So...who uses Excel? (Gluteraldehyde)

For Dirk, thank you for your reply. The comments I have made about glutaraldehyde, specifically my allergic reaction to it, involves the industrial product that most chemical companies use as a raw material; that is, 50% glutaraldehyde, 50% water. We are substantially more dilute than that. As noted, I must be gloved to work with 50% glutaraldehyde, but I dose 2 tanks 3 times weekly with Flourish Excel, ungloved and with no dermatitis. Concentration matters. As for the state of California, I used that state as an example of the most stringent of all the states with respect to public health and environmental concerns, especially with respect to chemicals of any sort. If they had evidence that it causes cancer, they would have published it. It seems that they will be doing their own studies, on this subject, and I am sure they will publish their results when they have some.

It is not, however, true, as California states, that it has not been studied. It may not have studied to the satisfaction of the state of California, but that is a different matter. Do a quick Google search with the terms "studies cancer glutaraldehyde" and the very first paper to pop up has the following statement in its abstract: "Formaldehyde and glutaraldehyde cause toxicity to the nasal epithelium of rats and mice upon inhalation. In addition, formaldehyde above certain concentrations induces dose-related increases in nasal tumors in rats and mice, but glutaraldehyde does not." There must have been at least one study to allow the authors to make that statement. Likewise, there must have been at least one study indicating that it is not carcinogenic in order for every material safety data sheet to state that it is not listed as a carcinogen by the American Conference of Governmental Industrial Hygienists, the International Agency for Research on Cancer, The National Toxicology Program (United States), and that it is not listed as a carcinogen by the state of California as required by Proposition 65.

As for how closely related the state of California believes glutaraldehyde and and formaldehyde to be, you are a chemist, so you will know what they state is not true. You will also know that differences even in two stereoisomers that are structurally identical, matter, especially as to whether the human body can use the material. The difference between ethanol and methanol is merely one CH2 group. You know the structural differences between glutaraldehyde and formaldehyde are much greater. That by itself is not determinative, it was meant as an example. What is determinative is the absence of any evidence that glutaraldehyde is carcinogenic. It has been studied, but with negative results to date.

I notice that the state of California will concern itself with vapor testing. The vapors from 50% glutaraldehyde can be overpowering. But these vapor properties are seriously affected by concentration. For example, a 50% glutaraldehyde solution will have a vapor pressure of 0.097 mm Hg. By the time it is diluted to a 2% solution, that vapor pressure drops to 0.003 mm Hg. We see similar results in vapor density and evaporation rate.

No, I have not made any anatomical analyses of fishes before and after extended treatment with Excel. I don't know whether any independent laboratory has done that, or not. What we have seen is what I posted earlier: no external evidence of physical maladies, and no decline in life span compared with control groups. We have a 27 year record of using this material in low concentrations in tanks. That isn't scientific evidence, but it certainly eases my mind.

I certainly have no intention of turning this into an unpleasant accusation session, as you stated. If I have said anything unpleasant, I apologize in advance, because it certainly wasn't intended. I have tried to present the facts that we have at hand. I understand that facts aren't everything: emotions can be powerful, and one of the most powerful is fear. The worst fear is that of the unknown, but glutaraldehyde is not unknown. It's been around awhile and we understand a good bit about it. However, if you (the second person plural you, not you personally) are not satisfied that glutaraldehyde is safe, then by all means, don't use it.

Warmest regards,

George