Do cleaning products cause breast cancer?

Julia Brody, from the Silent Spring Institute, USA, worked with a team of researchers to carry out telephone interviews with 787 women diagnosed with breast cancer and 721 comparison women. She said, "Women who reported the highest combined cleaning product use had a doubled risk of breast cancer compared to those with the lowest reported use. Use of air fresheners and products for mold and mildew control were associated with increased risk. To our knowledge, this is the first published report on cleaning product use and risk of breast cancer."

The researchers questioned women on product use, beliefs about breast cancer causes, and established and suspected risk factors. They found that cleaning products, air fresheners, and insect repellents were associated with breast cancer, but little association was observed with overall pesticide use. Women with breast cancer who believed that chemicals and pollutants contribute 'a lot' to the risk of developing the condition were more likely to report high product usage.

Speaking about this potential bias to the study, Brody said, "When women are diagnosed with breast cancer, they often think about what happened in the past that might have contributed to the disease. As a result, it may be that women with breast cancer more accurately recall their past product use or even over-estimate it. Or, it could also be that experience with breast cancer influences beliefs about its causes. For example, women diagnosed with breast cancer are less likely to believe heredity contributes 'a lot', because most are the first in their family to get the disease."

In order to avoid possible recall bias, the researchers recommend further study of cleaning products and breast cancer using prospective self-reports and measurements in environmental and biological media.