 Opposition also came from pediatricians and pediatric radiologists who pointed out if children ingested the aluminum pennies, they would be difficult to detect using X-ray imaging because the radiodensity of the metal inside the respiratory and gastrointestinal tracts was similar to that of soft tissue.In addition, the price of copper declined enough that making copper cents would again be economically viable, and conversely made hoarding pointless.The idea of changing the composition of the cent would not be explored again until the 1980s.