In 1974 the EPA passed the Safe Drinking Water Act (SDWA) in an effort to determine the level of contamination in drinking water to which no adverse health effects are likely to occur. There are numerous contaminants regulated by the SDWA and asbestos was added to the list in 1992. The various contaminants can be found in National Primary Drinking Water Regulations (NPDWR).
These regulations are legally enforceable primary standards that apply to public water systems only. For asbestos, the EPA has set a Maximum Contaminant Level (MCL) of 7 million fibers (>10 micron in length) per liter (MFL). The EPA periodically reviews this act to determine if the MCL still protects human health. States and other local agencies may set more stringent drinking water MCLs for asbestos than the EPA; so it is always best to check with your local authorities prior to interpreting your laboratory results.
EPA 100.1 versus 100.2
The EPA 100.1 method started out as the “Analytical Method for Determination of Asbestos Fibers in Water” (EPA-600/4-83-043) and was written in 1983. In 1992, with the establishment of the MCL, the EPA also added to the Federal Register that the analysis of asbestos in water should be conducted using Transmission Electron Microscopy (TEM). Since the 1983 EPA 100.1 method was not designed to specifically meet the needs of the 1992 regulation, the EPA issued a memorandum to clarify how the EPA 100.1 standard could be used for compliance.
The EPA 100.2 method was issued in 1994 (“Determination of Asbestos Structures Over 10 μm in Length in Drinking Water, (EPA/600/R-94/134) and was written specifically to respond to the asbestos drinking water standard. It also incorporated quality assurance objectives developed under the Asbestos Hazard Emergency Response Act (AHERA).
EPA 100.1 vs EPA 100.2
While these two methods are quite similar they differ in several ways- such as filter material, filter pore size, ozone/ultraviolet treatment and fiber identification. These differences arise from the intent of each method. EPA 100.1 was written as a refinement to an interim method and was designed more for research level work than regulatory compliance; whereas, the EPA 100.2 was streamlined for use specifically for compliance with the EPA MCL.
Asbestos in Water Testing Overview & FAQ