Final answer:
In 1990, McDonald's abandoned foam packaging and switched to coated paper packaging due to environmental concerns. This change led to a decrease in the demand for polystyrene and a subsequent decrease in polystyrene prices.
Step-by-step explanation:
In 1990, McDonald's made the decision to abandon foam packaging and switch to coated paper packaging. This change was primarily driven by environmental concerns, as foam packaging was not biodegradable and had a negative impact on the environment. Coated paper packaging, on the other hand, is more eco-friendly as it can be recycled.
The switch from foam to coated paper packaging had an impact on the prices of polystyrene, which is the material used to make foam packaging. With McDonald's, being one of the largest buyers of polystyrene in the fast-food industry, reducing its demand for foam packaging, it led to a decrease in the demand for polystyrene, which in turn resulted in a decrease in polystyrene prices.
Overall, McDonald's decision to switch from foam to coated paper packaging not only had a positive impact on the environment but also had implications for the polystyrene market.