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(NEXSTAR) – An estimated 41.9 million people in the United States have received a booster dose of the COVID-19 vaccine. If you’re among that group, do you still need to wear a mask in public spaces?

The need to wear a mask is dependent on who is around you, according to Dr. Anthony Fauci, the country’s top infectious disease specialist.

“Indoor type settings with family that you know is vaccinated, people that you know, you could feel safe with not wearing a mask and having a dinner, having a reception,” Fauci said on Wednesday during a press conference. “But when you are in a public, congregate setting in which you do not know the status of the vaccination of the people involved, it is very prudent to wear a mask, and that’s what I do.”

If you are going to be in one of these public places, Fauci explains it is OK to lower your mask when you are eating or drinking. If you aren’t doing either of these activities, the mask should stay on.

What type of mask should you wear?

Like the need to wear a mask, it depends on your situation, but health officials say it should cover your nose and mouth, and fit snugly so there aren’t any gaps on the sides of your face.

The U.S. Centers for Disease Control and Prevention also says to pick masks with two or more layers and a nose wire to prevent air from leaking out the top. It suggests holding your mask up to check if it blocks light, which means the fabric will probably filter out more particles.

If you want added protection, experts also suggest wearing two masks or pairing them with a mask fitter to ensure they don’t leave any gaps.

If supplies are available, people can opt for disposable N95 masks for personal use, the CDC says. Such masks are considered most effective at blocking virus particles. The agency had previously said N95 masks should be reserved for health care workers, but supplies have since expanded.

There are some masks designed and tested to perform at a consistent level, according to the CDC. These masks have labels to show what standard they meet.

Toxins found in disposable face masks

In 2020, production facilities, mainly in China, produced over 52 billion masks – some up to 450 million per day. Although they are “single-use” items, estimates show it could take up to 450 years for face masks to degrade. Making matters worse, a recent study finds these masks may be spreading harmful toxins into the environment.

Researchers at Swansea University found significant amounts of toxins (lead, copper, and antimony) coming out of several masks after they were exposure to water. Experts are now posing the question of whether plastic masks are safe enough for people to use every day. Moreover, considering the number of masks that do not make it to the trash bin, these results are alarming.

“All of us need to keep wearing masks as they are essential in ending the pandemic. But we also urgently need more research and regulation on mask production, so we can reduce any risks to the environment and human health,” says lead researcher Dr. Sarper Sarp of Swansea’s College of Engineering in a university release.

For more on the latest research, click here.

The Associated Press contributed to this report.