Enhanced effectiveness of medium-pressure ultraviolet lamps on human adenovirus 2 and its possible mechanism

Abstract

There has been growing concern over human exposure to adenoviruses through drinking water due to their apparent high resistance to UV irradiation and the anticipated widespread use of ultraviolet (UV) disinfection in drinking water treatment processes. However, most inactivation studies on adenoviruses were performed using only one type of UV technology--low-pressure (LP) UV, and little is known about the effectiveness of different UV technologies such as medium- pressure (MP) UV or other polychromatic UV technologies. In this work, the kinetics and extent of inactivation of a human adenovirus (adenovirus 2 (Ad2)) by both monochromatic LP and polychromatic MP UV were evaluated to determine the effectiveness of these UV technologies on human adenoviruses. Inactivation of Ad2 by LP UV was very slow and only 0.87 and 2.17 log(10) inactivation was achieved with UV doses of 30 and 90 mJ/cm(2), respectively. However, inactivation of Ad2 by MP UV was much faster and 2.19 and 5.36 log(10) inactivation was observed with the same UV doses (30 and 90 mJ/cm(2), respectively). It appears that MP UV is more effective against Ad2 than LP UV and the enhanced effectiveness of MP UV on Ad2 is likely due to its ability to inhibit the repair process in UV-irradiated Ad2.

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

“…Thus far, results from this study and those from recent studies on AD (10,20,21,22,27) have provided evidence regarding the superiority of MP UV disinfection rather than LP UV disinfection. MP UV results have provided a positive indication regarding its ability to inactivate AD, even at much lower UV doses than those used with LP UV inactivation.…”

“…Few studies on MP UV inactivation have been conducted, and they are limited to the inactivation of AD2 and AD40 (10,20,21,22,27). In this study, differences in LP UV dose requirements for 4-log inactivation of AD5, -40, and -41 were larger than those in MP UV dose requirements.…”

“…With MP UV dosing, approximately 90 mJ/cm 2 was required for 4-log inactivation of AD2 (A549) (21), which was comparable to that result for AD5 in this study. Shin et al (27) also observed that 2-log inactivation of AD2 (A549) was achieved with LP and MP UV doses of 80 and 32 mJ/cm 2 , respectively. To achieve 2-log inactivation of AD5 with HEK293 and PLC/PRF/5 cells, the LP UV doses required were 76 and 62 mJ/cm 2 , respectively, and the MP UV doses required were 45 and 43 mJ/cm 2 , respectively (this study).…”

“…Nevertheless, regardless of whether MP or LP UV was used, the choice of cell line does affect AD enumeration following UV irradiation to a certain extent. The different AD resistances of an AD strain enumerated with different cell lines were probably a result of (i) the selectivity of different host cells for different virus types (1, 37), (ii) the different availabilities of repair enzymes present in different cell types (12), and (iii) the type of lamp used for UV disinfection (27). Grabow et al (13) observed that the PLC/PRF/5 cell line was 100 times more sensitive to a laboratory strain of AD41 and 10 times more sensitive to a laboratory strain of AD40 than the HEK293 cell line.…”

“…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.…”