2021 年 4 巻 6 号 p. 182-192
In this study, we analyzed the volatile organic compounds (VOCs) emitted from a sample of bedding products. These items are intended for long-term use indoors and therefore will be present for long periods of time in the breathing zone of household occupants. Forty bedding products (20 pillows and 20 mattresses) were obtained from the Japanese domestic market for analysis. We have pioneered the measurement of VOCs from bedding products using the sampling bag method, and our measurements showed that a variety of VOCs were emitted from the items. In the pillow sample, polyethylene pillows emitted the most aliphatic hydrocarbons, while buckwheat hull pillows emitted fewer chemicals overall. All pillows emitted tetradecane, toluene, and xylene. VOCs emissions from the mattresses tended to be higher than from the pillows. The mattresses emitted 2-ethyl-1-hexanoic acid frequently and at high concentrations. To further understand the effects of indoor air pollution, it is necessary to continue research into testing the emissions from bedding products and other household items.
Volatile organic compounds (VOCs) emitted from indoor household items are known to contribute to health problems, such as sick building syndrome, in occupants of residential spaces. The negative health effects of VOCs exposure have promoted interest in understanding and improving indoor air quality. However, there is limited information on the indoor air pollution caused by household items introduced by residents, in particular bedding items, which will be present for a long time in the resident’s breathing zone. Therefore, to minimize the health effects of indoor air pollution, it is important to identify the chemical substances emitted from these household items. Although there have been studies measuring VOC emissions from mattresses using the chamber method,1,2) to the best of our knowledge, there are no published studies using the sampling bag method.
For this study, we obtained a sample of pillows and mattresses that had been marketed and distributed in Japan. VOCs emitted from the bedding items were collected using the sampling bag method, and were quantified using thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS). Aldehydes, one of the group of VOCs, were quantified using high-performance liquid chromatography (HPLC).
The target substances for analysis for every group are listed in Table 1. 48 Component Indoor Air Standard and TO11/IP-6A Aldehyde/Ketone-DNPH Mix were purchased from Supelco, Inc. 2-Ethyl-1-hexanol (98%) was purchased from Wako Pure Chemical Industries, Ltd. 3-Hydroxy-2,2,4-trimethylpentyl isobutyrate (Texanol; contains ca. 40% 2,2,4-trimethyl-1,3-pentanediol 3-monoisobutyrate) and 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB; > 97.0%) were purchased from Tokyo Chemical Industry Co., Ltd. Toluene-d8, purchased from Wako Pure Chemical Industries, Ltd., was used as an internal standard in the GC/MS analysis in this study.
TD-GC/MS analysis was performed using a TD-100xr (MARKES International Ltd.) equipped with Agilent 7890B/5977B GC/MSD series (Agilent Technologies, Inc.). MP-Σ30 NII sampling pumps (Sibata Scientific Technology Ltd.) was used for collection of VOCs except that MP-Σ300 NII sampling pumps (Sibata Scientific Technology Ltd.) was for aldehyde group. The sampling bag method was conducted using Skypia® bags (GL Sciences Inc.). Tenax® TA 60/80 (Camsco Co.) collection tubes were used for VOCs whereas InertSep® mini AERO DNPH (GL Sciences Inc.) collection tubes was for aldehyde group.Product Samples
We purchased 20 pillows and 20 mattresses from Japanese domestic internet markets. The pillows were composed of the following materials: polyester (P-1–P-7) in 7, urethane foam (P-8–P-14) in 7, polyethylene (pipe) (P-15–P-18) in 4, and buckwheat hull (P-19, P-20) in 2. All 20 mattresses were composed of urethane foam (M-1–M-20).Emissions Tests
As recommended by the Japanese Automotive Standards Organization M902 (JASO M902), 2018 edition,3) the sampling bag method was used to collect emitted chemical substances. For each test, one item of bedding was properly stored at room temperature until it was opened. Immediately after opening the package, we sealed in a sampling bag (100 L for pillows, 2,000 L for mattresses), alongside pure air (50 L for pillows, 1,000 L for mattresses). The sampling bag was then placed in a thermostat chamber at 40°C for 2 h. Subsequently, emitted VOCs were collected at a rate of 100 mL/min (2 L), and emitted aldehydes at a rate of 1,000 mL/min (20 L). A blank sample measurement was obtained by repeating this procedure without a test product in the bag.Analytical Methods TD-GC/MS
The TD conditions: Desorb temperature (time) was set at 270°C (10 min). Stripping temperature was held 5°C, increased at 280°C and held 11.5 min. Trap flow was 30 mL/min. Tenax® (a porous polymer based on 2,6-diphenylphenol) was used as cryofocusing trap devise.
The GC conditions: InertCap 1 column with an inner diameter of 0.25 mm × 60 m and a film thickness of 1.5 µm (GL Sciences, Inc.). Helium was used as the carrier gas. The flow rate was 1.3 mL/min as a constant pressure. GC Oven temperature sequence was held 35°C for 2 min, increased at 15°C/min to 65°C, then increased at 5°C/min to 95°C, increased at 2.5°C/min to 105°C, increased at 10°C/min and held 10 min to 280°C. Split ratio was 6:1. Transfer line temperature was set at 280°C.
The MS conditions: EI was used as an ionization type. Source temperature was set at 260°C. Quad temperature was set at 260°C. Acquisition type was Scan mode (m/z 35–450).
The concentration range of the calibration curve was 0.5–20 ng. Extrapolated values were calculated when this range was exceeded. Toluene-d8 was used as an internal standard. The total VOC (TVOC) concentration was calculated as a toluene equivalent value, using the sum of the peak areas of the total ion current chromatogram of scan mode eluting at the retention time between hexane and hexadecane. The 10 most intense VOC peaks each sample for scan measurements were identified using a similarity search of the GC/MS library (NIST 11.lib).HPLC
Quantification was performed using an external standard method with 2,4-dinitrophenylhydrazine (DNPH) derivatized standards. The concentration range of the calibration curve was 0.15–15 ng. Extrapolated values were calculated when this range was exceeded. The HPLC conditions were as follows: column, Inertsil ODS-3 (4.6 mm i.d. × 250 mm, 5 µm; GL Sciences, Inc); mobile phase, ultra-pure water (A) and acetonitrile (B) in the gradient mode: 60% B (0 min) → 60% B (14 min) → 100% B (40 min); injection volume, 10 µL; flow rate, 1.0 mL/min; detection, ultraviolet (360 nm).
Formula for calculating the bag VOC concentration
We characterized and quantified the VOCs emitted from 20 pillows. The results are summarized in Table 2. When comparing the mean TVOC emissions from each pillow material, showed that the emissions from the polyethylene products (475 µg/unit) were more than twice as high as from the urethane foam products (203 µg/unit). However, there was no notable difference in the median value for the polyethylene products (144 µg/unit) compared with the urethane foam products (121 µg/unit). These facts indicated that there was a polyethylene sample producing significantly higher emissions compared with the other samples. It was the case for P-18, which produced the highest TVOC emissions of the pillow samples at 1,570 µg/unit. Decane, undecane, and dodecane were emitted from P-18 at levels of 162 µg/unit, 60 µg/unit, and 48 µg/unit, respectively. We hypothesize that the source of these chemical species is the rigid carbon pipe within these pillows. The sample emitting the most formaldehyde (51 µg/unit) was P-7 from the polyester products. The sample emitting the most ethylbenzene (55 µg/unit) was P-8 from the urethane foam products. Overall, buckwheat hull pillows produced lower emissions compared with the other materials (Table 2D).
Table 3 shows that there were three VOCs emitted by all 20 of our pillow samples: tetradecane, toluene, and xylene. 1,4-Dichlorobenzene, which is often used as an insect repellent, was detected in 50% of the pillow samples. To identify chemical substances beyond the indoor air quality guideline substances that may have a considerable contribution to indoor air pollution, we identified compounds with a toluene equivalent value > 400 µg/m3 and a high emission frequency of > 50%. This assessment identified the compound hexamethylcyclotrisiloxane as a compound of interest (data not shown).
Since pillows are used for a longer time in the resident's breathing zone than other bedding items, further continuous monitoring is necessary, especially for polyethylene pillows, which showed relatively high emissions.Mattress Emissions
Twenty mattresses were subjected to the same emissions tests as the pillow samples. The results are shown in Table 4. M-1, a low-resilience urethane mattress, produced the highest TVOC emissions (11,200 µg/unit, toluene equivalent). Relatively high emissions of hexane (52 µg/unit), toluene (513 µg/unit), trichloroethylene (68 µg/unit), and tetrachloroethylene (13,400 µg/unit) were also detected from M-1. M-10 produced the highest emissions of xylene (92 µg/unit), 1,2-dichloroethane (54 µg/unit) and ethyl acetate (120 µg/unit). Relatively high emissions of dichloromethane from M-12, 1-butanol from M-16, and α-pinene from M-20 were also detected.
Ten compounds were emitted by all 20 of the mattresses: decane, dodecane, tetradecane, toluene, ethyl benzoate, xylene, styrene, ethyl acetate, butyl acetate, 1-butanol (Table 5).
As with the pillows, we surveyed the mattress emission results for chemical substances detected at a high concentration (> 400 µg/m3) and with a high emission frequency (> 50%). This assessment highlighted the compounds octamethyltetrasiloxane, 2-ethyl-1-hexanoic acid, and decamethylcyclopentasiloxane. 2-Ethyl-1-hexanoic acid is an oxide of 2-ethyl-1-hexanol, a possible causative chemical for sick building symptoms4–6) that needs to be continuously monitored.
In conclusion, we reported the VOCs emissions from a sample of bedding products (20 pillows and 20 mattress) using the sampling bag method for the first time. This sample represented items that are commonly present indoors for long periods of time and in the breathing zone of occupants. The emissions from these items therefore pose a potential health risk to the residents. Our results showed that a wide variety of VOCs are emitted by these items. The results from the polyethylene pillow sample showed higher TVOC emissions compared with the other pillow types tested, while buckwheat hull pillows produced lower emissions overall. Tetradecane, toluene and xylene were frequently emitted from our pillow sample. The mattresses showed an overall trend of higher emissions compared with the pillows. High concentrations of tetrachloroethylene, dichloromethane, 1-butanol and toluene were also detected. 2-Ethyl-1-hexnoic acid was detected at a high frequency and a high concentration from the mattress samples. The results of this study provide important evidence that can be used in the development of measures combatting the negative health effects of indoor air pollution, such as sick building syndrome. To further understand the effects of indoor air pollution, it is necessary to continue research into testing the emissions from bedding products and other household items.
This work was financially supported by the Grant-in-Aid for Research on Risk of Chemical Substances (H30-chemical/designation-002), provided by the Ministry of Health, Labour and Welfare, Japan. We thank Clare Fitzgerald, PhD, from Edanz (https://jp.edanz.com/ac) for editing a draft of this manuscript.Conflict of interest
The authors declare no conflict of interest.