A lawsuit filed today in federal court alleges a black substance coating the homes of residents in some areas of Louisville is caused by whiskey distilling. Attorney Bill McMurray says for years, residents have seen a black substance growing on metal surfaces, and it’s nearly impossible to remove. “And it’s only recently been understood within the last couple of years what the actual cause for that blackening is, and it’s this particular fungus,” he said. The so-called “whiskey fungus”—or Baudoinia compniacensis—coats metal surfaces. It's caused by ethanol—which is released during distilling—mixing with moisture. McMurray says the lawsuit seeks to force Diageo, Brown-Forman and Heaven Hill to install technology to reduce ethanol emissions. “To employ the kinds of ventilation that are not onerous, but certainly we have the capacity, the technologies available to begin to control these environments to protect neighboring communities,” he said. The suit also seeks unspecified damages. In a joint statement, the companies say the mold is naturally-occurring and not related to whiskey production.