WASHINGTON — Federal scientists have determined that a family of widely used pesticides poses a threat to dozens of endangered and threatened species, including Pacific salmon, Atlantic sturgeon and Puget Sound orcas.

The National Marine Fisheries Service issued its new biological opinion on three organophosphate pesticides – chlorpyrifos, diazinon and malathion – after a yearslong court fight by environmental groups. At the urging of pesticide manufacturers, the Trump administration had sought a two-year delay of a court-ordered deadline to issue the findings by the end of 2017, but it was unsuccessful.

Apples are shown at a farmers market. A pesticide used on citrus fruits and other crops would be restricted under an EPA proposal. Associated Press/J. Scott Applewhite

Environmental Protection Agency Administrator Scott Pruitt

The exhaustive 3,700-page federal review, dated Dec. 29, concludes that chlorpyrifos and malathion jeopardize 38 out of the 77 species under the jurisdiction of the fisheries service and that diazinon was found to jeopardize 25 of the listed species.

The report makes detailed recommendations to the Environmental Protection Agency for new restrictions on how and where the pesticides can be sprayed to help limit the harm.

EPA Administrator Scott Pruitt in March reversed an Obama-era effort to bar the use of chlorpyrifos on fruits and vegetables after peer-reviewed academic studies found that even tiny levels of exposure could hinder the development of children’s brains.

Organophosphorus gas was originally developed as a chemical weapon before World War II. Dow Chemical, based in Midland, Michigan, has been selling chlorpyrifos for spraying on citrus fruits, apples, cherries and other crops since the 1960s. It is among the most widely used agricultural pesticides in the United States, with Dow selling about 5 million pounds domestically each year.

The Associated Press first reported in April that lawyers representing Dow and two other pesticide companies sent letters to three of Trump’s Cabinet secretaries saying the academic studies were flawed. Dow wrote a $1 million check to help underwrite Trump’s inaugural festivities, and company CEO Andrew Liveris led a now-disbanded White House manufacturing working group.

Environmentalists and commercial fishermen have fought in court for more than a decade to spur the federal government to more closely examine the risk posed to humans and endangered species by organophosphates. Studies have shown that even low levels of pesticides can impair the growth, swimming ability and reproductive systems of salmon.

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