### Registration of a Product containing the New Active In gred ients, Nitro ge n dioxide and Dinitrogen tetroxide

Regulatory Act ion: EPA has granted an unconditional reg i strat ion ofNoxilize r N02 Steri lan t , an end use product, contain ing the new active ingredients, dinitrogen tetroxide and nitrogen diox id e (N02)

. Noxilizer , Incorporated requested this action under PRIA as an A420. Nitrogen dioxide and dinitrogen tetroxide exist in equ ilibrium in commerce. Once the formu lation is exposed to h eat during steri li zation, the equilibrium s hi fts, and dinitrogen tetroxide is converted to nitr ogen dioxide.
Noxilizer N0 2 Sterilant is a gaseous sterilant for use in industrial , commerc ial and institutional settings on laboratory equipment, isolators , medical devices , pharmaceuticals , and pharmaceutical equipment. Noxilizer N02 Sterilant is not labe led for use in ste ril e reprocessing of reusable medical devices.


### Human Health Ri s k Assess m e nt : Two exposure scenarios were assessed for sterilization workers who may inhale N0 2 in an occupational sett in g: I) peak (one hour) exposures to N02 during opening of sterilizat ion chamber doors or iso lation units after treatment; and 2) average dai ly (e ight hour time weighted average) exposure to N0 2 potentia ll y released into the room air resulting from multiple cycles of treatments and opening of sterili zat ion chamber door·(s) and i solation units during a single day.
The levels of concern (LOCs) are I 00 ppb for one hour time we i ghted average (TWA) exposures and 34 ppb for e ight hour TWAs. These LOCs are based on ep idemiology studies and are applicab le to sho rt , intennediate and long te1m exposures. Risk findings from the proposed use are presented below: (1) Sterilization worker inhalation exposures to N0 2 from opening of the i solator o r sterilization chamber door·(s) are not likely to be a risk of concern. The maximum measured concentration during the period of highest exposure (i

. e. door open in g) was 1 77 ppb for the isolator and !58 ppb for the ster ili zation chamber. Although these va lues are above the acute endpoint value of 100 ppb , they represent ma;-cimum exposures occur rin g over a span of on ly a few minutes from opening of the iso lator o r ster ili zation chamber doors. By compari son , the endpoint va lu e of I 00 ppb represents a one hour TWA. In light of the fact that expos ure from open ing of isolator or steri li zation chamber doors occurs for on ly a few minutes after each steri li zat ion cycle of90 minutes, the average exposure over any one hour period wou ld not likely exceed I 00 ppb. (2) Average Daily Exposure. Sterilization worker 8 hour TW A exposures for the isolator unit i s 29 ppb , which is below EPA's LOC of34 ppb based on room venti l ation requirements on the product labeling (five air changes per hour). Ster ili zation worker 8 hour TWA

### exposu res for the s t e rili zat ion chamber is 

### 23 ppb, w hi c h is less than LOC of 

### 34 ppb a nd is not of conce rn. 

### Ecological Risk Assessment : The use pattern ofNox ili ze r N02 Ster il a nt will not resu lt in any addi ti ona l expos ure to N02 in th e env ironment because the sterilant w ill be conta ined in the sterili zati on equipment. In add it io n , a ir scrubbers are required to be used as a safety m eas ure to remove N02 during the discharge process w hi c h w ill preclude accidental release to the e n v ironme nt and expos ure to non-target o rga ni s m s . Therefore, N02 exposure from the use of thi s product s ho uld not cause any adverse effects to non-target organisms

. A ll aquatic, av ian , and terrestrial plant eco logical effects stud ies have been waived. 

### Efficacy Assessment: The subm itted efficacy data demonstrated that Nox ili zer N 0 2 Steril a nt is an effecti ve s te ril ant by show in g a 100% kill of 

### Bacillus subtilis and 

### Clostr idium spo r ogenes w hen u se d acco rdin g to the p r

oposed p roduct label.

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