{Method for testing levels of chlorine dioxide}

1999 "studies have shown that pH has much less effect on pathogen inactivationfor viruses and cysts with chlorine dioxide than with chlorine in the pH range of 6 to 8.5. Unlikechlorine, studies on chlorine dioxide have shown the degree of inactivation of poliovirus 1 (Scarpinoet al., 1979) and Naegleria gruberi cysts (Chen et al., 1984) increase as the pH increases." "In the first disinfection mechanism, chlorine dioxide reacts readily with amino acids cysteine,tryptophan, and tyrosine, but not with viral ribonucleic acid (RNA)). From this research, it was concluded that chlorine dioxide inactivated viruses by altering theviral capsid proteins. However, chlorine dioxide reacts with poliovirus RNA and impairs RNA synthesis. It has also been shown that chlorine dioxide reacts with free fatty acids. At this time, it is unclear whether the primary mode ofinactivation for chlorine dioxide lies in the peripheral structures or nucleic acids. Perhaps reactions inboth regions contribute to pathogen inactivation.The second type of disinfection mechanism focuses on the effect of chlorine dioxide on physiologicalfunctions. It has been suggested that the primary mechanism for inactivation was the disruption ofprotein synthesis (Bernarde et al., 1967a). However, later studies reported the inhibition of proteinsynthesis may not be the primary inactivation mechanism. A more recent studyreported that chlorine dioxide disrupted the permeability of the outer membrane). The results of this study were supported by the findings of Olivieri et al. (1985) and Ghandbari et al. (1983), which found that the outer membrane proteins and lipids were sufficiently altered by chlorine dioxide to increase permeability"

***** {Includes chart of residuals in treated foods} "While the chlorite ion is stable in aqueous solution, under acidic conditions, chlorite forms a semi-stable intermediate, chlorous acid (HClO2). Chlorous acid disintegrates to chlorine dioxide (ClO2), which further degrades to chlorite (ClO2 ̄) and ultimately chloride (Cl ̄) is formed. The extent of each of the degradation pathways and thus the proportion of each of the oxy-chlorine species depends in part on the pH of the solution. Other factors such as temperature and alkalinity of the water also affect the composition of the oxy-chlorine constituents." "At a pH of 2.3, approximately 31% of chlorite (from sodium chlorite) is converted to chlorous acid" "The pH values at different concentrations of citric acid, phosphoric acid, and sodium hydrogen sulfate to prepare a 1000 mg/l sodium chlorite solution are presented in Figure 1" "The technical-grade of sodium chlorite used to prepare ASC is comprised of 80% of sodium chlorite, with sodium chloride, sodium carbonate, sodium hydroxide, sodium sulfate, and sodium chlorate making up the remainer of the composition." "Although levels of chlorine dioxide do not exceed 3 ppm in the solution initially, chlorine dioxide levels increase during aging of the solution." "Chlorine dioxide... is not present as a residue of the treated food-product." "Instead, the ASC solution is monitored for sodium chlorite concentration and pH, which are known to result in acceptable levels of chlorate, chlorite, and chlorine dioxide. Depending on the food application, the solution is characterized by a sodium chlorite concentration in the range of 50-150 mg/l and a pH of 2.8-3.2 or 500-1200 mg/l and a pH of 2.5-2.9."

****2018 Jan. {Very good technical info. Fumigation leaves no CD or by-product residue. Air treatments are more effective than Liquid. Includes several CD and SC trade names. Denied because of lack of public requests, available alternatives, etc.}

2000 Sept. {Evaluating RfC, RfD, carcinogenicity. Includes **injection report.} "what exists in water or the stomach is a mixture of these chemical species (i.e., chlorine dioxide, chlorite, chlorate) and possibly their reaction products with the gastrointestinal contents." "[after gavage dosing of rats] it was not clear from these reports whether the parent chlorine dioxide itself or the chlorite, chlorate, or chloride ion degradation products were absorbed"

The daily drinking water consumption for the 10 kg child and 70 kg adult are assumed to be 1 L/day and 2 L/day

2008 May ******* {in-depth info on concentrations, safety, efficacy & time for CD and other disinfectants} "The use of chlorine dioxide at 20 mg/l resulted in little or no difference in numbers of total aerobic bacteria on beef compared with using potable water. " "The reaction of the bromide ion (Br−) with chlorine dioxide is thermodynamically unfavourable. However, with intense sunlight and high concen-trations of chlorine dioxide, chlorine dioxide does oxidize the bromide ion to hypobromite (BrO−) and bromate (BrO3−)"

********!!!!!!********** {Safe levels. 2000 is most recent date noted.} "...chlorine dioxide rapidly disappeared from the stored water (within 2-4 hours) and water chlorite concentrations concomitantly increased. Once absorbed, chlorine dioxide and chlorite are cleared from the blood at similar rates and are similarly distributed throughout the body .. Additionally, chloride is the major in vivo degradation product for chlorine dioxide, chlorite, and chlorate. The available data suggest that chlorine dioxide and chlorite have similar targets of toxicity and potencies. Therefore, the toxicity information for chlorite is relevant to deriving an RfD for chlorine dioxide." Integrated Risk Information System (IRIS)

***!!!!**** 2002 " Some studies have been conducted via the oral route using aqueous solutions of chlorine dioxide. Several of these studies were conducted using “stabilized aqueous chlorine dioxide,” sometimes by maintaining a constant pH using sodium carbonate and sodium hydrogen carbonate. However, it is recognized that this would effectively lead to the formation of aqueous sodium chlorite (which can subsequently generate chlorine dioxide by acid dis-placement). These studies are felt to be less relevant than those using stabilized aqueous chlorine dioxide and are not summarized in this review. The reasons for this are that chlorine dioxide dissolves discretely in water (i.e., it does not dissociate into ions), forming a solution of around pH 5 or less, whereas an aqueous solution of sodium chlorite has a different, ionized composition and a pH of approximately 8. The explosive nature of this substance has limited the concentration of chlorine dioxide in aqueous solutions to a maximum of about 1% w/v" {******pg 4 -- ppm conversion info for air concentrations:} "0.1 ppm (0.28 mg/m3) 8-h time-weighted average (TWA) and 0.3 ppm (0.84 mg/m3) 15-min reference period" "It is predicted thatdermal exposure from contact with the aqueous solution in occupational settings will range from 0.1 to 5 mg/cm2 per day" "There are no quantitative human data, but chlorine dioxide is very toxic by single inhalation exposure in rats. There were no mortalities following exposure to 16 ppm (45 mg/m3) for 4 h, although pulmonary oedema and emphysema were seen in all animals exposed to 16–46 ppm (45–129 mg/m3) chlorine dioxide,the incidence increasing in a dose-related manner. The calculated mean LC50 was 32 ppm (90 mg/m3). In another study, ocular discharge, nosebleeds, pulmonary oedema, and death occurred at 260 ppm (728 mg/m3) for 2 h. Chlorine dioxide is toxic when administered in solution by a single oral dose to rats; at 40 and 80 mg/kg bodyweight, there were signs of corrosive activity in the stomach and gastrointestinal tract. The calculated oral LD50 was 94 mg/kg body weight."

**** 2017 Jan. "Any chlorine dioxide remaining at the consumer’s tap will be reduced to chlorite and chloride upon ingestion. *** Consequently, a guideline value for chlorine dioxide has not been established."..."For chlorite, JECFA established an ADIof 0–0.03mg/kg bw on the basis of the NOAEL of 3mg/kg bw per day...Using the upper bound of the chlorite ADI of 30 μg/kg bw, a typical human body weight of 60 kg, the assumption that drinking-water contributes80% of the total exposure and a typical consumption of 2 L of water per day, the provisional guideline value is calculated to be 0.7mg/L (rounded figure). This guideline value is designated as provisional because use of chlorine dioxide as a disinfectantmay result in the chlorite guideline value being exceeded, " "JECFA therefore established an ADIof 0–0.01 mg/kg bw for chlorate" "[Page 1] Conversion factor in air: 1 part per million (ppm) = 2.8 mg/m3"