build-up resulted in a solid mass which could not leave the body. a 1½-year-old girl required medical attention when she swallowed her gum and four coins, which got stuck together in her esophagus. a bezoar is formed in the stomach when food or other foreign objects stick to gum and build up, causing intestinal blockage. as long as the mass of gum is small enough to pass out of the stomach, it will likely pass out of the body easily, but it is recommended that gum not be swallowed or given to young children who do not understand not to swallow it. adults have choked to death on chewing gum in rare cases. a 2012 report describes a 42-year-old woman who fell on the stairs while chewing gum. due to the impact, the gum fell into the pharynx and was inhaled into the larynx, causing complete blockage and resulting in the woman's death by asphyxiation. environmental effects chewing gum on a sidewalk in reykjavíkchewing gum is not water-soluble and unlike other confectionery is not fully consumed. there has been much effort at public education and investment aimed at encouraging responsible disposal. despite this it is commonly found stuck underneath benches, tables, handrails and escalators. it is extremely difficult and expensive to remove once "walked in" and dried. gum bonds strongly to asphalt and rubber shoe soles because they are all made from polymeric hydrocarbons. it also bonds strongly with concrete paving. removal is generally achieved by steam jet and scraper but the process is slow and labour-intensive. most external urban areas with high pedestrian traffic show high incidence of casual chewing gum discard. in 2000 a study on oxford street, one of london's busiest shopping streets, showed that a quarter of a million black or white blobs of chewing gum were stuck to its pavement. gum removal from city streets, or even famous landmarks, can be a costly effort; in rome, 15,000 pieces of chewed gum are discarded on a daily basis and the removal of each piece costs the city one euro. however, likely as a consequence of singapore's ban, singapore's pavements are, perhaps uniquely amongst modern cities, free of gum. various teams of researchers have developed gum that is less adhesive and degrades within days or weeks. one example, rev7 gum, was briefly for sale from 2010 to 2012. bans many schools do not allow chewing gum because students often dispose of it inappropriately (leaving it under desks and chairs, behind vending machines, etc.). the chewing may also pose a distraction to class, and the gum might carry diseases or bacteria from other students. the singapore government outlawed chewing gum in 1992 citing the danger of discarded gum being wedged in the sliding doors of underground trains and general cleanliness. however, in 2004 the government allowed sugarless gum to be sold in pharmacies if a doctor or dentist prescribed it due to the singapore–united states free trade agreement. recycling gumdrop chewing gum collecting bin in 2018, the bbc published a news article on british designer anna bullus, who created a method of collecting and recycling chewing gum into plastic, noting that litter from chewing gum is the second most common form of litter, second only to cigarette litter. she uses a worcester recycling plant to make old chewing gum into plastic. she then uses that plastic at a plastic moulding specialist, amber valley, in leicester to make plastic objects. known objects made are collection containers for more chewing gum, shoe soles, rubber boots, and plastic cups. her company advertises itself as the "first company in the world to recycle and process chewing gum into a range of new compounds that can be used in the rubber and plastics industry". the company is called gum-tec, and the collection containers are dubbed "gumdrops". advertised products on the website are pencils, coffee mugs, guitar picks, a "bicycle spoke", rulers, sports cones, frisbees, boomerangs, door stops, "meal mates", lunch-boxes, and combs.