Chlorine inactivation of coliphage MS2 on strawberries by industrial-scale water washing units.

Fruits and vegetables (produce) intended for minimal processing are often rinsed or washed in water. Chlorine and other sanitizers are used during washing to inactivate produce spoilage microbes, but such procedures may also inactivate pathogens epidemiologically linked to produce, such as hepatitis A virus (HAV). However, no information exists on the efficacy of chlorinated wash water to inactivate HAV and other viruses on produce in actual practice, because of obvious safety concerns. In contrast, coliphage MS2 (a bacterial virus) is commonly used as a surrogate for some pathogenic viruses and may be safely used in field studies. In the present investigation, strawberries seeded with MS2 were passed through industrial-scale water washing units operated with or without added sodium hypochlorite. MS2 on strawberries was inactivated by 68%, 92% and 96% at free chlorine (FC) concentrations of < or = 2, 20 and 200 ppm in wash water, respectively. MS2 was detected in wash water containing < or = 2 ppm FC in one trial, but was not detected in water containing 20 or 200 ppm FC. The presence and absence of MS2 in wash water containing various levels of FC highlight the importance of controlling sanitizer levels to prevent viral cross contamination of strawberries.

Chlorine disinfection of produce to inactivate hepatitis A virus and coliphage MS2.

Disinfection of produce is principally used to inactivate spoilage microbes and may also reduce the risk of consumer exposure to enteric pathogens. However, the rate and extent of enteric virus inactivation by free chlorine on produce has not been adequately characterized. Experiments were performed to determine the kinetics of free chlorine inactivation of hepatitis A virus (HAV) and the indicator virus coliphage MS2 on strawberries (SBs), cherry tomatoes (CTs), and head lettuce (HL). The oxidant demand of these produce items also was determined. When produce items were exposed to approximately 20 parts per million (ppm) solution of free chlorine for 5-10 min, HAV and MS2 were inactivated by 90-99% and in some cases virus inactivation was > or =99%. Exposure of strawberries to approximately 200 ppm free chlorine resulted in more rapid and extensive inactivation of both viruses. The produce items tested in this study exhibited a demand for chlorine which varied by produce type, and chlorine residuals declined over time. These results demonstrate the potential for chlorine to reduce the levels of infectious viruses on different produce types, but adequate contact time and chlorine residual are required to achieve maximum virus inactivation. The difference in chlorine demand between SBs, CTs, and HL suggests that varying disinfection practices are needed for the wide variety of processed fruits and vegetables. The inactivation kinetics of MS2 and HAV were similar, suggesting that MS2 and perhaps other similar bacterial viruses may be used as process indicators and surrogates for determining the disinfection efficacy of produce in the laboratory or in actual practice.

Obtaining quantitative vapor emissions estimates of polychlorinated biphenyls and other semivolatile organic compounds from contaminated sites.

Soils contaminated with polychlorinated biphenyls (PCBs) and other semivolatile organic compounds (SVOCs) represent a potentially major, ongoing source of these compounds to the environment, especially during warmer temperatures. A great deal of work has been devoted to understanding the mechanisms that govern the vaporization of SVOCs from soil, but to date, few quantitative estimates have been published regarding emissions from contaminated sites. The present paper describes methods for obtaining quantitative estimates of SVOCs from soils based on flux chamber measurements, modeling, and ambient air measurements. On wet (i.e., H2O) soils, SVOCs at very low chemical loading levels on the adsorption sites (the so-called critical chemical concentration, critical loading, or saturation concentration) will behave, for volatilization purposes, as the pure-liquid substance would. For one soil, the PCB critical concentration was determined to be 775 ppm (95% confidence interval, 5.40E+02). Flux chamber-measured emissions from two contaminated sites were used and compared to model estimated values. The results agree reasonably well and indicate that the modeling approach used provided a conservative upper bound on the emissions. These approaches can be used to develop emissions estimates for SVOC-contaminated sites and inputs to air dispersion models.