Air pollution may increase breast cancer risk, study suggests

Long-term exposure to air pollution may increase the risk of breast cancer, with a study of more than 400,000 women showing higher rates in areas with poor air quality.

Researchers tracked 28,000 breast cancer cases over several decades, following participants for up to 10 years before diagnosis and monitoring changes in their home addresses.

They compared these data with pollution readings from more than 2,600 monitoring sites across the country.

The analysis was carried out by researchers from Oregon State University, the National Institutes of Health (NIH), Harvard University and several other US institutions.

A 10-parts-per-billion rise in nitrogen dioxide – a pollutant linked to vehicle exhaust – was associated with a 3 per cent increase in overall breast cancer incidence.

Based on an estimated 316,950 cases expected in the US this year, a 3 per cent reduction could mean 9,500 fewer diagnoses.

The study also found that a 5-microgram-per-cubic-metre increase in PM2.5 – fine airborne particles small enough to penetrate deep into the lungs – was linked to a higher incidence of hormone receptor-negative breast cancers.

These tumours lack oestrogen and progesterone receptors, making them generally harder to treat.

Average nitrogen dioxide levels in the study were below current Environmental Protection Agency guidelines, suggesting even legally acceptable pollution levels may still pose health risks.

Veronica Irvin is associate professor at Oregon State University’s College of Health.

She said: “It’s often not realistic for people to move to areas with better air quality in search of lower health risks, so we need stronger clean air laws to protect those most affected.

“We also need policies that help to reduce car traffic and promote alternative forms of transportation.”

Breast cancer rates in the US have risen over the past four decades, despite the country having lower pollution levels than many other populous nations.

The disease affects around one in eight women and is the second leading cause of cancer death among women after lung cancer.

There are currently more than 4 million breast cancer survivors living in the US.