The alarm was sounded on Wednesday, when federal officials announced that tests had detected a trace amount of iodine 131 in milk.

Although we may never know the extent of radiation exposure to the food supply; the alarm hasn’t gone off.

Be reasonably cautious about food purchases.

“I’ve had members call to ask whether we’ve seen the media, and media calling to ask how this is impacting our members,” said Michael Marsh, the chief executive of Western United Dairymen, the milk industry’s West Coast trade association. Mr. Marsh said he had repeated the assurances given by officials, but he also understood the fears in the supermarket’s refrigerated aisle.