By WC&P Staff

Since the passage of the Safe Water Drinking Act 30 years ago, the U.S. Environmental Protection Agency (U.S. EPA) has constantly evolved and updated its rules and regulations pertaining to contaminant reduction and source water protection against a host of specific microbial pathogens.

The latest addition, the Long Term 2 Surface Water Treatment Rule (LT2), deals specifically with Cryptosporidium and other microbial pathogens that are highly resistant to traditional disinfection practices. Concerns arise from the potential harm of the pathogens as well as the impact of increased levels of disinfection by-products (DBP).

LT2 was first proposed in 2000 and finalized two months ago. According to the U.S. EPA the purpose of LT2 is to reduce disease incidence associated with Crypto and other disease-causing microorganisms in drinking water. LT2 supplements existing regulations by targeting additional Crypto treatment requirements in higher risk systems. The rule also contains provisions to reduce risks from uncovered finished water storage facilities and to ensure that systems maintain microbial protection as they take steps to reduce the formation of DBPs. The rule will apply to all systems that use surface water or groundwater under the direct influence of surface water.

In addition to LT2, the U.S. EPA guidance with regard to Crypto and other microbial pathogens is interconnected to its guidance regarding the health impacts and risks associated with DBPs that result from microbial disinfection in drinking water. Issued alongside the finalized LT2 rule, the Stage 2 Disinfectants and DBPs Rule (Stage 2 DBP) is a set of interrelated regulations that address risks from microbial pathogens and disinfectants/DBPs. The Stage 2 DBP focuses on public health protection by limiting exposure to DBPs, specifically total trihalomethanes (TTHM) and five haloacetic acids (HAA5), which can form in water through disinfectants used to control microbial pathogens. This rule will apply to all community water systems and nontransient noncommunity water systems that add a primary or residual disinfectant other than ultraviolet (UV) light or deliver water that has been disinfected by a primary or residual disinfectant other than UV.

For more information on LT2 and Stage 2 DBP, visit


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