Airborne murine coronavirus response to low levels of hypochlorous acid, hydrogen peroxide and glycol vapors

Figures & data

Figure 1. Schematic of the 9 m³ environmental chamber used in these studies. This chamber contained four low power (4w) floor fans to ensure a well-mixed environment, a relative humidity and temperature monitor, a humidifier, Collison six-jet nebulizers to aerosolize purified murine coronavirus cultures, an optical particle counter and an aerosol condensation growth tube collector.

Figure 2. Particle size distribution of virus containing aerosol retained in the test chamber between 10 and 100 min of aerosol age in the presence of disinfectant vapors. (Inset) Aerosol concentration of optical diameters in range between 0.5 μm and 5 μm.

Figure 3. The average half-life and time for the two-log (99%) reduction of airborne MHV infectivity potential (TCID₅₀₎ and gene copy numbers (RT-qPCR). (a) Control conditions represent the MHV response in the absence of any chemical treatment; (b) exposure conditions with gas-phase dipropylene glycol (<20 ppm_v TVOC); (c) exposure conditions with HOCl vapor (<0.2 ppm_v); (d) exposure conditions with H₂O₂ vapor (<0.9 ppm_v). Bar heights represents the average and error bar presents the pooled standard deviation (n = 3 experiments each with analytical triplicates).

Figure 4. Airborne murine coronavirus (MHV) concentrations, as judged by TCID₅₀ (o) and gene copy numbers qRT-PCR (▲), in an environmental chamber maintained at 60% RH and 22°C. (a) Control conditions represent the MHV response in the absence of any gas-phase chemical treatment; (b) exposure conditions with gas-phase dipropylene glycol (<20 ppm_v TVOC); (c) exposure conditions with HOCl vapor (<0.2 ppm_v); (d) exposure conditions with H₂O₂ vapor (<0.9 ppm_v). Vertical lines (ǁ) represent termination of gas-phase disinfectant loading into the chamber. Declining horizontal lines are the regression slopes of independent exposure experiments used to calculate the average decay of triplicate experiments.

Table 1. The average half-life and 99% decay for each exposure condition. Respective decay times are reported as average ± SD (min).

	A: Baseline Control		B: Dipropylene glycol (<20 ppmv)		C: Hypochlorous acid (<0.2 ppmv)		D: Hydrogen peroxide (<0.9 ppmv)
	TCID50 /m^3	Gene Copies/m^3	TCID50 /m^3	Gene Copies/m^3	TCID50 /m^3	Gene Copies/m^3	TCID50 /m^3	Gene Copies/m^3
Half life, t1/2 (min)	32 ± 18	45 ± 4	5 ± 2	18 ± 2	2 ± 1	3 ± 1	6 ± 1	39 ± 14
99% Decay, t99 (min)	212 ± 120	296 ± 30	33 ± 15	122 ± 16	16 ± 4	17 ± 7	38 ± 10	258 ± 91

Respective decay times are reported here as average time ± SD min.

Table 2. Averaged decay rate constant ± SD (min⁻¹) or each exposure condition tabulated below graph.

	A: Baseline Control	B: Diropylene glycol (<20 ppmv)	C: Hypochlorous acid (<0.2 ppmv)	D: Hydrogen peroxide (<0.9 ppmv)
TCID50 /m^3	−0.026 ± 0.012 min^−1	−0.166 ± 0.092 min^−1	−0.305 ± 0.072 min^−1	−0.124 ± 0.028 min^−1
Gene Copies/m^3	−0.016 ± 0.002 min^−1	−0.038 ± 0.005 min^−1	−0.308 ± 0.147 min^−1	−0.019 ± 0.006 min^−1

Decay rate constants are reported here as an average (n = 3) ± SD min⁻¹.