Billows of fire and smoke filled the air above Florida’s Kennedy Space Center as the countdown clock reached zero. Flanked by two rocket boosters and strapped to the back of a giant red fuel tank, the space shuttle blasted off.

Within seconds, the shuttle disappeared from sight. In just over 8 minutes, it reached outer space. But NASA’s launches left more than a legacy of space exploration.

Before leaving Earth's atmosphere, each space shuttle spewed thousands of pounds of metals and other chemicals into the air. Some contaminants fell into a federal wildlife refuge surrounding the base that is home to alligators, sea turtles and other endangered animals.

“People think of a shuttle launch as a short-term, finite event, but each launch expels a huge amount of debris into the atmosphere with the potential for long-term effects on the surrounding ecosystem,” said John Bowden, an environmental chemist at Hollings Marine Laboratory in Charleston, S.C.

Immediately after each takeoff, metal concentrations spiked in the waters around the launch pads. And while the levels remained high for only a few days, these contaminants may have accumulated in the ecosystem’s top predator – the alligator. Gators near the launch pads have excessive levels of iron in their livers.

Effects on the creatures, however, are largely unknown. Alligators there have elevated thyroid hormones, which can disrupt growth. Nevertheless, the gators and other creatures in the 140,000-acre refuge appear healthier than animals in some highly developed, polluted parts of Florida.

From 1981 through 2011, NASA launched 135 space shuttles from Kennedy Space Center, which is surrounded by one of Florida’s last protected saltwater ecosystems. The 35-mile long Merritt Island National Wildlife Refuge is home to more than 1,500 species of plants and animals, including 14 at risk of extinction.

“If it wasn’t for the launching facilities, the feds would have never acquired this land, and I think it’s safe to say it would look a lot like the rest of the East Coast of Florida right now – condos,” said Mike Legare, the refuge's supervisory biologist.

Yet preservation comes at a price. “What we pay for all the positives is localized contamination, specifically at these launch pads,” Legare said.

The launches spew metal particles that fall back to earth and settle into the water. Where those particles ultimately go and what effects they may be having on animals in the refuge remain unclear.

Some scientists suspect the contaminants may be working their way up the food web.

Louis Guillette, a zoologist at the Medical University of South Carolina, has been studying alligators in Florida for decades. He found that gators in a lagoon near one of the launch pads had higher levels of iron and other metals, including lithium, nickel and mercury, in their livers than alligators from two other parts of Florida.

Their levels of iron were so high that the same amount would cause liver damage in mammals – humans, donkeys and deer, according to the research. However, few studies have investigated iron toxicity in reptiles, and no one knows what levels might cause liver damage in alligators.

In addition, baby alligators collected as eggs from the brackish waters of the Merritt Island refuge had elevated thyroid hormones. Some metals can target the thyroid gland, which regulates growth and metabolism. When they hatched in the lab, the refuge's gators were smaller and weighed less than gators taken from another Central Florida refuge.

The different thyroid hormones and weight may have more to do with Merritt Island’s salty, brackish water than its contaminants. Saltwater contains iodine that can alter thyroid hormones, and alligators aren’t very efficient at excreting salt because they are adapted to freshwater environments.

Still, Guillette said, it’s possible that the contaminants were behind the hormone differences. “Some of the heavy metals we saw are clearly not supposed to be there in the environment,” he said. In the juvenile alligators, for instance, they found lithium, nickel, bismuth and other metals used in the shuttles.

NASA officials said that the creatures around the Kennedy Space Center are healthy.

“We have robust ecological communities that appear to be thriving in these areas,” said Mike Deliz, NASA remediation project manager.

Guillette, for the most part, agrees. The alligators he tested near the space center are healthier by many markers than alligators at a contaminated lake near Orlando, Lake Apopka. Guillette is renowned for discovering in the 1990s that a pesticide spilled in the lake altered the gators’ sex hormones, leaving them feminized.

When the shuttle launches began, NASA-affiliated scientists began collecting water samples to observe the environmental effects, said Carlton Hall, program manager for the Kennedy Space Center Ecological Program.

The researchers collected water from 11 sites after 41 shuttle launches between 1996 and 2009. Some were within drainage lagoons adjacent to the launch pads. Others were located in nearby Mosquito Lagoon, Banana River and Banana Creek.

Immediately after launches, the researchers detected what they called “a dramatic increase” in four metals associated with launch operations. Manganese, aluminum, iron and zinc rose between 37 and 175 percent in the sampling sites closest to launch pads compared with other parts of the Merritt Island refuge.

“While there could be several natural and anthropogenic sources for metal deposition at KSC, the data in this report indicate that shuttle launch events are a significant source,” according to a study by Bowden, Guillette and other researchers published this month in the journal Environmental Science & Technology.

Yet within a day or two after the launch, the levels around the launch pads fell back to normal. The water in 2009 did not contain appreciably higher levels of metals than it did in 1996.

“The fact that we found no accumulation over time was really interesting. We know that each launch puts thousands of kilograms of matter into the environment. Where it goes is still a bit of a mystery,” Bowden said.

Unpublished research from Kennedy Space Center scientists showed the contaminants apparently were not accumulating in the sandy soils. Deliz said low levels of zinc and aluminum were found, but not at levels high enough to warrant cleanup.

In Merritt Island’s shallow water ecosystem, sediments are constantly moved around by tides and storms. The contaminants also may seep into groundwater and disperse throughout the refuge, Legare said.

Bowden suspects gases released by the shuttle may play a key role in the uptake of metals into wildlife. The plume contains hydrogen chloride, a strong acid. After launches, the pH of the lagoons may plummet for a short time, rendering the water nearly as caustic as battery acid.

Seashells and limestone soils quickly neutralize the water, restoring normal pH within hours. But acidity can make some metals more soluble, meaning they can be taken up by plants and animals.

Protected as a threatened species, the alligator, Guillette said, is a perfect animal for monitoring the health of the wetlands around Kennedy Space Center.

Gators may live 40 to 60 years, which means that the oldest ones at Merritt Island may even predate the moon landing. “It’s a long-lived, top predator. And unlike birds, they can’t get up and fly away,” he said.

Although the shuttle program ended in 2011, NASA scientist Lynne Phillips said it’s important to understand hazardous contaminants as the space center transitions to what she calls “the next generation of space launch.” The launch pads and buildings are being redesigned for future missions with commercial space partners.

“There are going to be environmental consequences any time you light off a Roman candle that big, but NASA itself has been a very good neighbor to wildlife by minimizing impacts to pristine parts of the wildlife refuge and seashore,” said Charles Lee, advocacy director of Audubon of Florida.

But Lee worries about the future. A proposal to build a commercial spaceport just north of Kennedy Space Center may jeopardize habitat in other parts of the refuge, in an area considered one of the most important sites on the East Coast for wading birds.

The most compelling issue, Lee said, is “whether the private space industry is going to confine its impacts to sites that have already been disturbed or attempt to chop up the remainder of the wildlife refuge.”

This article originally ran at Environmental Health News, a news source published by Environmental Health Sciences, a nonprofit media company.