EPA 100.1 is for determining the concentration of asbestos fibers in water samples and counts asbestos fibers >0.5 µm in length with aspect ratios of 3:1 or greater. Results are expressed in millions of fibers per liter (MFL). Excessive sediment in a water sample reduces the amount of water that can be filtered to achieve a “readable” grid, so lesser volumes must be filtered, raising the analytical sensitivity. An elevated analytical sensitivity may be reduced by analyzing more filter area, but often at additional cost. EPA 100.1 is only available in select EMSL laboratories.