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New Requirements for Public Water Systems: Cryptosporidium Testing

drinking water regulation

Disinfection of drinking water is one of the major public health advances in the 20th century.  There has been, however, growing concern over the safety of disinfection byproducts (DBPs), prompting amendments to the Safe Drinking Water Act ( These amendments to the Act are in the final stage of implementation and the US EPA is entering the second phase of implementation required by Congress to balance the risks between DBPs and microbial pathogens that are resistant to traditional disinfection practices; e.g., Cryptosporidium and Giardia.  This regulation applies to public water systems serving at least 10,000 people that use surface water or groundwater under the direct influence of surface water.

cryptosporidium parvum and giardia lamblia oocysts
Cryptosporidium parvum oocysts and Giardia lamblia (intestinalis) cysts imaged together for purposes of comparison. In the photomicrograph, the C. parvum oocysts are distinguished from neighboring G. lamblia cysts by their smaller size. Bar = 10 microns.
Photo Credit: H.D.A. Lindquist, US EPA

Beginning in April 2015, public water systems supplying over 100,000 people must begin monitoring for Cryptosporidium.  Each source water sample will initially need to be accompanied by a matrix spike sample – an analysis of a separate sample aliquot spiked with 100 – 500 oocysts – to determine the effect of the matrix (PWS’s raw water) on the methods oocyst recovery.  Significant variability between laboratories and matrices for spike recovery has been reported for the first phase of implementation.

Environmental Standards, Inc. has audited many of the laboratories that are certified by US EPA to perform Cryptosporidium testing and we can assist with finding the best laboratory to suit your needs.  Environmental Standards can serve as a third-party for transparent and independent sampling of your municipality, and will coordinate sample collection and matrix spike collection with your laboratory.  Furthermore, Environmental Standards can evaluate the data on this important pathogen to ensure that US EPA methods (e.g., Method 1623.1: Cryptosporidium and Giardia in Water by Filtration/IMS/FA) were properly followed and to ensure that clients are working with the most reliable and defensible data possible.

For further information, please contact Senior Biologist James Markwiese, Ph.D. in our Knoxville, Tennessee office at 865.376.7590 or via email at