure 1). In addition, these deposition fluxes of ∑16PAH were significantly different (t-test, p < 0.05) among the sampling sites.

Figure 2. Deposition flux of size-fractioned particle-bound PAHs in five regions of the human respiratory tract at exposure distances of 2 and 10 m and a background site. The red, yellow, and blue bars represent coarse (aerodynamic diameter (Dp) > 1.8 μm), accumulation mode (1.8 μm > Dp > 0.1 μm), and ultrafine (Dp < 0.1 μm) particles, respectively.

particles.28 Accordingly, the probability of respiratory tract infections related to atmospheric particle-bound PAHs is high for consumers with long-term exposure to barbecue fumes. This result further corroborated the previous views that particle size distribution is a critical factor dictating human inhalation exposure to particle-bound PAHs and related health risk.29,30 Inhalation of Gaseous Polycyclic Aromatic Hydrocarbons. The total BaPeq concentrations in the gaseous and particle phases examined in the present study are summarized in Table 1. The 2 m site had the lowest fraction of gaseous PAHs, i.e., approximately 30−45% of the total BaP eq concentrations (Table 1), probably because fume particles contain abundant heavy PAHs with high toxic equivalency factors.31 However, the gaseous and particle fractions contributed equally to the total BaPeq concentrations at the 10 m site. At the background site, the gaseous PAHs contributed more than 70% of the total BaPeq concentrations. A previous study suggested that approximately 60% of BaPeq concentrations and exposure was attributed to gaseous-phase PAHs for workers of a carbon black manufacturing plant and traffic officers in urban Beijing.32,33 Hence, the importance of exposure to gaseous-phase pollutants through inhalation should be adequately addressed, or human health risk would be underestimated. Uptake of Polycyclic Aromatic Hydrocarbons via Dermal Contact. The total fluxes of ∑16PAH due to dermal contact (0.2−50 ng day−1 of BaPeq, out of which ∼99% was attributed to the uptake of gaseous PAHs) were comparable to or larger than those via inhalation (2.8−26 ng day−1 of BaPeq) (Table 2), similar to what was reported previously.24

Figure 1. Deposition fluxes of particle-bound PAHs in the extrathoracic region (ET), including nasal passage (ET1) and pharynx (ET2), bronchial region (BB), bronchiolar region (bb), and alveolarinterstitial region (AR) of the human respiratory tract at the exposure distances of 2 and 10 m and a background site. Total exposure is the sum of ET, BB, bb, and AR.

Deposition fluxes of ∑16PAH in the regions of ET1, ET2, BB, bb, and AR were 1.1−33, 2.0−50, 0.0−2.2, 0.2−11, and 1.1−92 ng h−1, respectively (Figure 1). Furthermore, the mean deposition flux of ∑16PAH in the AR region at the 2 m site (93 ng h−1) was approximately 4−8 and 66−88 times those at the 10 m (12 ng h−1) and background sites (1.1 ng h−1) (t-test, p < 0.05). Figure 2 and Figure S2 show that more than 90% of the amounts of ∑16PAH deposited in the BB, bb, and AR regions were contributed by fine particles (aerodynamic diameter 10−4 indicates a high risk.48 Thus, the cancer risks for all age groups and three exposure scenarios (10−6) were at least moderate. In particular, the

Commission’s standard for smoked and grilled meat.44 Based on the results from the present study, dietary intake of BaPeq via consumption of popular charcoal-grilled foods in Xinjiang, such as grilled whole lamb and yangrou chuar (lamb kebabs), can be estimated. The daily meat consumption for local residents is approximately 50−150 g, with low consumption of vegetables. If all are charcoal-grilled foods, an upper limit of dietary exposure could be 22−220 ng day−1 of BaPeq for adults. Uncertainty analyses indicated that daily meat consumption (DIfood) had the greatest contribution (>85%) to dietary intake of BaPeq. Generally, diet is the primary source of human exposure to PAHs, contributing to more than 70% of the total exposure to PAHs.45 This is also true in the present study, such that the amounts (50−150 g) of charcoal-grilled meat consumed would lead to the upper limit of the estimated dietary exposure at 22− 220 ng day−1 of BaPeq, substantially greater than the inhalation of airborne PAHs (1.4−16 ng day−1 of BaPeq) and of dermal contact with particle-bound PAHs (