Complex sentence: Although lead-based paints were banned for use in housing in 1978, there are still approximately 24 million housing units in the United States that contain deteriorated leaded paints and high levels of lead-contaminated house dust.
Split into simpler sentences: Although lead-based paints were banned for use in housing in 1978. Approximately 24 million housing units in the United States have deteriorated leaded paint and elevated levels of lead-contaminated house dust.