There is strong evidence that chemicals that interfere with the hormone system can cause serious health problems, according to a scientific report from the Endocrine Society, now meeting in Washington, D.C. Although scientists still have many questions about the chemicals, the report says that it’s important for people to take a “precautionary approach” by reducing their exposures.

The report notes that hormone-disrupting chemicals behave differently than other toxins. For most toxins, the danger is in the dose, with larger doses posing more risk than small ones, says Andrea Gore, an author of the new statement from the University of Texas at Austin.

Because the body is exquisitely sensitive to hormones, Gore says, even small doses can cause serious problems, especially if babies are exposed during critical development windows, such as before birth. For hormones, the timing of exposure is often far more critical than the amount.