Later that year, he moved to Brașov, where he wrote a treatise on the mineral water of Arpătac, Bodoc and Covasna, considered the first Romanian-language medical work.
In 1820, Asachi invited several Transylvanian intellectuals, including Pop, to teach in Iași, the capital of Moldavia.
He visited the various mining towns in order to familiarize himself with the workers' conditions and drafted recommendations for better organizing medical and social services.
He became close friends with George Bariț; 39 of their letters, which touch on political and cultural matters, survive.
In early 1842, as Pop lay dying, the surrounding villages would send messengers to find out his state.