By Carey Gillam

(Reuters) - Farm workers, children and other people working or living near farm fields would have more protection from hazardous pesticides under changes proposed on Thursday by the U.S. Environmental Protection Agency.

"Today marks an important milestone for the farm workers who plant, tend, and harvest the food that we put on our tables each day," Gina McCarthy, EPA administrator, said in a statement.

EPA is proposing revisions to the agency's 22-year-old "Worker Protection Standard" that EPA officials say will help protect approximately 2 million U.S. farm workers and their families from exposure to pesticides used to protect crops from weeds, insects, and disease.

The EPA said pesticides are beneficial tools in agriculture when used in proper concentrations and with proper protections.

U.S. scientists are studying how human health is affected by the use of herbicides, insecticides and other farm chemicals in growing a variety of crops. Some consumer and environmental groups have been calling for greater controls on pesticide use.

The EPA, the United States Department of Agriculture, the National Institutes of Health, and the National Institute for Occupational Safety and Health have been overseeing an "Agricultural Health Study" of nearly 90,000 people in Iowa and North Carolina tracking the impact of factors including pesticide use.

The studies have linked a series of health problems to pesticide use, including various cancers and Parkinson's disease.

"Current medical research suggests that while farmers are generally healthier than the general U.S. population, they may have higher rates of some cancers, including leukemia, myeloma, non-Hodgkin lymphoma, and cancers of the lip, stomach, skin, brain, and prostate," the study states.

Among the changes proposed Thursday, the EPA would require annual training in pesticide protection, instead of once every five years. It would expand mandatory posting of signage warning people from entering fields newly treated with pesticides; prohibit children under 16 from handling pesticides unless they are part of a family farm; and set no-entry buffer areas of 25 feet to 100 feet around pesticide-treated fields to limit exposure from overspraying and fumes.

The EPA is seeking public comments on the proposed changes before making a final decision.

Also Thursday, a coalition led by residents of rural Minnesota announced a campaign to convince fast-food restaurant chain McDonald's to reduce pesticide use on farms where potatoes are grown for its French fries. The group said studies of air quality have shown contamination by the fungicide chlorothalonil, a farming chemical listed by the EPA as a probable carcinogen.

McDonald's said in a statement that it was working with suppliers to reduce pesticide use along with reduced water and fertilizer use and was making "significant progress."

And in Hawaii, the state department of agriculture and the U.S. Geological Survey are undertaking a statewide "pesticide sampling" project to check soil and water for pesticide residues.

(Reporting by Carey Gillam; Editing by David Gregorio and Eric Walsh)