Purposeful reduction of formaldehyde emissions began in the 60s-70s. However, classification as a known carcinogen has triggered the adoption of more strict formaldehyde emission recently. Consequently, the industry strives to develop "formaldehyde-free adhesives" that neither contain nor release formaldehyde.
Different solutions are being explored, including development of bio-based adhesives and use of existing synthetic monomers with crosslinkers other than formaldehyde. A critical review of the efficacy of current formaldehyde-free technologies has been carried out in this article by the International Journal of Adhesion and Adhesives. The performance of a few systems is not far from the current formaldehyde-based adhesives.
The graph below shows the development of formaldehyde content of industrially produced particleboards in Europe.
Source: P. Solt, et al. International Journal of Adhesion and Adhesives 94 (2019) 99-131