Shelf-Life of Chlorine Solutions Recommended in Ebola Virus Disease Response

Abstract

In Ebola Virus Disease (EVD) outbreaks, it is widely recommended to wash living things (handwashing) with 0.05% (500 mg/L) chlorine solution and non-living things (surfaces, personal protective equipment, dead bodies) with 0.5% (5,000 mg/L) chlorine solution. Chlorine solutions used in EVD response are primarily made from powdered calcium hypochlorite (HTH), granular sodium dichloroisocyanurate (NaDCC), and liquid sodium hypochlorite (NaOCl), and have a pH range of 5–11. Chlorine solutions degrade following a reaction highly dependent on, and unusually sensitive to, pH, temperature, and concentration. We determined the shelf-life of 0.05% and 0.5% chlorine solutions used in EVD response, including HTH, NaDCC, stabilized NaOCl, generated NaOCl, and neutralized NaOCl solutions. Solutions were stored for 30 days at 25, 30, and 35°C, and tested daily for chlorine concentration and pH. Maximum shelf-life was defined as days until initial concentration fell to <90% of initial concentration in ideal laboratory conditions. At 25–35°C, neutralized-NaOCl solutions (pH = 7) had a maximum shelf-life of a few hours, NaDCC solutions (pH = 6) 2 days, generated NaOCl solutions (pH = 9) 6 days, and HTH and stabilized NaOCl solutions (pH 9–11) >30 days. Models were developed for solutions with maximum shelf-lives between 1–30 days. Extrapolating to 40°C, the maximum predicted shelf-life for 0.05% and 0.5% NaDCC solutions were 0.38 and 0.82 hours, respectively; predicted shelf-life for 0.05% and 0.5% generated NaOCl solutions were >30 and 5.4 days, respectively. Each chlorine solution type offers advantages and disadvantages to responders, as: NaDCC is an easy-to-import high-concentration effervescent powder; HTH is similar, but forms a precipitate that may clog pipes; and, NaOCl solutions can be made locally, but are difficult to transport. We recommend responders chose the most appropriate source chlorine compound for their use, and ensure solutions are stored at appropriate temperatures and used or replaced before expiring.

Assessment of Recommendation for the Containment and Disinfection of Human Excreta in Cholera Treatment Centers

“…Another useful point to bear in mind when using chlorine-based approaches is that the 2% concentration seems to be more adequate (than other concentrations tested both here and in previous studies) for containing human excreta and wastewater. This also reinforces the importance of checking the shelf-life of chlorine solutions [41] and also of the need for adequate methods with which to test the concentration of such solutions in situ [42]. Although this research demonstrates that hyperchlorination (chlorine 2%) appears to be a potentially effective way to treat and contain human wastewaters, chlorine-based products are considerably less effective when it comes in more concentrated forms of human excreta, which seem to be better suited to lime-based treatment.…”

Assessment of recommended approaches for containment and safe handling of human excreta in emergency settings

“…Where possible, the accuracy should be checked using a range of commercially available methods for testing chlorine solution concentrations in emergency settings [ 49 ]. Furthermore, the shelf-life of chlorine solutions recommended for cholera and Ebola disease treatment centres should also be taken into consideration by healthcare practitioners, as chlorine concentrations tend to reduce with time [ 50 ].…”

The Disinfection Characteristics of Ebola Virus Outbreak Variants

“…The NaOCl solutions used in this study were prepared following the CDC guideline. A recent study identified that NaOCl concentrations mixed with water (called stabilized NaOCl), remained stable for up to 30 days when stored at 25–35 °C21. In our solutions, we used hard water (distilled water with 0.04% w/v calcium carbonate) to better reflect water impurities in an outbreak scenario.…”