Using women's stored blood samples from the 1960s, researchers determined that exposure to polychlorinated biphenyls (PCBs) may impact women's menstrual cycles.
PCBs were once used for a range of industrial and household products. They were banned in the United States in the late 1970s because of cancer risks. Yet, PCBs remain in the environment and accumulate in the fatty tissue of animals.
The exposure to the chemicals continues mainly through diet, such as consumption of contaminated fish. The researchers also said that some PCBs are thought to act as endocrine disrupters. Reporting in Epidemiology (March 2005), Glinda S. Cooper, PhD, said that the possible health consequences with humans are not fully understood.
The study involved >2300 women who were all pregnant when their blood samples were taken. The researchers found that women with higher blood PCB levels had a history of more time between monthly periods. The difference in cycle length between women with the highest and lowest PCB levels was equal to <1 day. The participants who fell into the high-PCB group also were more likely to have irregular periods.