- 1990:

- A market-based cap and trade program to regulate sulfur dioxide is proposed as an amendment to the Clean Air Act to eradicate acid rain.

- Koch’s Citizens for a Sound Economy creates a spinoff front group called “Concerned Citizens for the Environment” to battle proposed regulations to deal with acid rain. The Pittsburgh Post-Gazette reported that the group “has no citizen membership of its own,” but produced studies arguing that acid rain was a myth and that deregulation would benefit the environment.

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