Methyl Bromide Pesticide in Paradise Poisoning Case Still Used in U.S. Crops

The pesticide that sickened a Delaware family in the Virgin Islands is banned for indoor fumigation but U.S. growers will still legally use more than 375 metric tons of the chemical on fields this year through special waivers, federal regulators said.

Methyl bromide is blamed in the accidental poisonings of a mom, dad and their two teen sons at a Caribbean resort. The boys remained critically ill Monday at a Philadelphia hospital. Criminal investigators are examining how and why the bug killer got sprayed in a room beneath the family's rented villa two days before they arrived in mid-March.

U.S. law forbids exterminators from using methyl bromide but the Environmental Protection Agency grants a "critical use exemption" to certain farmers — primarily strawberry growers — letting them inject the chemical directly into their soil, the EPA said.

And some organic advocates are worried about the pesticide perhaps reaching grocery-store fruit.

"You have nurseries producing strawberry transplants — the nurseries are the main users of methyl bromide in the U.S. today. The plants in the fields are all started in nurseries. That ground at the nursery is all fumigated," said Jonathan Winslow, field services manager at Farm Fuel, Inc., a farmer-started, organic distribution and research company on the central California coast.

"The agency (EPA) is still working to determine how much methyl bromide to allow for critical uses in 2016 and 2017"

"So that strawberry transplant can get pulled out of the ground at the nursery and moved to an organic field and be produced under an 'organic' certification," Winslow said. "The use of methyl bromide has diminished, yes. But I am concerned about it. That's why I work for an organic company."

The pesticide is so nasty that, in 1987, the United States and 26 other nations signed a treaty called the Montreal Protocol, vowing to phase out methyl bromide mainly because it depletes the ozone layer. Today, nearly 200 countries have signed that agreement.

But the use of the neurotoxin goes on in farming.

"In the United States, strawberries and tomatoes are the crops which use the most methyl bromide," the EPA says on its website. "Other crops which use this pesticide as a soil fumigant include peppers, grapes, and nut and vine crops."

The EPA offers a "critical use exemption" for methyl bromide to users "who have no technically and economically feasible alternatives and where the lack of methyl bromide will result in a significant market disruption," the EPA said in a statement emailed to NBC News.