Enhanced UV Inactivation of Adenoviruses under Polychromatic UV Lamps

Abstract

Adenovirus is recognized as the most UV-resistant waterborne pathogen of concern to public health microbiologists. The U.S. EPA has stipulated that a UV fluence (dose) of 186 mJ cm ؊2 is required for 4-log inactivation credit in water treatment. However, all adenovirus inactivation data to date published in the peer-reviewed literature have been based on UV disinfection experiments using UV irradiation at 253.7 nm produced from a conventional low-pressure UV source. The work reported here presents inactivation data for adenovirus based on polychromatic UV sources and details the significant enhancement in inactivation achieved using these polychromatic sources. When full-spectrum, medium-pressure UV lamps were used, 4-log inactivation of adenovirus type 40 is achieved at a UV fluence of less than 60 mJ cm ؊2 and a surface discharge pulsed UV source required a UV fluence of less than 40 mJ cm ؊2 . The action spectrum for adenovirus type 2 was also developed and partially explains the improved inactivation based on enhancements at wavelengths below 230 nm. Implications for water treatment, public health, and the future of UV regulations for virus disinfection are discussed.UV disinfection is a well-accepted technology for inactivation of bacterial and protozoan pathogens. Until recently, UV was also considered a viable technology for disinfection of viruses. At UV fluences (doses) typically used in water disinfection, UV is very effective (Ͼ4-log inactivation) against almost all known pathogenic viruses, with the one exception of adenoviruses (5). Adenovirus has been recently listed on the U.S. EPA Candidate Contaminant List, which indicates that it is a high priority for possible future regulation and is known or anticipated to occur in public water systems, but significant data gaps need to be addressed before regulation can be invoked. According to recently published U.S. EPA regulations (17), the inactivation of adenoviruses to a level of 4 log requires a UV fluence of 186 mJ cm Ϫ2 , based on an 80% credible interval, as presented in the Draft UV Disinfection Guidance Manual (16). The U.S. EPA-regulated UV fluence for inactivation of all viruses is now based on the conservative case of adenoviruses. Yates et al. (18) provide an excellent review of the issues surrounding the UV inactivation of adenovirus.Although data sets for UV inactivation of adenovirus differ moderately, they all place adenovirus as the most UV-resistant health-related virus known. However, all peer-reviewed published studies to date have been performed using a low-pressure (LP) mercury vapor UV lamp source characterized by a monochromatic output in the UV range at 253.7 nm. Based on these LP UV irradiation studies, the UV fluence necessary to achieve 4-log inactivation of adenovirus varies from 120 to approximately 180 mJ cm Ϫ2 . For adenovirus type 5 (Ad5), the required UV fluence is 160 to 170 mJ cm Ϫ2 (1), which is similar to those required for Ad1 (9), Ad2 (1, 5), Ad6 (9), and Ad40 and Ad41 (8). However, there are two studies that repo...

Effect of Host Cells on Low- and Medium-Pressure UV Inactivation of Adenoviruses

“…UV reactors must be capable of delivering UV doses of 186 mJ/cm 2 for 4-log virus inactivation (33). Such a high UV dose requirement is more than 4 times that provided in most drinking water treatment plants.To date, many studies have been conducted to investigate the effect of low-pressure (LP) UV light on AD inactivation (12,18,23,25,30), but only five such studies have been published on medium-pressure (MP) UV inactivation (10,20,21,22,27). Despite numerous studies on LP UV inactivation, the UV dose requirements obtained from different studies were highly variable.…”

Effect of Exposure to UV-C Irradiation and Monochloramine on Adenovirus Serotype 2 Early Protein Expression and DNA Replication

“…Adenovirus, in particular, is more resistant to UV than any other viral, bacterial, and protozoan pathogen of current concern in drinking water (13,17,24,26,29,38,41,43,50). Furthermore, adenovirus is also resistant to inactivation by monochloramine (1,39), suggesting that a UV-monochloramine treatment scheme would be ineffective.…”

Longitudinal study on occurrence of adenoviruses and hepatitis A virus in raw domestic sewage in the city of Limeira, São Paulo

“…Among the enteric viruses, adenoviruses and hepatitis A viruses have their importance for Public Health due their resistance and high rate of outbreaks worldwide (8,10,15,18,25,34). In Brazil there is a lack of information on the occurrence of human enteric viruses in domestic sewage and its correlation with possible outbreaks.…”

“…The resistance of HAdV-40 and HAdV-41 to inactivation by UV light has already been demonstrated (15,34). The recent addition of HAdV in EPA's contaminant candidate list indicates a high priority for a possible recommendation of their use as an indicator of water quality (18).…”