Both slag and baghouse ash are waste products created by the electrosmelting process. Baghouse ash, which contains dioxins and heavy metals, is classified as "hazardous waste" and may not legally be recycled. Slag, however, contains relatively lower levels of heavy metals (although not necessarily lower levels of toxicity), and was in the past considered suitable for reuse in paving bridges and roads, along with similar engineering work.
爐碴、集塵灰均屬於「電爐煉鋼」（即「廢料煉鋼」）過程中產生的廢棄物，其中飽含戴奧辛及重金屬毒物的集塵灰，屬於「有害事業廢棄物」，依法不得再利用；而重金屬含量較低但未必毒性低的爐碴，過去卻被視為「資源物質」，廣泛運用在鋪橋、建路等工程上。