Health risk assessment of benzene, toluene, ethylbenzene, and xylene among occupational and residential populations at landfill, Indonesia

Personal monitoring of benzene, toluene, ethylbenzene and xylene (BTEX) exposure at municipal solid waste landfills remains scarce in Indonesia, despite its importance for capturing individual exposure variability and improving health risk assessment. This study evaluated inhalation health risks associated with personal BTEX exposure among occupational and residential populations living around an open dumping landfill. Personal air samples were collected from 56 participants, including scavengers, landfill workers, nearby residents and controls group. Personal monitoring was conducted using personal air sampling pumps at 0.045–0.2 L min −1, following NIOSH 1501 Method. BTEX concentrations were analyzed using GC-FID. Benzene was the dominant contributor to non-carcinogenic risk across all exposed groups. Scavengers exhibited the highest non-carcinogenic risk, with a mean Hazard Index (HI) of 3.73 ± 2.36 (p < 0.05). Although the average HI among landfill workers and nearby residents remained below the safety threshold, maximum values reached 3.72 and 1.54, respectively, indicating that some individuals exceeded the acceptable non-carcinogenic risk threshold (HI > 1). Benzene-related carcinogenic risk was also highest among scavengers (4.05 × 10 −5 – 1.50 × 10 −4). Compared with controls, both non-carcinogenic and carcinogenic risks were 13 times higher among scavengers and four times higher among landfill workers and nearby residents. These findings show open dumping landfills are significant sources of benzene exposure and associated inhalation health risks. They also highlight the urgent need for targeted interventions prioritizing scavengers, strengthened occupational protection and sustainable waste management strategies to reduce health risks among occupational and nearby communities.

Municipal solid waste (MSW) landfills are major sources of Volatile Organic Compounds (VOCs), particularly in developing countries where open dumping remains the predominant waste disposal practice, exposing millions of people to hazardous emissions (Manheim et al., 2021; Wang et al., 2021). Indonesia is among the countries that still rely extensively on open dumping for municipal waste disposal, with many disposal sites operating without adequate landfill gas collection or emission control systems. Consequently, landfill workers and surrounding communities may experience prolonged exposure to airborne contaminants generated during waste decomposition and landfill operations. Among these pollutants, benzene, toluene, ethylbenzene, and xylenes (BTEX) are of particular concern because of their persistence and toxicity (De Sá Borba et al., 2017; Lakhouit and Al-Rashed, 2022). BTEX are released through waste degradation, leachate volatilization, vehicle exhaust, heavy equipment operation, and other landfill-related activities (Duan et al., 2014, 2021; Pan et al., 2023). Because these compounds are often imperceptible at low concentrations, chronic exposure may occur unnoticed, particularly in open dumping system lacking effective emission controls (Hajivand et al., 2024; Li et al., 2023). Consequently, landfill workers and nearby residents may experience prolonged inhalation exposure, which has been associated with respiratory, hematological, neurological and carcinogenic health effects (Kamani et al., 2023; Liu et al., 2016; Saeedi et al., 2024; Wu et al., 2018; Khademi et al., 2022; Rahman et al., 2026; Nair et al., 2019).

Altough BTEX monitoring has been widely studied in urban and industrial settings, but investigation in landfill environments remain scarce, particularly those evaluating associated health risks (Dehghani et al., 2018; El-Hashemy and Ali, 2018; Fandi et al., 2020; Ghobakhloo et al., 2024; Ghosh et al., 2023; Hamid et al., 2019; Pradini Yudison, 2020). Several studies have reported that landfill-derived BTEX may pose carcinogenic risks exceeding accceptable thresholds, even among residents living several kilometers from disposal sites (Pan et al., 2023; Liu et al., 2016; Fang et al., 2022). However, comparative assessments of inhalation health risks among different landfill-exposed populations (landfill workers, scavengers, nearby residents, and non-exposed controls) remain limited, restricting a comprehensive understanding of the public health burden associated with landfill emissions.

Despite growing concern over landfill-related air pollution, comprehensive inhalation health risk assessments based on personal BTEX exposure remain limited. Previous investigations have largely evaluated occupational and residential populations separately (Abidin et al., 2023; Duan et al., 2021; Lakhouit and Alsulami, 2020; Lim et al., 2018; Liu et al., 2016; Wang et al., 2021), preventing direct comparison of health risks across different exposure groups. Moreover, health risk assessment based on direct measurements of personal exposure remain scarce (Liu et al., 2022; Tehrani et al., 2025). Many previous studies have relied on default exposure assumptions rather than site-specific concentration and anthropometric data, potentially leading to substantial uncertainty in risk estimates (Khademi et al., 2022; Lakhouit and Alsulami, 2020; Yousefian et al., 2020). According to the United States Environmental Protection Agency (US EPA), inhalation health risk assessment can be conducted using a tiered approach, in which higher tiers progressively incorporate more site-specific exposure information to reduce uncertainty in risk estimation. While Tier 1 assessments generally rely on conservative default assumptions, Tier 2 utilizes measured environmental concentrations together with receptor-specific exposure parameters, resulting in more realistic estimates of both non-carcinogenic and carcinogenic health risks. Therefore, Tier 2 is particularly appropriate for evaluating health risks in landfill environments where exposure characteristics vary considerably among different population groups. The application of Tier 2 inhalation risk assessment enables the integration of measured exposure concentrations and receptor-specific parameters, providing more accurate and representative estimates of health risks (Priestly and Ong, 2012). This knowledge gap is particularly evident in developing countries, where personal exposure data from landfill environments remain extremely limited.

Understanding health risks associated with personal exposure to BTEX from landfill is essential for protecting vulnerable population and generating scientific evidence to support Sustainable Development Goal (SDG) 3 (Good Health and Well-being) to reduce the adverse health impacts of environmental pollution. To our knowledge, this is the first study in Indonesia to integrate personal BTEX exposure monitoring with a Tier 2 inhalation health risk assessment across multiple landfill-exposed populations, including landfill workers, scavengers, nearby residents, and a non-exposed control group.

This study aimed to (i) determine personal exposure concentrations of BTEX, (ii) assess carcinogenic and non-carcinogenic inhalation health risks using a Tier 2 approach, and (iii) compare health risks among occupational and residential populations at the Sarimukti municipal solid waste (MSW) landfill, Indonesia, the primary disposal facility serving the Bandung metropolitan area. The findings provide scientific evidence to support evidence-based risk management strategies and public health protection for populations living and working around open dumpsites.

Study sites description

The study was conducted at the Sarimukti Municipal Solid Waste Landfill (107°20′59″E, 6°48′03″S), and surrounding residential areas (1–5 km), in Sarimukti Village, Cipatat District, West Bandung Regency, West Java, Indonesia (Figure 1). As the primary disposal facility for the Greater Bandung metropolitan area, the landfill covers 43.44 ha, with 16.48 ha actively used for waste disposal and additional expansion areas under development. Waste input ranges from 250 to 400 truckloads per day and receives 1,200–2,000 tons of waste daily, which increasing annually by 3–4%. It has experienced several major fire events in recent years, potentially increasing emissions of hazardous pollutants. The waste stream is dominated by food waste (42%), followed by paper and cardboard (31%), wood (25%), and residual materials (2%) (Jabar Provincial Government, 2024; West Java Environment Management Agency, 2023). Based on these conditions, inhalation health risk associated with landfill derived emissions among workers and nearby residents have not been comprehensively evaluated. Personal exposure monitoring was conducted at participant specific locations reflecting daily activity patterns, with sampling coordinates provided in Supplementary Table S1.

Participant and ethical clearance

A total of 56 adult male representing occupational and residential exposure groups were enrolled after providing written informed consent, and the study protocol was approved by the Research Ethics Committee of UNPAD (No. 904/UN6.KEP/EC/2024). Eligible participants were adult males (≥18 years old) who had worked or resided at the study site for at least one year (Abidin et al., 2024; Njoku et al., 2019). Individuals who were unwilling or unable to provide written informed consent were excluded. Participants were recruited using a purposive sampling approach to ensure representation of the principal occupational and residential populations potentially exposed to landfill emissions. Recruitment was conducted voluntarily, and all eligible individuals who agreed to participate during the study period were included. The study population comprised 30 landfill workers, 4 scavengers, and 22 residents, including 12 individuals from Sarimukti Village (residents living within a 1–3 km radius of the landfill) and 10 from Nanggeleng Village as a Control (residents living within more than 3 km radius of the landfill). The control was selected because it is located more than 3 km from the landfill in the predominant upwind direction and at a higher elevation than the landfill, reducing the potential influence of landfill-derived atmospheric pollutants. In addition, control participants had no occupational exposure to waste handling or other known BTEX sources. The relatively small number of scavengers reflects the limited number of eligible individuals available and willing to participate during the sampling period. Landfill workers included formal operational personnel responsible for waste handling, compaction, soil covering, leachate treatment, and facility maintenance. Monitored occupations comprised administrative coordinators, security personnel, heavy equipment operators, compost and warehouse operators, mechanics, fueling personnel, infrastructure staff, and wastewater treatment operators. Most operational workers followed an 8-h workday, 6 days per week, while security personnel worked 12-h shifts. Informal workers (scavengers) were also included due to their prolonged presence in active disposal zones. Their activities involved collecting recyclable materials such as metals, plastics, and bottles, with working durations ranging from 13 to 16 h per day in active landfill areas. Residential participants were recruited from Sarimukti and Nanggeleng villages located near the landfill. The characteristics of the study participants are presented in Table 1.

BTEX personal air sampling

Personal BTEX exposure was monitored during working hours among landfill workers, scavenger, and nearby residents performing routine activities. Monitoring was carried out for one month during the dry season (15 August–9 September Cantwell, 2025), as previous studies have reported higher emissions under elevated temperature conditions (Lim et al., 2018). Potential confounders such as smoking or other activities that could influence measurements were recorded throughout monitoring. Personal air sampling was conducted using calibrated low-flow pumps (GilAir Plus Personal Air Sampling Pump, Sensidyne FL 33716, USA) compliant with ISO 9001:2008, ISO/IEC 17025:2005, ISO/IEC 80079–34, ATEX Directive 94/9/EEC, and IECEx standards (Sensidyne, LP, 2017). The pumps were connected to activated coconut-shell charcoal sorbent tubes (100/50 mg; SKC Inc., Pittsburgh, PA, USA) consisting of a 7 cm glass tube (4 mm i.d., 6 mm o.d.) containing two sections of 20/40 mesh charcoal thermally treated at 600 °C, with 100 mg in the front section and 50 mg in the backup section separated by a 2 mm polyurethane foam plug (Ghobakhloo et al., 2024; Khademi et al., 2022). Sampling flow rates ranged from 0.045–0.135 L min −1 depending on sampling duration and maximum recommended volume following NIOSH Method 1501.

Sampling durations ranged from 6–12 h according to occupational schedules, including rotation division (6–7 h), security personnel (12 h), heavy equipment operators (6.5 h), operational and technical staff (8 h), and scavenger (≈11 h). Meteorological parameters obtained from a weather station during monitoring included temperature (22.8–31.7 °C, 28.3 ± 2.3 °C), atmospheric pressure (0.95–0.96 atm, 0.96 ± 0.002 atm), relative humidity (43–99%, 78.8 ± 14.3%), and wind speed (0.0–4.1 m s −1, 0.5 ± 0.7 m s −1). Temperature, pressure, and sampled air volume were recorded to calculate standard air volume, allowing BTEX concentrations to be corrected to standard conditions (25 °C, 1 atm). Samplers were positioned within the breathing zone of each participant during routine activities (Fandi et al., 2020; Liu et al., 2022). After sampling, sorbent tubes were sealed, stored at 4 °C, and analyzed within seven days to minimize analyte loss.

Sample preparation, analysis and determination of BTEX concentration

Personal air samples were collected using a calibrated low-flow personal air sampling pump (GilAir Plus Personal Air Sampling Pump, Sensidyne, FL 33716, USA), certified in accordance with ISO 9001:2008, ISO/IEC 17025:2005, ISO/IEC 80079–34, ATEX Directive 94/9/EC, and IECEx standards. The collected activated carbon tubes were transported to the laboratory, and the sorbent sections were extracted with 1 mL dichloromethane (99.9%, Merck) for 30 min under agitation and filtered through a 0.2 μm PTFE membrane (Santos and Teixeira, 2023). BTEX concentrations were determined using a modified NIOSH 1501 method with GC-FID (GC-2010 Plus, Shimadzu) equipped with a 30 m × 0.25 mm × 0.25 μm capillary column and 2 μL splitless injection (Ghobakhloo et al., 2024; Liu et al., 2022; Yousefian et al., 2020). Quality assurance and quality control (QA/QC) protocols were conducted following the Eurachem Guide. External calibration curves were established for each BTEX compound prior to sample analysis, demonstrating excellent linearity across the analytical range (Supplementary Figure S2). Based on replicate blank measurements, the limits of detection (LoD) and quantification (LoQ) ranged from 0.02 to 0.08 ppm and 0.05 to 0.24 ppm, respectively (Cantwell, 2025). Field blanks equivalent to 12.5% of the total samples were included to ensure analytical quality (Dehghani et al., 2018). The measured BTEX concentrations obtained from GC analysis were corrected to standard conditions (25 °C and 1 atm) prior to exposure assessment. Standard air volume was calculated using the appropriate correction equation, and the final BTEX concentrations were expressed in micrograms per cubic meter (μg.m −3).

Inhalation health risk assessment

Personal exposure assessment to BTEX through the inhalation pathway was evaluated in accordance with the Risk Assessment Guidance for Superfund (RAGS), Volume I: Human Health Evaluation Manual, Part F, Supplemental Guidance for Inhalation Risk Assessment were calculated to quantify individual exposure levels (US EPA, 1989, 2009). The inhalation exposure concentration, expressed as Exposure Concentration (EC), was calculated using Equation 1, (Li et al., 2023):

In these calculations, the following parameters were used: ECᵢ refers to Exposure Concentration of each compound i (μg.m −3), derived from the measured concentration of i compound in air (CAᵢ) obtained through GC–FID analysis of BTEX compounds (μg.m −3); ET represented exposure time as the total duration of daily exposure during working activities (hour.day −1); EF denotes exposure frequency referred to the number of exposure days per year (day.year −1); ED refers to exposure duration represented the total number of years an individual had worked (years); Averaging time (AT) was calculated differently for non-carcinogenic and carcinogenic risk assessments for non-carcinogenic effects, AT was calculated as ED × 365 days, the factor of 24 converts the daily exposure duration (hours day −1) to a 24-h time-weighted average exposure concentration, whereas for carcinogenic risk it was assumed to be 70 years × 365 days (25,550 days). The parameters used for inhalation risk assessment are presented in Supplementary Table S2 (US EPA, 1989, 2009; USEPA, 2014).

Human health risk characterization associated with inhalation exposure to BTEX was evaluated by estimating both non-carcinogenic and carcinogenic risks. Non carcinogenic risk refers to the likelihood of adverse health effects, excluding cancer, arising from exposure to chemical contaminants at levels exceeding established safety thresholds. Conversely, lifetime cancer risk reflects the probability of developing cancer following long term exposure to carcinogenic compounds (Tehrani et al., 2025; US EPA, 2002). Non-carcinogenic and carcinogenic risks were assessed using the Hazard Quotient (HQ) and Lifetime Cancer Riks (LCR), respectively (Liu et al., 2022; Yousefian et al., 2020). Non-carcinogenic risk (HQ) was calculated as the ratio of the Exposure Concentration (EC i) to the reference concentration (RfC) for each compound (Equation 2). The cumulative non-carcinogenic risk from multiple contaminants was estimated using the Hazard Index (HI), calculated as the sum of individual HQ values Equations (3, 4). Lifetime carcinogenic risk (LCR) was estimated by multiplying the exposure concentration (ECᵢ) by the inhalation unit risk (IUR) (Equation 5).

Data for the health risk assessment were collected through structured questionnaires administered on the sampling day to characterize individual exposure parameters. These data facilitated the estimation of the magnitude and probability of potential adverse health effects among the exposed population under both current and potential future exposure scenarios. Toxicological reference values for BTEX inhalation exposure were obtained from the Integrated Risk Information System (IRIS) database and the Office of Environmental Health Hazard Assessment (OEHHA) (OEHHA, 2003; US EPA, 2003; USEPA, 2014).

Where HQ i, ECi, RfC, HI, LCR, CDI and CSF are represented as Hazard Quotient of i compound, Exposure Concentrations of i compound (μg.m −3), Reference Concentrations of i compound (μg.m −3), Hazard Index, Lifetime Cancer Risk, and Inhalation Unit Risk (μg.m −3) −1, respectively. Reference Concentrations (RfC) and Inhalation Unit Risk (IUR) values for the inhalation health risk assessment presented in Supplementary Table S3 (Masekameni et al., 2018; OEHHA, 2003; US EPA, 2003, 2005, 2017a, 2017b).

According to established risk assessment guidelines, for non-carcinogenic effects, a hazard index (HI) value <1 indicates no significant health risk, whereas HI values >1 suggest the potential for adverse health effects and indicate that the cumulative non-carcinogenic risk has exceeded the safety threshold (US EPA, 2009). For carcinogenic risk, lifetime cancer risk (LCR) values ≤1 × 10 −6 are considered negligible, risk levels within the range of 1×10 −6 –1×10 −4 are generally regarded as possible/acceptable but concern (minor carcinogenic risk), risk levels within the range of 1×10 −4 –1×10 −3 indicates a moderate carcinogenic risk (unacceptable); while risks exceeding 1.0 × 10 −3 indicate a high risk or significant carcinogenic concern (Li et al., 2023; Li and Yan, 2022; Liu et al., 2022; US EPA, 1989; Yousefian et al., 2020).

Statistical analysis

Data normality was assessed using the Shapiro–Wilk test. Group differences in BTEX concentrations (C A i) and health risk metrics (HQ, HI, and LCR) were evaluated using the Kruskal Walis test, followed by pairwise Mann–Whitney U tests when significant differences were detected. Binary logistic regression models were constructed, with non-carcinogenic risk (HQ; coded as 1 = HQ > 1 and 0 = HQ ≤ 1) as the dependent variables. The independent variables included exposure status (1 = exposed, 0 = control), age (years), smoking status (1 = smoker, 0 = non-smoker), PPE use (1 = not used, 0 = used), and residential proximity to the landfill (1 = ≤ 3 km, 0 = > 3 km) (Tiotiu et al., 2021; He et al., 2022; Abiola et al., 2021; Akparorue et al., 2020). Variables were selected based on biological plausibility and previous evidence, and multicollinearity was assessed using the variance inflation factor (VIF) before model fitting. Adjusted odds ratios (AORs) with 95% confidence intervals (CIs) were reported. A two-sided p -value < 0.05 was considered statistically significant.

Study participant’s characteristics

A total of 56 male participants were included in the study, comprising 30 landfill workers, 4 scavengers, 12 nearby residents, and 10 control participants (Table 1). The mean age ranged from 34 ± 8 years among scavengers to 44 ± 8 years among nearby residents. Landfill workers had the longest occupational exposure duration (13 ± 5 years), whereas scavengers experienced the longest daily exposure time (24 ± 0 h day −1). PPE use was generally low across all groups, with only 21% of participants reporting PPE use. Smoking prevalence was high, ranging from 75 to 100% across the study groups.

BTEX concentration in air (C A i) and exposure concentration (EC)

BTEX concentrations were determined by GC-FID. Quality assurance and quality control (QA/QC) evaluation confirmed robust analytical performance, with calibration curves for all BTEX compounds showed excellent linearity (R 2 > 0.995) across 0.01–10 ppm (Supplementary Figure S2). Recovery rates were 79% for benzene, 99% for toluene, 88% for ethylbenzene, and 75% for m, p-xylene and o-xylene. Exposure concentration (EC) was derived from measured concentrations in air (C A i) obtained through personal exposure monitoring using a personal sampler pump, followed by GC-FID analysis. The mean concentrations of BTEX compounds in air (C A i) were 61.99 ± 72.04 μg.m −3 for benzene, 29.08 ± 25.01 μg.m −3 for toluene, 3.00 ± 3.43 μg.m −3 for ethylbenzene, 20.12 ± 20.19 μg.m −3 of m, p-xylene, and 6.82 ± 4.49 μg.m −3 for o-xylene. Benzene was the dominant BTEX species, exhibiting the highest concentrations across nearly all sampling locations. The highest benzene concentration was detected among landfill workers (387.22 μg.m −3), especially heavy equipment operators and also relatively high benzene levels were also observed among mechanics (356.85 μg.m −3) (Supplementary Table S4). These concentrations were subsequently incorporated into the EC calculation by accounting for exposure time (ET), exposure frequency (EF), and exposure duration (ED), and normalized by the averaging time (AT). The BTEX concentrations in air (C A i) by study group shown in Figure 2.

Figure 2 reveals significant group differences in benzene, toluene, ethylbenzene, and m, p-xylene exposure concentrations (p < 0.05), but not o-xylene (p = 0.288). Scavengers exhibited the highest BTEX exposure, followed by landfill workers, whereas residents and controls showed lower levels. Among all compounds, benzene displayed the greatest variability, particularly within the scavenger and landfill worker groups.

The Kruskal Walis test demonstrated significant differences among the study groups for benzene, toluene, ethylbenzene, and m, p -xylene concentrations (p < 0.05), whereas o-xylene did not differ significantly (p = 0.288) (Table 2). Post hoc Mann–Whitney U analysis showed that scavengers and landfill workers generally exhibited significantly higher BTEX concentrations than nearby residents and the control group. In contrast, benzene and ethylbenzene concentrations did not differ significantly between landfill workers and scavengers, while no significant differences were observed between nearby residents and the control group for benzene, ethylbenzene, and o-xylene.

Mean non-carcinogenic EC values were highest for benzene (24.53 ± 35.88 μg.m −3), followed by toluene (11.51 ± 15.89 μg.m −3), ethylbenzene (1.09 ± 1.22 μg.m −3), m, p-xylene (8.63 ± 13.95), and o-xylene (2.83 ± 2.79) (Supplementary Table S5). Scavengers experienced the greatest cumulative BTEX exposure, followed by landfill workers, while residents and controls showed considerably lower levels (Figure 3). Benzene accounted for the largest share of total BTEX exposure across all groups. The lifetime EC for benzene used in carcinogenic risk assessment was 3.29 ± 3.70 μg.m −3 (Supplementary Table S6), reflecting the longer averaging time applied for cancer risk estimation.

Health risk assessment of BTEX

The cumulative non-carcinogenic risk of BTEX compounds was assessed using the hazard index (HI), calculated as the sum of individual hazard quotients (H Q i). The results showed elevated HI values across occupational and residential groups, with a predominance of non-carcinogenic risk exceeding the acceptable threshold (HI > 1) (Figure 4). Across all exposure groups, benzene was identified as the major contributor to total HI, with HQ values consistently exceeding unity and substantially surpassing those of the other BTEX compounds.

Figure 4a shows that benzene was the predominant contributor to the hazard quotient (HQ) among all exposure groups. The highest HQ values were observed among scavengers, followed by landfill workers, residents and controls exhibited substantially lower levels. Scavenger exhibited the highest non carcinogenic risk (HI = 3.73 ± 2.36, with range 2.49–8.50), approximately 13 times greater than that of the control group (p < 0.05) (Figure 4b). Landfill workers (0.75 ± 0.80) and nearby residents (0.74 ± 0.45) also showed elevated HI values, approximately threefold higher than controls, whereas post hoc comparisons between landfill workers and nearby residents exhibited comparable HI-BTEX values (p > 0.05) (Table 2). The proportion of individuals exceeding the acceptable non carcinogenic risk threshold (HI > 1) was highest among scavengers (100%), followed by residents (42%) and landfill workers (17%), while no exceedances were observed in the control group (Figure 4c). The ranked HI distribution further demonstrated that elevated risks were concentrated primarily among scavengers, with all samples exhibiting substantially higher HI values than other exposure groups (Figure 4d).

The carcinogenic risk assessment indicated elevated benzene LCR values among occupational and residential exposure groups (Figure 5a). Scavengers exhibited the highest risk levels (4.05 × 10 −5 –1.50 × 10 −4), followed by landfill workers (1.25 × 10 −6 –1.10 × 10 − 4) and nearby residents (2.12 × 10 −6 –8.06 × 10 −5), whereas controls showed substantially lower risks, with most values approaching or below 1 × 10 −6. As shown in Figure 5b, most participants were classified within the acceptable carcinogenic risk range (1 × 10 −6 –1 × 10 −4), while unacceptable risks (>1 × 10 −4) were observed primarily among scavengers and a small proportion of landfill workers. Compared with controls, carcinogenic risks of benzene were approximately 13-fold higher among scavengers and fourfold higher among landfill workers and nearby residents. The Kruskal Wallis test confirmed significant differences among exposure groups (p < 0.001), with post hoc comparisons using Mann-Withney U indicating significantly higher risks in scavengers than in all other groups (p < 0.05). In contrast, landfill workers and nearby residents exhibited comparable benzene carcinogenic risks (p > 0.05) (Table 2).

Logistic regression analysis

Binary logistic regression analysis was performed to evaluate the associations between potential confounding factors and non-carcinogenic health risk (HQ > 1). Adjusted odds ratios (AORs), 95% confidence intervals (CIs), and p -values are presented in Table 3. None of the evaluated variables, including exposure status, PPE use, smoking status, age, and residential proximity to the landfill, showed a statistically significant association with non-carcinogenic health risk (p > 0.05).

BTEX concentration in air (C A i) and and exposure concentration (EC)

Benzene was the dominant BTEX compound across all exposure groups, confirming its prominence as the primary landfill related airborne contaminant. The highest BTEX concentration in Air (CA i) were observed among occupationally exposed groups, particularly landfill workers and scavengers, reflecting their close proximity to active waste disposal and combustion related emission sources (Dehghani et al., 2018; Khademi et al., 2022; Popoola et al., 2023; Duan et al., 2021; Shinohara et al., 2019). Among landfill workers, the highest benzene concentration was observed in heavy equipment operators (387.22 μg m −3), followed by mechanics (356.85 μg m −3) (Supplementary Table S4). The elevated benzene concentrations observed among these occupations likely reflect the combined influence of occupation-specific activities, including engine exhaust, fuel combustion, and equipment maintenance, together with heterogeneous landfill emissions. Variations in waste composition, waste age, and active disposal areas may create localized BTEX hotspots, resulting in higher exposure among workers assigned to specific operational zones rather than uniform exposure across the landfill. This finding is consistent with previous studies identifying benzene as the major contributor to BTEX emissions in landfill environments (Liu et al., 2022; Yousefian et al., 2020). Significant differences in BTEX concentrations among exposure groups indicate heterogeneous exposure patterns driven by occupational activities and distance from emission sources. Post-hoc Mann–Whitney U analysis (Table 2) further demonstrated that landfill workers had significantly higher concentrations of benzene, toluene, ethylbenzene, and m, p-xylene than nearby residents. In contrast, benzene and ethylbenzene concentrations did not differ significantly between landfill workers and scavengers, indicating similarly high occupational exposure within the active disposal area. Notably, comparable benzene concentrations between landfill workers and nearby residents suggest that BTEX emissions are not confined to occupational settings but may also affect surrounding communities. These findings highlight the need for exposure control measures that address both on site workers and populations residing near landfill facilities.

Exposure concentration (EC) integrates pollutant concentrations with exposure duration, frequency, and activity patterns, providing a more realistic estimate of inhalation exposure. Scavengers exhibited the highest EC values for both non-carcinogenic and carcinogenic assessments, primarily due to their prolonged daily exposure and continuous presence within active disposal areas and continuous residential exposure near landfill (Li et al., 2023; Lombardi et al., 2023; Masekameni et al., 2018). This finding was supported by the post-hoc analysis, which showed significantly higher HQ, HI, and LCR values for scavengers than for nearby residents and the control group (Table 2), highlighting the combined influence of prolonged exposure duration and close proximity to emission sources.

In contrast, landfill workers experienced intermittent occupational exposure, whereas nearby residents were exposed through indirect atmospheric dispersion from landfill operations (Roffe et al., 2017). Nevertheless, the comparable exposure levels observed between these groups indicate that landfill emissions may affect surrounding communities beyond the occupational environment. Interestingly, nearby residents also exhibited significantly higher HI and LCR values than the control population, indicating that measurable health risks may extend beyond the landfill boundary despite lower exposure concentrations than occupational groups. The observed exposure gradient highlights the combined influence of proximity to emission sources and exposure duration on inhalation exposure. Benzene contributed the largest proportion of total EC across all exposure groups, consistent with its persistence and continuous release from waste degradation and combustion related activities (Duan et al., 2021; Liu et al., 2022). The predominance of benzene highlights its importance as a priority pollutant for exposure reduction and risk management strategies (Rahman et al., 2026). This finding underscores the importance of considering both exposure characteristics and environmental concentrations when assessing health risks associated with landfill emissions.

Non-carcinogenic risk assessment of BTEX

Scavengers experienced the highest non carcinogenic risk from BTEX exposure, with all individuals exceeding the acceptable threshold (HI > 1), whereas elevated risks were observed in only a subset of landfill workers and nearby residents. This pattern reflects differences in exposure intensity, duration and proximity to emission sources, with scavengers facing continuous exposure within active disposal areas. Benzene was the predominant contributor to total hazard quotients across all exposure groups, indicating its central role in driving non carcinogenic risk. Similar findings have been reported in previous landfill and BTEX exposure studies, which identified benzene as the primary determinant of health risk due to its high abundance and persistence in ambient air (Al-Harbi et al., 2021; Kasemy et al., 2019). Its dominance is likely associated with continuous emissions from waste degradation and combustion related activities within the landfill (Khademi et al., 2022; Liu et al., 2022; Yousefian et al., 2020).

Despite lower risk levels than occupational groups, a considerable proportion of nearby residents exceed the acceptable threshold, indicating that landfill derived BTEX emissions may affect surrounding communities. Windrose analysis supported this observation, showing predominant airflow toward residential areas (Supplementary Table S7; Supplementary Figure S1), consistent with the role of atmospheric dispersion in transporting airborne pollutants beyond landfill boundaries (Roffe et al., 2017). The absence of threshold exceedances in the control group further suggests that elevated risks were primarily attributable to landfill related emissions. Collectively, these findings highlight the need for improved emission control and routine environmental health monitoring to protect both occupationally and environmentally exposed populations.

Carcinogenic risk assessment of benzene

Benzene carcinogenic risk varied substantially across exposure groups, with scavengers exhibiting the highest lifetime cancer risk (LCR). More than 20% of scavengers exceed the unacceptable risk threshold (1 × 10 −4), while landfill workers and nearby residents also showed elevated risks relative to the control group. The observed risk gradient (scavengers>landfill workers>residents>controls) highlights the influence of prolonged exposure and proximity to landfill emission sources. The predominance of benzene as a carcinogenic risk driver is consistent with its established hematotoxic and leukemogenic effects. Following inhalation, benzene is metabolized into reactive intermediates that induce oxidative stress, DNA damage, and hematopoietic dysfunction, thereby increasing the risk of leukemia and other hematological disorders (Boogaard, 2022; Ladeira et al., 2020).

The LCR values observed in this study were comparable to those reported in landfill environments in Iran and China, although several participants approached or exceeded the acceptable risk threshold (Khademi et al., 2022; Ma et al., 2023). Differences among studies may reflect variations in landfill characteristics, waste composition, meteorological conditions, and exposure assessment approaches. In particular, the use of personal exposure monitoring in this study likely provided a more representative estimate of actual inhalation exposure than area-based measurements. Overall, these findings reinforce the critical role of benzene in landfill related cancer risk and highlight the need for effective emission control and long-term health surveillance for both occupationally and environmentally exposed populations.

Comparison with previous studies

Similar elevated BTEX concentrations have been reported in landfill environments in several countries (Supplementary Table S8), indicating that waste disposal activities act as persistent sources of aromatic hydrocarbon emissions. For example, studies in Canada reported substantially higher BTEX concentrations and elevated cancer risks, whereas studies in China showed relatively lower concentrations. Meanwhile, the BTEX concentrations observed in this study remained within the range reported for landfill environments in Iran (Khademi et al., 2022; Lakhouit and Alsulami, 2020; Liu et al., 2022). Compared with other environmental settings, the BTEX concentrations and associated health risks observed in this study were generally higher than those reported for urban populations, including traffic police, and comparable to or exceeding those reported for several occupational environments such as gas stations and paint manufacturing (Fandi et al., 2020; Ghobakhloo et al., 2024; Shinohara et al., 2019; Dehghani et al., 2018; Moolla et al., 2015). These findings suggest that open dumping landfills represent an important source of chronic BTEX exposure, with exposure levels approaching those observed in occupations traditionally recognized as having elevated VOC exposure. The observed differences among studies may be attributed to variations in climatic conditions, which influence volatilization and atmospheric dispersion of BTEX, as well as differences in landfill operational characteristics, including waste age, disposal practices, waste composition, landfill size, and the frequency of landfill fire events. In addition, methodological differences, such as sampling season, personal versus ambient air monitoring, analytical techniques, and exposure assessment approaches, together with the presence of surrounding emission sources (e.g., traffic and industrial activities), may further contribute to variability in reported BTEX concentrations and health risk estimates. Overall, the concentration levels observed in this study fall within the upper range reported globally, highlighting that BTEX exposure in open dumping landfills may equal or surpass that reported in several urban and industrial environments, thereby emphasizing the need for targeted exposure control and health risk management in landfill-affected populations.

Confounding factors and public health implications

Consistent with the binary logistic regression results (Table 3), age, smoking status, PPE use, and residential proximity to the landfill were not significant predictors of non-carcinogenic health risk (all p > 0.05). Although the adjusted odds ratio for age was marginally above unity, the association was not statistically significant (95% CI: 0.921–1.085; p = 0.995). All predictor variables exhibited VIF values below 5 (range: 1.040–1.118), indicating the absence of problematic multicollinearity (Supplementary Table S9). Similar findings have been reported in landfill environments, where exposure intensity and duration exert a greater influence on health risk than individual demographic characteristics (Liu et al., 2022). The absence of a significant effect of residential proximity further suggest that atmospheric dispersion may extend BTEX exposure beyond landfill boundaries, consistent with studies reporting measurable health risks among nearby communities (Fang et al., 2022; Roffe et al., 2017). These findings highlight the need for continuous monitoring and emission control to reduce landfill related health risks among exposed populations.

Study limitation

Several limitations should be considered when interpreting these findings. First, the relatively small sample size, particularly among scavengers, reflects the limited availability of eligible participants during the study period and may reduce the statistical power, representativeness of this high-exposure subgroup, and the reliability of comparisons among exposure groups. Therefore, findings related to scavengers should be interpreted with caution. Second, personal exposure monitoring was conducted during a single sampling period and therefore may not capture seasonal or long-term variations in BTEX concentrations. Third, the health risk assessment focused exclusively on BTEX compounds, whereas landfill emissions comprise a complex mixture of pollutants that may contribute to cumulative health effects. Finally, risk estimates were derived using standard exposure assessment assumptions and may not fully reflect individual variability in exposure patterns. Despite these limitations, the use of personal exposure monitoring provides a realistic characterization of inhalation exposure and offers valuable evidence regarding BTEX related health risks in landfill environments.

This study identifies open dumping landfills as important sources of BTEX exposure and associated health risks, with benzene emerging as the dominant compound contributing to both non-carcinogenic and carcinogenic risks. Personal exposure monitoring showed that scavengers experienced the highest non-carcinogenic and carcinogenic risks (approximately 13-fold higher than controls), while landfill workers and nearby residents exhibited comparable risk levels, indicating that landfill emissions affect both occupational and surrounding populations. The occurrence of unacceptable benzene-related carcinogenic risks highlights the need for greater attention to landfill-related air pollution as a public health concern. Strengthening emission control, implementing routine exposure monitoring, and improving landfill management practices are critical to reducing long-term health risks in vulnerable populations living and working near open dumping sites. These interventions support the achievement of Sustainable Development Goal (SDG) 3 through improved environmental health protection and risk management.