Complex sentence: The Landfill operated without regulation until the 1970s, while the gluefactory and tanner dump toxic heavy metals in the nearby cattaraugus creek, into the air until the 1980s.
Split into simpler sentences: The Landfill operated without regulation until the 1970s. At this time the glue factory and tannery dumped toxic heavy metals into the nearby Cattaraugus Creek and polluted the air until the 1980s.