Abstract
Background
Petroleum-derived products (PDPs) often contain carcinogens such as benzene and ethylbenzene. However, exposure risks significantly increase during high-temperature workplace processes (120°C-180°C). We evaluated the thermal release of various carcinogens in PDPs, focusing on benzene, ethylbenzene, and other European Union Regulation on Classification, Labelling, and Packaging 1A/1B compounds under elevated temperatures.
Methods
Thirty PDPs were categorized into four groups: viscous liquid of lubricant (VL), aerosol of lubricant, semisolid of grease, and aerosol of remover. Qualitative and quantitative analyses were performed using gas chromatography-mass spectrometry (GC/MS). Headspace analysis was conducted at temperatures from 30°C to 180°C to evaluate volatile carcinogens.
Results
The number of carcinogens increased systematically with temperature. At 180°C, European Union Regulation on Classification, Labelling, and Packaging 1A/1B compounds were found in 40–75% of samples. Benzene was detected in 13 products (43.33%) and ethylbenzene in 29 products (96.67%). Increasing temperature enhanced benzene concentrations in 20-50% of products and ethylbenzene concentrations in 17-80% of products, with VL products showing the highest concentrations. Notably, several carcinogens not listed on standard Safety Data Sheets (SDSs) were detected at temperatures exceeding 120°C.
Conclusion
Benzene and ethylbenzene should be removed from PDPs when possible. Elevated temperatures release additional “hidden” carcinogens not listed on SDSs. VL products should be avoided in high-temperature environments, and adequate ventilation and worker education are essential when using these products in confined spaces.
Keywords: Benzene, Carcinogens, Ethylbenzene, GC-MS, Petroleum-derived products
1. Introduction
Petroleum-derived products (PDPs) exist all around us in our daily lives and are used worldwide. Over 800 million tons of PDPs were supplied in the USA in 2024 [1]. In Republic of Korea, PDPs are widely used in the workplace as a variety of products. Chemical composition and hazard information of PDPs are provided through Safety Data Sheets (SDSs). In the Republic of Korea, SDSs are managed by various platforms, such as Toxfree (https://toxfree.kr/; Wonjin Institute for Occupational and Environmental Health, Seoul, Republic of Korea), which has product information that is used at workplaces and lists the chemical components of products. According to the Toxfree database, 29% of products (4,421/15,301) contain petroleum substances. However, when classified as chemicals, only 3% (123/3,780) were classified as petroleum chemicals [2].
These petroleum substances are classified as substances of unknown or variable composition, complex reaction products and biological materials (UVCBs) because they consist of numerous substances with similar carbon numbers and boiling points, making it difficult to identify all individual components [3]. Due to these UVCB characteristics, accurate identification and risk assessment of hazardous components are limited, prompting various studies worldwide [[4], [5], [6], [7]]. These issues pose serious occupational exposure problems.
Also, many epidemiological studies have reported that petroleum workers who made PDPs were associated with elevated rates of cancer than were nonexposed workers [[8], [9], [10]]. These PDPs are known to contain benzene and ethylbenzene. The International Agency for Research on Cancer (IARC) categorizes benzene as Group 1 (“Carcinogenic to humans”), ethylbenzene as Group 2B (“Possibly carcinogenic to humans”) [11].
Numerous studies have focused on the concentrations of benzene in PDPs. For example, cleaning products have been shown to contain 1,700–15,000 ppm [12], aerosol brake cleaners 1–930 ppm [13], and lubricants up to 11,000 ppm [14]. However, these studies did not systematically evaluate how the concentrations of benzene and ethylbenzene change with temperature, particularly under workplace-relevant conditions. Benzene and ethylbenzene are primary volatile organic compounds (VOCs), and it is generally known that VOC emissions increase as temperature rises. Notably, Anyakudo et al reported that VOC concentrations in commercial fuel oil samples increased with temperature [15], and Cetin et al observed higher VOC concentrations in ambient air around a petrochemical complex during warmer periods [16]. Nevertheless, these studies did not specifically investigate carcinogenic VOCs in PDPs or simulate the temperature ranges encountered in actual industrial processes. Some workplace operations are performed at elevated temperatures. For example, the automotive painting process operates at 125–160°C [17], rubber compression molding at 150°C [18] where mold release agents are sprayed onto hot dies, and polyester fiber manufacturing at 100–160°C [19] where lubricants are applied to heated drawing rollers. Additionally, the furnace process in a continuous annealing line is conducted at approximately 800°C in steel mills [20]. These processes can trigger the thermal release of hazardous VOCs, including carcinogens not listed on standard SDSs.
Therefore, the goals of this study were to (1) qualitatively screen for carcinogens in PDPs, (2) quantitatively measure benzene and ethylbenzene concentrations, and (3) evaluate the effect of temperature increases (up to 180°C) on the volatilization and concentration of these carcinogens. Our hypothesis is that higher temperatures, representative of industrial processes, will significantly increase both the number and concentration of carcinogenic VOCs released from PDPs.
2. Materials and methods
2.1. The outline of this study
Eighty-four PDPs were collected, which were readily available on the market and commonly used in the workplace. Tens of thousands of chemicals are used in the workplace; however, “chemicals to be managed under the law,” consist of only 171 kinds and 1,197 hazardous substances. Therefore, Yoon et al suggested detailed guidelines to classify all chemicals by health hazards [21]. As per the guide, 16 petroleum chemicals were designated as Special Management Materials among the chemicals in the Republic of Korea Survey of Distribution of Chemicals (KSDC) database. These chemicals were classified as Carcinogen 1A (“Known to have carcinogenic potential humans”) or Carcinogen 1B (“Presumed to have carcinogenic potential for humans”) by the Globally Harmonized System of Classification and Labeling of Chemicals [22]. Among the 16 chemicals, “Distillates (petroleum), hydrotreated-heavy-paraffinic (CAS No: 64742-54-7)” and “Distillates (petroleum), hydrotreated-light-paraffinic (CAS No: 64742-55-8)” are the most frequently used in the Republic of Korea Survey of Distribution of Chemicals database [2]. Using mainly these two types of chemicals, 30 PDPs were filtered from the collected PDPs.
The 30 PDPs were categorized into four groups. S-01 to S-10 belonged to the viscous liquid of lubricant (VL) group, S-11 to S-20 belonged to the aerosol of lubricant (AL) group, S-21 to S-26 belonged to the semisolid of grease (SG) group, and S-27 to S-30 belonged to the aerosol of remover (AR) group (Table 1, Table S1). The 30 PDPs were analyzed qualitatively and quantitatively in two steps. First, bulk samples were analyzed to identify carcinogens and quantify benzene and ethylbenzene. Second, an analysis was conducted at room temperature to 180°C to evaluate volatile substances.
Table 1.
The basic characteristic of information about 30 petroleum-derived products
| Product use (State of matter) | n | Major petroleum chemical composition of PDPs |
EU CLP | K-MOEL | |
|---|---|---|---|---|---|
| Chemical name | CAS No | ||||
| Lubricant (viscous liquid) | 10 | Distillates (petroleum), hydrotreated heavy paraffinic | 64742-54-7 | Carc. 1B | Carc. 1B |
| Distillates (petroleum), hydrotreated light paraffinic | 64742-55-8 | Carc. 1B | Carc. 1B | ||
| Lubricant (aerosol) | 10 | Distillates (petroleum), hydrotreated heavy paraffinic | 64742-54-7 | Carc. 1B | Carc. 1B |
| Distillates (petroleum), hydrotreated light | 64742-47-8 | — | — | ||
| Grease (semisolid) | 6 | Distillates (petroleum), hydrotreated heavy paraffinic | 64742-54-7 | Carc. 1B | Carc. 1B |
| Residual oils (petroleum), hydrotreated | 64742-57-0 | Carc. 1B | Carc. 1B | ||
| Remover (aerosol) | 4 | Ligroine; petroleum ether | 8032-32-4 | Carc. 1B | Carc. 1B |
| Distillates (petroleum), hydrotreated light | 64742-47-8 | — | — | ||
Carc, carcinogen; CAS, Chemical Abstracts Service; EU CLP, European Union Regulation on Classification, Labelling, and Packaging; K-MOEL, Ministry of Employment and Labor in the Republic of Korea; n, numbers of PDPs; PDPs, petroleum-derived products.
Thirty PDPs were categorized into four groups. Representative chemicals among the chemicals which were mostly contained in each group were presented.
EU CLP and K-MOEL Carcinogen classifications–Carc (Carcinogen) 1B: Presumed to have carcinogenic potential for humans.
2.2. Chemicals and reagents
Benzene and ethylbenzene were obtained from Sigma-Aldrich (St. Louis, MO, USA) and Fluka (Buchs, Switzerland), respectively. High-performance liquid chromatography (HPLC) grade methylene chloride and methanol were from J.T. Baker (Phillipsburg, NJ, USA). Methylene chloride was used as a solvent for analyzing bulk samples, and methanol was used as a solvent of stock solution for evaluating volatile carcinogens in PDPs.
2.3. Sample preparation and analysis
2.3.1. Identification carcinogens in PDPs
To prevent the loss of benzene and ethylbenzene from the PDPs owing to evaporation, all items were refrigerated at 4°C. VOCs contained in PDPs were analyzed after 1/100 dilution with methylene chloride. Samples were vortexed, sonicated (30 min), and then analyzed. During a sample analysis, lab blanks included every five samples.
GC-MS (7890A/5975C, Agilent, USA) analyzed bulk samples. A volume of 1 μl extracted sample was injected in the split mode (3:1) by an autosampler (Combi PAL, CTC Analytics, Switzerland). DB-624 UI column (122-1334 UI, Agilent, USA) was used with high purity helium gas (≥99.999%) at 1.3 ml/min constant flow. GC temperature program is as follows: 35°C (3 min), 6°C/min to 100°C, 12°C/min to 180°C, and 20°C/min to 200°C, hold 7 min. Injector and MS interface temperatures were 225°C and 230°C, respectively. Mass spectrometers were obtained under electron ionization (EI) mode at 70 eV and the quadrupole and ion source temperatures were at 150°C and 230°C, respectively. To quantify target compounds and to screen carcinogenic substances, synchronous selected ion monitoring (SIM)/scan mode was used and scan range was m/z = 35-225. The target and qualifier ions for the SIM analysis were split into two different ion groups based on compound elution order and retention time [23] (Table S5).
2.3.2. Identification volatile carcinogens in PDPs with increasing temperature
The full evaporation technique was employed to identify the volatile components with increases in temperature and to overcome matrix effects [24]. Samples were prepared by weighing a 0.1 g sample into a 20 ml headspace vial. The vials were sealed with Polytetrafluoroethylene (PTFE)/silicone septum. A headspace syringe (2.5 ml volume, MSH 02-00B, Hamilton, Germany) was used for this analysis.
Samples were agitated (10 min, 500 rpm) at 30°C, 60°C, 120°C, 150°C, and 180°C. The prepared 10 μl of standard solution was filled into a 20 ml headspace vial. Standard solutions were agitated (10 min, 500 rpm) at 180°C. After agitation, an injection of 500 μl of the headspace gas was performed into the GC-MS at the rate of 1000 μl/s with headspace syringe heated for 95°C by autosampler. Lab blanks were included every 10 samples.
For headspace analysis, DB-5MS UI column (122-5532 UI, Agilent, USA) was used. Helium carrier gas was maintained at 1 ml/min constant flow. GC temperature program is as follows: initial 40°C for 1 minute and then 10°C/min to 245°C for 2 minutes. The injector and MS interface temperature were set at 250°C. Mass spectrometers were obtained under the EI mode at 70 eV and the quadrupole and ion source temperatures were 150°C and 230°C, respectively. To quantify target compounds and to screen carcinogenic substances, synchronous SIM/scan mode was used and scan range was m/z = 35-250. The target and qualifier ions for the SIM analysis were split into two different ion groups based on compound elution order and retention time [15].
2.4. Quality control and data analysis
2.4.1. Quality control
Quality control was performed to evaluate the accuracy and precision of the analysis. Relative standard deviations (%RSDs) were determined by analyzing the 5 mg/L (bulk sample) and 50 mg/kg (headspace) of the standard solution over five repetitions. We confirmed that the %RSD of benzene and ethylbenzene was within the 20% limit recommended by the US Environmental Protection Agency [21].
The limit of detection (LOD) was three times the standard deviation based on seven replicates of the lowest level of the standard solution [25] (Table S2).
2.4.2. Data analysis
R software (version 4.5.1, R Foundation for Statistical Computing, Vienna, Austria) was used to perform the statistical analyses. A database containing concentrations of benzene and ethylbenzene based on temperature conditions was transformed using a logarithmic function. Not detected (ND) values were set to a half of that of the LOD for data analysis [26]. However, for benzene, some samples were below the detection limit in both bulk samples and under elevated temperature conditions. Therefore, these samples were excluded from the benzene analysis rather than being substituted with one-half the LOD.
The MS Workstation data files were translated into MassHunter Data format using GC-MS translator (Agilent, USA) to acquire more accurate qualitative analysis. Because of many overlapping chromatograms of total ion chromatogram in the analysis results, every total ion chromatogram was extracted by the Unknown Analysis software (version B.09.00, Agilent, USA) as a deconvoluted ion chromatogram (DIC), which is a structure used to potentially match the mass spectrum provided by the W11N17 (Wiley11-Nist17, Wiley, USA). All DICs were used for the identification of unknown compounds detected in the analysis results based on the matching rate (>80%) of mass spectra archived in the W11N17 library.
The following databases were used to identify carcinogens in PDPs. Tox-Info database which has IARC and National Toxicology Program (NTP) [27], the European Union Regulation on Classification, Labelling, and Packaging (EU CLP) database [28], and theMinistry of Employment and Labor in the Republic of Korea (K-MOEL) [29].
The carcinogen information and classification were based on criteria suggested by each agency. IARC 1: Carcinogenic to humans, Group 2A: Probably carcinogenic to humans, Group 2B: Possibly carcinogenic to humans. NTP Carcinogen classifications K: Known to be carcinogenic to humans, R: Reasonably anticipated to be carcinogenic to humans. EU CLP and K-MOEL carcinogen classifications are Carcinogen 1A: Known to have carcinogenic potential humans, Carcinogen 1B: Presumed to have carcinogenic potential for humans, and Carcinogen 2: Suspected human carcinogens.
3. Results
3.1. Qualitative analysis of carcinogens in PDPs
3.1.1. Identification and detection frequency of various carcinogens
Qualitative analysis was conducted in PDPs. Although more than several hundred mass spectra were generated from the DIC in each temperature condition, approximately 90 compounds per temperature condition were well-matched (>80%) with the W11N17 library.
As the temperature increased, the number of detected carcinogens showed a consistent upward trend. The total relative abundance also exhibited a significant rise at elevated temperatures (≥120°C); specifically, it peaked at 120°C, slightly decreased at 150°C, and increased again at 180°C (Fig. 1). The highest-risk carcinogens from four classification systems—IARC Group 1, NTP K, EU CLP Carcinogen 1A, and K-MOEL Carcinogen 1A—were generally not detected at 30°C but emerged from 60°C to 180°C. According to the IARC criteria (Fig. 1C), two carcinogens classified as Group 1 and three classified as Group 2A were detected at 180°C. Based on EU CLP regulations (Fig. 1B), high-risk carcinogens (1A and 1B) comprised approximately 64% (7/11) of the total carcinogens identified at 180°C.
Fig. 1.
The number of carcinogens and their relative abundance at different temperatures in four classification systems. The panels display classifications according to (A) NTP, (B) EU CLP, (C) IARC, and (D) K-MOEL. The stacked bars (left axis) represent the number of distinct carcinogenic species identified at each temperature. The line graph (right axis) indicates the total relative abundance (sum of peak areas) of these carcinogens. Error bars represent the standard error.
Abbreviations: EU CLP, European Union Regulation on Classification, Labelling, and Packaging; IARC, International Agency for Research on Cancer; K-MOEL, Ministry of Employment and Labor in Republic of Korea; NTP, National Toxicology Program. For detailed classification criteria, see Section 2.4.2.
Detection rates of carcinogens 1A and 1B classified by EU CLP regulations [30] were analyzed by product groups at 180°C. VL showed the highest rate at 75% (3/4), followed by AL at 43% (3/7), and SG and AR each at 40% (2/5) (Table S3).
3.1.2. Detection patterns of carcinogens as a function of temperature
We identified specific detection patterns for individual carcinogens (Table 2). Methylene chloride (IARC 2A) and ethene, 1,1-dichloro (IARC 2B) showed “Consistent Detection”, appearing consistently from 30°C, mainly in the SG and AR groups. In contrast, other carcinogens such as oxirane, methyl- (IARC 2B), propane, 2-nitro- (IARC 2B), and hydrazine, 1,2-dimethyl (IARC 2A) showed “Thermally Induced Detection”. These compounds were not detected at ambient temperatures (30–60°C) but appeared clearly at elevated temperatures (≥120°C). Meanwhile, 1,3-butadiene (IARC 1) showed “Irregular Detection” at high temperatures without a clear pattern.
Table 2.
Classification of carcinogenic emission patterns in petroleum-derived products based on temperature
| Detection pattern | Representative carcinogen (IARC group) | Count at 30°C | Max count at ≥120°C | Primary product type | Temperature trend |
|---|---|---|---|---|---|
| Consistent detection (Present from 30°C) | Methylene chloride (2A) | 4 | 4 | SG, AR | Stable |
| Ethene, 1,1-dichloro- (2B) | 2 | 2 | SG, AR | Stable | |
| Thermally induced detection (Only at High Temp.) | Oxirane, methyl- (2B) | 0 | 4 (at 180°C) | SG, AL | Increase |
| Propane, 2-nitro- (2B) | 0 | 3 (at 120°C) | VL, AL, AR | Increase | |
| Hydrazine, 1,2-dimethyl-(2A) | 0 | 4 (at 180°C) | AL, SG | Increase | |
| Irregular detection (Unclear Pattern) | 1,3-Butadiene (1) | 1 | 1 (at 150/180°C) | AR, SG, AL | Unclear |
Note: Detection counts represent the number of products (n = 30) in which each carcinogen was detected (>80% library match). “Consistent detection” refers to compounds present from room temperature (30°C). “Thermally induced detection” refers to compounds absent at 30°C that emerge at elevated temperatures (≥120°C).
AL, aerosol of lubricant; AR, aerosol of remover; IARC, International Agency for Research on Cancer; SG, semisolid of grease; VL, viscous liquid of lubricant.
3.2. Quantitative analysis of benzene and ethylbenzene in PDPs
3.2.1. Concentrations of benzene and ethylbenzene in PDPs
Benzene was detected in 14 of 30 (46.67%) PDPs (Table 3). The highest benzene concentrations were 11.82 mg/L in lubricants for a 2-stroke motorcycle engine oil (S-08), followed by 6.09 mg/L in a sticker stain remover (S-30), and 4.78 mg/L in lubricants for a 2-stroke motorcycle engine oil (S-03). Ethylbenzene was detected in 29 of 30 (96.67%) PDPs. The highest ethylbenzene concentrations were 364.60 mg/L in lubricants for a 2-stroke motorcycle engine oil (S-08) followed by 143.96 mg/L in lubricants for a 2-stroke motorcycle engine oil (S-03) (Table S1).
Table 3.
Benzene and ethylbenzene concentrations in petroleum-derived products by groups. Petroleum-derived products were categorized into four groups
| Product use (State of matter) | Benzene |
Ethylbenzene |
||||
|---|---|---|---|---|---|---|
| Detected in products | Concentrations (mg/L) |
Detected in products | Concentrations (mg/L) |
|||
| AM±SD | Range | AM±SD | Range | |||
| Lubricant (viscous liquid) | 3/10 (30%) | 6.22 ± 4.10 | ND – 11.82 | 10/10 (100%) | 54.87 ± 111.27 | 2.99 – 364.60 |
| Lubricant (aerosol) | 7/10 (70%) | 2.69 ± 0.76 | ND – 4.07 | 9/10 (90%) | 23.96 ± 39.85 | ND – 135.37 |
| Grease (semisolid) | 2/6 (33.33%) | 2.21 ± 0.16 | ND – 2.37 | 6/6 (100%) | 4.12 ± 0.23 | 3.77 – 4.42 |
| Remover (aerosol) | 2/4 (50%) | 4.30 ± 1.79 | ND – 6.09 | 4/4 (100%) | 7.79 ± 6.08 | 3.81 – 18.30 |
AM±SD, arithmetic mean ± standard deviation; Max, maximum; Med, median; Min, minimum; ND, not detected.
The limit of detection is as follows: benzene, 0.62 mg/L and ethylbenzene, 0.88 mg/L.
In the four groups, benzene was most often detected in AL (70%, 7/10) followed by AR (50%, 2/4). VL had the highest average concentrations (ND–11.82 mg/L), followed by AR, AL, and SG. Ethylbenzene was detected in all samples except for one sample in AL (S-19). VL had the highest average concentrations (2.99–364.60 mg/L), followed by AL, AR, and SG. The average concentrations of benzene and ethylbenzene were the highest in VL and lowest in SG (Table 3).
3.2.2. Concentrations of benzene and ethylbenzene in PDPs as a function of temperature
Benzene concentrations in some PDPs increased with increasing temperature compared to that of the bulk sample, specifically S-03 and S-08 in VL, S-12, S-14, and S-15 in AL, S-26 in SG and S-30 in AR. Benzene was ND in AL for S-13, S-17, and S-19 when analyzing bulk samples; however, benzene concentrations increased with increasing temperature (Table S1, Table S4). Benzene concentrations in VL, AL, and AR increased as temperature increased compared to that of the bulk sample. SG groups increased at 60°C but not 30°C compared to that of the bulk sample. The VL group showed the highest concentration at 120°C, while AL, SG, and AR groups showed maximum concentrations at 180°C (Table 3, Fig. 2).
Fig. 2.
Concentrations of benzene and ethylbenzene in petroleum-derived products as a function of temperature. The line plots represent the mean values and error bars represent the standard error. For benzene analysis, three samples (S-24, S-28, S-29) were excluded as they were consistently non-detectable.
The limit of detection is as follows: benzene, 0.14 mg/kg and ethylbenzene, 0.11 mg/kg.
Ethylbenzene concentrations in some PDPs increased with increasing temperature among the PDPs in which ethylbenzene was detected by analyzing the bulk sample for all PDPs, except S-17 and S-20 in AL, and S-28 in AR (Table S1, Table S4). Ethylbenzene concentrations in VL, AR, and SG increased from 60°C to 180°C compared to that of the bulk sample. The VL group increased at 30°C, 60°C, and 120°C, reaching a peak at 120°C, then decreased at 150°C, and reached its maximum at 180°C. The AL group peaked at 120°C and then decreased at 150°C and 180°C. The SG group continuously increased at all measured temperatures. The AR group peaked at 150°C with a slight decrease at 180°C (Table 3, Fig. 2).
4. Discussion
The quantitative analysis showed that benzene was detected in 70% of products in AL, 50% in AR, 33.33% in SG, and 30% in VL. Ethylbenzene was identified in all PDPs except one. Benzene and ethylbenzene concentrations rose steadily from 30°C to 120°C in AL and SG. Benzene and ethylbenzene concentrations rose steadily from 30°C to 120°C in AL and SG.
Benzene and ethylbenzene concentrations increased with temperature in most PDPs, consistent with enhanced VOC volatilization at elevated temperatures. However, some products showed different patterns at higher temperatures. The VL group for benzene peaked at 120°C, not at 180°C. There are several possible explanations for this result. First, the equilibrium between the sample (condensed) phase and gas phase (headspace) is important in headspace techniques [31]. It is believed that thermal equilibrium had not been established between the condensed phase and headspace in the vial at 180°C. Second, the PDP matrix was complex [32,33]. The adsorption rates of benzene and ethylbenzene may not have been optimized because of other chemicals.
Concentrations of benzene and ethylbenzene were the highest in S-08 followed by S-03. These two products are in the VL group and are used for small engines, such as weed mowers, leaf blowers, and chainsaws. Weed mowers and leaf blowers are hand-held machines. With hand-held machines, the effect on the health of toxic substances in the exhaust is locally amplified by their stationary use very close to the worker [34]. It should be purified like any other PDPs such that the concentrations of benzene and ethylbenzene remaining as impurities are removed.
Previous studies reported benzene concentrations of 1–930 ppm in brake cleaners, 1,700–15,000 ppm in cleaning products, and up to 11,000 ppm in lubricants [[12], [13], [14]]. In this study, the average concentration of benzene in PDPs was 6.23 mg/L (ND–11.82 mg/L).
There are reasons as to why the benzene concentrations in PDPs were lower than those detected in previous studies. First, filtered PDPs were readily available on the market for consumers. Household chemical products undergo a hazard and risk assessment following the Safety of Household Chemical Products and Biocidal Products Act [35] before they are sold on the market. Therefore, industrial chemical PDPs that are not managed under this law tend to have higher concentrations of benzene and ethylbenzene. According to other study that investigated the health hazards of cleaner agents used in the workplaces, benzene was detected in four of the five cleaner products. The benzene concentrations of the four products were 700, 1,700, 2,100, and 9,300 ppm [36]. Second, the benzene concentrations in the PDPs were gradually reduced. Exposure criteria have been reduced worldwide with an awareness of benzene risk. Studies have shown that continuous exposure to 1 ppm during working hours increases mortality from leukemia [37,38]. The time-weighted average of 0.5 ppm exposure showed that the incidence of deaths from leukemia was not significantly different from that of the non-exposure groups. To prevent the risk of developing leukemia from occupational exposure to benzene, the current guidelines for benzene exposure is the threshold limit value (TLV)-TWA of 0.5 ppm and TLV–short term exposure limit (STEL) of 2.5 ppm [39]. In the Republic of Korea, exposure criteria for benzene were also revised from TLV-TWA 1 ppm and TLV-STEL 5 ppm [40] to TLV-TWA 0.5 ppm and TLV-STEL 2.5 ppm [41]. The concentration of benzene in gasoline has gradually decreased from 6.0% in 1992 to 0.7% in 2009 after the risk of benzene was recognized [42,43].
Benzene and ethylbenzene were not listed on the 30 SDSs for the PDPs as ingredients because carcinogens must be specified in the SDS when they represent 0.1% or higher in the mixture [44]. However, because only trace levels of benzenes can cause cancer, many epidemiological studies have suggested maintaining a low exposure standard (ppb level) to prevent diseases caused by occupational exposure to benzene [[45], [46], [47]]. Therefore, benzene should be listed as an ingredient on SDSs, as suggested by Kopstein, even if the benzene concentrations in the PDPs are much less than 0.1% [48].
The number of carcinogens increased as the temperature rose. The workplace temperature varies depending on the work process. Some manufacturing processes are conducted at high temperatures in confined places, such as automotive processes, and workers often enter these spaces for maintenance. Aromatic hydrocarbons, such as benzene, exist in high concentrations at high temperatures because they are relatively very stable compared to aliphatic hydrocarbons [49]. Therefore, workers are more easily exposed to high concentrations of benzene or ethylbenzene.
The identification of “thermally induced detection” patterns is critical for industries utilizing high-temperature processes. Beyond automotive painting (125–160°C), elevated temperatures are frequently encountered in rubber compression molding (150°C) and special fiber manufacturing (100–160°C), where lubricants or mold release agents are often applied by spraying them onto hot molding dies or rollers. Our findings suggest that these practices can lead to the thermal release of carcinogens, such as methyl oxirane, which are not listed on standard SDSs because they are not volatile at ambient temperatures. While these hazards may not occur in every instance, the potential for “hidden” risk at temperatures exceeding 120°C is significant. This underscores the need for industrial hygienists to perform risk assessments under actual operational temperatures rather than relying solely on room temperature chemical composition.
This study had several limitations. First, VOCs evaporate easily when sampling propellant spray products because of the compressed gas in the propellant spray products. To minimize loss, the propellant spray products are collected into the mouth of the vial with the cap closing as rapidly as possible. Second, the headspace analysis technique was not optimized at 180°C. Therefore, some products did not show the highest concentrations at 180°C. Third, exposure assessment in actual high temperature workplaces is required to validate our findings under industrial conditions.
It is suggested that further study should be undertaken in the following areas. First, it is necessary to quantify chemicals that were present in the qualitative analysis using reagents. Second, it is necessary to identify volatile carcinogens in PDPs considering vapor pressure and to evaluate volatile carcinogens in PDPs above 180°C (for example, the furnace process is performed at 800°C).
This study conducted a quantitative and quantitative analysis of benzene and ethylbenzene in PDPs and identified an increase in the concentrations of benzene and ethylbenzene according to temperature. Furthermore, it was found that the number of carcinogens increased as the temperature rose. Benzene and ethylbenzene needed to be eliminated as much as possible in PDPs. If it is impossible to remove, we suggest that it is clearly stated in the SDS because workers have the right to understand their risk. Various carcinogens appeared at high temperatures compared to that of the bulk samples. PDPs, such as lubricants and removers, contained trace levels of benzene and ethylbenzene. If these products are used in confined workplaces, it is necessary to provide sufficient ventilation and to inform workers of the chemical hazards before entering the manufacturing area.
CRediT authorship contribution statement
Dongwon Kim: Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Investigation, Conceptualization. Jimin Kim: Software, Investigation, Data curation, Conceptualization. Nahyun Lee: Validation, Methodology, Data curation, Conceptualization. Taeyeon Kim: Methodology, Formal analysis.
Statement on the use of AI tools
During the preparation of this work, the author(s) used Perplexity in order to improve readability and clarity. After using this tool, the author(s) reviewed and edited the content as needed and take(s) full responsibility for the content of the publication.
Conflicts of interest
The authors declare no conflict of interest.
Acknowledgments
This study was supported by the National Research Foundation of Korea (BK21 FOUR 5199990214126).
Footnotes
Supplementary data to this article can be found online at https://doi.org/10.1016/j.shaw.2026.01.005.
Appendix A. Supplementary data
The following are the Supplementary data to this article:
References
- 1.United States Energy Information Administration (US EIA) US EIA; 2024. US product supplied for crude oil and petroleum products. [Google Scholar]
- 2.Yoon C., Jeong J., Lee K., Park M., Ryu S., Jeomg W., Oh Y., Kim D., Cho H., Song S., Kim M. Occupational Safety and Health Research Institute; Korea: 2019. A study on the impact analysis of the change in the classification system and management standard of hazardous substances under the occupational safety and health. Report No.: OSHRI 2019-1477. [Google Scholar]
- 3.Clark C., McKee R., Freeman J., Swick D., Mahagaokar S., Pigram G., Roberts L., Smulders C., Beatty P. A GHS-consistent approach to health hazard classification of petroleum substances, a class of UVCB substances. Regul Toxicol Pharmacol. 2013;67:409–420. doi: 10.1016/j.yrtph.2013.08.020. [DOI] [PubMed] [Google Scholar]
- 4.Kwon M., Kang M., Lee K., Jung S. A study on the CMR criteria for domestic petroleum stream UVCB substances. J Korean Soc Environ Eng. 2020;42:645–653. [Google Scholar]
- 5.House J., Grimm F., Klaren W., Dalzell A., Kuchi S., Zhang S., Lenz K., Boogaard P., Ketelslegers H., Gant T., Wright F., Rusyn I. Grouping of UVCB substances with new approach methodologies (NAMs) data. Altex. 2020;38:123. doi: 10.14573/altex.2006262. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.House J., Grimm F., Klaren W., Dalzell A., Kuchi S., Zhang S., Lenz K., Boogaard P., Ketelslegers H., Gant T., Rusyn I., Wright F. Grouping of UVCB substances with dose-response transcriptomics data from human cell-based assays. Altex. 2022;39:388–404. doi: 10.14573/altex.2107051. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7.Lai A., Clark A., Escher B., Fernandez M., McEwen L., Tian Z., Wang Z., Schymanski E. The next frontier of environmental unknowns: substances of unknown or variable composition, complex reaction products, or biological materials (UVCBs) Environ Sci Technol. 2022;56:7448–7466. doi: 10.1021/acs.est.2c00321. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8.Heibati B., Pollitt K.J., Charati J.Y., Ducatman A., Shokrzadeh M., Karimi A., et al. BTEX exposure assessment and quantitative risk assessment among petroleum product distributors. Ecotoxicol Environ Saf. 2017;144:445–449. doi: 10.1016/j.ecoenv.2017.06.055. [DOI] [PubMed] [Google Scholar]
- 9.Kirkeleit J., Riise T., Bratveit M., Moen B.E. Increased risk of acute myelogenous leukemia and multiple myeloma in a historical cohort of upstream petroleum workers exposed to crude oil. Cancer Causes Control. 2008;19:13–23. doi: 10.1007/s10552-007-9065-x. [DOI] [PubMed] [Google Scholar]
- 10.Sathiakumar N., Delzell E., Cole P., Brill I., Frisch J., Spivey G. A case-control study of leukemia among petroleum workers. J Occup Med. 1995;37:1269–1277. doi: 10.1097/00043764-199511000-00005. [DOI] [PubMed] [Google Scholar]
- 11.International Agency for Research on Cancer (IARC) IARC; France: 2025. IARC list of classifications monographs. [Google Scholar]
- 12.Gwak S. The graduate school catholic university of Daegu; Korea: 2014. Estimation of occupational exposure associated with petroleum-derived products containing trace levels of benzene [master's thesis] [Google Scholar]
- 13.Fries M., Lee S., Kenyon E. Airborne exposures associated with the typical use of an aerosol brake cleaner during vehicle repair work. J Occup Environ Hyg. 2018;15:531–540. doi: 10.1080/15459624.2018.1467017. [DOI] [PubMed] [Google Scholar]
- 14.Choi S., Lim C., Kim H. Potential risk of benzene in petroleum-derived products used from 1974 to 2012 in Korea. Aerosol Air Qual Res. 2019;19:548–558. [Google Scholar]
- 15.Anyakudo F., Omo-Irabor O.O., Martincigh B.S. Analysis of volatile organic compounds in fuel oil by headspace GC-MS. Int J Environ Anal Chem. 2018;98:323–337. [Google Scholar]
- 16.Cetin E., Odabasi M., Seyfioglu R. Ambient volatile organic compound (VOC) concentrations around a petrochemical complex and a petroleum refinery. Sci Total Environ. 2003;312:103–112. doi: 10.1016/S0048-9697(03)00197-9. [DOI] [PubMed] [Google Scholar]
- 17.Akafuah N.K., Poozesh S., Salaimeh A., Patrick G., Lawler K., Saito K. Evolution of the automotive body coating process - a Review. Coatings. 2016;6:24. [Google Scholar]
- 18.Hamed G.R. Anisotropy induced during compression molding of rubber. J Appl Polym Sci. 1982;27:4081–4083. [Google Scholar]
- 19.Fujimoto K., Kato J. Process for producing a polyester fiber. US Patent No. 2004;6(692):671 B2. [Google Scholar]
- 20.Ginzburg V.B., Ballas R. CRC Press; Boca Raton (FL): 2000. Flat rolling fundamentals. [Google Scholar]
- 21.Yoon C., Jeong J., Lee K., Park M., Park J., Ryu S., Jeong W., Oh Y., Kim D., Hwang G., et al. Occupational Safety and Health Research Institute; Korea: 2018. A study on the improvement of the classification system and management standard of hazardous substances under the occupational safety and health act. Report No.: OSHRI 2018-848. [Google Scholar]
- 22.United Nations Economic Commission for Europe (UNECE) United Nations; 2019. Globally Harmonized System of classification and labelling of chemicals (GHS) eighth revised edition. [Google Scholar]
- 23.United States Environmental Protection Agency (US EPA) US EPA; 2017. Method 8260d volatile organic compounds by gas chromatography/mass spectrometry. [Google Scholar]
- 24.Markelov M., Guzowski J.P. Matrix independent headspace gas chromatographic analysis. This full evaporation technique. Anal Chim Acta. 1993;276:235–245. [Google Scholar]
- 25.United States Environmental Protection Agency (US EPA) US EPA; 2015. Detection limit/quantitation limit summary table. [Google Scholar]
- 26.Hornung R.W., Reed L.D. Estimation of average concentration in the presence of nondetectable values. Appl Occup Environ Hyg. 1990;5:46–51. [Google Scholar]
- 27.National Institute of Food and Drug Safety evaluation (NIFDS) 2025. Tox-info. Korea: nifds. [Google Scholar]
- 28.European Chemicals Agency (ECHA) Table of harmonised entries in Annex VI to CLP_ATP13. Finland: ECHA. 2025 [Google Scholar]
- 29.Ministry of Employment and Labor (MoEL) MoEL; Korea: 2020. Exposure limits for chemical substances and physical agents (MoEL Public Notice No. 2020-48) [Google Scholar]
- 30.European Parliament & European Council . European Parliament; Belgium: 2008. REGULATION No 1272/2008. [Google Scholar]
- 31.Kolb B., Ettre L.S. John Wiley & Sons; New York (NY): 2006. Static headspace-gas chromatography: theory and practice. [Google Scholar]
- 32.Mushrush G. CRC Press; Boca Raton (FL): 1995. Petroleum products: instability and incompatibility. [Google Scholar]
- 33.Oppenlaender T., Walton N., Cane A. JSTOR; 2007. Petrochemicals; pp. 1698–1732. [Google Scholar]
- 34.Neri F., Foderi C., Laschi A., Fabiano F., Cambi M., Sciarra G., Aprea M., Cenni A., Marchi E. Determining exhaust fumes exposure in chainsaw operations. Environ Pollut. 2016;218:1162–1169. doi: 10.1016/j.envpol.2016.08.070. [DOI] [PubMed] [Google Scholar]
- 35.Ministry of Environment (ME) 2020. Safety of Household chemical products and biocidal products act. Korea: ME. [Google Scholar]
- 36.Jeong K., Ahn Y., Kim H., Ju Y., Cho S., Jeong H., Cho M., Song H., Choi S., Ju S., Kim H., Park Y., Lee H., Lee J., Kim M., Kim B., Lee H., Eom K., Park C. Cleaner handling condition and health hazard investigation- focus on unregulated cleaners by occupational safety and health act.Occupational. Safety and Health Research Institute; Korea: 2018. Report No.: OSHRI 2018-866. [Google Scholar]
- 37.Crump K.S. Risk of benzene-induced leukemia: a sensitivity analysis of the pliofilm cohort with additional follow-up and new exposure estimates. J Toxicol Environ Health. 1994;42:219–242. doi: 10.1080/15287399409531875. [DOI] [PubMed] [Google Scholar]
- 38.Paxton M.B., Chinchilli V.M., Brett S.M., Rodricks J.V. Leukemia risk associated with benzene exposure in the pliofilm cohort. I. Mortality update and exposure distribution. Risk Anal. 1994;14:147–154. doi: 10.1111/j.1539-6924.1994.tb00039.x. [DOI] [PubMed] [Google Scholar]
- 39.Paustenbach D.J., Bass R.D., Price P. Reevaluation of benzene exposure for the Pliofilm (rubber-worker) cohort (1936-1976) J Toxicol Environ Health. 1992;36:177–231. doi: 10.1080/15287399209531633. [DOI] [PubMed] [Google Scholar]
- 40.Ministry of Employment and Labor (MoEL) MoEL; Korea: 2013. Exposure limits for chemical substances and physical agents (MoEL Public Notice No. 2013-38) [Google Scholar]
- 41.Ministry of Employment and Labor (MoEL) MoEL; Korea: 2016. Exposure limits for chemical substances and physical agents (MoEL Public Notice No. 2016-41) [Google Scholar]
- 42.Sheen D.H. Trends of qualities of gasoline and diesel fuels. Trans Korean Soc Automot Eng. 2001;23:13–19. [Google Scholar]
- 43.Ministry of Environment (ME) 2012. Clean air pollution act enforcement rules. Asterisk 33. Automotive fuel, additives or manufacturing of catalyst. Ordinance Ministry Environ No 463 Korea: ME. [Google Scholar]
- 44.Ministry of Employment and Labor (MoEL) MoEL; Korea: 2016. Standards on the classification, labeling and material safety data sheets of chemicals (MoEL Public Notice No. 2016-19) [Google Scholar]
- 45.Alexander C.C., Leonard S.L. An overview of occupational benzene exposures and occupational exposure limits in Europe and North America. Chem Biol Interact. 2005;153–154:43–53. doi: 10.1016/j.cbi.2005.03.007. [DOI] [PubMed] [Google Scholar]
- 46.Ciarrocca M., Tomei G., Fiaschetti M., Caciari T., Cetica C., Andreozzi G., Capozzella A., Schifano M., Andre J., Tomei F., Sancini A. Assessment of occupational exposure to benzene, toluene and xylenes in urban and rural female workers. Chemosphere. 2012;87:813–819. doi: 10.1016/j.chemosphere.2012.01.008. [DOI] [PubMed] [Google Scholar]
- 47.Weisel C.P. Benzene exposure: an overview of monitoring methods and their findings. Chem Biol Interact. 2010;184:58–66. doi: 10.1016/j.cbi.2009.12.030. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 48.Kopstein M. Potential uses of petrochemical products can result in significant benzene exposure: MSDSs must list benzene as an ingredient. J Occup Environ Hyg. 2006;3:1–8. doi: 10.1080/15459620500430581. [DOI] [PubMed] [Google Scholar]
- 49.Klippenstein S.J., Georgievskii Y., Harding L.B. On the formation and decomposition of C7H8. Proc Combust Inst. 2007;31:221–229. [Google Scholar]
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