We all know air pollution can damage our lungs, worsening illnesses such as asthma. Last summer, researchers writing in the journal Environmental Science & Technology Letters warned that air pollution is shaving up to two years off the lives of people in big cities.
But it’s not just our lungs that are in danger. These fumes also contain chemicals that can cause cancer — in particular, endocrine disrupters, which are chemicals that interfere with hormones and are recognised risk factors for breast cancer.
Traffic emissions also contain metals such as mercury and cadmium, which can be deposited in the breast tissue.
These fumes also contain chemicals that can cause cancer — in particular, endocrine disrupters, which are chemicals that interfere with hormones and are recognised risk factors for breast cancer (file image)
There is growing evidence that air pollution can greatly increase a woman’s risk of getting the disease.
One of the key indicators of breast cancer risk is how dense a woman’s breast tissue is. Studies show that women with dense breasts can be six times more likely to develop breast cancer than those with less dense breasts, making it a greater risk factor than alcohol, obesity or hormone replacement therapy (HRT).
Breasts are made up of fatty, fibrous and glandular tissue. The more fibrous and glandular tissue in the breast, the denser it is. In women undergoing routine mammogram screening, around 10 per cent have breasts that are almost entirely fatty, 40 per cent have dense breasts and 10 per cent have extremely dense breasts, according to the U.S. Breast Imaging Reporting and Data Systems Lexicon.
Dense breasts contain more glandular tissue, which is where cancerous changes happen, as well as higher concentrations of growth factor, which makes cells replicate faster — making it more likely that they will mutate into cancerous cells.
Although dense breasts can be inherited, we think pollution actually causes breasts to become denser. We don’t know the mechanism for this but large studies, including one published in Breast Cancer Research in April 2017, have shown that women living in urban areas may have higher breast density compared with women living in rural environments with lower air pollution.
One theory is that very small pollution particles called PM 2.5 (smaller than 2.5 micrometres) can pass through the lung lining into the bloodstream and accumulate in fatty areas such as the breasts.
The highest risk of all was in the square mile of the City of London, where pollution is at its highest (file image)
Our team at the London Breast Institute published a study in 2007 in the Current Medical Research and Opinion journal
