Fireworks are made of plastic and can contribute to plastic pollution in the environment in several ways: Microplastic pollution Fireworks can release plastic particles that are 5 millimeters in diameter or less into the water, which can harm wildlife and contaminate water systems. Plastic debris When fireworks explode, the plastic components can spread over large areas and end up on land and sea, where they can be difficult to collect. Heavy metals Fireworks contain heavy metals like barium, an