The United States Fish and Wildlife Service plans to expand hunting and fishing opportunities at 13 national wildlife refuges across nine states, which includes opening up big-game hunting in Colorado’s 92,000-acre Baca National Wildlife Refuge for the first time.

That’s good news for America’s hunters, who will have more chances to target big-game species such as elk and deer as well as prairie chickens, quail, pheasant, ducks, doves, and pigeons.

But conservationists fear the move will expose wildlife to lead poisoning and other threats.

“The best purpose for our national wildlife refuges is the original purpose: to provide an inviolate sanctuary for the protection of our native wild spaces and wildlife,” said Jennifer Place, program associate at Born Free USA in Washington, D.C.

Of the 562 national wildlife refuges, 336 permit some sort of hunting and 275 allow fishing. These refuges encompass more than 150 million acres of land that hundreds of species of mammals, birds, reptiles, amphibians, and fish and 240 endangered species call home.

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According to the Fish and Wildlife Service, wildlife refuges are intended for multiple human uses, such as wildlife photography, birding, hunting, and fishing. More than 90 million people pursue some sort of wildlife-related recreation, and these refuges conserve space for people and animals to share.

But lately the agency has been opening up more opportunities for hunters and anglers; it has proposed to expand hunting options in wildlife refuges every year for the past four years. States where hunting opportunities could expand include Indiana, Louisiana, Michigan, New York, Oklahoma, South Carolina, and Texas.

“There has been strong pressure at the national level for the Fish and Wildlife Service to expand hunting and fishing on federal land, including within the National Wildlife Refuge System,” Place said.

That increases the potential for negative environmental impacts on all wildlife—not just those targeted by hunters. That’s owing to the continued use of lead ammunition and lead fishing gear, which expose animals to health risks.

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According to The Humane Society of the United States, data show that more than 130 species have been exposed to or killed by ingesting lead shot, bullet fragments, or prey contaminated with spent lead ammunition. California’s condors are one of the most famous victims of lead poisoning.

“The opening of additional national wildlife refuges to hunting likely means more lead ammunition entering our refuges, posing significant health risks to wildlife as well as humans and can have serious implications for the environment,” said Nicole Paquette, vice president of wildlife protection at The Humane Society.

The government has banned the use of lead ammunition to hunt waterfowl, but it is still allowed for the hunting of other species.

In 2014, conservation groups petitioned the Department of the Interior to ban lead ammunition in national wildlife refuges. So far, only California’s Department of Fish and Wildlife has moved to ban lead ammunition, which will be phased out in that state by 2019.