There has been some environmental concern over metalized nylon balloons, as they don't biodegrade or shred as rubber balloons do, and a helium balloon released into the atmosphere can travel a long way before finally bursting or deflating. Release of these types of balloons into the atmosphere is considered harmful to the environment. This type of balloon can also conduct electricity on its surface and released foil balloons can become entangled in power lines and cause power outages.

Released balloons can land almost anywhere, including on nature preserves or other areas where they pose a serious hazard to animals through ingestion or entanglement. Latex balloons are especially dangerous to marine life because latex retains its elasticity for 12 months or more when exposed to sea water rather than air. Because of the harm to wildlife and the effect of litter on the environment, some jurisdictions even legislate to control mass balloon releases. Legislation proposed in Maryland, USA was named after Inky, a pygmy sperm whale who needed 6 operations after swallowing debris, the largest piece of which was a Mylar balloon.