The 2:00 - 2:44 section of this video references a study that claims the presence large swaths of very fine dust in the interstellar areas of galaxies. Mr. Davidson of Suspicious Observers puts a spin on this observation and says that these areas of dust could be structured by an electric charge flowing. Either way, the presence of this dust throws a monkey wrench in the parameters used searching for dark matter. Combine the dust (matter) with electro-magnetism, and the rotational problems that prompted the search for dark matter could be solved. https://www.youtube.com/watch?v=pkJDyfpuc1w