Polystyrene is very difficult and costly to recycle. Most recycling facilities are unable to process EPS because, unlike other plastics, it is challenging to get back in its base form. Cost is not the only issue, however. Polystyrene’s brittle form means it easily breaks into tiny pieces and disperses.

Polystyrene is chemically stable, non-biodegradable, and neither bacteria or microorganisms feed on it. 

The International Agency for Research on Cancer named it as a possible human carcinogen. So does a 2014 National Toxicological Program report on carcinogens which classifies styrene as "reasonably anticipated to be a human carcinogen" and being linked to occurrence of leukemia and lymphoma cancer. As a sustainable alternative consider using starch-based bioplastics or mycelium-based materials, or Wood / cellulose-based foams.