Chemicals used to color or straighten hair have been a cause for concern for many years, but a large new study published in the International Journal of Cancer aims to provide a direction. According to the study, women who used permanent hair dye or straighteners had a higher risk of developing breast cancer. The link was particularly evident in black women — their use of permanent dye was associated with 45 percent higher breast cancer risk. The findings are based on data collected from over 46,000 women. Hair products contain more than 5,000 chemicals that may damage DNA or interfere with the body’s endocrine system, the study noted. The authors conclude that while the risks are meaningful they are small.