A new retrospective study has reported that household cleaning product and air freshener use contribute to increased breast cancer risk. The study was designed to investigate the associations between use of household cleaning products and air fresheners and risk of breast cancer. Such products are plausible contributors to breast cancer risk because many of them contain estrogen-like chemicals or known carcinogens. The study included 787 women residing in Cape Cod diagnosed with breast cancer between 1988 and 1995, as well as 721 cancer-free controls. Telephone interviews were used to gather information concerning product use, beliefs about the causes of breast cancer, and established and suspected breast cancer risk factors.

Breast cancer risk was found to increase two-fold in the highest compared with the lowest fourth of self-reported cleaning product use. Similar results were found for air freshener use. Little association was observed between household pesticide use and risk of breast cancer. The authors attempted to control for recall bias by examining the product use risks according to the womens' beliefs concerning whether chemicals and pollutants contribute to breast cancer. Cleaning products risks were found to be higher among participants who believed pollutants contribute "a lot" to breast cancer and moved towards no risk among the other participants. The authors comment that the study results highlight the difficulty of distinguishing in retrospective self-report studies between valid associations and the influence of recall bias. Recall bias may result in higher calculated risks for product use among participants who believed that chemicals and pollutants contribute to breast cancer. Nevertheless, because exposure to chemicals from household cleaning products is a biologically plausible cause of breast cancer and avoidable, the associations should be further examined in prospective studies.

Comments concerning the study

As the authors point out, the possibility that recall bias heavily influenced the results of this study cannot be ruled out. In fact, Cape Code has a high rate of breast cancer compared to most other U.S. communities and this area has been the subject of several studies concerning the possible association between local sources of environmental pollution and breast cancer. Residents tend to be aware of the problem.

Interest in this topic is presistent, in part, because some of the chemicals used in household cleaners and air fresheners are known or suspected carcinogens. It makes sense to avoid breathing the fumes of these products and to avoid skin contact. Products designed to provide intermittent bursts of air freshener in the home and fresheners designed to be sprayed on furniture upholstery might result in a significant cumulative level of exposure to harmful chemicals.