Economic measures are directed at those who cause the most environmental costs.

directed 是动词 direct 的过去分词形式，direct 的意思是"指向、针对"，在句中表示被动含义。 at 是介词，表示"朝向、针对"某个目标或对象。 directed at 这个短语表示"针对、指向"某个特定对象或群体。