Mortality risks rise with long-term, low exposure to nonoccupational ambient benzene

Key takeaways:

• The risk for all-cause mortality significantly went up as the average annual benzene concentration went up by 0.22 μg/m³.
• The degree of increased risk changed based on age and ethnicity.

In a nonoccupational setting, low ambient benzene exposure over a year was linked to a heightened mortality risk, according to results published in American Journal of Respiratory and Critical Care Medicine.

“Benzene is one of the most common air pollutants, affecting human health through environmental exposure in addition to occupational contact,” Jianing Wang, BS, of Tongji Medical College, Huazhong University of Science and Technology in China, and colleagues wrote. “Previous studies were focused mainly on the health impacts of exposure to high concentrations of benzene on occupational populations.”

Using data from the UK Biobank, Wang and colleagues conducted a prospective cohort study to determine how yearly exposure to low concentrations of ambient benzene in nonoccupational environments impacts mortality risk in a population of 393,042 individuals (mean age, 56.1 years; 54.4% women; 91% white) who did not have stroke, myocardial infarction or cancer at baseline.

Air dispersion models aided in the collection of average yearly benzene concentrations in the 11.7-year median follow-up period.

Over the course of the study, 20,390 individuals died. Around half of these individuals died because of cancer (n = 10,236), followed by cardiovascular disease (n = 4,145) and respiratory disease (n = 1,469).

The average benzene concentration per year was 0.48 μg/m³.

The risk for all-cause mortality significantly went up as the average annual concentration of benzene went up by 0.22 μg/m³, which is the equivalent of one interquartile range (adjusted HR = 1.26; 95% CI, 1.24-1.27), in a model adjusted for several covariates.

Further, researchers found significant heightened risks for three cause-specific mortalities per average annual concentration of benzene rises of 0.22 μg/m³: cancer mortality (aHR = 1.27; 95% CI, 1.25-1.29), respiratory disease mortality (aHR = 1.25; 95% CI, 1.2-1.3) and cardiovascular disease mortality (aHR = 1.24; 95% CI, 1.21-1.28).

This elevated mortality risk with benzene exposure held true across several subtypes of cardiovascular disease and cancer, including:

• ischemic heart disease (aHR = 1.23; 95% CI, 1.18-1.28);
• cerebrovascular disease (aHR = 1.22; 95% CI, 1.16-1.29);
• multiple myeloma (aHR = 1.45; 95% CI, 1.3-1.62);
• respiratory cancer (aHR = 1.29; 95% CI, 1.25-1.34);
• lung cancer (aHR = 1.29; 95% CI, 1.24-1.34);
• leukemia (aHR = 1.27; 95% CI, 1.15-1.39); and
• non-Hodgkin’s lymphoma (aHR = 1.27; 95% CI, 1.16-1.39).

No threshold was found based on “monotonically increasing exposure-response curves.” Additionally, in the 1-year period, researchers observed no plateau.

When divided according to age, researchers observed a slightly greater all-cause mortality risk with rises in average annual benzene exposure among younger individuals (aHR = 1.27; 95% CI, 1.25-1.3) vs. older individuals (aHR = 1.25; 95% CI, 1.23-1.27).

The degree of risk also changed based on ethnicity, with a more increased all-cause mortality risk in the cohort of white individuals (aHR = 1.27; 95% CI, 1.25-1.28) vs. non-white individuals (aHR = 1.14; 95% CI, 1.09-1.19).

“Further investigation into the potential human health risks posed by ambient benzene is essential to develop effective strategies for regulating its concentration and protecting public health,” Wang and colleagues wrote.