The Efficacy of Common Household Cleaning Agents for SARS-CoV-2 Infection Control

Abstract

The COVID-19 pandemic caused by SARS-CoV-2 is having devastating effects on a global scale. Since common household disinfectants are often used to minimise the risk of infection in the home and work environment, we investigated the ability of some of these products to inactivate the virus. We tested generic brands of vinegar, bleach, and dishwashing detergent, as well as laboratory-grade acetic acid, sodium hypochlorite, and ethanol. Assays were conducted at room temperature (18-20 °C, 40% relative humidity), and two time points were used to reflect a quick wipe (30 s) and a brief soak (5 min). Vinegar, and its active ingredient, acetic acid, were completely ineffective at virus inactivation even when exposed to the virus at 90% v/v (a final concentration equivalent to 3.6% v/v acetic acid). In contrast, ethanol was capable of inactivating the virus at dilutions as low as 40% v/v. Dishwashing detergent effectively rendered SARS-CoV-2 inactive when diluted 100-fold (1% v/v). Bleach was found to be fully effective against SARS-CoV-2 at 0.21 g/L sodium hypochlorite after a 30 s exposure (1/200 dilution of commercial product). Given reports of infectious virus recovered from the surface of frozen packaging, we tested the persistence of infectiousness after multiple freeze-thaw cycles and found no change in infectious SARS-CoV-2 titre after seven freeze-thaw cycles. These results should help inform readers of how to effectively disinfect surfaces and objects that have potentially been contaminated with SARS-CoV-2 using common household chemicals.

Keywords: COVID-19; SARS-CoV-2; antiseptic; disinfectant; pandemic; virucidal.

Figure 1

Cytotoxicity of household chemicals on Vero cells: Vero cells were exposed to (A) vinegar or its active component, acetic acid, (B) ethanol, (C) bleach, or its active component, sodium hypochlorite, or (D) detergent, at various concentrations for 1 h at 37 °C, 5% CO₂. Cells were microscopically examined for morphology, and after removal of the test-solution, replicate dilutions were pooled and stained with the live/dead marker 7AAD by flow cytometry within 1 h. Graphs show mean % viable cells ±SEM of data pooled from four independent experiments. The dotted line represents cell viability when in media alone (i.e., not exposed to any chemical).

Figure 2

TCID₅₀ reduction and Quench assays. Diagrammatic representation of workflow for (A) TCID₅₀ reduction assay and (B) Quench Assay. Briefly, at room temperature (18–20 °C, 40% relative humidity), SARS-CoV-2 in suspension was mixed with an equal volume of test solution containing known concentration of active ingredients for 30 s or 5 min. Serial dilutions of the active ingredients were tested in order to determine the lowest concentration of active ingredient required for virus neutralisation. Following this, either: (A) a TCID₅₀ was performed (n = 4 replicates/test dilution), or (B) the reaction was quenched with the addition of 900 μL infection media in order to prevent further activity at the starting dose. Samples (n = 4 replicates/test dilution) were then directly added to washed Vero cell monolayers and 3 days later, observed for SARS-CoV-2-induced CPE.

Figure 3

Vinegar is incapable of rendering SARS-CoV-2 non-infectious. At room temperature (18–20 °C, 40% relative humidity), exposure of SARS-CoV-2 to vinegar or acetic acid for 30 s or 5 min prior to detection of infectious virus by the (A) TCID₅₀ reduction assay, (n = 3 replicates/test dilution) or (B) Quench assay (n = 4 replicates/test dilution). (C) Vinegar and acetic acid solutions (n = 3 replicates/test dilution), at the concentrations indicated, were spiked with 10^{4.54 ± 0.3} TCID₅₀/mL SARS-CoV-2 and 30 s or 5 min later assayed for infectious virus titre. Graphs show mean ± SEM of data pooled from three independent experiments. ** p < 0.01 acetic acid (5 min) vs. no treatment (5 min), one-way ANOVA. Key applicable to both (B) and (C).

Figure 4

Ethanol renders SARS-CoV-2 non-infectious when used at more than 40% v/v: (A) % wells positive for virus induced cytopathic effect after SARS-CoV-2 was exposed to a range of dilutions of ethanol for 30 s or 5 min using the Quench assay. Graph shows mean + SEM of data pooled from four independent experiments. (B) A fixed amount of SARS-CoV-2 (10^{4.69 ± 0.6} TCID₅₀/mL) was spiked into a range of diluted ethanol solutions and 30 s or 5 min later assayed for remaining infectious virus titre by TCID₅₀. Experiments were performed at room temperature (18–20 °C, 40% relative humidity). Graph shows mean ± SEM of data representative of 3 independent experiments. ND = virus induced CPE was not detectable.

Figure 5

Household bleach can render SARS-CoV-2 inactive. Exposure of SARS-CoV-2 to bleach or sodium hypochlorite (n = 4 replicates per dilution) for 30 s or 5 min revealed a concentration dependent reduction in infectious virus titre by the (A) TCID₅₀ reduction assay, or (B) Quench assay. Experiments were performed at room temperature (18–20 °C, 40% relative humidity). Graphs shows mean ± SEM of collated data from three independent experiments. ND = virus induced CPE was not detectable.

Figure 6

Preparation of bleach in infection media adversely affects the virucidal concentration. Using the quench assay to test virucidal activity, sodium hypochlorite and bleach were diluted in either infection media or water, then exposed to SARS-CoV-2 for (A) 30 s or (B) 5 min. ND = virus-induced CPE was not detectable. (C) pH of bleach and sodium hypochlorite solutions diluted in either media or water. * Bleach: p < 0.05 when diluted in water compared to media at final concentration 10 g/L and p < 0.001 water compared to media at concentrations less than 10 g/L. ** Sodium hypochlorite: p < 0.001 when diluted water compared to media from 0.046–20 g/L. Two-way ANOVA with Tukey’s multiple comparisons test. Experiments were performed at room temperature (18–20 °C, 40% relative humidity). Graphs show mean ± SEM of data pooled from four independent experiments for (A) and (B) and 2 experiments for (C).

Figure 7

A 1 in 500 dilution of dishwashing detergent rendered SARS-CoV-2 non-infectious. (A) TCID₅₀/mL of SARS-CoV-2 after 5 min exposure to dishwashing detergent diluted in water (n = 4 replicates/test dilution), Graphs show mean ± SEM of data pooled from two independent experiments. ns = data not significant, one-way ANOVA. (B) % wells positive for virus induced cytopathic effect after SARS-CoV-2 was exposed to a range of dilutions of detergent for 30 s or 5 min using the quench assay. Experiments were performed at room temperature (18–20 °C, 40% relative humidity). ND = CPE was not detectable. The more concentrated the solution (% given in x-axis below), the darker the colour.

Figure 8

Combining detergent with bleach does not increase efficacy of SARS-CoV-2 inactivation. Using the quench assay to test virucidal activity, detergent was added to bleach or sodium hypochlorite (SH) diluted in water then then exposed to SARS-CoV-2 for (A) 30 s or (B) 5 min. Experiments were performed at room temperature (18–20 °C, 40% relative humidity). Graphs show mean ± SEM of data pooled from four independent experiments. ND = virus-induced cytopathic effect was not detectable.

Figure 9

SARS-CoV-2 remains infectious after multiple freeze-thaw cycles. Four aliquots of SARS-CoV-2 stocks (10^5.24 TCID₅₀/mL) stored at −80 °C, were thawed to room temperature (18–20 °C) (cycle 1) and assayed for infectious virus titre, then the remaining aliquot re-frozen at −20 °C. The freeze-thaw cycle was repeated every 24 h for 6 days and infectious titre determined by TCID₅₀ upon each thaw. Data not significantly different (one-way ANOVA). Graph shows mean ± SEM.