January 9, 1998

Summary of suggestions made during the January 7, 1998 NDWAC Working Group Conference Call regarding changes the Drinking Water Candidate Contaminant List (CCL) for Microorganisms

For microorganisms, the following suggestions were made during the January 7, 1998 NDWAC Working Group Conference Call regarding changes to the CCL. These suggested changes were later confirmed via follow-up conference calls and discussions with EPA microbiologists and other personnel in Cincinnati and Headquarters. This summary, in and of itself, does not reflect the final recommendations on microorganisms.

Viruses

Rotavirus should be added to the CCL in light of public comments received and the groundwater occurrence survey that indicates it is a more prevalent problem than previously thought.

Hepatitis E should not be added to the CCL. There is not agreement with commenters that the virus is a serious problem in other parts of the world, and evidence indicates that it is not found within the United States.

Protozoa

Toxoplasma gondii should be removed from the CCL. The organism is the same size or larger than giardia and therefore would be controlled by the same mechanisms that control giardia and crytosporidium for which regulations are currently under development.

Blastocystis and Entamoeba histolytica should not be added to the CCL, as outbreaks have not occurred at all (blastocystis) or have not occurred in the last 30 years (entamoeba histolytica).

Algae

Blue-Green Algae (cyanobacteria) and related toxins, including micotoxin should be added to the CCL . They have caused outbreaks and are not currently being tracked, and the Agency needs to learn more about these organisms. The Working Group recommended that "freshwater algae and related toxins" be listed in lieu of "blue-green algae," because there are freshwater algae in addition to blue-green algae that produce toxins.

Pfiesteria should be added to the CCL. All indications are that Pfiesteria's habitat is estuarine or brackish water. Current data indicate that, like most other dinoflagellates, the organism grows poorly in fresh water and does not elaborate toxins in fresh water conditions. Moreover, the size ranges from 5-450 m, with the dormant cyst stages 7-60 m in diameter. Thus filtration that is effective for removing Cryptosporidium (4-6 m) would be effective for removing Pfiesteria.

Bacteria

Aeromonas hydrophila should remain on the CCL. Although it has not caused an outbreak, aeromonas does grow well on the inside of the drinking water distribution system, and researchers need to determine if the harmful strains that cause disease grow in water distribution systems.

Pseudomonas aeruginosa should be on the CCL. It is an organism that requires additional research.

Salmonella, Shigella, V. cholerae, Y. enterocolitica, E. Coli O157:H7, Campylobacter, and the Arcobacter, should not be included on the CCL. They are all a product of fecal contamination and therefore would be addressed by the Total Coliform Rule, as well as by the Surface Water Treatment Rule, and by the upcoming Groundwater Disinfection Rule and Enhanced Surface Water Treatment Rule.

Indicators

Coliphage should not be added to the CCL. These organisms pose no health threat, but are an indicator of fecal contamination and as such are being considered for inclusion in the upcoming Groundwater Disinfection Rule.