Occupational benzene exposure heightens lung cancer likelihood

Key takeaways:

• Benzene exposure length and the amount of time since exposure impacted the odds for lung cancer.
• An elevated likelihood for lung cancer with benzene exposure was observed in current, former and never smokers.

Having been exposed to benzene during work heightened the odds for lung cancer development, according to results published in American Journal of Respiratory and Critical Care Medicine.

“Benzene has been regulated extensively over the past several decades, and, as a result, occupational exposure to benzene has declined to [less than] 1 ppm among most occupational groups in North America and Europe,” Wenxin Wan, MSc, PhD research student at Utrecht University, and colleagues wrote.

“However, benzene exposure at unregulated workplaces and in low- and middle-income countries remains of great concern because higher exposure levels are still often observed,” they continued.

Through a pooled analysis of 14 case-control studies, Wan and colleagues assessed 12,329 individuals with lung cancer and 15,719 individuals without lung cancer (controls) to determine how occupational benzene exposure is linked to lung cancer risk.

Researchers estimated this type of chemical exposure via a quantitative job-exposure matrix.

In the group of patients with lung cancer, 5,838 individuals (47.4%) had exposure to benzene, whereas the remaining 6,491 individuals did not experience exposure.

The control cohort included 6,253 (39.8%) exposed individuals and 9,466 unexposed individuals.

In the exposed population, the three occupations with the greatest mean exposure levels included “painters and related workers,” “varnishes and related painters” and “shoemakers and related workers.”

Following adjustment for study, age group, sex, smoking and occupational lung carcinogens of asbestos, hexavalent chromium, polycyclic aromatic hydrocarbons, silica and diesel engine exhaust, researchers observed elevated odds for lung cancer among ever vs. never exposed individuals (adjusted OR = 1.17; 95% CI, 1.1-1.24).

More specifically, those with more than 5 ppm of benzene exposure a year vs. those without exposure had greater odds for lung cancer (aOR = 1.32; 95% CI, 1.18-1.48).

Even individuals in the lowest cumulative exposure group (> 0 ppm to 1 ppm of benzene a year) had a higher likelihood for lung cancer than individuals unexposed to benzene (aOR = 1.12; 95% CI, 1.03-1.22).

Further, both exposure length and the amount of time that passed since exposure impacted the odds for lung cancer.

Compared with unexposed individuals, individuals with 1 to 9 years and 10 to 19 years of benzene exposure faced heightened odds for lung cancer (aOR = 1.1), and these odds went up as more time was spent exposed (20 to 29 years, aOR = 1.23; 95% CI, 1.1-1.37; > 29 years, aOR = 1.34; 95% CI, 1.21-1.48).

The likelihood for lung cancer gradually decreased as more time passed since being exposed to benzene. Those with less than 5 years since last exposure had a high odds ratio of 1.43 (95% CI, 1.2-1.7), but this went down in the 5 to 9 years since exposure group (aOR = 1.12; 95% CI, 0.94-1.33), the 20 to 29 years since exposure group (aOR = 1.06; 95% CI, 0.94-1.21) and the more than 39 years since exposure group (aOR = 1.02; 95% CI, 0.89-1.16).

Taking a more detailed look at the odds for lung cancer revealed that individuals with ever vs. never benzene exposure had heightened odds for four different types of lung cancer: adenocarcinoma (aOR = 1.13; 95% CI, 1.04-1.23), squamous cell carcinoma (aOR = 1.2; 95% CI, 1.1-1.3), small cell carcinoma (aOR = 1.18; 95% CI, 1.05-1.32) and large cell carcinoma (aOR = 1.26; 95% CI, 1.04-1.51).

In this lung cancer subtype analysis, researchers noted similar patterns to the main analysis when evaluating the odds for lung cancer based on cumulative exposure and exposure length. Squamous cell carcinoma was the only cancer subtype with a significant decreasing trend in lung cancer odds as time passed since benzene exposure.

Notably, ever vs. never benzene exposure while working raised the odds for lung cancer in former smokers (aOR = 1.2; 95% CI, 1.08-1.33), current smokers (aOR = 1.14; 95% CI, 1.04-1.24) and never smokers (aOR = 1.18; 95% CI, 1-1.38).

Never smokers with more than 5 ppm of benzene exposure a year vs. no exposure faced an elevated likelihood for lung cancer (aOR = 1.8; 95% CI, 1.26-2.53), but this went down in the lowest cumulative exposure group (aOR = 1.09; 95% CI, 0.89-1.32).

Researchers again found similar patterns to the main analysis when assessing the odds for lung cancer in never smokers based on exposure length and time since last exposure.

Specific occupational groups, exposures and studies did not influence the main findings, according to researchers.

“Our findings support the hypothesis of an effect of occupational benzene exposure on lung cancer risk and warrant revisiting the published epidemiological and molecular data addressing the pulmonary carcinogenicity of benzene,” Wan and colleagues wrote.