Some Republican senators and farm groups are worried about a report from the Make America Healthy Again Commission that could attack modern farming techniques. The health and human services secretary, Robert F. Kennedy Jr., says he will release the report on Thursday.

President Trump signed an executive order during Mr. Kennedy’s swearing-in ceremony to form the commission and ordered a report within 100 days featuring an action plan to fight childhood diseases and chronic illness. 

Senator Hyde-Smith, a Mississippi Republican, quizzed Mr. Kennedy about it during his appearance before a Senate appropriations subcommittee on Tuesday.

Ms. Hyde-Smith said credible sources had reported that the initial assessment “may unfairly target American agriculture, modern farming practices, and the crop protection tools that roughly 2 percent of our population relies on to help feed the remaining 98 percent.”

She asked if farmers and ranchers could trust his findings. “It’s no secret that you were involved in pesticide litigation prior to becoming secretary,” Ms. Hyde-Smith said. “Has your past or personal opinions influenced the initial assessment?”

Mr. Kennedy denied any bias. “Your information about the report is just simply wrong,” Mr. Kennedy responded, breathing heavily directly into his microphone. “The drafts that I have seen, there is not a single word in them that should worry the American farmer.”

Senator Grassley, an Iowa Republican, has also raised concerns about the possible findings of the MAHA Commission. He joined a group of Republican senators and representatives in sending a letter to Mr. Kennedy urging the commission to use “sound science and risk-based analysis in its policy decisions, particularly on crop protection tools and food-grade ingredients.”

“I’ve heard from a lot of stakeholders that the creation of this MAHA report has lacked transparency,” Mr. Grassley said, adding that he wants to know if Mr. Kennedy’s staff has met with food and agriculture stakeholders or only environmental groups in the creation of the report.

Major agriculture groups released a statement on Tuesday echoing major concerns about what the report will contain. “Despite the effort of many of our organizations to work with the MAHA Commission to provide factual information about American food production, we have heard disturbing accounts that the commission report may suggest U.S. farmers are harming Americans,” the letter states. “Nothing could be further from the truth.”

They are urging Mr. Trump to ensure the report is based on sound science and not the word of activists: “Should the MAHA Commission report baselessly attack and, worse yet, make claims that are simply untrue against the hardworking men and women who feed our nation, it will make further cooperation on this initiative very difficult and potentially put American food production at risk.”

Mr. Kennedy said the report will be fair. “There’s nobody that has a greater commitment to the American farmer than we do,” he said at the subcommittee hearing. “The MAHA movement collapses if we can’t partner with the American farmer in producing a safe, robust, and abundant food supply.”