In this study, we used pooled data from the survey, biological data, and exposure data from 2018 to 2021 to investigate the level of VOC exposure and the health effect of residents in vicinity of the industrial complex. From the results, subjects from the exposure group were exposed to higher pollutant levels than the residents living far from the industrial complex. Several studies have highlighted the higher ambient VOCs level area near the industrial complex, especially in petrochemical industries [6, 12–16]. Pinthong et al. used Positive Matrix Factorization(PMF) to evaluate the source of VOCs and showed that industrial processes and petrochemical industries were the major sources of the VOCs [6]. A study from Beijing also revealed that the main source of VOCs is the vehicle exhaust and industrial emissions [13]. The external VOC exposure assumed by the personal monitoring level showed that the exposure group was exposed to a higher VOC level compared to the control group, which is consistent with the previous studies. Bang et al. showed a higher BTX level in areas around industrial complexes by CMAQ simulation result [17]. Moreover, according to the Pollutant Release and Transfer Register(PRTR) data of Ulsan (Table 9), xylene and toluene are among the top 5 chemicals released in both Ulsan National and Onsan Industrial Complexes. Also from Fig. 2, higher amount of VOC release is demonstrated at the regions around the industrial complexes which is based on the emission data analysis from the Clean Air Policy Support System.
Table 9
Main chemical pollutants release from Ulsan Mipo and Onsan industrial complexes (2002–2019 average amount of air emission, top 5)a
Industrial Complex | District | Pollutant | Air emision ton/yr (%) |
2002 ~ 2019 average | 2019 |
Ulsan Mipo | Namgu | Xylene | 315.5(18.5) | 275.5(16.4) |
Methyl alcohol | 130.4(7.6) | 181.0(10.8) |
Prophylene | 124.4(7.3) | 205.7(12.2) |
Toluene | 102.6(6.0) | 52.0(3.1) |
n-Hexane | 80.4(4.7) | 75.5(4.5) |
Total | 1,705.0(100) | 1,683.3(100) |
Onsan | Uljugun | Xylene | 308.6(26.8) | 607.0(43.6) |
Toluene | 116.3(10.1) | 103.4(7.1) |
Methyl alcohol | 75.5(6.6) | 64.9(6.3) |
n-Hexane | 52.8(4.6) | 6.5(0.7) |
Methyl ethyl ketone | 46.6(4.0) | 37.1(3.1) |
Total | 1,151.8(100) | 1,392.0(100) |
a cited from Evaluating of Exposure to Environmental Pollutants and Health Effects of Inhabitants in Industrial Complexes Area(3rd stage)- (Ulsan·Onsan, 4th year) |
Biomonitoring of VOCs can be performed by various biological samples, including blood, urine, exhaled breath, and saliva [18]. In our study, we used the urinary metabolite of benzene, toluene, xylene, styrene, and ethylbenzene, which are t,t-MA, BMA, MHA, MA, and PGA, respectively. Responding to the high personal VOCs level, the internal exposure assumed by the urinary metabolite was also higher in the exposure group. The urinary t,t-MA, MA, and MHA were significantly higher in the exposure group. However, Gromiec et al. investigated association of the ethylbenzene exposure and excreted MA level, and found out that the excreted MA constituted 55 ± 2% of retained ethylbenzene. Also, many studies have used urinary MA as exposure monitoring for ethylbenzene and styrene.
The differences in health status reported by residents from each group were consistent with previous studies conducted on the health effects of industrial complexes. The respiratory symptoms except for cough were more frequently reported by the exposure group. Hong et al. investigated the pulmonary function level of the residents of the industrial complex and found out that pulmonary function was negatively affected by living in the vicinity of the industrial complex [7]. Others have reported that air pollution can increase the incidence of respiratory symptoms as well as cardiovascular symptoms.
It has been reported that chronic exposure to VOCs can induce chronic disease, respiratory disease, liver dysfunction, cancer, and allergic disease. Marquès et al. reviewed the health outcomes other than cancer in the population living near the petrochemical industrial complex. There, they revealed that most studies reported increased asthma and respiratory symptom prevalence both in children and adults [19]. In our study, wheezing, ever asthma symptom, ever allergic rhinitis symptom, and ever atopic dermatitis diagnosis were more frequent in the exposure group, which is consistent with other studies [20–24]. Elbarabry et al. investigated the association between long-term exposure to air pollution and anemia prevalence and showed that PM10, PM2.5, PM1, and NO2 were positively associated with the anemia prevalence and decreased hemoglobin levels significantly. The anemia reported by subjects in our study showed higher prevalence in the exposure group, but hemoglobin levels did not show a difference between the two groups [25]. Several studies on occupational or environmental exposure to VOCs can increase the risk of cardiovascular disease and have also been demonstrated by several animal studies as well. Everson et al. measured the BTEX and NO2 exposure at the personal level and found out that those exposure and blood pressure have a positive association even in both short-term and long- term exposure as well as in lower concentrations [26]. Other than blood pressure, VOC is associated with increased cardiovascular mortality, heart failure hospitalizations, and ischemic heart disease mortality [27, 28], and the mechanism underlying these health risks is assumed to be through the endothelial damage. Moreover, VOCs can exert an effect on insulin resistance which is the main factor in the development of diabetes [27, 29–32]. Yang et al. also reported that high urinary t,t-MA increased the risk of diabetes regardless of smoking status and sex [33]. Sim et al. demonstrated that urine muconic acid and mono- (2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) levels, which are metabolites of benzene and phthalate, increased the risk of metabolic syndrome even after adjusting for confounders by 1.34 and 1.39, respectively [34]. The result of our study did not show complete consistency with the previous studies as the design of the study and measurement method differ. The frequency of hypertension, diabetes, and anemia [35, 36] showed consistent result with previous studies while thyroid disease found out to be lower in exposure group. Allergic disease, respiratory disease, and cardiovascular disease showed no significant result between the two groups.
Chemicals of VOCs share common health risks, such as neurological and hematological effects, though each can express its specific health impact on the human body [37–39]. The health risks of each chemical component of VOCs are widely studied and confirmed in the context of occupational exposure where the exposure is in high concentration. The characteristic clinical finding of chronic benzene exposure is cytopenia which is manifested as anemia, leukopenia or thrombocytopenia demonstrated by several epidemiological studies even at low dose. According to a population-based study on the effect of BTEX exposure on hematological and biochemical indexes, BTEX and styrene significantly increased hemoglobin and total WBC count. Total xylene, styrene, and toluene show a positive association with the platelet level. Creatinine showed an inverse relationship with all VOCs. Lower GGT level was significantly associated with increased benzene and styrene levels, whereas, AST significantly increased with higher ethylbenzene, toluene, and total xylene level [40]. All VOCs showed a negative association with the creatinine level. Consistent with these results, RBC showed a higher level in the exposure group, while WBC, parameters of the liver function test, and creatinine level did not show a significant difference between the two groups. Another study on the hematological effect of BTEX exposure on tobacco-smoke non-exposed participants showed a negative association between BTEX and platelet level, which is similar to our study [41]. Although studies on VOC exposure and hematological parameters show controversial results in detailed parameters, the overall result reveals that VOCs can induce abnormal hematologic outcomes even at the environmental level.
Factors affecting the urinary VOC metabolites extensively varied across the researches. Smoking, drinking, BMI, simultaneous solvent exposure, work time, exposure gradient, climate, genetic factors, dietary intake, and ethnicities are factors that are suggested to affect urinary metabolite level, even though the results are controversial [42–47]. From the result of our study, t,t-MA was only significantly related to sex which is inconsistent with previous studies suggesting smoking and roast food intake are the factors affecting urinary t,t,-MA level [46, 48]. On the contrary, urinary MA showed an unexpected result. Even though urinary MA is a metabolite of styrene, xylene and ethylbenzene showed significant association as well as education level. Most studies have suggested that biomarkers of styrene and ethylbenzene have a significant positive association as those are the contents of tobacco smoke [44]. In accordance with the previous study, smoking increased the urinary PGA level significantly. Factors affecting urinary BMA were education level and traffic load. Previous studies suggested that smoking, sex, and age are the factors related to the toluene biomarker [49, 50]. In one study conducted with the first Korea National Environmental Health Study, urinary MHA was significantly associated with residential factors of the participants, including remodeling within 6 months and the existence of a major road within 100m of the residence [51]. Another study suggested that smoking is an important source of xylene exposure measured by urinary MHA, which is consistent with our result [52].
Our study has the following limitations:
-
Due to the cross-sectional design of this study, a causal relationship cannot be established.
-
Due to the nature of the annual project, the pollutant measurement data and biological sample data varied every year, resulting in an increase in missing values when pooling the database.
-
Measurement of health outcome variables was carried out using a questionnaire that heavily relied on participants' attitudes toward answering each question.
-
The temporality between the residence and disease occurrence cannot be confirmed.
-
Due to the nature of environmental exposure, exposure to VOCs cannot occur at a single pollutant level. Therefore, study on exposure to the multipollutant level is needed.
Usually, petrochemical industries give rise to benzene, toluene, xylene, and ethylbenzene together, so they exist in the air simultaneously, interacting with each other and with other air pollutants in the atmosphere [53]. Thus, to accurately estimate the public health risk from ambient VOCs level from the industrial complexes, assessment should be based on exposure to the whole BTEX mixture. Therefore, further study is needed to make up for the limitations of our study to clarify the effect of ambient pollutant levels on the health outcomes. Despite these limitations, this study accumulated annual data to construct 4 year pooled database to analyze the difference in pollutant levels and health outcomes between residents of the industrial region and control region. Also, previous studies on the health effects of ambient VOC exposure mostly used estimated exposure levels using modeling techniques, but our study measured personal monitoring data. Apart from external exposure data assumed by personal monitoring data, we were able to presume the internal exposure using urinary metabolite level.
This study showed that residents living near the industrial complex are exposed to higher VOCs level, confirmed by personal monitoring data and biological monitoring data which stands for internal exposure. Furthermore, even though a causal relationship cannot be confirmed, respiratory symptoms and some chronic diseases were more frequent among the residents living near the industrial complex as well as abnormal hematologic parameters. The result of our study can be used to raise awareness among policymakers and employers to develop countermeasures to regulate the environmental pollution from the industrial complexes. Moreover, it can be used as basic data when establishing plans to reduce the VOCs exposure to manage the health of residents of the industrial complexes.