“Global textile production releases more than 58,000 tonnes of microfibres into the environment every year.”

58,000 tonnes is confirmed: Earth Action's report From Shedding to Solutions states that of an estimated 92,000 tonnes of microfibre losses generated annually during textile production, 63% — more than 58,000 tonnes — reaches the environment. Source 2 (Earth Action, the report's publisher) is the better authority and Source 1 (Printwear & Promotion) reports the same figures without contradiction. Note the scope both sources set: the figure covers the production/manufacturing phase of the textile value chain, not consumer washing or other lifecycle stages.