The detrimental effect of benzene exposure on human health has become a major public concern around the world. Benzene exerts both carcinogenic and noncarcinogenic effects in humans. The carcinogenic effects of benzene exposure include not only hematological cancers such as leukemia and lymphoma but also solid tumors such as breast, lung, renal, and nasal cancers. Non-carcinogenic effects of benzene exposure include respiratory abnormalities, deteriorated renal function, central nervous depression, skin irritation, hepatotoxicity, myelotoxicity, hematological alterations, and immunotoxicity.
Previously, we reported that benzene exposure significantly altered the hematological and hepatic functions in children, adults, and elderly subjects. In addition, recently, we reported that children exposed to benzene experienced a range of illness symptoms and an altered profile of urinary phenol, suggesting their vulnerability to increased adverse health complications. The analyses in this study sought to further assess the illness symptom profiles following benzene exposure from the prolonged toxic release of the BP flaring event in adults, building on our earlier study findings.
The findings of this study show that adult subjects exposed to benzene from the BP flaring event experienced a wide range of adverse health symptoms, including neurological, respiratory, cardiac, dermatological, gastrointestinal, and a host of other adverse symptoms. Each benzene-exposed adult experienced multiple adverse neurological symptoms such as headaches, memory loss, unsteady gait, and dizziness.
Similarly, multiple upper respiratory symptoms such as shortness of breath, sore throat, difficulty in breathing, bronchitis, nose bleeds, hoarseness, and sinusitis were seen in each benzene-exposed subject. Over 25% of the subjects experienced cardiac, gastrointestinal, and dermatological symptoms; painful joints; diarrhea; and cough following their exposure to benzene. Currently, the literature is sparse evaluating the adverse health symptoms of benzene exposure in adults or children.
A study by Gordian et al reported that residents exposed to evaporative emissions of gasoline had more severe symptoms of asthma affecting their respiratory health. Tunsaringkarn et al reported that gas station workers who were exposed to benzene experienced health symptoms such as dizziness, headache, skin irritation, eye irritation, fatigue, sore throat, nausea, and depression. The findings of our current study are comparable with those findings reported by Tunsaringkarn et al in that significant proportions of subjects experienced these adverse health symptoms following their exposure to benzene.
To determine whether the subjects’ gender contributed to the observed findings, we assessed and compared the incidence of adverse health symptoms between male and female subjects exposed to benzene. The overall frequency of adverse health symptoms was higher in women (5.5 symptoms per female subject) than in men (5.0 symptoms per male subject). Previously, we reported that the overall frequency of adverse health symptoms was higher in female children (2.9 symptoms per female child) than in male children (2.7 symptoms per male child). These findings collectively suggest that female subjects are more vulnerable than male subjects to the effects of benzene exposure.
Multiple regression analysis was performed to evaluate the association between the subjects’ age and individual illness symptoms among the benzene-exposed adults. The findings indicated that urinary symptoms and painful joints were positively associated with increasing age in the benzene-exposed subjects. The levels of beta-2-microglobulin in serum are considered to be a marker for the activation of the cellular immune system, as well as a tumor marker in certain hematologic malignancies.
Therefore, in this study, we measured the levels of beta-2-microglobulin in the serum of subjects exposed to benzene. Although the serum levels of beta-2-microglobulin were within the normal range (0.6 – 2.4 mg/L), levels increased significantly with increasing age in the benzene-exposed subjects. The association of serum beta-2-microglobulin with the distance from the site of the disaster was evaluated by using scatter plots in benzene-exposed subjects.
The findings suggested that subjects living closer to the disaster facility had higher levels of serum beta-2-microglobulin than did those living further away from the disaster site, indicating perturbations in the cellular immune system among subjects living closer to the disaster facility. These findings further support the decreased illness symptoms with distance away from the disaster site in benzene-exposed subjects.
However, additional studies are required to determine the precise role of serum beta-2-microglobulin levels in subjects exposed to benzene. Phenol is one of the predominant metabolites derived from the metabolism of benzene and is excreted in the urine.39Themeasurement of the phenol excreted in the urine is routinely used as a marker for benzene exposure. Therefore, in the current study, we measured the amount of phenol excreted in the urine of the subjects exposed to benzene.
The findings showed that subjects exposed to benzene excreted considerable amounts of phenol in the urine. Note that only trace or undetectable amounts of phenol are found in the urine of healthy subjects who were not exposed to benzene. Moreover, these findings also revealed that the urinary excretion of phenol was significantly higher with increasing age among the subjects exposed to benzene.
The association of urinary phenol with distance from the site of the disaster was evaluated by using scatter plots in benzene-exposed subjects. The findings suggest that subjects living closer to the disaster facility excreted higher levels of phenol in the urine than did those living further away from the disaster site. This finding indicates that subjects living closer to the disaster facility had higher levels of benzene exposure than did those living further away from the disaster site.
The observed findings on urinary phenol further support the reduction in illness symptoms with distance from the site of the disaster in benzene-exposed subjects. Nonetheless, additional studies are warranted to assess the adverse health consequences and the significance of the elevated urinary levels of phenol in subjects exposed to benzene.
Our study had some limitations, and the study findings should be interpreted as such. Foremost, this study was conducted by use of a cross-sectional design. This study design allows only for generating a hypothesis for further investigation and not for investigating causality. The major limitation was a lack of baseline data prior to the flaring event at the BP refinery. In addition, this investigation was retrospective in nature. Thus, it is difficult to infer causality using such a study design because the outcomes were measured at a one-time point after exposure to benzene. The major limitation was the lack of the subjects’ baseline data prior to the flaring event at the BP refinery. Moreover, there may have been a self-report bias of our outcome classification, as the subjects were aware of the benzene pollution in their community. This may have resulted in an overestimation of the reported outcomes. To minimize this potential bias, study subjects who reported experiencing any adverse health symptoms were asked to describe the health symptoms to the interviewers.
Regardless of these limitations, the results of our study indicate that benzene exposure from the refinery disaster was associated with significant adverse health effects among those exposed subjects. Since benzene is a carcinogen, people who were exposed to the benzene flaring disaster need to be followed periodically over time to detect any long-term or progressive abnormalities and adverse health complaints. Periodic health checkups, including routine laboratory blood, pulmonary, cardiac, neurologic, and other organ function evaluations, should be performed to monitor the long-term adverse health consequences of their benzene exposure. Thus, future longitudinal studies are required to explore the importance and nature of the health effects on humans exposed to benzene.
Together, the results of this retrospective study indicate that subjects exposed to benzene experienced a broad range of adverse health symptoms, including neurological, respiratory, and cardiac symptoms; painful joints; gastrointestinal symptoms; and dermatological symptoms. In addition, a majority of these subjects reported cough, diarrhea, nausea/vomiting, and other adverse health symptoms following their exposure to the benzene BP flaring disaster. These findings support our previous study findings in which we reported that subjects exposed to benzene experienced significant and adverse alterations in their vital organ functions, including hematological, hepatic, and renal functions. It is, therefore, crucial to monitor these subjects on a long-term basis to detect adverse toxicities of their benzene exposure, especially the development of secondary malignancies. Further prospective studies are required to understand the potential adverse health consequences of the benzene exposure from this flaring disaster at the BP refinery facility in Texas City, Texas.
About the Authors
University Cancer and Diagnostic Centers, Houston, Texas.Correspondence and reprint requests to G. Kesava Reddy, Ph.D., MHA, UniversityCancer and Diagnostic Centers, 12811 Beamer Road, Houston, TX 77089(e-mail: firstname.lastname@example.org).
- Fenga C, Gangemi S, Costa C. Benzene exposure is associated with epigenetic changes [Review]. Mol Med Rep. 2016;13:3401-3405.
- Protano C, Scalise T, Orsi GB, et al. A systematic review of benzene exposure during pregnancy and adverse outcomes on intrauterine development and birth: still far from scientific evidence.Ann Ig.2012;24:451-463.
- Khalade A, Jaakkola MS, Pukkala E, et al. Exposure to benzene at work and the risk of leukemia: a systematic review and meta-analysis.EnvironHealth. 2010;9(1):31. https://doi.org/10.1186/1476-069X-9-31.
- Smith MT. Advances in understanding benzene health effects and susceptibility.Annu Rev Public Health. 2010;31(1):133-148. https://doi.org/10.1146/annurev.publhealth.012809.103646.
- Costantini AS, Benvenuti A, Vineis P, et al. Risk of leukemia and multiple myeloma associated with exposure to benzene and other organic solvents: evidence from the Italian Multicenter Case-control study.Am JInd Med. 2008;51(11):803-811. https://doi.org/10.1002/ajim.20592.
- Snyder R. Overview of the toxicology of benzene. J Toxicol EnvironHealth A. 2000;61(5-6):339-346. https://doi.org/10.1080/00984100050166334.
- Marchetti F, Eskenazi B, Weldon RH, et al. Occupational exposure to benzene and chromosomal structural aberrations in the sperm of Chinese men.Environ Health Perspect. 2012;120(2):229-234. https://doi.org/10.1289/ehp.1103921.
- Chang CC, Tsai SS, Chiu HF, et al. Traffic air pollution and lung cancer in females in Taiwan: petrol station density as an indicator of disease development. J Toxicol Environ Health A. 2009;72(10):651-657. https://doi.org/10.1080/15287390902733515.
- Villeneuve PJ, Jerrett M, Brenner D, et al. A case-control study of long-term exposure to ambient volatile organic compounds and lung cancer in Toronto, Ontario, Canada. Am J Epidemiol. 2014;179(4):443-451.https://doi.org/
- 1093/aje/kwt289.10. Costantini AS, Gorini G, Consonni D, et al. Exposure to benzene and risk of breast cancer among shoe factory workers in Italy.Tumori.2009;95:8-12.
- Hansen J. Elevated risk for male breast cancer after occupational exposure to gasoline and vehicular combustion products.Am J Ind Med.2000;37(4):349-352. https://doi.org/10.1002/(SICI)1097-0274(200004)37:4<349::AID-AJIM4>3.0.CO;2-L.
- Hystad P, Villeneuve PJ, Goldberg MS, et al. Exposure to traffic-related air pollution and the risk of developing breast cancer among women in eight Canadian provinces: a case-control study.Environ Int.2015;74:240-248. https://doi.org/10.1016/j.envint.2014.09.004.
- Dundarz MR, Turkbay T, Akay C, et al. Antioxidant enzymes and lipid peroxidation in adolescents with inhalant abuse.Turk J Pediatr.2003;45:43-45.
- Dere E, Ari F. Effect of benzene on liver functions in rats (Rattusnorvegicus).Environ Monit Assess. 2009;154(1-4):23-27. https://doi.org/10.1007/s10661-008-0374-7.
- Kotseva K, Popov T. Study of the cardiovascular effects of occupational exposure to organic solvents.Int Arch Occup Environ Health. 1998;71(suppl): S87-S91.
- Baslo A, Aksoy M. Neurological abnormalities in chronic benzene poisoning. A study of six patients with aplastic anemia and two with preleukemia.Environ Res. 1982;27(2):457-465. https://doi.org/10.1016/0013-9351(82)90100-1.
- Mandiracioglu A, Akgur S, Kocabiyik N, et al. Evaluation of neuropsychological symptoms and exposure to benzene, toluene, and xylene among two different furniture worker groups in Izmir.Toxicol IndHealth. 2011;27(9):802-809. https://doi.org/10.1177/0748233711399309.
- Bahadar H, Mostafalou S, Abdollahi M. Current understandings and perspectives on non-cancer health effects of benzene: a global concern.Toxicol Appl Pharmacol. 2014;276(2):83-94. https://doi.org/10.1016/j.taap.2014.02.012.