Rubber latex balloons are made from Natural Rubber Latex (NRL), which is collected from the Hevea Brasiliensis Pará rubber trees that are grown in certain areas of the tropics and is fully sustainable.
A rubber balloon begins to decompose from the moment it is manufactured and in contact with the natural elements. Decomposition is rapidly accelerated when the balloon is inflated and exposed to sunlight and oxygen.
This process of decay causes the balloon to oxidise. Oxidation begins within approximately one hour of inflation and is visible in some types of balloon as a cloudy or misty appearance.
In the same way that the wood from a tree will rot, a latex balloon is made from the sap of the tree, and will disintegrate in the same way.
Recent biodegradability tests have confirmed that natural rubber balloons biodegrade to approximately 90% within 2 years, under test conditions.
Hevea brasiliensis, the Pará rubber tree, sharinga tree, seringueira, or most commonly, rubber tree or rubber plant, is a flowering plant belonging to the spurge family Euphorbiaceae originally native to the Amazon basin, but is now pantropical in distribution due to introductions. It is the most economically important member of the genus Hevea because the milky latex extracted from the tree is the primary source of natural rubber.
Rubber tree plantation.
In the wild, the tree can reach a height of up to 140 feet (43 m). The white or yellow latex occurs in latex vessels in the bark, mostly outside the phloem. These vessels spiral up the tree in a right-handed helix which forms an angle of about 30 degrees with the horizontal, and can grow as high as 45 feet (14 m).
In plantations, the trees are generally smaller for two reasons: 1) trees grow more slowly when they are tapped for latex, and 2) trees are generally cut down after only 30 years, because latex production declines as trees age, and they are no longer economically productive. The tree requires a tropical or subtropical climate with a minimum of about 1,200 mm (50 in) per year of rainfall, and no frost. If frost does occur, the results can be disastrous for production. One frost can cause the rubber from an entire plantation to become brittle and break once it has been refined.
The natural rubber tree takes between seven and ten years to deliver the first harvest.  Harvesters make incisions across the latex vessels, just deep enough to tap the vessels without harming the tree’s growth, and the latex is collected in small buckets. This process is known as rubber tapping. Latex production is highly variable from tree to tree and across clone types.
As latex production declines with age, rubber trees are generally felled when they reach the age of 25 to 30 years. The earlier practice was to burn the trees, but in recent decades, the wood has been harvested for furniture making.