Friday January 13 2012
Parabens were found in breast cancer, but the link is not proven
“Chemical found in deodorants, face cream and food products is discovered in tumours of ALL breast cancer patients”, reported the Daily Mail. The newspaper said that the chemical, which is widely used as a preservative in cosmetics, has been found in tissue samples of 40 women with breast cancer.
The headline is based on a laboratory study that investigated how a group of chemicals called parabens are deposited in human tissue. It examined the distribution of five types of paraben at four different parts of the breast in tissue samples from 40 women who had undergone a mastectomy due to breast cancer. The researchers detected parabens in 99% of the samples. They also found differences in the concentrations of individual parabens and where they were predominantly located in the breast.
This analysis only looked at tissue taken from 40 women with breast cancer and did not compare them with tissue samples from women who had not had cancer. It does not prove that parabens caused these cancers, and it does not suggest that parabens have any association with breast cancer development. The study found that all 40 women with breast cancer had parabens in their breast tissue, but it is not known whether this would be the case in all women with breast cancer. It is also not known whether parabens would be found in the breast tissue of all women (including those with healthy breast tissue) and men.
The potential link between cosmetic chemicals and cancers will continue to be investigated. Many factors are known to increase the risk of breast cancer, and as the researchers conclude, it is unlikely that any single chemical would be a dominant risk factor.
Where did the story come from?
The study was carried out by researchers from the University of Reading and was funded by Genesis Breast Cancer Prevention Appeal. It was published in the peer-reviewed Journal of Applied Toxicology.
The Daily Mail exaggerated the implications of this finding. Parabens were found in all breast cancer samples tested, but it is not known whether this is representative of all breast cancers. Parabens may be present in the breast tissue of all women and just as prevalent in women with healthy breast tissue as those with cancer. Indeed, the authors cite earlier research that found parabens in 100% of urine samples from children and pregnant women.
What kind of research was this?
This laboratory study examined breast tissue samples, taken from women who had undergone a mastectomy for breast cancer, to see if they contained parabens (modified versions of the chemical p-hydroxybenzoic acid).
The researchers explained that five parabens (n-propylparaben, methylparaben, n-butylparaben, ethylparaben and isobutylparaben) are widely used as preservatives in consumer products, in the pharmaceutical and cosmetic industry, despite the possibility that they are slightly toxic. They said that some studies have shown that parabens have similar properties to oestrogen, which is known to play a role in the development and progression of breast cancer, and there has been speculation that there could be a link between parabens and cancer.
What did the research involve?
With patient consent, breast cancer tissue samples from 40 women who had undergone a mastectomy for breast cancer were collected from the Manchester Genesis Breast Cancer Prevention Centre between 2005 and 2008. None of the women had received chemotherapy or radiotherapy before the mastectomy. As cancer is more often found in the upper, outer quarter of the breast (closer to the armpit), the researchers examined four tissue samples from each of the 40 women, taken from four locations across the breast from the armpit region (axilla) in towards the breast bone (sternum). They used laboratory methods to look at the concentration of parabens in each of these samples.
What were the basic results?
The researchers detected one or more parabens in 99% of tissue samples (158 of 160 analysed) and all five parabens in 60% of samples (96 of 160). They found that the highest concentration was for n-propylparaben and methylparaben, with lower concentrations of n-butylparaben, ethylparaben and isobutylparaben. The overall average total paraben concentration was 85.5ng (85.5 billionths of a gram) per gram of breast tissue. They observed that the concentrations of parabens varied between women. They also found a variation in concentration according to the location in the breast: n-propylparaben was found at significantly higher concentration towards the armpit than in samples taken from the middle of the breast.
It is not possible to identify the source of the parabens in the individual women. Seven of 40 women reported never having used an underarm cosmetic in their lifetime but still had detectable parabens in their breast tissue. The researchers also found no associations between paraben concentration and patient age (which varied from 37 to 91 years), history of breastfeeding, tumour location or whether the tumour was oestrogen receptor positive (this influences whether or not the cancer can be treated with hormones).
How did the researchers interpret the results?
The researchers concluded that their study expands on previous work demonstrating that parabens can be measured in breast tissue. However, they acknowledge that although parabens have been found in breast cancer tissue, this does not imply that these chemicals caused the cancer.
This laboratory study has furthered our understanding of whether chemicals called parabens are deposited in human tissue. It is one of the first studies to have investigated the distribution of parabens at different parts of the breast, and has done so in a reasonably large sample of women who had received a mastectomy due to breast cancer.
Nevertheless, this is an analysis of tissue taken from only 40 women with breast cancer. It certainly does not prove that parabens caused these cancers. Also, as the researchers did not look at samples of tissue from women who had not had breast cancer, the study cannot suggest that parabens have any association with breast cancer development at all. That parabens are present in the breast tissue of all breast cancer patients is a statement that needs careful interpretation. Though the study found that the breast tissue from all 40 women did contain parabens, it is not known whether this would be the case if samples from other women with breast cancer were examined. Most importantly, it is not known whether parabens could be identified in the breast tissue of all women (including those with healthy breast tissue) or men as well.
The researchers did not fully analyse the personal care products used by these women and could not identify the source of the parabens. Because so many cosmetic products contain parabens, they may be absorbed at low level through the skin. However, similar concentrations of parabens were found in the breast tissue of all women regardless of whether they used, no longer used or never used underarm cosmetics. This suggests that underarm cosmetic application is not the only source of parabens. This study also cannot say whether increasing build-up of parabens occurs over time, or whether they are gradually broken down by the body.
As the researchers themselves concluded, the fact that parabens are present in breast tissue samples taken from women with breast cancer does not mean that parabens caused the cancer. Breast cancer is known to have many risk factors, and it is unlikely that any single chemical would be a dominant risk factor.