Additionally, a United States Environmental Protection Agency (EPA) study that tracked the price of clear glass from 15 July to 2 August 1991, found that the average cost per ton ranged from $40 to $60 while a USGS report shows that the cost per ton of raw silica sand from years 1993 to 1997 fell between $17.33 and $18.10.
另外，美国环保局的一份研究追踪1991年7月15日至8月2日透明玻璃价格，发现每吨平均成本在40至60美元左右，而美國地質調查局一份报告显示1993至1997年间原沙料每吨成本在17.33至18.1美元左右。