The herbicide, used widely on crops including broccoli and onions, can cause low birth weight and impaired brain development, regulators said.

In a move not seen for almost 40 years, the Environmental Protection Agency on Tuesday issued an emergency order suspending all uses of a weedkiller linked to serious health risks for unborn babies.

The pesticide dimethyl tetrachloroterephthalate, also known as DCPA or Dacthal, is used on crops such as broccoli, brussels sprouts, cabbage and onions. Babies whose pregnant mothers are exposed to it could suffer from low birth weight, impaired brain development, decreased I.Q., and impaired motor skills later in life, the E.P.A. said.

“DCPA is so dangerous that it needs to be removed from the market immediately,” Michal Freedhoff, the E.P.A. assistant administrator for the Office of Chemical Safety, said in statement. “In this case, pregnant women who may never even know they were exposed could give birth to babies that

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