Hi, @David.
Thank you for sharing your deep insights. I appreciate your help. The number of available nitrosamines with reliable toxicological information is not large. And selecting the best surrogate for NDSRIs is challenging in many cases. A conservative class-specific threshold(18 ng/day) tends to apply to complex nitrosamines.
I understand not only local similarity but also global similarity are important to select the surrogates in the read-across method. The other features are also worth addressing. But we know there are gaps between current regulation and knowledge. I hope the gaps will solve in the future.