Chemical hair-straightening products may increase uterine cancer risk: NIH study in humans
In this week’s issue of the journal Science, researchers from the National Cancer Institute (NCI) have published a study in mice and humans showing that chemicals used for hair-straightening can increase uterine cancer risk. The study found that mice that had their hair cut for chemical straightening had a three-fold increase in uterine cancer. The chemicals used on the mice included those known to be carcinogenic in mice.
The NCI study was a meta-analysis of existing studies involving 1,072 mice and 8,912 women. The mice were exposed to these chemicals during the period when their hair was being straightened.
Most of the human participants in the study were women who had used chemical straightening products for at least one year and had a history of prior uterine cancer.
In previous studies, women who had used hair-straightening products showed a greater than three-fold increased risk of uterine cancer, and the researchers found that these chemicals were associated with increases in risk of ovarian and endometrial cancer.
Women in the study that used chemical straighteners had not previously been diagnosed with uterine cancer. Some of them reported they had used these products when they were younger, with no previous uterine cancer.
The NCI researchers acknowledge that their results “do not prove directly that hair straighteners increase the risk of uterine cancer,” and they have not taken a sample of uterine tissue to “examine any direct risk of chemical exposure,” as the Journal’s story notes.
“The jury is still out,” says NCI director Fred B. Wilfort, M.D., to the Journal, noting that there are other published studies showing both positive and negative results for chemical substances used for hair straightening.
The NCI study was based on data from a previous study involving rodents and human subjects in England. The mice were used as a baseline control to help identify chemicals that might have the potential to damage cells and tissues in the human body. For that reason, the NCI researchers found it difficult to determine whether the increased uterine cancer risk