Any kind of wood based panel create emission due to formaldehyde glue either Urea based, melamine based, phenolic, or a combination of these. Evaporation of Formaldehyde creates emission, and this have adverse effect on human health.
These glue is must for binding either as glue line in plywood, or binding wood particles/chips in case of mdf or particle boards.
These glue can not be avoided, these are must and over a period of time these create emission which may be harmful.
There are various emission norms set by various countries to make wood panel boards safer.
In developed countries such as Japan accepted norm is E0, which can be read as Zero emission, which is safest norms or highest standard.
Other countries may have E1 or E2 , like India follows E2 emission norms as per mandatory requirements. Though we may not call is E2 in India, however it is comparable.
Now a days there is increased awareness related to emission and effect on health, so voluntarily companies are adopting and users are asking better products in terms of emission.
This is one of the reason, may companies in wood panel boards (Plywood, MDF & Particleboards) have started manufacturing higher grades such as E0 & E1.
Further, many multinational companies have mandated use of higher rated boards for furniture.
One more reason for use of E0 or E1 grade board is export to countries where better emission norms are followed.