Birthday parties and graduations are occasions when people celebrate with balloons, often releasing them into the sky with gusto. But what happens to those plastic balloons once they deflate? Where do they end up?

For years, many environmental groups have pushed for mass balloon releases to be banned, saying that balloon pieces and strings are dangerous to wildlife.

"They are a serious threat to wildlife simply because they are colorful and bright, so wildlife might mistake them for food, and the strings can wrap around their bodies and make it difficult for them to swim or breathe," Emma Tonge, communications and outreach specialist at the National Oceanic and Atmospheric Administration, told USA Today.

Yet releases still happen. The opening of a new Church of Scientology in Ventura, California, was marked with the release of hundreds of balloons, garnering the wrath of Mayor Matt LaVere, who told CNN, "...we will not stand for this type of assault on our environment and animal life."

There's plenty of evidence to suggest that his environmental "assault" label is no exaggeration.

Researchers in Australia analyzed the effects that soft plastics like balloons have on seabirds. They discovered that soft plastics are more likely than hard plastics to cause obstructions in seabirds' gastrointestinal tracts. Of the birds examined, nearly one out of five died as a result of ingesting a balloon or balloon pieces.

"If seabirds eat plastic their risk of mortality increases, and even a single piece can be fatal," wrote lead study author Lauren Roman, PhD student at University of Tasmania. "The evidence is clear that if we want to stop seabirds from dying from plastic ingestion we need to reduce or remove marine debris from their environment, particularly balloons."

Balloons aren't supposed to be up here. Valechek/Shutterstock

States and cities take a stand

Several states have already cracked down on large balloon releases. California, Connecticut, Florida, Tennessee and Virginia have banned them while other states have similar bills under consideration. In Florida, all balloons are banned from Palm Beach County beaches and public parks.

Clemson University also decided to end its tradition of releasing up to 10,000 balloons during football games. One Rhode Island town, New Shoreham, took it a step further and banned the sale, use and distribution of balloons.

"Balloons pose a risk and nuisance to the environment, particularly to wildlife and marine animals. Anyone who walks the beach or spends time on the water has seen that balloons have become common in the local marine ecosystem," according to a statement on the town's website.

Kenneth Lacoste, first warden of the town council, told CNN, "We are very concerned about the environment. There's a lot of information out there of damages that balloons do to the wildlife."

Lacoste said balloons have frequently been found in the water around the town. In December, the town voted to ban most single-use plastic bags for the same reason. He said the balloon bill is essentially a follow-up to that earlier legislation.

Many other cities have banned the release of balloons, including Atlantic City, New Jersey, and Nantucket and Provincetown in Massachusetts. Other places are considering them have laws that regulate the number of balloons that can be released at once. The list of places with some type of ban is constantly changing.

Eco-friendly alternatives to balloons

Pinwheels can be just as colorful as balloons, but can be used over and over again. Otota DANA [CC BY 2.0]/Flickr

Balloons Blow, a nonprofit organization, is dedicated to educating people about the dangers released balloons can have on animals, people and the environment. The group points out that all released balloons return back to the ground as litter. Animals like birds, whales and sea turtles can die after swallowing balloons. Mylar/foil balloons can cause power outages and spark fires. Plus, helium is a nonrenewable resource.

The group suggests environmentally friendly alternatives to balloons, including banners, pinwheels and wildflower seed bombs.