The betel quid presents a problem that most plants in this atlas do not, which is that it is unambiguously harmful and thoroughly woven into everyday religious and social life.
Areca nut is classified by the International Agency for Research on Cancer as carcinogenic to humans, on its own and in the quid, with or without tobacco. It is a principal cause of oral cancer and of oral submucous fibrosis, a progressive stiffening of the mouth, and the burden falls on the regions where chewing is most common. Tobacco is added to the quid in many places, which compounds it.
That sits awkwardly beside the fact that offering betel is a courtesy, that refusing it can be an insult, that it is presented to deities, and that in some communities a wedding cannot properly proceed without it. Public health campaigns that treat it purely as a habit make little progress, because it is not only a habit.
Some responses have tried to work with the structure rather than against it: substituting other items in offerings, separating the ritual presentation of the nut from its chewing, and targeting the added tobacco as the most harmful component. None has been broadly successful.
The atlas records the ritual use because it is genuine, ancient and enormous in scale, and records the harm because it is established. Neither fact cancels the other, and an entry that gave only one would be misleading.