Chemical sterilization

Calcium hypochlorite

20 ppm available; Cl₂, pH 8.0, 20ºC

3 x 10⁵–4 x 10⁵ spores of Bacillus subtilis in 5.0 mL sterile distilled H₂O

4.8 min

99% killed

8

25 ppm available; Cl₂, pH 6.0, 20ºC

2 x 10⁷ spores/mL of B. metiens in 10 mL of sterile distilled H₂O

2.5 min

0.061 (log of average % survivors) 99% killed

9

Free available chlorine

2.4–2.3 mg/L available; CL₂, pH 7.2, 22ºC

1.1 x 10⁵ spore suspension of B. anthracis

1 h

>99.99% killed (1 spore/mL survived)

10

Sodium hypochlorite (NaOCl)

0.05%, pH 7.0, 20°C

Spore suspension of B. subtilis globigii, representing 1.6–2.2 x 10⁹ CFU/mL

30 min

99.99% killed

11

0.05%, pH 11.0, 20°C

50% spores survived

Hydrogen peroxide (H₂O₂)

25.8%, 24°C

B. subtilis globigii spore suspension
(no concentration)

15 min

0.001% survived

12

25.8%, 76°C

<1 min

<0.0001% survived

0.88 mol/L, pH 5.0

10⁶ CFU/mL B. subtilis spore suspension

3 h

100% killed

13

0.88 mol/L, pH 4.3

10 mL B. subtilis spore suspension coated onto stainless steel carriers

6 h

100% killed

Peracetic acid (CH₃COOOH)

0.13 mol/L, pH 5.0, 6.5, 8.0

10⁶ CFU/mL B. subtilis

<30 min

100% killed

13

0.39 mol/L, pH 4.0, 7.0, 9.0

10 mL B. subtilis spore suspension coated on stainless steel carriers

24 h

100% killed

Formaldehyde (CH₂O)

4% in water

10⁸/mL B. anthracis

2 h

10⁴ inactivation factor

14

400 mg/m³, 30% RH

10²–3 x 10⁸ B. globigii NCTC 10073 dried on disks

22 min

1 log₁₀ reduction, at 23.5°C–25°C

15

280 mg/m³, 50%RH

31 min

250 mg/m³, 80% RH

16 min

400 mg/m³, 98% RH

9 min

Glutaraldehyde (C₅H₈O₂)

2% in water, pH 8.0

10⁸/mL spores B. anthracis

15 min

10⁴ inactivation factor

14

Sodium hydroxide (NaOH)

5%, 27.8ºC

7 x 10⁹ spores/mL B. subtilis

1.5 h

99% killed

16

5%, 21.1ºC

3.6 h

99% killed

Gaseous sterilization

Ethylene oxide (C₂H₄O)

Exposed to constant boiling HCL at 20°C for 30 min before exposure to ethylene oxide at room temperature

B. globigii and B. anthracis dried onto suture loop carriers (no concentration)

1 h

100% killed

17

500 mg/L, 30%–50% RH, 54.4°C

~10⁶ spores B. globigii on nonhygroscopic surfaces

30 min

4-log reduction

18

~10⁶ spores B. globigii on hygroscopic surfaces

6-log reduction

Chlorine dioxide (ClO₂)

40 mg/L, 60%–80% RH, 25°C–27ºC

1.4 x 10⁶/0.2 mL B. subtilis subsp. Niger dried on paper and aluminum foil strips

1 h

100% killed

19

30 mg/L, 80%–85% RH, 30ºC

10⁶ spores/biologic indicator; B. subtilis subsp. Niger

30 min

100% killed (estimated time to kill 90%, 4.4 min)

20

6–7 mg/L, 20%–40% RH, 23ºC

10⁶ spores/biologic indicator; B. subtilis subsp. Niger

30 min

10¹ CFU/biologic indicator (estimated time to kill 90%, 4.2 min)

21

70%–75% RH for 0.5 before exposure, 23ºC

15 min

0 CFU/biologic indicator (estimated time to kill 90%, 1.6 min)

Hydrogen peroxide (H₂O₂) plasma

0.208 mg/L, 1.5 Torr pretreatment for 10 min; 2.49 MHz, 150 W of pulsed plasma in a cycle of 0.5 ms plasma on, 1.0 ms plasma off

3.4 x 10⁵ B. subtilis subsp. globgii spores on paper disks and packaged in spun-bonded polyethylene

15 min

100% killed

22

Methylene bromide (CH₃Br)

3.4–3.9 g/L, room temperature in the presence of moisture

1 x 10⁵–5 x 10⁷ spores of B. anthracis dried on sterile filter paper strips

24 h

100% killed

23

Peracetic acid vapor (CH₃COOOH)

1 mg/L, 80% RH

6 x 10⁵ – 8x 10⁵ B. subtilis niger dried on filter-paper disks and glass squares

10 min

<1 spore remained on paper and glass

24

1 mg/L, 60% RH

2 spores remained on paper; 38 spores remained on glass

1 mg/L, 40% RH

24 spores remained on paper; 1,530 spores remained on glass

Propylene oxide (C₃H₆O)

1,250 mg/L, 86% RH, 36°C–38ºC

9.5 x 10⁵–1.1 x 10⁶ spores B. subtilis niger dried on filter paper

1.05 h

90% killed

25

1,000 mg/L, 37°C

2.5 x 10⁷ spores B. subtilis niger in cereal flakes

3 h

3.7% survived

Ozone (O₃)

1.0 mg/L generated in water pH 3

1.8 x 10⁵ spores/mL B. cerus

5 min

<10¹ CFU/mL survived

26

3.0 mg/L, preconditioned at 54% RH

10⁸–2 x 10⁸ B. subtilis dried on filter paper

1.5 h 95% RH

<0.001% survived

27

10⁸–2 x 10⁸ B. cerus dried on filter paper

1.5 h 95% RH

<0.001% survived

900 ppm, preconditioned at 65%–70% RH for 15 h

5 x 10⁷ spores/glass coupon

30 min 80% RH

10⁰ survived

28

60 min 70% RH

10⁰ survived

Radiation

UV

85% 2537A

B. anthracis (mixed spores and vegetative forms) in beef extract agar pH 7.4 (no concentration)

452 ergs/mm²

90% killed

29

4,800 mWs/cm²

0.1 mL of 10⁸ B. anthracis spore suspension dried on aluminum carriers

<96 h

2.4 log reduction, unreliable results

30

450,000 mWs/cm²

0.1 mL of 10⁸ B. anthracis spore suspension dried on ceramic carriers

<96 h

2.03 log reduction, unreliable results

52.8 x 10⁶ mWs/cm²

0.1 mL of 10⁸ B. anthracis spore suspension dried on wood carriers

30 h

0.67 log reduction

Gamma irradiation

10⁶ spores/mL B. anthracis

Dose of 1 x 10⁶ rad

100% killed

31