During the last decades, increasing ecology in reduction of environmental impact caused by traditional plastics is contributing to growth more sustainable with aim reduce consumption non-renewable resources for their production [...]

(31 Aug., p. 819) argue that, because current pricing practices do not internalize environmental costs, some mechanism other than the market is needed to protect environmental values. They propose a system of environmental credits-natural resource units (NRU's)-to be allocated to individuals and industrial organizations. Although their system is ingenious, I offer the following objections. 1) T...