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. Author manuscript; available in PMC: 2022 Dec 1.
Published in final edited form as: Environ Int. 2021 Aug 25;157:106840. doi: 10.1016/j.envint.2021.106840

Primary Aromatic Amines in Indoor Dust from 10 Countries and Associated Human Exposure

Sridhar Chinthakindi 1, Kurunthachalam Kannan 1,*
PMCID: PMC8490295  NIHMSID: NIHMS1735744  PMID: 34450547

Abstract

Although primary aromatic amines (AAs) are widely used in consumer products, little is known about their occurrence in indoor dust. A liquid chromatography – tandem mass spectrometry (LC-MS/MS) method was applied for the determination of 29 AAs and two tobacco smoke markers (nicotine and cotinine) in 256 house dust samples collected from 10 countries. Of the 29 target AAs analyzed, p-anisidine, o-anisidine, 2,6-dimethylaniline (2,6-DMA), p-cresidine (p-CD), p-toluidine (p-TD), 4,4’-methylenedianiline (4,4’-MDA), ortho/meta-toluidine (o/m-TD), 4-chloroaniline (4-CA), 2,4-diaminotoluene (2,4-DAT), aniline, and 2-naphthylamine (2-NA) as well as the two tobacco markers, nicotine and cotinine, were found prevalent in house dust samples. Sum median concentrations of AAs and tobacco smoke markers varied from 29.6 to 576 ng/g (overall median: 200 ng/g) and 10.8 to 2920 ng/g (415 ng/g), respectively. Among AAs, aniline was the abundant contaminant, found at median concentrations ranging from 19.6 ng/g (Colombia) to 334 ng/g (South Korea). Nicotine was detected in all indoor samples at median concentrations ranging from 9.92 ng/g (Colombia) to 2790 ng/g (India) ng/g. Estimated daily intake (EDI) of select AAs through the ingestion of house dust was in the range of 0.019 to 3.03 ng/kg-bw/day, which was five orders of magnitude below the tolerance limits.

Keywords: Aromatic amines, Indoor dust, LC-MS/MS, Aniline, Nicotine

Graphical Abstract

graphic file with name nihms-1735744-f0001.jpg

1. Introduction

Primary aromatic amines (AAs), especially aniline and its derivatives, n-substituted phenylenediamine and diphenylamine, are widely used as intermediates in the production of dyes, pharmaceuticals, pesticides, cosmetics, and textiles (Bruschweiler et al., 2014; Fishbein 1981; Ismail et al., 2015; Perez et al., 2019). AAs are also used as antioxidants in rubber (Rapta et al., 2009). AAs are present in consumer products such as hair dyes, kitchen utensils, polyurethane foam, colored textiles, and tobacco smoke (Beldean-Galea et al., 2018; Preiss et al., 2000; Sanchis et al., 2019; Stabbert et al., 2003; Szabo et al., 2021; Trier et al., 2010; Xiao et al., 2014; Yang et al., 2009; Yavuz et al., 2016). The estimated annual global production of aniline in 2016 and 2020 was 5.62 and 8.4 million tons, respectively (Mohammed et al., 2020).

Several primary aromatic amines are carcinogens and mutagens (Chung et al., 1997; Norinder et al., 2018; Skipper et al., 2010). The carcinogenic potential of AAs was known from the early nineteenth century through the observation of high urinary bladder cancer rates among dye industry workers (Richter and Branner 2002). Five AAs, namely 2-naphthylamine, o-toluidine, 4,4’-methylenebis(2-chloroaniline), benzidine, and 4-aminobiphenyl have been classified as known human carcinogens (Group 1) and many other AAs are classified as probable (Group 2A) or possible carcinogens (Group 2B) by the International Agency for Research on Cancer (IARC) and the World Health Organization (WHO) (Szabo et al., 2021).

Human biomonitoring studies have assessed occupational exposure of textile industry workers to AAs (Guo et al., 2018; Letasiova et al., 2012; Pira et al., 2010; Talaska 2003). Non-occupational sources of exposure to AAs include tobacco smoke and consumer products (Skipper et al., 2003; Smith et al., 1997). Whereas tobacco smoke is a well-known source of exposure to AAs (Luceri et al., 1993), other sources are poorly known. One study reported the occurrence of aniline, toluidine, dimethylamines, 2-naphthylamine, and 4-aminobiphenyl in indoor air (Palmiotto et al., 2001). The sum concentration (except aniline) of AAs in indoor air was reported to be in the range of 3 – 207 ng/m3. Aniline concentration reported in indoor air of a smoke-free office was in the range of 53 to 1930 ng/m3 (Palmiotto et al., 2001).

Indoor dust is a reservoir for many volatile and semi-volatile chemicals (Mercier et al., 2011). Ingestion and inhalation of dust can be a major source of human exposure to environmental chemicals such as tetrabromobisphenol A (TBBPA), poly- and perfluoroalkyl substances (PFAS), and microplastics (Liao et al., 2012; Zhang et al., 2020; Zhu and Kannan 2018). No earlier study reported the occurrence of AAs in indoor dust. In this study, we determined 29 AAs and nicotine and cotinine in house dust collected from seven Asian and three western countries to elucidate the distribution profiles in indoor dust. Human exposure to AAs through dust ingestion was calculated. To the best of our knowledge, this is the first study to describe occurrence of and human exposure to AAs in house dust collected from several countries.

2. Materials and Methods

2.1. Sample Collection

A total of 256 house dust samples were collected from 10 countries, namely Colombia (n = 42), Greece (n = 25), India (n = 26), Japan (n = 6), Kuwait (n = 27), Pakistan (n = 25), Romania (n = 20), Saudi Arabia (n = 27), South Korea (n = 41), and Vietnam (n = 17) during 2011–2014. Further details of samples including sampling locations are given in Table S1 of supplementary information (SI). Samples were collected using vacuum cleaners in all countries, except India, where samples were collected by sweeping floors with a nylon brush. Only those samples collected from homes (living rooms and bedrooms) were included in the study. Prior to extraction, dust samples were sieved through a 150-μm sieve to remove debris, homogenized, packed in aluminum foil, and stored at 4 °C until analysis.

2.2. Chemicals and Reagents

Thirty-one native (unlabeled) and 16 isotopically labeled internal standards (Table S1; chemical names and their abbreviations are shown) of 95–99% purity were purchased from Toronto Research Chemicals (TRC; Toronto, ON, Canada), AccuStandard (New Haven, CT, USA) and Sigma-Aldrich (St. Louis, MO, USA). High performance liquid chromatography (HPLC)-grade solvents namely water, methanol, acetonitrile, methyl tert-butyl ether (MTBE), hexane, ethyl acetate, and dichloromethane (DCM) were purchased from J. T Baker (Center Valley, PA, USA). HPLC-grade diethyl ether was purchased from Alfa Aesar (Tewksbury, MA, USA). Analytical grade formic acid (HCOOH), 30% ammonium hydroxide in water (NH4OH), and hydrochloric acid (HCl; 37% v/v) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Screw cap glass tubes (16 × 100 mm) were purchased from Fisher Scientific (Waltham, MA, USA).

2.3. Sample Extraction

Approximately 200 mg of dust sample was weighed into a clean glass tube. Sample was fortified with 10 ng each of 16 isotopic labelled internal standards. After equilibration for 30 min, dust sample was extracted with 5 mL of MTBE by ultra sonication (frequency of 40 kHz) for 30 min at room temperature (22°C) (Branson 3510 R-DTH; Branson Ultrasonics Corporation, Danbury, CT, USA). The extraction was repeated one more time and the extracts were combined and centrifuged at 3500 rpm for 10 min (Eppendorf Centrifuge 5804, Hamburg, Germany). The supernatant was decanted into a clean 15 mL polypropylene tube and 15 μL of 0.25 N HCl was added prior to evaporation to near-dryness under a gentle stream of nitrogen. The residue was reconstituted in 200 μL of water:methanol mixture (9:1, v/v) and transferred into a LC vial with 300-μL glass insert.

2.4. Instrumental Analysis

An ultra-high performance liquid chromatography – tandem mass spectrometry (UPLC-MS/MS) was used in the analysis of AAs, nicotine and cotinine as described previously (Chinthakindi and Kannan 2021). Separation of target analytes was achieved using an UPLC (Shimadzu LC-30 AD; Shimadzu Corporation, Kyoto, Japan) connected with an Ultra BiPh column (100 mm × 2.1 mm, 5 μm; Restek, Bellefonte, PA, USA) and a Betasil C18 guard column (20 mm × 2.1 mm, 5 μm; Thermo Scientific, West Palm Beach, FL, USA). The mobile phase consisted of 0.1% formic acid in water:methanol (95:5, v/v) (A) and 0.1% formic acid in methanol (B), pumped at a flow rate of 0.3 mL/min. The gradient program was as follows: 0.0 min (95% A), 0.01–2.50 min (95–58% A), 2.50–6.50 min (58%−25% A), 6.50–8.70 min (25–5% A, hold for 1 min), and 9.70–10.0 min (5–95% A, hold for 2.50 min) with a total run time of 12.5 min. The LC column was set at room temperature (22°C) and auto sampler temperature was maintained at 15 °C. The sample injection volume was 5 μL.

The mass spectrometer (Sciex Triple Quad 5500, ESI-MS/MS; Applied Biosystems, Foster City, CA, USA) was operated in electrospray ionization (ESI) positive ionization mode. Data acquisition was performed through multiple reaction monitoring (MRM). Compound specific MRM parameters, declustering potential (DP), entrance potential (EP), collision energy (CE), and collision exit potential (CXP) were optimized for each target compound by direct infusion of individual analytical standards at 10 ng/mL using an in-built syringe pump (Table S2). The electrospray ionization source was operated at 4.5 kV and 500 °C. The curtain gas flow rate was set at 10 psi and collision gas, nebulizer gas and ion source gas flows were set at 8, 30, and 30 psi, respectively.

2.5. Quality Control

Quality control samples analyzed include reagent blanks, procedural blanks and matrix blanks. For the reagent blank, HPLC grade water was used in place of samples whereas for procedural and matrix blanks, a dust sample collected from an apartment in New York City was used. These blank samples were fortified with target analytes and passed through entire analytical procedure (to determine recoveries). A nine-point matrix matched calibration standard, at concentrations of 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, and 50 ng/mL with 10 ng/mL of internal standard, was prepared by fortifying matrix blanks. A weighted linear regression was used to fit the calibration curve and the regression coefficients were >0.999 for all analytes. Accuracy and precision of the extraction method was determined using fortified matrix at three concentrations: 5, 10, and 20 ng (in 0.2 g sample) along with 10 ng of each internal standard. None of the target analytes was detected in reagent blanks. Procedural blanks contained 2,6-DMA, nicotine, and aniline at concentrations in the range of 0.08 – 1.25 ng/g and these values were subtracted from sample values. Relative recoveries of target compounds ranged from 75 to 130% with a relative standard deviation (%RSD) of <12% at the three fortified concentrations. Samples were extracted in 10 batches, with each batch containing samples from a particular country and associated quality control samples. An instrumental blank (running mobile phase) and a midpoint calibration standard were injected after every 10 samples to check carryover of target analytes from sample to sample, and drift in mass spectrometer sensitivity. The repeatability of sample extraction was determined by replicate (n=5) analysis of 10 randomly selected dust samples. Intra- and inter-day %RSD were <12% and <14.2%, respectively. The limit of detection (LOD) was determined based on the lowest acceptable calibration standard (that yielded a signal to noise ratio of >3), a nominal sample weight of 200 mg, and the dilution factor of 5 (Table S3). The LODs of target analytes in dust samples ranged from 0.025 to 0.500 ng/g (Table S3). The extraction efficiency of the method was examined through sequential extraction of 10 randomly selected dust samples. No target compounds were found after the second extraction except for three analytes: 2,4-DAT, nicotine, and cotinine, which were found at a concentration range of 2 – 10 ng/g in the third extraction. However, these concentrations measured in the third extraction were <0.5% of the total concentrations measured in dust samples. All plots were created in Microsoft Excel 2020. SPSS ver. 17 was used in statistical analysis. The statistical significance was set at a probability value of p ≤ 0.05.

3. Results and Discussion

3.1. Optimization of Extraction

Sample extraction procedure was optimized using several extraction solvents: methanol, acetonitrile, diethyl ether, ethyl acetate, MTBE, hexane; and a combination of solvents: MTBE + acetonitrile, MTBE + hexane, MTBE + ethyl acetate; and 0.1% NH4OH in methanol. Optimal recoveries of target analytes between 70 and 130% were obtained with MTBE and MTBE + hexane. The recoveries of analytes extracted with MTBE alone were relatively higher than those of other solvent combinations. Thus, MTBE was selected as an extraction solvent. Other solvent combinations yielded turbid extract, poor recoveries, and/or significant matrix effects. The volume of MTBE was optimized by extracting dust samples with 1, 2, 3, 4, 5, 6 and 7 mL for 30 min by ultra-sonication. The highest recoveries were found with 5 mL MTBE and this volume was chosen for analysis. Furthermore, it was found that the recoveries were higher with ultra-sonication than with shaking the samples in a horizontal shaker.

3.2. Concentrations in Indoor Dust

Of 29 AAs analyzed, 11 compounds namely, p-anisidine, o-anisidine, 2,6-DMA, p-CD, p-TD, o/m-TD, 4-CA, 4,4’-MDA, 2,4-DAT, aniline, and 2-NA were detected frequently in indoor dust samples (Table 1). The detection frequencies of these 11 AAs were in the range of 40–100% in all samples except for p-anisidine, o-anisidine, p-TD and 2,6-DMA (<40% df for some countries). Among other 18 AAs, 4-CTD, BD, and 2,4,5-TMA were detected in <15% of the samples, while others remained undetected in all samples. The median concentrations of ∑AAs in indoor dust ranged from 29.6 (Colombia) to 576 ng/g (South Korea), among the 10 countries studied (Table S4). A significant correlation existed between sum median concentrations of AAs measured between countries (p = 0.003). Aniline was the most abundant compound found in all house dust samples. Dust samples collected from South Korea contained the highest concentrations of aniline (range: 61.0 – 985 ng/g; median: 334 ng/g), followed by samples from Saudi Arabia (range: 1.35 – 432 ng/g; median: 155 ng/g) and Japan (range: 34.6 – 560 ng/g; median: 145 ng/g). In other countries, the median concentration of aniline ranged from 19.6 (Colombia) to 52.5 ng/g (Vietnam) (Table 1). 2,6-DMA was the second abundant AA found in all indoor dust samples. The highest concentrations of 2,6-DMA were found in dust samples collected from South Korea (median: 87.5 ng/g), followed by those from Saudi Arabia (median: 54.5 ng/g) (Table 1). The median concentrations of p-TD, p-CD, 4-CA, and 4,4’-MDA were in the range of <LOD to 34.7 ng/g. . The percentage composition of individual AA to the sum of total median concentration of 11 AAs is shown in Fig 1. Aniline accounted for 45.4 ± 10.9% (mean ± SD; for the entire sample set) of the total concentrations, followed in descending order by 2,6-DMA (18.5 ± 9.51%), and p-CD (8.54 ± 7.07%) (Table S5).

Table 1.

Concentrations (nanograms per gram) of aromatic amines, nicotine and cotinine in indoor dust collected from 10 countries.a

P-anisidine o-anisidine 2,6 DMA p-CD p-TD o/m-TD 4-CA 4,4’ MDA 2,4-DAT aniline 2-NA nicotine cotinine
Colombia (n = 2) min <LOD <LOD <LOD <LOD <LOD <LOD <LOD <LOD <LOD <LOD <LOD 6.79 <LOD
max 3.81 104 117 59.0 0.56 9.60 17.6 6.60 10.6 164 64.5 475 108
mean 0.25 6.98 11.47 9.68 0.01 2.09 1.52 0.77 0.96 32.5 8.15 33.1 3.38
median <LOD 1.37 <LOD 4.44 <LOD 0.95 <LOD <LOD <LOD 19.6 3.16 9.92 0.91
df % 16.6 38.1 61.9 61.9 0.10 76.1 42.8 42.8 15.1 85.1 71.4 100 66.6
Greece (n = 25) min <LOD 6.20 1.10 <LOD <LOD 0.89 <LOD <LOD <LOD 63.5 <LOD 20.7 3.43
max 2.131 64.5 211 240 11.9 32.1 63.1 158 127 381 114 3820 1010
mean 0.21 21.4 50.6 29.7 3.04 4.87 4.38 9.55 32.8 155 14.1 661 188
median <LOD 16.3 43.1 9.55 1.86 3.67 2.32 0.08 24.5 129 <LOD 385 76.8
df % 20.0 100 100 56.0 96.0 100 96.0 40.0 96.0 100 16.0 100 100
India (n = 26) min <LOD <LOD <LOD 0.98 <LOD 0.18 <LOD <LOD <LOD 9.51 <LOD 14.8 <LOD
max 39.5 45.4 127 143 115 11.4 4.89 5.15 44.6 203 51.0 7930 2150
mean 1.57 13.9 25.1 39.4 6.18 3.25 1.74 1.84 9.99 55.4 7.66 3350 415
median <LOD 10.8 13.2 34.7 1.45 2.82 1.73 1.71 4.11 46.3 6.23 2790 137
df % 0.19 0.85 80.8 100 84.1 100 80.7 80.8 73.1 100 92.3 100 92.3
Japan (n = 6) min <LOD 2.03 6.05 1.44 <LOD 0.83 <LOD 2.38 12.7 34.6 <LOD 16.9 7.49
max 2.18 21.0 360 20.3 5.85 18.4 3.70 15.1 66.1 560 20.1 187 97.3
mean 0.62 11.0 72.4 13.7 2.33 4.78 1.09 5.55 33.8 216 7.03 77.3 31.2
median 0.08 10.2 18.4 14.3 0.97 2.18 0.71 3.26 27.7 145 5.29 34.1 21.1
df % 50.0 100 100 100 83.3 100 66.6 100 100 100 83.3 100 100
Kuwait (n = 27) min <LOD <LOD <LOD <LOD <LOD <LOD <LOD <LOD <LOD 13.1 <LOD 6.59 <LOD
max 9.75 43.2 746 29.8 49.4 27.8 10.5 27.5 55.1 910 255 2400 746
mean 1.62 10.5 365 2.60 8.44 5.73 1.48 2.86 8.39 193 30.4 337 39.3
median 0.57 7.15 54.1 <LOD 4.82 4.13 <LOD 0.51 0.12 125 4.94 114 4.98
df % 62.9 85.2 27.2 44.4 85.1 96.2 44.4 55.5 66.6 100 62.9 100 77.7
Pakistan (n = 25) min <LOD <LOD <LOD <LOD <LOD <LOD <LOD <LOD <LOD 4.62 <LOD 37.1 0.99
max 4.15 28.1 388 115 21.4 18.8 7.05 17.1 64.5 79.1 21.3 2580 1110
mean 0.37 7.10 51.7 18.6 1.57 1.57 1.38 2.23 12.2 30.9 4.05 540 137
median <LOD 4.58 15.9 10.4 <LOD 0.61 0.50 1.80 7.80 26.4 0.20 301 66.8
df % 32.1 88.0 88.0 80.0 36.0 88.0 56.0 80.0 84.0 100 56.0 100 100
Romania (n = 20) min <LOD 2.81 <LOD <LOD 0.18 1.31 0.73 <LOD 3.691 40.9 <LOD 132 11.4
max 5.60 111 339 49.8 8.90 9.30 20.1 24.9 208 685 443 4400 2780
mean 1.03 19.2 60.5 9.59 2.10 4.29 5.05 4.96 39.4 154 36.2 806 275
median 0.40 16.7 44.6 7.10 1.59 3.94 4.22 2.91 18.7 122 2.22 515 36.2
df % 60.2 100 95.1 85.2 100 100 100 90.1 100 100 65.2 100 100
Saudi Arabia (n = 27) min <LOD <LOD <LOD <LOD <LOD <LOD <LOD <LOD <LOD 1.35 <LOD 6.43 <LOD
max 26.7 156 610 218 21.7 19.1 7.15 69.0 209 432 85.1 7270 497
mean 3.23 43.9 93.5 17.5 3.12 3.56 1.36 5.52 36.0 160 14.7 783 61.2
median <LOD 23.2 54.5 3.28 1.55 2.13 <LOD <LOD 21.8 155 <LOD 445 19.2
df % 44.4 96.3 96.3 55.5 55.5 62.9 40.7 40.7 96.3 100 44.4 100 70.4
South Korea (n = 41) min <LOD 6.60 <LOD <LOD <LOD 0.76 <LOD 2.69 8.10 61.0 <LOD 66.9 4.94
max 3.65 146 905 87.1 18.2 73.5 121 379 348 985 75.1 5950 2360
mean 0.85 31.3 148 21.5 5.43 6.57 5.6 29.2 112 373 14.2 1280 322
median 0.56 24.9 87.5 17.2 4.21 4.64 2.18 8.40 84.5 334 7.25 759 107
df % 70.7 100 70.73 90.2 97.5 100 82.9 100 100 100 85.36 100 100
Vietnam (n = 17) min <LOD <LOD <LOD <LOD <LOD 0.34 <LOD 2.16 <LOD 8.551 <LOD 13.5 9.68
max 5.15 99.1 11.2 51.3 2.58 3.89 3.36 273 5.05 143 5.60 757 273
mean 0.70 9.46 0.95 11.9 0.40 1.78 0.50 30.2 0.74 55.8 0.76 183 118
median <LOD 2.31 <LOD 7.18 0.02 1.43 <LOD 3.69 <LOD 52.5 <LOD 93.9 77.5
df % 23.5 82.3 11.7 70.5 64.7 100 47.1 100 35.2 100 82.3 100 100
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a

p-anisidine; o-anisidine; 2,6 DMA, 2,6-dimethylaniline; p-CD, para-cresidine; p-TD, para-toluidine; o/m-TD, ortho/meta-toluidine; 4-CA, 4-chloroaniline; 4,4’-MDA, 4,4’-methylenedianiline; 2,4-DAT, 2,4-diaminotoluene; aniline; 2-NA, 2-naphthylamine; nicotine; cotinine.

Fig. 1.

Fig. 1.

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Composition profiles of primary aromatic amines (∑AAs) in indoor dust collected from 10 countries. Mean concentrations were used to calculate the percent contribution

Our results suggest widespread occurrence of AAs, especially aniline, in house dust. Aniline and other AAs have been used in more than 300 consumer products. These chemicals may arise from tobacco smoke, dyes, rubber, varnishes, perfumes, and polyurethane foam used in indoor environments. The concentrations of several other emerging classes of pollutants have been measured in the same indoor dust samples. The measured concentrations of AAs were similar to those reported for environmental phenols, PFAS and select persistent organic pollutants (Johnson-Restrepo and Kannan 2009; Wang et al., 2013; Wang et al., 2012; Wang et al., 2015). One study measured aniline in indoor and outdoor air and found concentrations in the range of 53 ng/m3 (office of non-smokers) to 1930 ng/m3 (discotheque) (Palmiotto et al., 2001). Aniline is a probable human carcinogen which warrants further studies of exposure doses to this chemical in humans.

3.3. Concentrations and Profiles of Nicotine and Cotinine

Nicotine and cotinine are nitrogen containing aromatics which were determined in dust samples using the same analytical method. Nicotine was detected in 100% samples from all countries. The highest median concentration of nicotine was found in indoor dust collected from India (median: 2790 ng/g) and the lowest was found in samples collected from Colombia (median: 9.92 ng/g). The mean concentration of nicotine in indoor dust was found in the following decreasing order: India (3350 ng/g) > South Korea (1280 ng/g) > Romania (806 ng/g) > Saudi Arabia (783 ng/g) > Greece (661 ng/g) > Pakistan (540 ng/g) > Kuwait (337 ng/g) > Vietnam (183 ng/g) > Japan (77.3 ng/g) > Colombia (33.2 ng/g) (Table 1). The concentrations of nicotine in house dust were significantly different between countries (p = 0.028). ∑(nicotine+cotinine) concentrations were higher than those of AAs in dust from India, Pakistan, Greece, Romania, Saudi Arabia, South Korea and Vietnam. Cotinine was detected in 100% of dust samples from six countries, and 66–92% of samples from the remaining four countries. The highest and the lowest median concentrations of cotinine were found in dust samples from India (median: 137 ng/g) and Colombia (median: 0.91 ng/g), respectively (Table 1). A significant (p = 0.015) positive correlation (r = 0.739) existed between sum median concentrations of nicotine and cotinine in dust samples. The percentage contribution of nicotine and cotinine (based on mean concentrations, Table S5) to the sum of mean concentrations of these two chemicals is presented in Fig. 2. Nicotine accounted for 80.6 ± 10.2% of the sum concentrations in indoor dust samples. The source of nicotine in dust samples is primarily the tobacco smoke. The highest median ∑(nicotine & cotinine) concentrations were found in dust samples collected from India (2920 ng/g), while the lowest was from Colombia (10.8 ng/g) (Table S4). Cotinine concentrations were approximately one tenth of the nicotine concentrations in majority of the indoor dust samples. Nevertheless, samples from Vietnam and Japan contained approximately similar concentrations of cotinine and nicotine. Overall, the concentrations of AAs, nicotine and cotinine varied significantly among the 10 countries (p > 0.05). Correlations among sum concentrations of AAs and nicotine showed significant but weak relationships, which suggested sources of AAs other than tobacco smoke in the indoor environment (Table S6).

Fig. 2.

Fig. 2.

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Composition profiles of nicotine and cotinine in indoor dust collected from 10 countries. Mean concentrations were used to calculate the percent contribution

Few earlier studies reported nicotine concentrations in indoor dust. House dust collected from Baltimore, the United States (n = 30; from September 2001 to December 2003) contained median concentrations of nicotine in non-smokers and smokers homes at 11700 and 43400 ng/g, respectively (Kim et al., 2008). House dust collected from European countries in 1991 contained median concentrations of nicotine in non-smokers and smokers homes at 18000 and 242000 ng/g, respectively (Hein et al., 1991). Nicotine concentrations in house dust collected from homes of smokeless tobacco users were higher than (median: 22000 ng/g) those of active smokers and tobacco-free homes (Whitehead et al., 2013). Our nicotine concentrations were relatively less than those reported previously in indoor dust. We did not collect information regarding tobacco usage and therefore its association with measured nicotine concentrations in dust could not be established. Cotinine concentrations were rarely reported in indoor dust samples. Although cotinine was thought to be a biological metabolite of nicotine, occurrence of cotinine in dust suggests environmental transformation or breakdown of nicotine to cotinine. One study reported photolytic transformation of nicotine to cotinine and therefore the measured concentrations of cotinine in indoor dust are a result of abiotic transformation of nicotine (Alberti et al., 2021).

3.4. Exposure to AAs through Dust Ingestion

The sources and pathways of human exposure to AAs are not well understood. We estimated daily intakes (EDIs) of AAs for those compounds that were found in indoor dust for various age groups [infants (<1 year), toddlers (1–5 years), children (>5–11 years), teenagers (>11–19 years), and adults (≥20 years)] following the US Environmental Protection Agency’s (EPA) exposure factors as shown in eq 1.

EDI=C×DIRBW (1)

Where C is the median concentration of analytes in indoor dust (ng/g), DIR is the dust ingestion rate (mg/day), and BW is the body weight (kg). The body weights for infants, toddlers, children, teenagers, and adults in Asian countries were 5, 19, 29, 53, and 63 kg, respectively, whereas those for western countries were 7, 15, 32, 64, and 80 kg, respectively. The mean DIR for infants, toddlers, children, teenagers, and adults were 20, 100, 50, 50, and 50 mg/day, respectively (Zhu and Kannan 2018).

The EDIs of AAs through dust ingestion have been summarized in Table 2. Among 10 countries studied, the daily intake of ∑AAs in toddlers was the highest in South Korea (3.032 ng/kg-bw/day) and the least in Colombia (0.197 ng/kg-bw/day) (Table 2). Similarly, the daily intake of ∑nicotine in toddlers was the highest in India (14.7 ng/kg-bw/day) and the lowest in Colombia (0.066 ng/kg-bw/day). The acceptable daily intakes (ADI) for 2,5-DAT, 2,6-DAT, and 4-CA were reported to be 0.56, 0.16, and 2.0 mg/kg-bw/day, respectively, by the World Health Organization (WHO) (EPA 1984; WHO 2013). The ADI for nicotine is 0.0008 mg/kg-bw/day as set by the European Food Safety Authority (EFSA) (EFSA 2009). Our EDI values for AAs and nicotine were 5 and 1–2 orders of magnitude below the regulatory threshold values, respectively. It should be noted that TDI values for many of AAs are not currently available, which precludes us from drawing further conclusions.

Table 2.

Median estimated daily intakes (EDI, ng/kg-bw/day) of aromatic amines, nicotine, and cotinine via house dust ingestion for different age groups in 10 countries.

EDI (ng/kg-bw/day)
Aromatics Amines (AAs) nicotine cotinine
infants toddlers children teenagers adults infants toddlers children teenagers adults infants toddlers children teenagers adults
Colombia 0.085 0.197 0.046 0.023 0.019 0.028 0.066 0.016 0.008 0.062 0.003 0.007 0.002 0.001 0.007
Greece 0.657 1.533 0.359 0.180 0.144 1.100 2.567 0.602 0.301 2.406 0.219 0.512 0.120 0.060 0.480
India 0.492 0.647 0.212 0.116 0.098 11.15 14.67 4.805 2.629 2.212 0.548 0.721 0.236 0.129 0.109
Japan 0.912 1.200 0.393 0.215 0.181 0.136 0.180 0.059 0.032 0.027 0.084 0.111 0.036 0.101 0.017
Kuwait 0.700 0.921 0.302 0.165 0.139 0.456 0.602 0.197 0.108 0.090 0.020 0.026 0.009 0.005 0.004
Pakistan 0.273 0.359 0.118 0.064 0.054 1.204 1.584 0.235 0.284 0.603 0.267 0.352 0.115 0.063 0.053
Romania 0.640 1.493 0.350 0.175 0.140 1.471 3.433 0.805 0.402 3.219 0.103 0.241 0.056 0.029 0.225
Saudi Arabia 1.044 1.374 0.450 0.246 0.207 1.776 2.337 0.766 0.419 0.352 0.077 0.101 0.033 0.018 0.015
South Korea 2.304 3.032 0.993 0.543 0.457 3.038 3.997 1.309 0.716 0.603 0.430 0.565 0.185 0.101 0.085
Vietnam 0.268 0.353 0.116 0.063 0.053 0.376 0.494 0.162 0.089 0.075 0.310 0.408 0.134 0.073 0.062
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4. Implications and Limitations

This is the first study to report the concentrations of AAs in indoor dust samples. Eleven of 29 target AAs and nicotine and cotinine were found frequently in indoor dust samples from several countries. The concentrations of AAs, nicotine and cotinine varied significantly among countries. Aniline was the abundant AA and the concentrations of nicotine and cotinine, on average, were an order of magnitude higher than those of AAs. The estimated exposure dose to AAs through dust ingestion was several orders of magnitude below the current regulatory limits. However, it should be noted that our estimation of exposure dose could be an underestimate of actual exposure as other sources and pathways of exposure were not included in the calculation. It is possible that sampling with vacuum cleaners result in evaporation of some volatile AAs from dust. Furthermore, our exposure assessment is tempered by limited sample size from each country. Nevertheless, this study establishes baseline values for aromatic amines, cotinine and nicotine in indoor dust from several countries.

Supplementary Material

1

Highlights.

  • Aromatic amines (AAs), nicotine and cotinine were found in indoor dust from 10 countries.

  • The overall median concentration of AAs in dust was 200 ng/g.

  • Aniline was the abundant AA found in indoor dust.

  • Daily intake of AAs via indoor dust ingestion was on the order of few nanograms per day.

Acknowledgements

We thank Drs. B. Johnson-Restrepo (Colombia), A. G. Asimakopoulos (Greece), R. K. Sinha (India), H. Nakata (Japan), B. Gevao (Kuwait), T. A. Kumosani (Saudi Arabia), H-B. Moon (South Korea), G. Malarvannan (Belgium), A. Covaci (Belgium), and T. B. Minh (Vietnam). Research reported here was supported, in part, by the National Institute of Environmental Health Sciences (NIEHS) under the award number U2CES026542 (KK). The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIEHS.

Footnotes

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Declaration of Competing Interest

The authors declare that they have no known competing financial interest or personal relationships that could have appeared to influence the work reported in this paper.

Supplementary Information (SI)

The SI contains details of samples including sampling cities in each country (Table S1); list of target analytes with mass spectrometric MRM transitions (Table S2); limit of detection values of target analytes (Table S3); sum median concentrations of analytes in indoor dust samples (Table S4); Percentage composition based on sum of mean concentrations of AAs in indoor dust samples (Table S5).

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