Rule reminder
Both pertanto and quindi express consequence ('therefore', 'so'). Pertanto is more formal and belongs to written academic, legal, or journalistic Italian. Quindi is register-neutral and works in both spoken and written language. Pertanto can follow a semicolon mid-sentence; quindi typically precedes the verb directly.
Completa: the formal report: 'Le analisi confermano l'aumento delle emissioni. ___, si raccomanda l'adozione di misure immediate.'