Sciencemadness Discussion Board - How toxic is chlorine dioxide, compared to chlorine?

How toxic is chlorine dioxide, compared to chlorine?

Draeger - 26-8-2020 at 08:00

So, I've been thinking about making a small amount of dilute chloric acid to test its extreme oxidizing capabilities out. But I'm worried about the toxicity of chlorine dioxide should I miscalculate stoichiometry. I know it explodes very easily when exposed to UV/daylight, but since it's only small amounts, I'm worried more about toxicity. Is it like chlorine where you'll run away from pain before you get harmed, or is it sneakier?

macckone - 26-8-2020 at 09:44

10ppm is the upper limit before fatality and no reported effects at 1ppm.
https://www.who.int/ipcs/publications/cicad/en/cicad37.pdf

I would say it is about the same toxicity wise.
It is noticable below the toxic level.
Chlorine dioxide is more soluble in water 8g/L compared to 7g/L.

B(a)P - 26-8-2020 at 20:18

Immediately dangerous to life and health (IDLH) concentrations range from 5 to 10 ppm depending on jurisdiction.
The odour threshold is 0.1 to 0.3 ppm and becomes irritating from 0.5 ppm.
For me a factor of 10 to 20 between odour threshold and IDLH doesn't quite cut it to support the 'if you smell it leave the area' approach for amateur chemistry. As long as you don't have an abrupt release you should be ok I guess.

woelen - 27-8-2020 at 01:35

ClO2 is much more solublke in water than Cl2 (I think that Cl2 has solubility of 3 g/l). ClO2 has a really intense color and you'll see even very low concentrations.

Chloric acid is fairly stable, when dilute. If you dissolve some NaClO3 in dilute H2SO4 (e.g. 20% by weight), then you get a dilute solution of HClO3 (and NaHSO4, which does not disturb the oxidizing properties of the HClO3). The solution indeed is strongly oxidizing, but it is not really special. The solution will remain colorless and even withstands some heating. Do NOT add NaClO3 or KClO3 to conc. H2SO4!

If you add chloride ion to the mix, then you'll get a lot of ClO2. HClO3 and chloride ion react, giving a mix of Cl2 and ClO2. You can see that happen if you add some solid KClO3 or NaClO3 to concentrated HCl: https://woelen.homescience.net/science/chem/exps/clo2/index....

Herr Haber - 27-8-2020 at 10:58

I was surprised to learn a couple of months ago that gaseous chlorine dioxide is used as a disinfectant for areas.

There are are many companies like this one:
https://www.clordisys.com/

My knowledge of it being summarized in OP's first line I was of course intrigued about how they generated the gas safely, diluted it and dispersed it.
All this curiosity prompted by the current Covid crises of course.

AJKOER - 21-9-2020 at 08:20

I argue that exposure to ⋅ClO2, a stable free radical, may even present longer term toxicity issues from associated generated products (namely, chlorite and chlorate) in excess of regulatory limits occurring in conditions rich in oxygen and transition metal presence.

My understanding on the chemistry leading to such conditions starts with the superoxide radical anion (⋅O2-) generated by a metal auto-oxidation reaction from dissolved oxygen interacting with ferrous rich water/blood, as follows:

Fe(II) + O2 <-> Fe(III) + ⋅O2−

⋅O2− + ⋅ClO2 -> O2 + ClO2−

Fe(II) + ⋅ClO2 -> Fe(III) + ClO2−

Basis for the above, a Dutch study, 'Chlorine Dioxide as a Post-Disinfectant for Dutch Drinking Water', linking the removal of ⋅ClO2 to dissolve oxygen content at https://pubmed.ncbi.nlm.nih.gov/2038663/ which I claim likely proceeds via corresponding superoxide creation. Also, support for chlorite creation per this work: 'Influence of drinking water treatments on chlorine dioxide consumption and chlorite/chlorate formation' at https://pubmed.ncbi.nlm.nih.gov/24534637/ .

And further, the cycling of a soluble ferric via the reversible metal auto-oxidation reaction:

Fe(III) + ⋅O2− <-> Fe(II) + O2

Also:

⋅ClO2 (g) + ⋅ClO2 (g) -> Cl2O4 (g) (slow)

Cl2O4 (g) + H2O (l) -> HClO2 (aq) + HClO3 (aq)

So, an associated presence of chlorite in human blood, and ClO2 also possibly introducing chlorate ions.

Further with Na+, NaClO3, which per a government study: 'Toxicology and carcinogenesis studies of sodium chlorate (Cas No. 7775-09-9) in F344/N rats and B6C3F1 mice (drinking water studies)' at https://pubmed.ncbi.nlm.nih.gov/16362061/ is problematic. To quote:

"Conclusions: We conclude that sodium chlorate caused some thyroid gland neoplasms in male and female rats. The pancreatic islet cell tumors in female mice may have been related to sodium chlorate exposure."

So, the longer term consequences of chlorite/chlorate exposure (as sourced from ClO2) may be more of a fundamental health concern.

[Edited on 21-9-2020 by AJKOER]

unionised - 21-9-2020 at 08:46

Quote: Originally posted by Draeger

So, I've been thinking about making a small amount of dilute chloric acid to test its extreme oxidizing capabilities out. But I'm worried about the toxicity of chlorine dioxide should I miscalculate stoichiometry. I know it explodes very easily when exposed to UV/daylight, but since it's only small amounts, I'm worried more about toxicity. Is it like chlorine where you'll run away from pain before you get harmed, or is it sneakier?

If I was able to tell you that ClO2 was exactly 16.3 times more toxic (that's a made up number, btw) what help would it be?

What equipment have you got for determining the concentration of either?
How accurate is it?

Draeger - 21-9-2020 at 10:09

Quote: Originally posted by unionised

Quote: Originally posted by Draeger

I asked if you could determine it's concentration by the pain from breathing it in as easily as with chlorine before one would get harmed in the actual post, the title was not really beneficial to getting to know what I wanted to actually know.

[Edited on 21-9-2020 by Draeger]

macckone - 21-9-2020 at 11:46

Draeger,
There is little difference between chlorine and chlorine dioxide from a toxicity, odor or pain perspective.
If you get a good whiff of either you should seek medical attention before pulmonary edema sets in.
It is detectable at around a hundredth of the fatal dose.
But injury is probably closer to 20 times range.