Balloon manufacturers will often state that a latex balloon is perfectly safe to release into the environment as it is made from a natural substance and will biodegrade over time.
Any methanol that unavoidably escapes into the environment will have little long-term impact, and with sufficient dilution will rapidly biodegrade with little to no environmental damage due to toxicity.
Other fluorochemicals also persist, like antibiotics and antidepressants in treated sewage, and agrichemicals in farmland runoff and nearby rivers, since they do not biodegrade easily.
This type of cleaning involves the use of products that biodegrade into compounds that are environmentally friendly and do not pose detrimental environmental concerns.