Risk Quotient Analysis of Ozone Pollutants on the Occupational Health of Scavengers at Sarimukti Landfill, West Bandung Regency, Indonesia

The Ministry of Environment and Forestry reported that in 2021, the volume of waste generated in Indonesia reached 18.2 million tons per day [1]. This figure increased to 19.57 million tons per day in 2022 according to the National Waste Management Information System (SIPSN) [2]. Despite this significant volume, approximately 23.05% of the waste remained unmanaged [3], with food, plastics, and organic materials constituting the primary components [4]. Waste management practices in Indonesia still rely predominantly on landfilling, with 33 out of 46 major cities using landfills as the main disposal method, including West Bandung Regency [5].

One of the largest landfill sites in this region is the Sarimukti Landfill. Initially intended to serve 15 sub-districts, it is now jointly used by Bandung City, West Bandung Regency, and Cimahi City. In 2022, the waste volume received at the Sarimukti Landfill reached 146,676.44 tons/year, representing an increase of 33.94% compared to 2021 [4]. This landfill operates under an open dumping system, which has been associated with recurring fire incidents, including a major fire starting on August 19, 2023 [6]. The open dumping system contributes significantly to uncontrolled emissions of gases such as methane and volatile organic compounds [7], [8], which are precursors to ground-level ozone formation.

In landfill environments, ozone is generated through photochemical reactions involving methane and nitrogen oxides in the presence of sunlight. Methane, the third-largest anthropogenic greenhouse gas in the United States, alters radical chemistry in the troposphere and acts as a global precursor to ozone formation [8], [9]. Open dumping accelerates these emissions due to uncontained waste decomposition, leachate evaporation, and spontaneous combustion. Consequently, landfill workers, particularly informal scavengers, are exposed to elevated ozone levels without proper protection or regulatory oversight.

Ozone is a potent oxidizing agent that can cause a range of adverse health effects through inhalation, including respiratory inflammation, decreased lung function, cardiovascular stress, and increased risk of premature death [10], [11]. Studies have confirmed that prolonged or high-level exposure to ozone is associated with both acute and chronic health risks. While several studies have applied the Environmental Health Risk Assessment (EHRA) approach to evaluate urban air pollution risks [12], [13], [14], [15], very few have focused specifically on informal landfill workers such as scavengers, who experience disproportionate exposure levels and vulnerabilities.

This study addresses this research gap by assessing the Risk Quotient (RQ) of ozone exposure among scavengers at the Sarimukti Landfill. It further evaluates safe exposure thresholds, including concentration, duration, and frequency, under both real-time and 30-year projected exposure scenarios. The findings are expected to provide evidence-based input for the development of targeted interventions for improving occupational health in landfill settings.

This study employed a quantitative method to calculate the RQ value of ozone pollutants and to determine the limits of safe concentration, exposure duration, and exposure frequency among scavengers at the Sarimukti Landfill, West Bandung Regency. A longitudinal study design was applied, in which ozone concentration measurements were conducted for three months at two points in the landfill area. The measurements were performed by the Bandung Occupational Safety and Health Center, PT Ubar Jalindo Chemical and Environmental Laboratory, and Binalab Environmental Quality Testing Laboratory.

This study was conducted across three sampling periods, with the first sampling carried out on November 12, 2024, the second on January 24, 2025, and the third on February 2, 2025. All measurements were obtained from two points in the Sarimukti landfill. Additionally, air sampling was conducted during the rainy season.

Two types of research subjects were included. The first subject was ambient air, for which ozone concentration (C) in air was measured. The second subject consisted of 101 scavengers, from whom data were collected on daily exposure duration (tE), annual exposure frequency (fE), total exposure duration in years (Dt), body weight (Wb), and the average time period for non-carcinogen effects. Additional parameters included the inhalation rate (R), defined as the volume of air inhaled per hour, and the reference concentration (RfC) for ozone as an inhalation risk agent.

EHRA was conducted in several stages. First, the intake value (I) was calculated using the mathematical equation presented in Eq. (1). Subsequently, the RQ value was calculated by dividing the intake value by the reference concentration, as shown in Eq. (2). Safe concentrations were determined using the equations presented in Eqs. (3)−(5), which describe the calculation of non-carcinogenic safe exposure concentration, safe exposure duration (inhalation) and safe exposure frequency (inhalation).

Data were analyzed descriptively to determine the mean, minimum, and maximum values of pollutant concentration, RQ, exposure duration and frequency, as well as safe exposure concentration.

Under real-time conditions, the minimum intake values in Table 1 showed a mean of 0.886 $\mu$g/m$^3$/day with a standard deviation of 0.253. The values ranged from a minimum of 0.259 $\mu$g/m$^3$/day to a maximum of 1.509 $\mu$g/m$^3$/day. These results indicate that under current conditions, the lowest levels of ozone exposure exhibit notable inter-individual variability. The real-time maximum intake values were substantially higher, with a mean of 12.523 $\mu$g/m$^3$/day and a standard deviation of 3.576. The minimum recorded value was 3.654 $\mu$g/m$^3$/day, while the maximum reached 21.313 $\mu$g/m$^3$/day. This range suggests that some scavengers experience considerably elevated ozone exposure. Meanwhile, the real-time average intake values yielded a mean of 5.562 $\mu$g/m$^3$/day, with a standard deviation of 1.588. The values ranged from 1.623 $\mu$g/m$^3$/day, to 9.467 $\mu$g/m$^3$/day, indicating that the average exposure remains quite significant among most respondents.

Under the 30-year projected scenario, the minimum intake values were lower than those under real-time conditions. The mean minimum intake was 0.243 $\mu$g/m$^3$/day with a standard deviation of 0.188, indicating a narrower distribution. Intake values ranged from 0.000 $\mu$g/m$^3$/day to 0.823 $\mu$g/m$^3$/day, suggesting that some scavengers may experience negligible exposure in the long term. The projected maximum intake over the 30-year period showed a mean of 3.297 $\mu$g/m$^3$/day and a standard deviation of 0.941, with values ranging from 0.962 $\mu$g/m$^3$/day to 5.613 $\mu$g/m$^3$/day. Although these values are lower than the real-time maximum intake values, they indicate that some scavengers may still accumulate relatively high ozone exposure. Finally, the projected average intake values over 30 years exhibited a mean of 1.526 $\mu$g/m$^3$/day with a standard deviation of 1.182. The minimum and maximum values were 0.003 $\mu$g/m$^3$/day and 5.164 $\mu$g/m$^3$/day, respectively. These findings demonstrate that considerable ozone exposure persists for some individuals.

Under real-time conditions, the minimum RQ values presented in Table 2 showed a mean of 4.433 with a standard deviation of 1.265. The values ranged from a minimum of 1.293 to a maximum of 7.545. These results indicate that even at the lowest exposure levels, the majority of respondents exceeded the acceptablerisk threshold (RQ $>$ 1), indicating potential health problems. The real-time maximum RQ values were markedly elevated, with a mean of 62.619 and a standard deviation of 17.881. The minimum and maximum values were 18.269 and 106.567, respectively. This range demonstrates that some scavengers are exposed to exceptionally high ozone concentrations that pose health risks in the short term. Meanwhile, the real-time average RQ values yielded a mean 27.183 with a standard deviation of 7.941, ranging from 8.114 to 47.333. These findings indicate that most respondents are consistently exposed to ozone concentrations far exceeding safe limits in the short term.

Under the 30-year projected scenario, the minimum RQ values exhibited a mean of 1.216 with a standard deviation of 0.942. The values ranged from a minimum 0.002 to a maximum of 4.115. These indicate that despite the potential for risk reduction in the long term, some scavengers continue to experience exposure exceeding the threshold. The projected maximum RQ values over the 30-year period showed a mean of 16.489 and a standard deviation of 4.708. The minimum and maximum values were 4.811 and 28.063, respectively. Although these values are lower than the real-time RQ values, they still reflect a high risk for some individuals. Finally, the projected average RQ values over 30 years exhibited a mean of 7.630 and a standard deviation of 5.914, with minimum and maximum values of 0.014 and 25.818, respectively. These results suggest that ozone-related health risks persist among scavengers although long-term risk levels are generally lower and more variable than current conditions.

Under real-time conditions, the average Cnk$_{\text {(safe)}}$ value as presented in Table 3 was 1.970, with a standard deviation of 0.745. The values ranged from a minimum of 1.047 to a maximum of 6.108. Under the 30-year projected scenario, the average Cnk$_{\text {(safe)}}$ value increased dramatically to 109.085, with a standard deviation of 490.137, indicating considerable inter-individual variability. The minimum Cnk$_{\text {(safe)}}$ value over the 30-year period was 1.920, while the maximum reached 3444.228. This wide range suggests that long-term cumulative ozone exposure may be substantial for some scavengers, especially those residing in areas with high ozone concentrations or engaging in activities that increase the risk of exposure.

For the minimum t$_{\text {Enk(safe)}}$ value, Table 4 shows an average of 2.077 with a standard deviation of 0.419. The minimum and maximal values were 1.314 and 3.653, respectively. These findings indicate that under the lowest conditions, most scavengers can tolerate ozone exposure for only approximately two hours before exceeding the safe threshold. This relatively low duration suggests that ozone exposure tends to quickly pose potential health risks for individuals with direct and continuous exposure.

In contrast, the maximum t$_{\text {Enk(safe)}}$ value represents the longest allowable exposure duration under elevated ozone concentrations. The maximum t$_{\text {Enk(safe)}}$ value showed an average of only 0.147, with a standard deviation of 0.030. The values ranged from 0.093 to 0.259. These results demonstrate that under elevated ozone concentrations, the duration of safe exposure becomes extremely limited. This indicates that high-level exposure rapidly exceeds the tolerance capacity of the human body.

Finally, the average t$_{\text {Enk(safe)}}$ value reflects the general safe exposure duration for ozone inhalation. The mean value was 0.331, with a standard deviation of 0.066, and ranged from 0.210 and 0.582.

Under conditions of minimum ozone concentration (Table 5), the mean value of safe exposure frequency was 73.972 days/year, with a standard deviation of 27.848. The values ranged from a minimum of 41.749 days/year to a maximum of 259.773 days/year. These findings indicate that under the lowest ozone pollution conditions, scavengers can be exposed relatively frequently without exceeding the risk threshold, although considerable inter-individual variability remains evident. In contrast, under conditions of maximum ozone concentration, the safe exposure frequency decreased dramatically. The mean value was only 5.237 days/year, with a standard deviation of 1.972. The minimum and maximum values were 2.956 and 18.392 days/year. These results demonstrate that during periods of poor air quality, only limited exposure can be tolerated before health risks arise, and the tolerance between individuals becomes considerably narrower. At the average ozone concentration, the mean f$_{\text {Enk(safe)}}$ value was 11.791 days/year, with a standard deviation of 4.439 and values ranging from 6.655 to 41.409 days/year. This suggests that under typical ozone exposure conditions, scavengers have a moderate but limited tolerance for exposure, with most individuals able to be safely exposed for approximately 12 days/year.

Based on the EHRA analysis of ozone exposure among 101 scavengers at the Sarimukti Landfill in West Bandung Regency in 2024, several parameters were measured to characterize ozone-related health risks. These parameters included intake value, RQ, Cnk, t$_{\text {Enk(safe)}}$, and f$_{\text {Enk(safe)}}$. Each parameter was assessed under two scenarios: real-time conditions representing current exposure and a 30-year projection.

For the intake parameter, the results showed that the highest average real-time ozone intake occurred under maximum exposure conditions, with a value of 12.523 $\mu$g/kg/day. The average intake was 5.562 $\mu$g/kg/day, while the minimum intake was 0.886 $\mu$g/kg/day. Under the 30-year projected exposure scenario, the highest intake value was 3.297 $\mu$g/kg/day, with an average intake of 1.526 $\mu$g/kg/day and a minimum intake of 0.243 $\mu$g/kg/day. In general, the intake values decreased with longer exposure duration, reflecting a more evenly distributed accumulation process over the long term. However, the maximum intake values under both scenarios indicate a substantial potential health risk under extreme conditions or environments with persistently elevated ozone concentrations [16], [17].

RQ calculations, which serves as a parameter to assess the magnitude of potential health risks, revealed concerning results under real-time conditions. The maximum real-time RQ reached 62.619, while the average and minimum RQ values were 27.183 and 4.433, respectively. These findings suggest that most individuals were exposed to ozone concentrations exceeding the acceptablerisk threshold, as RQ values greater than 1 signify potential adverse health effects. Under the 30-year projected exposure scenario, RQ values decreased significantly, with a maximum of 16.489, an average of 7.630, and a minimum of 1.216. Nevertheless, the average RQ remaining above 1 indicates that long-term chronic health risks may still occur for some individuals [18], [19], [20].

These findings must be contextualized within Indonesia’s environmental policies. According to the Decree of the Minister of Environment and Forestry No. 10 of 2021, ambient ozone concentration limits are set at 235 $\mu$g/m$^3$ for a one-hour average and 157 $\mu$g/m$^3$ for an eight-hour average. However, the present study demonstrates that real-time exposures among scavengers poses health risks even when concentrations remain below these regulatory thresholds. This discrepancy is likely attributable to the vulnerability of the scavenger population and their prolonged exposure patterns. Furthermore, the absence of specific occupational exposure limits for ozone under Indonesia’s labor regulations complicates the assessment of workplace safety for informal workers such as scavengers. When compared with the American Conference of Governmental Industrial Hygienists threshold limit value for ozone of 0.1 ppm or approximately 196 $\mu$g/m$^3$ for heavy work, the average concentrations observed in this study indicate that the landfill is considered to be an unsafe environment.

In addition, the wide variation in safe Cnk observed in Table 3, especially under the 30-year projected exposure scenario, may be attributed to individual differences in exposure parameters such as inhalation rate, body weight, and exposure duration. The mathematical model used to calculate Cnk is highly sensitive to these variables, resulting in the broad range of outcomes. This heterogeneity reflects the diverse working conditions experienced by scavengers. Some individuals are exposed for longer durations or in areas with higher ozone concentrations, thereby influencing the risk profiles. These findings underscore the urgent need for the development of localized occupational standards and the implementation of targeted protective measures.

The health risks identified in this study, as reflected by elevated RQ values under both real-time and 30-year projection scenarios, are consistent with established biological mechanisms of ozone toxicity. Ozone is a strong oxidizing agent that reacts rapidly upon contact with the epithelial lining of the respiratory tract. According to Xue et al. [20], inhaled ozone disrupts epithelial cell integrity, leading to oxidative stress, lipid peroxidation, and activation of inflammatory signaling pathways such as nuclear factor kappa B (NF-$\kappa$B) and mitogen-activated protein kinase (MAPK). This process triggers the release of cytokines (e.g., IL-6, IL-8), promotes immune cell infiltration, and sustains chronic inflammation, ultimately resulting in structural and functional impairments of the lungs [20].

Repeated or chronic exposure to zone even at relatively low concentrations can lead to persistent respiratory inflammation, decreased lung capacity, airway remodeling, and heightened susceptibility to allergens or pathogens. These mechanisms underpin the elevated RQ values observed in the 30-year projection scenario despite lower intake values. Although intake appears numerically lower due to time-averaged accumulation, the RQ remains high because chronic exposure amplifies biological vulnerability. In addition, the RfC applied in the calculations reflects long-term health sensitivity rather than immediate toxicological response.

Moreover, individual vulnerability factors such as pre-existing health conditions, inadequate nutrition, and the lack of protective equipment likely exacerbate the physiological response to ozone exposure, especially among informal workers such as scavengers. Therefore, even modest long-term exposure may translate into substantial cumulative health risks, thereby justifying the persistently elevated RQ values across projected exposure scenarios.

Furthermore, the safe Cnk value showed a marked contrast between real-time and long-term conditions. The average real-time Cnk was 1.969 $\mu$g/m$^3$ with a standard deviation of 0.745 and a maximum value of 6.108 $\mu$g/m$^3$. In comparison, the 30-year projected Cnk increased dramatically, with an average of 109.084 $\mu$g/m$^3$ and a maximum value reaching 3444.228 $\mu$g/m$^3$. This pattern suggests that longer exposure durations correspond to higher concentration thresholds considered acceptablewithin the risk assessment framework, based on the assumption that risk is distributed over an extended time period [21], [22], [23].

The t$_{\text {Enk(safe)}}$ parameter, or safe exposure duration, describes the maximum time an individual can be exposed to ozone without incurring health risks and is calculated under various concentration scenarios. At minimum concentrations, the average safe exposure duration was 2 hours/day, with a maximum of 3.6 hours/day. In contrast, at maximum concentrations, the average safe exposure duration dropped drastically to 0.14 hours/day, with a maximum of only 0.25 hours/day. At average concentrations, the safe exposure duration was 0.33 hours/day. These values indicate that the higher ozone concentrations substantially reduce the duration during which exposure can be considered safe [24], [25], [26].

Finally, the f$_{\text {Enk(safe)}}$ parameter, or safe exposure frequency, further supports the findings. At minimum ozone concentrations, the average safe exposure frequency was 73.972 days/year, indicating that in low-ozone environments, individuals may be exposed quite frequently without jeopardizing their health. Conversely, at maximum concentrations, the average safe exposure frequency was only 5.237 days/year, with a minimum of 2.956 days/year. At average ozone concentrations, the safe exposure frequency was 11.791 days/year. This pattern aligns with earlier findings that elevated ozone concentrations limit both the duration and frequency of exposure considered safe for human health [27].

Ozone exposure in humans, especially at high concentrations or over prolonged periods, can lead to a range of adverse health effects, particularly involving the respiratory system [28]. Ozone is a strong oxidizing gas that, when inhaled, can irritate the respiratory tract, induce lung inflammation, decrease lung function, and exacerbate chronic conditions such as asthma and bronchitis [29]. At higher levels of exposure, ozone may also trigger oxidative stress in body tissues, leading to systemic effects, especially among vulnerable groups such as children, the elderly, and individuals with pre-existing respiratory conditions [30]. The primary mechanism underlying these effects involves oxidative reactions that damage the epithelial lining of the respiratory tract, increase cell membrane permeability, and activate inflammatory immune responses.

Based on the aforementioned EHRA results, it was found that most ozone intake values exceeded the safe thresholds, particularly under real-time conditions. Although a decrease was observed under the 30-year duration scenario, the average RQ values remained above one. This indicates that both short-term and long-term health risks remain significant. The high Cnk values in the long-term projection also suggests that the safe threshold standards for ozone exposure should be considered more adaptively in the context of chronic exposure scenarios. Additionally, the safe exposure duration and frequency are increasingly limited as ozone concentrations rise, underscoring the urgency of implementing public health interventions. It is also necessary to control ozone emissions and their precursors such as nitrogen oxides and volatile organic compounds around the landfill area, including from open waste burning, vehicles, or nearby industries [31]. Furthermore, it is important to use appropriate personal protective equipment, such as high-filtration masks, to reduce direct exposure among scavengers [32].

This study demonstrates that ozone exposure among scavengers at the Sarimukti Landfill in West Bandung Regency poses a significant health risk. The EHRA approach revealed that the RQ values under both real-time and 30-year projected scenarios exceeded the safe threshold (RQ $>$ 1), indicating both acute and chronic exposure risks. The average real-time RQ value reached 27.183, while the projected 30-year average remained at 7.630. Additionally, the safe exposure duration and frequency were found to be extremely limited, especially under maximum concentration scenarios, where individuals could only be safely exposed for an average of 0.147 hours/day and 5 days/year. These findings highlight the urgent need for comprehensive ozone exposure control measures, particularly for informal workers in landfill settings. Effective interventions, including emission reductions, protective equipment provision, regulated working hours, and health monitoring, are essential to mitigate long-term health risks and improve occupational safety for vulnerable populations.