Gaston Wu says that there are currently more than 12 million synthetic materials worldwide, but the uses and properties of most of them are not yet known. Only 70-80,000 of them are used frequently, and of those several thousand can be used in cleaning formulas.
台師大化學系教授吳家誠指出，目前全球化學合成物的數量已超過 1,200 萬種，但多數的用途、特性都未經確認，經常拿來使用的只有六、七萬種，而其中能夠拿來做清潔劑的成分就有好幾千種。