Full Terms & Conditions of access and use can be found at https://www.tandfonline.com/action/journalInformation?journalCode=tfac20 Food Additives & Contaminants: Part A ISSN: 1944-0049 (Print) 1944-0057 (Online) Journal homepage: www.tandfonline.com/journals/tfac20 Occurrence of toluene in Canadian total diet foods and its significance to overall human exposure Xu-Liang Cao, Luc Pelletier, Melissa Sparling & Robert Dabeka To cite this article: Xu-Liang Cao, Luc Pelletier, Melissa Sparling & Robert Dabeka (2018) Occurrence of toluene in Canadian total diet foods and its significance to overall human exposure, Food Additives & Contaminants: Part A, 35:1, 110-117, DOI: 10.1080/19440049.2017.1395520 To link to this article: https://doi.org/10.1080/19440049.2017.1395520 Published online: 31 Oct 2017. 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However, dietary exposures to VOCs can be significant to overall exposures if elevated concentrations of VOCs are present in foods consumed in high amounts and/or on a regular basis, and this was demonstrated in this study with the occurrence data of toluene from the recent 2014 Canadian Total Diet Study (TDS). Concentrations of toluene in the composite samples of most food types from the 2014 TDS are low and similar to the results from the previous 2007 TDS with some exceptions, such as beef steak (670 ng/g (2014 TDS) vs. 14 ng/g (2007 TDS)), poultry, chicken and turkey (307 ng/g (2014 TDS) vs. 8.8 ng/g (2007 TDS)). Toluene concentrations in most of the grain-based and fast food composite samples from the 2014 TDS are considerably higher than those from the 2007 TDS, with the highest level of 4655 ng/g found in the composite sample of crackers from the 2014 TDS (compared to 18 ng/g from 2007 TDS). Dietary exposure estimates for toluene based on the occurrence results from the 2014 TDS show that for most of the age groups, grain-based foods are the primary source, accounting for an average of 77.5% of the overall toluene intake from the diet. The highest dietary exposures to toluene were observed for the adult age groups, with estimated average exposures ranging from 177.4 to 184.5 µg/d. Dietary exposure estimates to toluene are well below oral doses associated with toxicological effects and also below the maximum estimated intake (819 µg/d) from air inhalation for adult group (20 – 70 years) based on the results from CEPA (Canadian Environmental Protection Act) assessment in 1992. ARTICLE HISTORY Received 13 July 2017 Accepted 29 September 2017 KEYWORDS VOCs; toluene; total diet; food; headspace; SPME; GC-MS Introduction Volatile organic compounds (VOCs) are ubiquitous in the environment due to evaporation and incom- plete combustion of fuels, use of consumer and personal care products, tobacco smoke, etc. As a result of their presence in the environment, low levels of VOCs may be found in foods. Some VOCs found in foods can also be from the proces- sing and preparation of foods, such as benzene formed by the reaction of benzoate salt with ascorbic acid (US FDA 2015), and from food packaging due to migration, such as styrene from polystyrene food packaging and containers (Durst and Laperle 1990; Lickly et al. 1995). Some VOCs are toxic; for exam- ple, benzene is a well-known human carcinogen (IARC 1987), while others may be less toxic but still a health concern at high levels; for example, exposure to toluene at high levels can cause head- aches, dizziness, feeling of intoxication, and irrita- tion to eye, nose and throat (Health Canada 2011). Levels of most VOCs in foods are usually low because of their volatility, thus human exposure to VOCs is expected to be mainly via inhalation of ambient and indoor air. This may not be necessarily true for VOCs found at high levels, especially in foods with high consumption rates; dietary intakes of VOCs in this case could be approaching, if not higher than, intakes from air inhalation, and thus become significant for overall human exposure. However, this has not been demonstrated previously. The Canadian Total Diet Study (TDS) has been ongoing since 1969 to monitor various chemical con- taminants in the Canadian food supply and plays an important role in generating occurrence data for human exposure assessments. For the first time CONTACT Xu-Liang Cao xu-liang.cao@canada.ca Food Research Division, Bureau of Chemical Safety, Health Canada, AL: 2203D, Ottawa, Ontario, Canada, K1A 0K9 FOOD ADDITIVES & CONTAMINANTS: PART A, 2018 VOL. 35, NO. 1, 110–117 https://doi.org/10.1080/19440049.2017.1395520 © 2018 Informa UK Limited, trading as Taylor & Francis Group http://orcid.org/0000-0002-8094-062X http://www.tandfonline.com http://crossmark.crossref.org/dialog/?doi=10.1080/19440049.2017.1395520&domain=pdf various food samples from the 2007 TDS were ana- lysed for 13 VOCs using a GC-MS method based on headspace and solid phase microextraction (SPME), and some VOCs were detected at relatively high levels (Cao et al. 2016). In the follow-up study, VOCs were analysed in 159 different composite food samples from the more recent 2014 TDS; toluene was detected in many foods, especially the highly consumed grain- based foods, at much higher levels than those from previous 2007 TDS and also from studies in the United States (140 – 456 ppb) (Fleming-Jones and Smith 2003) and Belgium (71.8 µg/kg) (Vinci et al. 2015). Thus, its results were selected in this study to estimate exposure from foods to demonstrate the significance of dietary exposures relative to the overall human exposures to toluene. Materials and methods Reagents and materials Sodium chloride (>99.0%) was obtained from VWR (Mississauga, Ontario, Canada). The following che- micals were purchased from Sigma-Aldrich (Mississauga, Ontario, Canada): toluene-d8 (99.8%) and other labelled VOC standards, methanol (99.8%), and EPA VOC Mix 2 in methanol contain- ing toluene and other VOCs at 2000 µg/mL. The 100 µm polydimethylsiloxane (PDMS) SPME fibre was purchased from Supelco (Bellefonte, PA, USA). The 20-mL SPME crimp clear glass vials were pur- chased from Labsphere (Quebec, Canada). Details for preparation of the standard solutions of VOCs can be found elsewhere (Cao et al. 2016). Briefly, a stock composite standard solution of deuterated VOCs was prepared in methanol at a concentration of 100 ng/µL. Composite standard solutions in metha- nol with deuterated VOCs at ca. 2 ng/µL and native VOCs at different concentrations (ca. 0, 0.2, 1, 3, 5, 8, and 10 ng/µL) were prepared by adding 200 µL stock solution of deuterated VOCs (100 ng/µL) and 0, 1, 5, 15, 25, 40, and 50 µL EPA VOC Mix 2 to 10 mL methanol. Composite standard solutions in water with deuterated VOCs at ca. 4 ng/mL and native VOCs at different concentrations (ca. 0, 0.4, 2, 6, 10, 16, and 20 ng/mL) were prepared by adding 20 µL stock solutions of deuterated VOCs (2 ng/µL) and native VOCs (0, 0.2, 1, 3, 5, 8, and 10 ng/µL) to 10 mL water. All solutions were stored at 4°C. Sample collection and preparation A total of 636 (159 × 4) food samples were collected from four different stores in Winnipeg, Canada, over a five week period in 2014. The foods were prepared (include cooking) as for consumption according to the established procedures (Dabeka and Cao 2013), and individual samples of each type of food were combined into a total of 159 different food compo- sites. Composites for foods that can be consumed both raw and cooked (e.g. cauliflower, carrots, broc- coli, tomatoes, spinach) were prepared as a mixture of the raw and cooked (1:1). The food composites covered a variety of food categories including dairy products, meat, poultry, fish, cereal, vegetable, fruit, beverage, and other miscellaneous foods. As part of the standard preparation procedures, kitchen staffs do not use any perfumes, hair spray, cologne, fra- grant soap, make-up or talcum powder. Stainless steel or glass vessels were used for all processing. Drinking water was used for food processing. Food composites were stored frozen in 250-mL glass jars at −20°C until analysis. About 5 g of NaCl (pre-heated at 650°C overnight and then stored at 200°C) was weighed into a 20-mL clear glass vial pre-cooled at 4°C. For most of the samples, about 1 g of sample was weighed into the 20-mL vial, but smaller amounts were weighed for samples containing fat due to matrix effects. The sample was spiked with internal standard solution, followed by adding 10 mL of deionised water. The vial was capped and then vortexed for 10 – 15 s to speed up dissolution of NaCl and mixing of the sample with water. All vials containing samples were placed on a metal tray, cooled with ice and samples were spiked within 15 s to minimise any loss of target compounds during sample preparation. Headspace solid phase microextraction and instrument conditions An Agilent 6890 gas chromatograph (GC) coupled to a 5973 mass selective detector (MSD) was used for analysis. The GC-MSD was equipped with a MultiPurpose Autosampler (MPS 2) from Gerstel (Baltimore, MD, USA), set-up in SPME operation mode. At the beginning of analysis, the sample vial was transported from the tray to the agitator held at 30°C. After incubating for 1 min, the PDMS SPME FOOD ADDITIVES & CONTAMINANTS: PART A 111 fibre was inserted through the septum into the head- space. Vial penetration depth was set at 25 mm. Agitation speed was set at 250 rpm. After extraction for 10 min, the SPME fibre was inserted into the GC injector fitted with a 0.75 mm I.D. liner for deso- rption. The injector temperature was set at 250°C. Injection penetration depth was set at 65 mm, and the SPME fibre was desorbed for 5 min in splitless mode. Analytes were separated on a DB-624 capil- lary column (60 m × 0.25 mm × 1.4 µm, Agilent Technologies). The GC oven temperature program was set at an initial temperature of 50°C for 5 min, raised to 250°C at 15°C/min, and held for 5 min. The flow rate of the helium carrier gas was 1.2 mL/min. The MSD was operated with electron impact ioni- sation in selected ion monitoring (SIM) mode. The ions selected for the native and labelled VOCs can be found elsewhere (Cao et al. 2016); they were m/z 91 and 92 for toluene, and 98 for toluene-d8. The GC- MSD interface and the MS system source tempera- ture were 250 and 230°C, respectively. Quantitation and quality control The calculation of concentrations in samples was based on the isotope dilution method. Confirmation of compound identity was based on the retention time and the ion ratio of the analytical standard. For each batch of analysis, each sample was analysed in four replicates, two of which were spiked with both native and deuterated VOCs to check accuracy, and the other two were spiked with deuterated VOCs only to deter- mine VOC concentrations in the sample. Three blank samples (water) were also included in each batch. Some VOCs were not detected in blanks, blank levels of other VOCs were low, 1.6 ng for toluene. Results of all samples were corrected for method blanks. New PDMS SPME fibre was initially cleaned by heating at 260°C for 30 min prior to use. This fibre was also cleaned after analysis of each sample by heating in the injector (250°C) for an additional 5 min after desorption of the exposed fibre. Carryover was not observed. Dietary intake estimates Dietary intakes of toluene for different age-sex groups of children and adults were calculated by multiplying the average concentration of toluene in a food composite by the average per capita con- sumption rate of that food product for various age groups, obtained from the 2004 Canadian Community Health Survey (CCHS), Cycle 2.2 (Statistics Canada 2004). The total toluene exposures for each age category were then calculated by sum- ming the individual intakes from each food compo- site. Estimates were converted to a body weight basis using measured and self-reported body weight data from the 2004 CCHS. Results and discussion The headspace SPME GC-MS method has been vali- dated for toluene and other VOCs previously (Cao et al. 2016). Linearity of the instrument and the headspace SPME method was demonstrated using six standard solutions (0.4 – 20 ng/mL) and R2 values were better than 0.999 for the calibration plots of toluene. The average recoveries for toluene were 102 ± 0.22% for water spiked at 5 ng/ml, and 101 ± 0.48% for water spiked at 20 ng/ml. Since toluene was detected in method blanks, at about 1.6 ng, the method detection limit (MDL) for toluene was calculated as 10 times the standard deviation of method blanks and also 10 times the signal-to-noise ratio for each food sample, and the higher value was taken as the MDL for toluene in this food sample. The MDLs of toluene for the 159 different food composite samples ranged from 0.030 to 1.9 ng/g with an average of 0.31 ng/g. Among the various VOCs analysed for the 159 different composite food samples, toluene was deter- mined to be the most significant with respect to potential dietary exposure as it was most frequently detected at relatively higher concentrations (in 146 of the 159 food composite samples, or 91.8%). Table 1 depicts the toluene concentrations in the various food composite samples from the 2014 TDS with a comparison to the results previously obtained in samples from the 2007 TDS (Cao et al. 2016). Each result is the average of two replicate analyses with the average relative standard deviation of 6.6%. Table 2 demonstrates the percentile distri- butions of toluene concentrations in the 2014 TDS composite food samples. Concentrations of toluene in the composite sam- ples of most food types from the 2014 TDS are low and similar to the results from the 2007 TDS with 112 X.-L. CAO ET AL. Table 1. Concentrations (ng/g) of toluene in food composite samples from 2007 and 2014 TDS. Food Composite Concentration (ng/g) Food Composite Concentration (ng/g) 2014 TDS 2007 TDS 2014 TDS 2007 TDS Dairy Fruit Milk, whole 3.2 4.2 Applesauce, canned < 0.027 1.7 Milk, 2% 3.1 3.6 Apples, raw 0.50 1.6 Milk, 1% 2.5 2.1 Bananas 0.16 <2.1 Milk, skim 1.9 1.6 Blueberries 1.5 4.3 Evaporated milk, canned 2.3 3.5 Cherries 0.24 <2.1 Cream 2.1 7.3 Citrus fruit, raw 5.0 <2.1 Ice cream 4.6 12 Grapes 0.20 <2.1 Yogurt 40 2.9 Melons 0.16 <2.1 Cheese 23 12 Peaches 0.79 <2.1 Cheese, cottage 0.88 4.0 Pears 1.0 <2.1 Cheese, processed 6.9 12 Pineapple, canned 0.33 1.7 Butter 23 54 Plums and prunes 4.7 2.2 Chocolate milk, 1% 1.3 2.3 Raisins 1.3 1.1 Butter milk, 1% < 0.09 2.1 Raspberries 3.7 19 Meat Strawberries 1.1 0.76 Beef, steak 670 14 Kiwi fruit 0.82 4.4 Beef, roast 42 8.2 Apricot 4.4 1.4 Beef, ground 15 14 Fat and oil Pork, fresh 12 10 Cooking fats & salad oils 13 20 Pork, cured 3.9 12 Margarine 8.5 17 Veal, cutlets 123 13 Mayonnaise 3.9 6.3 Lamb 24 12 Salad dressing 10 na Luncheon meats, cold cuts 14 13 Beverage Luncheon meats, canned 6.5 12 Alcoholic drinks, beer < 0.027 0.18 Organ meats 3.5 14 Alcoholic drinks, wine 0.17 0.51 Wieners & sausages 6.6 12 Coffee 11 0.77 Poultry Soft drinks, canned 0.46 2.6 Eggs 6.3 8.6 Tea 8.1 0.77 Poultry, chicken & turkey 307 8.8 Soy beverage, fortified < 0.0903 2.2 Poultry, liver pate 15 75 Fruit drinks (cocktails) 0.75 na Fish Apple juice, canned < 0.027 1.4 Fish, marine 7.5 17 Citrus juice, frozen 0.38 1.3 Fish, fresh water 0.77 11 Citrus juice, canned 0.42 0.68 Fish, canned 132 10 Grape juice, bottled < 0.09 0.57 Shellfish 20 25 Tap water, kitchen 0.16 0.78 Soup Tap water, sample area 0.32 0.80 Soups, meat, canned 20 1.5 Water, natural spring < 0.027 0.73 Soups, creamed, canned 21 2.8 Water, natural mineral < 0.027 <0.089 Soups, broth, canned 13 1.2 Baby food Soups, dehydrated 0.37 1.8 Cereals, mixed 11 4.7 Cereal Desserts 3.1 1.4 Bread, white 175 7.0 Dinners, cereal + vegetable + meat 3.1 3.7 Bread, whole wheat 1974 7.8 Dinners, meat or poultry + vegetable 3.7 3.3 Bread, rye 635 6.4 Formulae, milk base 5.1 6.3 Cake 8.3 14 Formulae, soya base 0.27 2.5 Cereal, cooked wheat 14 2.4 Fruit, apple or peach 3.8 1.3 Cereal, corn 53 7.2 Meat, poultry or eggs 17 22 Cereals, oatmeal 39 3.1 Vegetables, peas 8.0 4.0 Cereals, rice & bran 804 7.7 Fast food Cookies 269 19 Popcorn, microwave 482 55 Crackers 4655 18 Frozen entrees 27 6.7 Danish, donuts & croissants 329 12 Pizza 32 12 Flour, white (wheat) 1830 9.1 French fries 25 5.2 Muffins 73 13 Hamburger 290 15 Pancakes & waffles 27 8.8 Chicken burger 37 29 Pasta, mixed dishes 38 6.7 Hot dogs 100 20 Pasta, plain 190 4.4 Chicken nuggets 249 27 Pie, apple 302 15 Beef chow mien, carry-out 2.3 20 Pie, other 87 25 Fried rice (Chicken and veg) 4.3 na Rice 37 5.6 Prepared Breakfast sandwiches 6.8 na Buns & rolls 681 6.5 Fast food sandwiches 8.1 na Breads, other 4.2 4.0 Others Vegetable Chocolate bars 21 59 Baked beans, canned 12 2.9 Candy 2.4 3.1 Beans, string 10 0.87 Gelatine dessert 0.17 2.1 Beets 0.31 1.1 Honey, bottled 0.30 2.5 Broccoli 0.67 2.8 Jams 0.67 3.6 Cabbage 3.0 1.8 Peanut butter 30 28 Carrots 0.35 2.5 Puddings 2.5 2.8 (Continued ) FOOD ADDITIVES & CONTAMINANTS: PART A 113 some exceptions, such as yogurt (40 ng/g (2014 TDS) vs. 2.9 ng/g (2007 TDS)), beef steak (670 ng/ g (2014 TDS) vs. 14 ng/g (2007 TDS)), veal cutlets (123 ng/g (2014 TDS) vs. 13 ng/g (2007 TDS)), poultry, chicken and turkey (307 ng/g (2014 TDS) vs. 8.8 ng/g (2007 TDS)), canned fish (132 ng/g (2014 TDS) vs. 10 ng/g (2007 TDS)), corn chips (177 ng/g (2014 TDS) vs. 20 ng/g (2007 TDS)). Toluene concentrations in most of the grain-based and fast food composite samples from the 2014 TDS are considerably higher than those from the 2007 TDS, with the highest level of 4655 ng/g found in the composite sample of crackers from the 2014 TDS (compared to 18 ng/g from 2007 TDS). Toluene concentrations in the grain-based foods from the 2014 TDS are also much higher than those in grain-based products reported from studies in the United States (140 – 456 ppb) (Fleming-Jones and Smith 2003) and Belgium (71.8 µg/kg) (Vinci et al. 2015). The high concentrations of toluene in breads (175 – 1974 ng/g), buns and rolls (681 ng/g), and some fast foods are consistent with the high concen- tration (1830 ng/g) in flour samples from the 2014 TDS. It is not clear why the concentrations of toluene in most of the grain-based products from the 2014 TDS are so different from those of the 2007 TDS or those reported from studies conducted in other countries. Toluene is a common aromatic hydrocarbon pollutant in air and its relatively high concentrations in grain-based foods may be related to air pollution and deposition of air particulates on crops. Food samples from the 2007 TDS and 2014 TDS were collected from two different locations, Vancouver and Winnipeg, respectively. It is not clear whether the grain-based food samples collected at these two loca- tions were from imported or locally grown products, or whether the grains were cultivated in an area with air and air particulate matter high in toluene concen- tration. However, the limited number of samples with elevated toluene concentrations and the lack of con- sistency of elevated toluene concentrations in samples from different years and different cities, suggest that elevated concentrations of toluene in foods are not chronically occurring at a concerning rate. With respect to results from the 2014 TDS only, since grain-based products are highly consumed Table 1. (Continued). Food Composite Concentration (ng/g) Food Composite Concentration (ng/g) 2014 TDS 2007 TDS 2014 TDS 2007 TDS Cauliflowers 0.47 1.7 Sugar, white 0.18 0.84 Celery 0.18 1.7 Syrup 4.1 1.4 Corn 1.2 2.7 Seeds, shelled 15 50 Cucumbers 15 2.0 Nuts 24 na Lettuce 0.13 0.94 Chewing gum 60 81 Mushrooms 18 1.5 Condiments 5.6 8.4 Onions 0.26 1.0 Salt 0.22 0.50 Peas 0.90 2.4 Baking powder 0.90 2.4 Peppers 0.50 2.8 Yeast 6.1 9.1 Potatoes, peeled and boiled 0.26 2.5 Vanilla extract 0.52 0.89 Potatoes, chips 130 84 Herbs and spices 125 157 Rutabagas 0.63 1.3 Soya sauce < 0.027 0.63 Vegetable juice, canned 13 2.5 Tomatoes 1.4 1.1 Tomatoes and tomato sauce, canned 1.6 2.9 Spinach 0.37 1.9 Asparagus 0.26 1.4 Brussel sprouts 0.84 5.3 Potatoes, baked with skins 0.43 1.2 Corn chips 177 20 na: not available Table 2. Percentile distribution of toluene concentrations (ng/g) in food composite samples from the 2014 TDS. Percentile Concentrations, ng/g Minimum 0.13 10th 0.30 20th 0.61 30th 1.3 40th 3.7 50th 6.5 60th 12 70th 21 80th 41 90th 187 95th 467 99th 1915 Maximum 4655 114 X.-L. CAO ET AL. foods by most of the age groups of the population, high toluene concentrations in these types of foods may increase dietary exposures to toluene. In order to investigate its significance to overall human expo- sure, average dietary exposures to toluene were esti- mated for different age-groups based on per capita food consumption data from the 2004 CCHS, Cycle 2.2 (Statistics Canada 2004) and are shown in Table 3. Dietary exposures to toluene based on 2007 TDS results were also calculated as a compar- ison and summarised in Table 3. The percent of toluene exposure from different food groups to the total dietary exposures to toluene was also calculated for different age groups, and the results are shown in Table 4 and Table 5. It can be seen that dietary intakes of toluene based on 2014 TDS results are considerably higher than those based on 2007 TDS for all age groups. For 2014 TDS, the highest dietary exposures for toluene were observed in the adult age groups (18+ years) with exposure estimates ranging from 177.1 to 184.5 µg/d. However, on a body weight basis, highest exposure estimates were calcu- lated for young children (8.1 µg/kg body weight/d for children 2–3 years of age). For children 6 to 11 months, dietary exposures of toluene are mainly from dairy, baby food, and grain-based foods, accounting for approximately 12.0%, 30.4%, and 48.2% of the total dietary exposures of toluene, respectively. For the other age groups, grain-based foods are the primary source of dietary intake for Table 3. Average dietary exposures to toluene for different age groups based on results from 2007 and 2014 TDS. Age groups Dietary exposures (2014 TDS) Dietary exposures (2007 TDS) µg/day µg/kg body weight/day µg/day µg/kg body weight/day 6–11 months 15.3 2.2 9.7 1.4 1 year 88.6 5.9 6.7 0.45 2 – 3 years 121.8 8.1 8.4 0.56 4 – 8 years 158.3 6.3 9.2 0.37 9–13 years 169.3 3.8 11.2 0.25 14–18 years 174.8 2.9 12.5 0.21 19–30 years 177.1 2.5 11.8 0.17 31–50 years 184.5 2.6 11.9 0.17 51–70 years 177.5 2.5 10.7 0.15 71+ years 184.5 2.6 9.3 0.13 Table 4. Percent (%) of toluene exposures from different food groups relative to the total dietary exposures of toluene for different age groups from 2014 TDS. Age groups Food groups Dairy Meat Poultry Fish Soup Grain-based Vegetable Fruit Fat Beverage Baby food Fast food Others 6–11 months 12.0 0 8.3 0 0 30.4 0.15 0.24 0 0 48.2 0 0.67 1 year 3.6 0.74 6.9 0.72 0.63 85.0 0.43 0.36 0.049 0 1.0 0.34 0.22 2 – 3 years 2.8 1.8 5.4 0.55 0.84 85.8 0.75 0.32 0.068 0.083 0.73 0.59 0.34 4 – 8 years 2.0 1.9 4.9 0.55 0.48 87.8 0.89 0.23 0.080 0.14 0.0092 0.71 0.37 9–13 years 1.8 2.1 7.2 0.61 0.81 84.0 1.3 0.23 0.11 0.26 0 1.1 0.46 14–18 years 1.7 3.0 8.3 0.62 0.72 81.8 1.4 0.20 0.14 0.73 0 0.86 0.50 19–30 years 1.7 3.4 9.3 0.72 0.77 79.3 1.2 0.21 0.15 1.9 0 0.82 0.51 31–50 years 1.4 4.4 8.5 1.3 0.83 77.7 1.1 0.20 0.14 3.2 0 0.70 0.49 51–70 years 1.3 3.5 7.5 1.7 0.92 79.1 1.1 0.25 0.13 3.6 0 0.55 0.41 71+ years 1.0 2.3 5.3 1.4 1.2 84.4 0.62 0.23 0.091 3.0 0 0.15 0.30 Table 5. Percent (%) of toluene exposures from different food groups relative to the total dietary exposures of toluene for different age groups from 2007 TDS. Age groups Food groups Dairy Meat Poultry Fish Soup Grain-based Vegetable Fruit Fat Beverage Baby food Fast food Others 6–11 months 10.7 0 0.38 0 0 2.1 0.34 0.60 0 0 83.3 0 2.7 1 year 37.1 5.3 3.5 2.3 1.2 17.1 4.5 7.2 0.96 0.54 13.7 0.51 6.1 2 – 3 years 31.0 7.2 3.7 1.9 1.7 19.1 6.7 5.1 1.4 1.1 10.9 0.98 9.1 4 – 8 years 28.4 10.8 3.5 2.7 1.2 22.6 9.5 4.9 1.8 2.0 0.15 1.4 11.0 9–13 years 24.5 10.9 4.3 2.7 1.7 20.0 11.3 4.8 1.9 3.5 0 1.9 12.5 14–18 years 22.0 12.6 4.5 2.5 1.4 18.5 11.8 3.1 2.0 6.8 0 1.4 13.4 19–30 years 18.0 11.8 5.5 3.6 1.6 18.8 11.6 3.7 2.3 7.6 0 1.4 14.1 31–50 years 16.0 13.0 5.5 5.7 1.8 17.5 11.5 4.6 2.3 7.4 0 1.3 13.4 51–70 years 15.3 12.7 5.4 7.6 2.1 16.8 12.1 5.9 2.5 7.3 0 1.0 11.4 71+ years 17.5 11.6 4.7 7.6 3.2 20.4 10.5 6.0 2.2 5.9 0 0.33 10.2 FOOD ADDITIVES & CONTAMINANTS: PART A 115 toluene, accounting for 77.7 – 87.8% of the total dietary exposures to toluene,while for 2007 TDS, grain-based foods only account for 2.1 – 22.6% of the total dietary exposures to toluene. It is noted that these estimates are based solely on toluene concen- trations from a single TDS year (2014) and therefore exposure estimates are not likely representative of long-term exposures. It is also noted that summing exposure estimates from each food based on average per capita food consumption data is expected to overestimate average daily dietary exposures to toluene. When summing average per capita food consumption rates, the estimated total amount of food consumed for each age group is more than the 90th percentile of expected total food consumed in a day. Exposure estimates based on the 2014 TDS results, where elevated toluene concentrations in grain-based foods were observed, are well below the chronic oral reference dose of 80 µg/kg bw per day derived by the United States Environmental Protection Agency (U.S. EPA 2005). Toluene is a common air pollutant, and indoor air levels are generally higher than ambient air levels due to indoor sources such as building materials and consu- mer products, thus Canadians’ exposure to toluene is attributed predominantly to indoor air (Health Canada 2011). Based on the median concentrations of toluene in Canadian residences (5.5 – 24.7 µg/m3) (Zhu et al. 2005; Health Canada 2011) and the average inhalation rates for the age groups of 21 – <31 years (15.7 m3/d), 31 – <41 years (16.0 m3/d), 41 – <51 years (16.0 m3/d), and 51 – <61 years (15.7 m3/d) (US EPA 2011), toluene exposures from indoor air for the age group of 21 – <61 are estimated to be 87.2 – 391.5 µg/d. Estimated expo- sures based on the average concentrations of toluene in Canadian residences (11.5 – 34.4 µg/m3) range from 182.3 to 545.2 µg/d (Zhu et al. 2005; Health Canada 2011). Results from this study indicate that dietary exposure to toluene may be within the range of expo- sures from inhalation based on median toluene air concentration and approach the low-end inhalation exposures based on average toluene air concentrations. While toluene exposures from inhalation are still expected to exceed oral exposures from food consump- tion on a long-term basis, toluene exposures from food could occasionally approach those from inhalation. Therefore, elevated occurrences of toluene in highly consumed foods may contribute a non-negligible pro- portion of the overall exposures to toluene. In summary, relatively high concentrations of toluene were found in some of the grain-based food samples from the 2014 TDS, although in com- parison, results from the 2007 TDS for the same food samples indicate much lower toluene concen- trations. Estimated dietary exposures to toluene based on the results of the 2014 TDS indicate that grain-based foods are the primary source for most age groups of the population. However, overall dietary intakes for toluene are well below any oral dose associated with toxicological effects and also below the maximum estimated intake (819 µg/d) from air inhalation for adult group (20 – 70 years) based on the results from CEPA (Canadian Environmental Protection Act) assessment in 1992 (Government of Canada 1992). Exposure estimates also demonstrate that occasional oral exposures to toluene may approach those estimated from inhala- tion, which is considered the primary source of overall exposure. This is most likely to be the case when relatively high concentrations of toluene are observed in highly or frequently consumed foods. Monitoring of VOC concentrations in total diet samples of other years and different locations should continue in order to investigate possible temporal trends and identify potential sources in foods. Acknowledgment Xu-Liang Cao would like to thank Gurmit Singh (Health Canada) for reviewing the manuscript. The authors also thank the Canadian Food Inspection Agency for the col- lection of the individual food items, Karen Pepper (Health Canada) for coordination of the total diet study and Masresha Asrat (Health Canada) for sample allocation. Disclosure statement No potential conflict of interest was reported by the authors. ORCID Xu-Liang Cao http://orcid.org/0000-0002-8094-062X 116 X.-L. CAO ET AL. References Cao X-L, Sparling M, Dabeka R. 2016. Occurrence of 13 volatile organic compounds in foods from the Canadian total diet study. Food Addit Contam Part A. 33:373–382. Dabeka R, Cao X-L. 2013. The Canadian total diet study design: 1992-1999. Food Addit Contam Part A. 30:477–490. 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FOOD ADDITIVES & CONTAMINANTS: PART A 117 http://www.hc-sc.gc.ca/ewh-semt/pubs/contaminants/psl1-lsp1/toulene/index-eng.php http://www.hc-sc.gc.ca/ewh-semt/pubs/contaminants/psl1-lsp1/toulene/index-eng.php http://healthycanadians.gc.ca/publications/healthy-living-vie-saine/toluene/alt/toluene-eng.pdf http://healthycanadians.gc.ca/publications/healthy-living-vie-saine/toluene/alt/toluene-eng.pdf http://www.inchem.org/documents/iarc/suppl7/benzene.html http://www.inchem.org/documents/iarc/suppl7/benzene.html http://www23.statcan.gc.ca/imdb/p2SV.pl?Function=getSurvey%26SDDS=5049%26lang=en%26db=imdb%26adm=8%26dis=2 http://www23.statcan.gc.ca/imdb/p2SV.pl?Function=getSurvey%26SDDS=5049%26lang=en%26db=imdb%26adm=8%26dis=2 http://www23.statcan.gc.ca/imdb/p2SV.pl?Function=getSurvey%26SDDS=5049%26lang=en%26db=imdb%26adm=8%26dis=2 https://www.epa.gov/foia/toxicological-review-toluene-cas-no-108-88-3-pdf https://www.epa.gov/foia/toxicological-review-toluene-cas-no-108-88-3-pdf https://ofmpub.epa.gov/eims/eimscomm.getfile?p_download_id=526167 https://ofmpub.epa.gov/eims/eimscomm.getfile?p_download_id=526167 https://wayback.archive-it.org/7993/20161022184011/http://www.fda.gov/Food/FoodborneIllnessContaminants/ChemicalContaminants/ucm055815.htm https://wayback.archive-it.org/7993/20161022184011/http://www.fda.gov/Food/FoodborneIllnessContaminants/ChemicalContaminants/ucm055815.htm https://wayback.archive-it.org/7993/20161022184011/http://www.fda.gov/Food/FoodborneIllnessContaminants/ChemicalContaminants/ucm055815.htm https://wayback.archive-it.org/7993/20161022184011/http://www.fda.gov/Food/FoodborneIllnessContaminants/ChemicalContaminants/ucm055815.htm Abstract Introduction Materials and methods Reagents and materials Sample collection and preparation Headspace solid phase microextraction and instrument conditions Quantitation and quality control Dietary intake estimates Results and discussion Acknowledgment Disclosure statement References