Utilize the input text as a context reference, choose the right relationship between smelting and metal from the options. Options: product/material produced, manufacturer, distributed by, industry, position held, original broadcaster, owned by, founded by, distribution format, headquarters location, stock exchange, currency, parent organization, chief executive officer, director/manager, owner of, operator, member of, employer, chairperson, platform, subsidiary, legal form, publisher, developer, brand, business division, location of formation, creator.

Keller Rohrback has also handled environmental litigation involving home heating oil, contaminated drinking water, contaminated sediments, landfill leachate, metal smelting and finishing wastes, tank farms, chemical plants, gas stations, and major manufacturing concerns.

Answer: product_or_material_produced