was flown in the 1790s. A century later the first hydrogen-filled weather balloons were launched in France. The first modern rubber balloons on record were made by Michael Faraday in 1824. He used these to contain gasses he was experimenting with, especially hydrogen. By 1825 similar balloons were being sold by Thomas Hancock, but like Faraday's they came disassembled, as two circles of soft rubber. The user was expected to lay the circles one on top of the other and rub their edges until the soft, gummy rubber stuck, leaving the powdered inner part loose for inflation. Modern, preassembled balloons were being sold in the US by the early 20th century. Safety and environmental concerns Release There has been some environmental concern over metallised Mylar balloons, as they do not biodegrade or shred as rubber balloons do. 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 anywhere, including on nature reserves or other areas where they can pose a hazard to animals through ingestion or entanglement. Because of the potential harm to wildlife and the effect of litter on the environment, some jurisdictions even legislate to control mass balloon releases. Legislation proposed in Maryland, US, was named after Inky, a pygmy sperm whale who needed six operations after swallowing debris, the largest piece of which was a Mylar balloon. The Balloon Council, a trade organization that represents the interests of balloon businesses, claims that there is no documentary evidence to suggest that the death of any sea mammal has been attributed to foil balloons as a sole cause, to date. In the United Kingdom, foil balloons sold at major theme parks and zoos have balloon weights attached to help prevent accidental release into the environment. When balloons eventually return to the ground, they begin the degradation process. Latex balloons are the most used because of their ability to biodegrade. The problem with this is that it can take at least 4 weeks to show substantial degradation of the polymer in the environment, and around 6 months in aquatic environments. This issue can have an effect on the wildlife on both land and in aquatic systems because animals will confuse deflated balloons as food, nesting material,