Background Workers engaged in benzene-exposed or benzene-containing solvent-exposed operations in China are predominantly subjected to a low concentration of benzene series compounds, and prolonged exposure to low concentrations of benzene, toluene, and xylene (BTX) may have implications for blood pressure.

Objective To investigate the influence of low-concentration BTX exposure on the blood pressure of workers, aiming to provide a basis for enterprises to devise associated health management strategies to mitigate the occurrence of hypertension among workers exposed to low concentrations of BTX.

Methods Using a cross-sectional design, 884 workers from a petroleum refining enterprise in Hainan who participated in an occupational health examination in 2022 were selected as the study population, and were divided into an exposure group of 649 workers and a control group of 235 workers based on their reporting of BTX exposure or not. Data on workplace BTX concentrations and health examinations of the study subjects were collected and questionnaires were administered. In addition, S-phenylmercapturic acid (S-PMA), hippuric acid (HA), and methyl hippuric acid (MHA, including the three isomers 2-MHA, 3-MHA, and 4-MHA) were measured in the urine of the workers using high-performance liquid chromatography-tandem triple quadrupole mass spectrometry to assess internal BTX burden. The effects of low-concentration BTX exposure on blood pressure were analyzed.

Results In 2022, the concentrations of benzene, toluene, and xylene of all monitoring points did not exceeded the national limits by either time-weighted average (TWA) or short-term exposure limit (STEL), indicating low-concentration BTX exposure. Regarding the internal burden of BTX, the concentrations of benzene metabolite S-PMA, toluene metabolite HA, and xylene metabolites 3-MHA and 4-MHA in the urine samples in the exposure group were higher than those in the control group (P < 0.05). The correlation analysis showed a positive correlation between urinary S-PMA concentration and diastolic blood pressure in the workers (r=0.265, P < 0.05). Differences in systolic and diastolic blood pressure distributions were statistically significant among workers grouped by sex, age, work years, educational levels, monthly income, body mass index (BMI), alcohol use, dietary oil, and types of residential address (P < 0.05). Significant differences in systolic blood pressure distribution were observed among workers by smoking status and levels of labor intensity (P < 0.05). Compared with the control group, the workers in the exposure group exhibited a significant increase in diastolic blood pressure (P < 0.05). The results of multiple linear regression showed that age, sex, and BMI had statistically significant effects on systolic blood pressure (P < 0.05), while age, work years, and BMI had statistically significant effects on diastolic blood pressure (P < 0.05). The systolic blood pressure of age > 35 years, male, overweight and obese workers was significantly higher than that of age ≤ 35 years, female, and underweight workers, and the diastolic blood pressure of age > 35 years, work years > 5 years, and obese workers was higher than age ≤35 years, ≤5 years of service, and underweight workers. Low-concentration BTX exposure was one of the main influencing factors for elevated diastolic blood pressure, and the exposed workers showed a 1.337 mmHg increase in diastolic blood pressure compared to the control group (P < 0.05).

Conclusion Low-concentration BTX exposure, work years > 5 years, and obesity may elevate blood pressure among petroleum refininig workers. Regular blood pressure monitoring and enhanced health interventions for this occupational group are warranted.