Biofilm is a plaque-like sludge that can grow in damp environments. Biofilm is especially concerning for public health experts because it can grow inside tap water pipelines if they are not properly maintained. The pathogen-filled sludge is often credited for causing water-borne illness outbreaks, including E. coli infections.

Biofilm growth is common in old household pipes, but that is not the only location where it can grow. Biofilm can also grow on containers that are not properly washed including in reusable water bottles and straws. 

This post is part of a weekly series on environmental myths. You can find more myths here.