Keywords
Benzene, malondialdehyde, kidney function, car painting workshops, safe work
Car painting workers are at risk because of the use of solvents containing benzene as the main ingredient in the car painting process. One of the clinical effects of systemic benzene is kidney disorders. Therefore, the purpose of this study is to analyze the relationship between benzene and Risk Quotient (RQ) benzene concentrations with Malondialdehyde (MDA), Blood Urea Nitrogen (BUN), and creatinine levels in workers exposed to benzene in car painting workshops in Surabaya.
This study used an observational design with a cross-sectional method conducted at two car paint workshops in Surabaya. The study population was all workers exposed to benzene in the two car paint workshops, aged between 20-65 years in 2019. The sample was taken using an accidental sampling method, involving 30 respondents. Inclusion criteria included workers exposed to benzene and willing to participate, while exclusion criteria included workers with a liver or kidney disease history. The variables studied included benzene concentration, benzene RQ (benzene metabolite), malondialdehyde (MDA) levels as a marker of oxidative stress, and indicators of kidney function (BUN and creatinine levels). Data were analyzed using descriptive and bivariate analysis with Pearson correlation test.
There was no significant relationship between concentrations, RQ benzene, and MDA levels in workers in painting in Surabaya (p> 0.05). There was no significant relationship between benzene concentration, BUN levels, and creatinine levels in paint workers in Surabaya (p> 0.05). There was no significant relationship between benzene RQ and BUN and creatinine levels in paint workers in Surabaya (p> 0.05).
This study's results indicate that benzene's effects do not lead to impaired kidney function. The benzene RQ variable in this study did not become a determining factor in BUN and creatinine levels in workers.
Benzene, malondialdehyde, kidney function, car painting workshops, safe work
Our revisions have enhanced clarity throughout the manuscript. In the abstract and methods sections, we've explicitly defined the subject group, sampling method, inclusion/exclusion criteria, and utilized parameters. The discussion section now incorporates an explanation of Cytochrome P450 enzymes and their role in detoxification. Additionally, we've included a description of antioxidant activity in both the discussion and limitations sections. Finally, the methods section has been improved to clarify how exposure doses are determined or calculated for specific substances and effects.
See the authors' detailed response to the review by Said Moselhy
Benzene is a carcinogenic unsaturated closed-chain aromatic hydrocarbon compound (ATSDR, 2007). Benzene has been known as a good organic solvent for various processes in the industry such as the rubber industry, shoes, paint solvents, components in motor fuels, components in detergents, pesticides, and pharmaceutical manufacturing (Paustenbach et al., 1992; Wijaya, 1993). One informal sector that is often exposed to benzene is the car paint shop. The car painting work area is one of the areas that requires attention due to its increasing number with a large risk of occupational diseases. The car painting process uses solvents containing benzene as the main ingredient in the work process which can have a detrimental effect on health. These materials enter the body through absorption with more presentation through inhalation due to exposure to steam in the process of spray painting (Coresh et al., 2007).
Continuous benzene exposure can cause health effects. The body is continually exposed to benzene which causes symptoms and signs of chronic poisoning such as headaches, dizziness, nausea to vomiting, and slow-in-pale reactions due to anemia which is often accompanied by bleeding under the skin and mucosa. The clinical effects of benzene systemically cause cardiovascular, respiratory, neurological, gastrointestinal, liver, kidney, endocrine and reproductive systems, dermatology, local effects, hematological, immunological, metabolic, and allergic reactions (ATSDR, 2007; Cronkite et al., 1989; McHale et al., 2012; Tunsaringkarn et al., 2013).
In 2007 the (American Conference of Governmental Industrial Hygienists (ACGIH), 2007) issued a benzene chemical threshold of 0.5 ppm and since 1997 benzene has been confirmed to have carcinogenic properties in humans (Al = confirmed human carcinogen). The National Institute for Occupational Health and Safety (NIOSH) in 2010 set a recommended exposure limit or REL (Recommended Exposure Limit) of 0.1 ppm for 8 working hours (NIOSH, 2010). The threshold value of chemical factors at work according to Minister of Manpower and Transmigration number 13 in 2011 is 0.5 ppm. The benzene exposure pathway enters the human body in three ways, namely absorption through the skin, inhalation, and ingestion. Inhalation is a very important route to consider because benzene has volatile properties (ATSDR, 2007).
Benzene which enters the body oxidizes to proteins, lipids and produces Malondialdehyde (MDA). An increase in MDA levels is a sign of an increase in free radicals in the blood. Increased MDA levels even become a benchmark to determine the risk of cancer that will occur in workers exposed to benzene. Exposure to benzene in high content causes narcotic effects and irritation to the eyes and airways (Ho et al., 2006). Long-term exposure to low content can result in bone marrow suppression and can be associated with leukemia events or other blood cell disorders. The population of workers who work in the car painting industry or use benzene can be exposed to the highest exposure levels. For this reason, special attention needs to be paid to workers for occupational safety and health.
Exposure to benzene and alkyl benzene has been linked to kidney and liver injury and kidney cancer (Brautbar et al., 2006; Henderson, 2001). Other research conducted in Indonesia also stated that as many as 256 child workers in the Cibaduyut Bandung slipper and shoe industry were listed as being threatened by various types of diseases such as liver and/or kidney damage and even leukemia (ILO, 2004). That is due to bad habits and an unhealthy work environment so workers in the Cibaduyut Bandung sandal and shoe industry inhale and ingest benzene compounds contained in the glue they use to make sandals.
Examination of creatinine level in the blood is one of the parameters used to assess kidney function, because the concentration in plasma and its excretion in urine in 24 hours is relatively constant (Soedaman, 1995). This serum creatinine reflects the most sensitive kidney damage because it is produced constantly by the body (Lewis et al., 2014). In addition, high Blood Urea Nitrogen (BUN) levels have been associated with adverse kidney effects suggesting that BUN is a useful marker for predicting the development of kidney disease (Seki et al., 2019). Therefore, the purpose of this study is to analyze the relationship between benzene concentration and RQ benzene with MDA, BUN, and creatinine levels in workers exposed to benzene in a car painting workshop in Surabaya.
This research is an observational study with a cross-sectional design conducted in two car painting workshops in Surabaya that use benzene as a solvent in the production process, namely in Kalijudan and Jemursari. The population in this study were all workers exposed to benzene in two car painting workshops in Surabaya, totaling 90 people aged 20-65 years in 2019. The research sample was taken using an accidental sampling method involving 30 respondents. Inclusion criteria were workers between 20-65 years old who had worked in the workshop for at least 1 year. Exclusion criteria were workers with a previous history of liver or kidney disease and workers not willing to provide blood samples.
The variables studied included benzene concentration, RQ of benzene (a metabolite of benzene), malondialdehyde (MDA) levels as a marker of oxidative stress, and indicators of renal function such as blood urea (BUN) and creatinine levels. Benzene concentration and benzene RQ were considered as exposures, representing the level of exposure to benzene and its metabolic products. MDA levels were examined as an outcome reflecting oxidative stress status. Renal function parameters (BUN and creatinine levels) are outcomes that indicate potential renal effects. To account for possible influences on these relationships, age, and duration of exposure were considered as possible confounding variables. In contrast, smoking status was considered a modifier effect due to its potential to interact with benzene exposure.
Data measurements were made by sampling workplace air using gas chromatography for benzene concentration and benzene RQ. MDA levels were measured using spectrophotometric assay on blood samples. Renal function markers, BUN, and creatinine levels were assessed through blood tests conducted at a clinical laboratory. An attempt was made to overcome participant selection bias through the incidental sampling method, although this method may introduce some bias due to its non-randomized nature.
Benzene concentration and RQ benzene data were collected through air sampling in the workplace, utilizing gas chromatography as the assessment method. MDA levels, indicative of oxidative stress, were measured using spectrophotometric assays on blood samples. Kidney function markers, BUN, and creatinine levels, were assessed through blood tests conducted at a clinical laboratory. Efforts were made to address participant selection bias through the accidental sampling method. While this method might introduce some bias due to its non-random nature, its pragmatic approach allowed for data collection from the available workforce, considering practical constraints. The sample size, comprising 30 respondents, was determined based on available resources while aiming to capture a representative subset of the population.
The study employed a comparative approach between the two workshops to explore potential differences in variables of interest and their interactions. This approach facilitated a more nuanced understanding of the relationship between benzene exposure, MDA levels, and kidney function within the specific context of the car painting workshops in Surabaya.
Exposure doses in the context of benzene exposure for car painting workers in Surabaya are typically calculated based on various parameters and factors: Benzene concentration levels in the workplace air, measured in parts per million (ppm), serve as a primary indicator of exposure intensity. Worker-specific factors like body weight, duration of exposure (hours/day, days/year), and exposure duration (years) are considered in dose calculations. Breathing rate (m3/hour) is also factored in to estimate the amount of benzene inhaled by workers during their shifts.
The research paper provides insights into the calculation of benzene exposure doses using a Risk Quotient (RQ) approach: RQ values are calculated by dividing the benzene intake by a reference concentration (RfC), indicating the level of health risk associated with benzene exposure. Higher RQ values (≥1) suggest increased health risks due to benzene exposure, while lower values (<1) indicate a lower risk level. Understanding exposure doses is crucial for assessing the health risks associated with benzene exposure and implementing appropriate preventive measures to safeguard the well-being of car painting workers in Surabaya.
Respondent characteristics include age, sex, level of education, and work area. Table 1 presents the distribution of characteristics of workers exposed to Benzene in a car painting workshop in Surabaya.
Most (33.3%) industrial workers aged 36-45 years and the majority (96.3%) was male with the highest level of education being SMA/SMK (44.4%). Most (63%) workers work in the Kalijudan area.
Based on Table 2 of 27 respondents there were 21 respondents (77.8%) with benzene concentrations above the Threshold Value (> 0.5 ppm) and 6 respondents (22.2%) with benzene concentrations below the Threshold Value (≤ 0.5 ppm).
Health risk characteristics are stated as Risk Quotient (RQ, Risk Level), shown in Table 3 and are calculated by dividing the intake or intake (Ink) by reference (RfC). The calculation results of Risk Quotients (RQ) can indicate the level of health risks of workers due to exposure to benzene in the work environment. If the RQ value is more than or equal to 1 (RQ> 1) then workers exposed to benzene have health risks due to benzene exposure. If the RQ value is less than 1 (RQ <1), then workers exposed to benzene are safe from health risks due to benzene exposure. Based on the RQ calculation in Table 4, the majority of workers (92.6%) have RQ≥1 values for benzene exposure, which means the majority of them have health risk impacts due to benzene exposure.
Based on the test results in Table 5 there is no significant relationship between Benzene concentration and MDA levels in workers exposed to benzene in a car painting workshop in Surabaya with a P value> 0.05.
Based on the test results in Table 6 there is no relationship between RQ Benzene and MDA levels of workers exposed to benzene in a car painting workshop in Surabaya (P> 0.05).
Based on the test results in Table 7 there was no significant relationship between Benzene concentrations, BUN levels and creatinine exposure of workers exposed to benzene in car painting workshops in Surabaya (P> 0.05).
Based on the test results in Table 8 there was no significant relationship between Benzene concentrations, BUN levels, and creatinine exposure of workers exposed to benzene at a car painting workshop in Surabaya (P> 0.05).
The results showed that there was no significant relationship between concentration, RQ benzene, and MDA levels in workers in a car painting workshop in Surabaya (p> 0.05). This is in line with research conducted on workers in shoe factories that benzene concentrations do not have a significant relationship with MDA levels (Tualeka et al., 2019). However, according to research conducted by (Odewabi et al., 2014) in Nigeria, exposure to free radicals especially benzene in gas station workers can increase MDA levels in workers. Research by (Suparno et al., 2018) also stated that high plasma malondialdehyde (MDA) levels are markers of oxidative stress that will cause DNA and RNA disturbances. Previous research suggests that oxidative stress might be related to pathogenesis and the development of kidney disease, where it is suspected that malondialdehyde might play an important role in the pathogenesis of glomerulosclerosis (Kuo et al., 2005). In other studies, oxidative stress has progressively increased and is associated with the degree of kidney dysfunction in patients with chronic kidney failure (Dounousi et al., 2006; Terawaki et al., 2004). Antioxidant activity plays a crucial role in mitigating the oxidative stress induced by benzene exposure in car painting workers in Surabaya. Benzene exposure leads to the generation of reactive oxygen species (ROS) and free radicals, causing oxidative damage to cells and tissues. Antioxidants help neutralize ROS and free radicals, thereby protecting cells from oxidative stress and potential damage.
There was no significant relationship between benzene exposure, BUN levels and creatinine in painting workers in Surabaya (p> 0.05). Research conducted by (D’Andrea & Reddy, 2018) in children showed no significant differences in serum creatinine levels between groups exposed to benzene and those not exposed. Although BUN levels were found to be significantly reduced in groups exposed to benzene compared with unexposed group (P = 0.001). Although studies related to the effects of benzene exposure specifically on kidney function (creatinine and BUN) are limited, previous studies related to the exposure of organic solvents to kidney function have been conducted to support this study. Research conducted by (Elfar et al., 1998) found no statistically significant differences between the groups exposed to organic solvents and the control group regarding kidney function and there was no significant relationship between the two and the length of exposure to organic solvents. This opinion is also strengthened by research conducted by (Kaukiainen et al., 2004) who found a negative relationship between serum creatinine levels and exposure to organic solvents.
Cytochrome P450 enzymes (CYP450) play a crucial role in the detoxification of various xenobiotics, including benzene. CYP450 enzymes are involved in the metabolism of benzene to less toxic metabolites through a process known as biotransformation. In the context of benzene exposure, CYP450 enzymes are responsible for converting benzene into reactive metabolites, which can then be further metabolized and excreted from the body. The detoxification process mediated by CYP450 enzymes helps in reducing the harmful effects of benzene on the body, particularly in preventing the accumulation of reactive intermediates that can lead to oxidative stress and cellular damage. Understanding the role of CYP450 enzymes in benzene metabolism is essential for assessing the detoxification capacity of individuals exposed to benzene and for developing strategies to mitigate the toxic effects of benzene exposure on various organs, including the kidneys.
Hoek et al. (2003) did not find any effect from exposure to organic solvents on effects to the kidneys. The lack of an association between kidney effects and the intensity or duration of exposure can be associated with individual vulnerability. Vulnerability to benzene can vary due to its effects which arise, in part, from genetic variations in metabolism, DNA repair, genome stability, and immune function (D’Andrea & Reddy, 2018). In the present study, the effects of benzene have not led to impaired kidney function, yet limited to acute exposure. In addition, the presence of toluene exposure inhaled by labor (measured at the same time as the measurement of benzene exposure using the OVM method) has antagonistic properties against benzene toxicity. According to (Inoue et al., 1988) workers exposed to a combination of benzene and toluene will experience decreased levels of phenol in the urine compared to those exposed to benzene or toluene separately. Therefore, further research can find out whether there is an antagonistic effect between benzene and toluene on creatinine and BUN levels.
There was no significant relationship between benzene RQ, BUN levels and creatinine levels in paint workers in Surabaya (p> 0.05). RQ calculation is calculated by dividing the intake or intake (ink) by reference (RfC). Therefore, one factor that influences the value of RQ is the amount of benzene intake. Based on the theory of (Louvar & Louvar, 1998) in determining the assessment of exposure (exposure assessment) regarding the amount of chemical intake received by individuals, the exposure time factor, duration of exposure, body weight and frequency of exposure have a significant contribution in determining the intake of xenobiotic material intake at body to cause health effects. Other factors such as duration of exposure, time of exposure, frequency of exposure, nutritional status, etc. can contribute in the event that there is no effect of the benzene RQ variable on kidney function. In this study, benzene intake in workers was relatively small and the work period of the worker was also not long at 8.2 years (<10 years). In sum, the benzene RQ variable in this study was not a determining factor in its effect on the results of BUN and creatinine levels.
Cross-sectional design restricts the ability to establish causal relationships between variables, which means that it captures data at a single point in time. Longitudinal studies would provide more robust evidence of the relationship between these variables. The study is conducted in only two car painting workshops in Surabaya, potentially limiting generalizability to other settings. The utilization of the accidental sampling method might introduce selection bias, as workers with greater awareness of health risks might be more inclined to participate, affecting the external validity of findings. Furthermore, age range selection (20-65 years) might lead to varying susceptibility levels and differences in exposure duration, potentially influencing the direction and magnitude of associations observed. The limited sample size (30 respondents) might hinder the ability to detect small but significant effects, impacting the study's statistical power. As the study relies on self-reported data for certain variables and uses laboratory assessments for others, measurement bias and misclassification could occur.
Assessing antioxidant activity, such as levels of glutathione (GSH) and other antioxidants, could provide valuable insights into the protective mechanisms against benzene-induced oxidative stress. Antioxidant status can influence the susceptibility of individuals to benzene toxicity and may modulate the impact of benzene exposure on kidney function. Further studies investigating antioxidant activity in relation to benzene exposure and kidney function could enhance our understanding of the mechanisms underlying benzene-induced nephrotoxicity and oxidative damage in exposed populations. Despite these limitations, the study's findings contribute to the existing understanding of the complex interplay between benzene exposure, oxidative stress, and kidney function in car painting workshops.
In this study, the majority of respondents (77.8%) were exposed to benzene concentrations above the Threshold Value (>0.5 ppm). The majority of workers (92.6%) had RQ≥1 against benzene exposure, which means the majority of workers were affected by benzene exposure. There was no significant relationship between benzene concentration and RQ on MDA level in workers (p>0.05). There was no significant relationship between benzene concentration, BUN level, and creatinine level in workers (p>0.05). There was no significant relationship between benzene RQ, BUN level, and creatinine level in workers (p>0.05).
The authors would like thank to the rector of Airlangga University. The authors would like to acknowledge Relationship between Benzene Concentration, MDA Levels and Kidney Function in Car Painting Workshops in Surabaya.
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Is the work clearly and accurately presented and does it cite the current literature?
No
Is the study design appropriate and is the work technically sound?
Partly
Are sufficient details of methods and analysis provided to allow replication by others?
No
If applicable, is the statistical analysis and its interpretation appropriate?
Partly
Are all the source data underlying the results available to ensure full reproducibility?
Partly
Are the conclusions drawn adequately supported by the results?
Partly
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: Occupational Safety and Health; Industrial Hygiene
Is the work clearly and accurately presented and does it cite the current literature?
No
Is the study design appropriate and is the work technically sound?
Partly
Are sufficient details of methods and analysis provided to allow replication by others?
No
If applicable, is the statistical analysis and its interpretation appropriate?
Partly
Are all the source data underlying the results available to ensure full reproducibility?
Partly
Are the conclusions drawn adequately supported by the results?
No
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: Epidemiology and biostatistics
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: Biochemistry
Is the work clearly and accurately presented and does it cite the current literature?
No
Is the study design appropriate and is the work technically sound?
No
Are sufficient details of methods and analysis provided to allow replication by others?
No
If applicable, is the statistical analysis and its interpretation appropriate?
No
Are all the source data underlying the results available to ensure full reproducibility?
No
Are the conclusions drawn adequately supported by the results?
No
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: Biochemistry
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