July 20, 2010 -- Frequent use of household cleaning products may boost breast cancer risk, according to a new study that drew criticism from medical experts and the cleaning industry.
Air fresheners and products to control mold and mildew were particularly linked, says researcher Julia Brody, PhD, executive director of the Silent Spring Institute in Newton, Mass., who led the study.
It is published in the journal Environmental Health.
The study is believed to be the first published report linking household cleaning products and breast cancer risk. "Many laboratory studies led us to be concerned about particular compounds in cleaning products and air fresheners," Brody tells WebMD.
While Brody sees a link, others are not convinced. ''What this study really shows is, when a study relies on people's memory of their exposure, and people are concerned about that exposure, you don't get reliable answers," says Michael Thun, MD, vice president emeritus of epidemiology for the American Cancer Society.
Cleaning Products and Breast Cancer: Study Details
Brody and her co-researchers conducted telephone interviews with 787 women who had been diagnosed with breast cancer and 721 women who did not have breast cancer. "We asked women about past use of cleaning products -- in the past year, their typical use," Brody says.
''For pesticide use, we asked about use in houses they lived in in the past," she says.
The strongest link, she says, is looking at all cleaning products combined. "For combined cleaning product use, the risk is about twice as high [for breast cancer] for women who said they used the most compared to women who said they used the least."
Insect repellent use seemed to be linked, Brody says, but there was very little association found between other pesticides and breast cancer risk.
Specifying exactly how much exposure to the products may raise risk is difficult, she says. For combined products use, women were divided into four groups; those in the fourth group, who used the most, had about twice the risk as those in the group that used the least.
For solid air fresheners, for instance, those who used it seven or more times a year had twice the risk of breast cancer as those who never used it.
Brody also found that women who had breast cancer and thought that chemicals and pollutants contribute much to cancer risk were more likely to report high use of cleaning products. But Brody isn't sure what's driving what -- whether women who get breast cancer then begin to wonder if cleaning products played a role, or other factors.
When studies look at data from the past -- what scientists call retrospective studies -- and ask people to rely on their memories, "the results aren't going to be interpretable," says Thun, who reviewed the study findings for WebMD.
''I'd say that the study really isn't informative about their actual risk," he says. "It's much more informative about why this particular line of study is not reliable. It's not informative. And it is not going to answer the questions."
As to the risk of cleaning products, Thun says, "The jury's out. We know there is a lot of concern about cleaning products from environmental groups."
Ideally, the way to study the potential link, he says, is to define the exposure to cleaning products in advance, then follow the women. He concedes this is difficult and time consuming and ''probably not going to happen."
Still, the "self-report" technique is unreliable, he says, especially in those already diagnosed. "If I have breast cancer, I am going to be looking for a reason," he says.
''There's concern because of recall bias," agrees Susan Brown, director of health education at Susan G. Komen for the Cure in Dallas. Understanding the effects of cleaning products will take more study, including research that follows a group of women over time, she tells WebMD.
''It is our experience that once people are diagnosed with breast cancer, they are so interested in trying to figure out what caused it, they look at things in a different way,'' Brown says."They look at every exposure, every behavior as suspect, perhaps part of the reason they got breast cancer. It's perfectly natural, but that doesn't necessarily lead to good science."
What should women concerned about cleaning products do until more research is in? Thun says environmental groups offer suggestions on using simpler cleaning products, such as soap and water and baking soda.
Thun also suggests focusing on known ways to reduce breast cancer risk, including maintaining a healthy weight, engaging in physical activity, minimizing alcohol intake, and avoiding hormone replacement therapy.
In a statement, the American Cleaning Institute challenged the findings. The research, according to the statement, "far overreaches in its conclusions based on self-reported uses of cleaning products by persons diagnosed with breast cancer."
It continues that ''the research is rife with innuendo and speculation about the safety of cleaning products and their ingredients."
Also taking issue with the look-back approach, the statement notes that women were asked to recall products they used in the past.
Brody defends her study. "This is a first look and there are cautions about interpreting it," she says.
In ongoing research, her team is testing air and dust in women's homes and finding compounds from consumer products that could be harmful, she says. "We are focusing on understanding exposures from consumer products," she says, to identify which are potentially harmful.