In October 2020, a third stability study was initiated to assess the stability of the four CORESTA Reference Products (CRPs) manufactured in 2016, and to provide repeatability (r) and reproducibility (R) results and z-scores to support laboratory accreditation. The participating laboratories reported the levels of nicotine, pH, moisture (oven volatiles), and tobacco specific nitrosamines (TSNAs) in the CRPs using CORESTA Recommended Methods (CRMs).

The results from this 2021 stability analysis generally compared well to the 2016 and 2019 analyses. The only statistically significant differences from the 2016 and 2019 results were slight changes in moisture for CRP3.1 and CRP 2.1.

The TTPA recommends that the stability of the 2016 CRPs continue to be monitored on a biennial basis.