Effective in 1979, this rule requires quarterly monitoring for trihalomethanes and sets a maximum contaminant level for the annual average. The regulation was strengthened and updated in the 1998 Stage 1 Disinfectants and Disinfectant Byproducts rule. Trihalomethanes (THM) are a group of four chemicals that are formed along with other disinfection byproducts when chlorine or other disinfectants react with naturally occurring materials in water.

The EPA published the Stage 1 Disinfectants/Disinfection Byproducts Rule to regulate total trihalomethanes (TTHM) at a maximum allowable annual average level of 80 parts per billion. This standard replaced the original maximum allowable annual average level of 100 parts per billion for public water systems. The standard became effective in December 2003 for small surface water and all ground water systems.

This example of evolving regulation shows the importance of maintaining close watch over the most current drinking water standards. Our expert staff continually monitors federal guidelines to provide our clients with the laboratory analysis they need to remain compliant. Neilson Research Corporation is unsurpassed in our laboratory technique, client service, and the production of unquestionable scientific data.

For more information about trihalomethanes, visit the Stage 1 Disinfectants and Disinfection Byproducts Rule Quick Reference Guide: http://www.epa.gov/safewater/mdbp/qrg_st1.pdf