Nitrogen Dioxide Linked to Higher Risk of Uterine Cancer

Greater exposure to nitrogen dioxide (NO₂), a marker of traffic-based air pollution, is associated with an increased risk of uterine cancer, according to research published in the Journal of the National Cancer Institute.

Researchers found that a 5 parts-per-billion (ppb) increase in NO₂ exposure was associated with a 23% higher risk of uterine cancer. However, residential exposure to particulate matter less than 2.5 µm in diameter (PM_2.5) was not associated with an increased risk of uterine cancer. 

The researchers evaluated these risks using data from 33,417 women participating in the Sister Study. They were enrolled between 2003 and 2009 and followed through October 2020. They were 35-74 years of age at baseline, had at least 1 sister diagnosed with breast cancer, had no prior history of breast cancer or uterine cancer, and had an intact uterus at baseline.

The researchers estimated annual average air pollutant concentrations at the participants’ geocoded primary residential addresses and evaluated the association between time-varying 12-month PM_2.5 and NO₂ averages and uterine cancer incidence.

Over a median follow-up of 9.8 years, 319 cases of uterine cancer were reported. This included cases of endometrial cancer, uterine sarcoma, and other cancers in the uterus.

In an adjusted analysis, a 5-ppb increase in NO₂ was associated with an increased risk of uterine cancer (hazard ratio [HR], 1.23; 95% CI, 1.04-1.46). The researchers found similar results when their analyses were restricted to medically confirmed uterine cancer (HR, 1.25; 95% CI, 1.04-1.50) or endometrial cancer (HR, 1.28; 95% CI, 1.06-1.54).

The associations with NO₂ did not vary by Area Deprivation Index, region, or body mass index. However, there were variations by residence type. There was a significant association between NO₂ and uterine cancer among women who lived in urban areas at enrollment (HR, 1.53; 95% CI, 1.13-2.07) but not among women who lived in rural areas (HR, 0.92; 95% CI, 0.61-1.40) or suburban areas (HR, 1.06; 95% CI, 0.78-1.45).

The researchers also found that a 5 µg/m³ increase in PM_2.5 was not associated with an increased risk of uterine cancer (HR, 0.83; 95% CI, 0.54-1.27), medically confirmed uterine cancer (HR, 0.86; 95% CI, 0.54-1.38), or endometrial cancer (HR, 0.89; 95% CI, 0.55-1.43).

“Our findings highlight air pollution as a plausible risk factor for uterine cancer, particularly pollution arising from vehicular traffic emissions,” the researchers wrote.

This article originally appeared on Cancer Therapy Advisor