Acidic particulates emitted by heavy industry on the US side of the Great Lakes were being blown elsewhere, killing large numbers of trees in the forests on the western slopes of the Appalachian Mountains and acidifying Canadian lakes near the US-Canadian border. When the pH of these lakes fell to less than 5.0, they became fishless "dead lakes."
由美國 5 大湖重工業區所排放的酸性污染物質隨風飄浮、沈降至他地，不但造成美東阿帕拉契山區西側迎風面原本蒼翠蓊鬱的常綠原始林大量白化、死亡，鄰近美加邊境的加拿大眾多湖泊也嚴重酸化，湖水的 pH 值低至 5.0 以下，已形成「魚蹤絕跡」的死湖。