NITROX - Enhanced Lung Cancer Risk ?

[Hillmorton Scubie]

I regularly dive with Nitrox EAN 32% (32% Oxygen)
Here's an article that suggests a link between Oxygen and lung cancer.
What are your thoughts ?

https://uk.news.yahoo.com/oxygen-air-linked-lung-cancer-144539996.html#PPHy47o

 

[knotical]

Fascinating.

Whether diving nitrox or air, our lungs are exposed to much higher partial pressures of oxygen. But the relatively short durations are such that I wouldn’t change either my scuba or nitrox habits.

otoh if there were an epidemiological study showing a higher rate of lung cancer among scuba divers ...

 

[TSandM]

It isn't implausible, but it's also important to remember that, prior to the widespread adoption of smoking by both sexes, lung cancer was so rare that professors would call people in to see a case. Also, compared with the hours and years that one is exposed to atmospheric oxygen over a lifetime, a few hours of elevated ppO2 just doesn't loom that large, at least to me.

 

[tursiops]

The original article is pretty interesting...https://peerj.com/articles/705/...but not very compelling.
In fact, it argues that a 11% decrease in PPO2 (1000m standard atmosphere) produces a 12.7% decrease in lung-cancer incidence. Just seems unlikely...

Even so, if you did 100 dives a year on 32% at 1h per dive and an average depth of 20m, that would roughly be the same as spending the year at a slightly below sea-level location, by about 150m, I reckon. Any increase in lung-cancer would be well within the (considerable) noise level of their statistics.

 

[tech_diver]

ok .. so I'm not a doctor or scientist so someone check me on this....

The article reports a link to altitude and cancer, where does the link to O2 come in? We know there is a little less oxygen at altitude but aren't there decreased particulates too? There are a lot on environmental changes associated with altitude other than O2. Was there some control in the study that pointed to oxygen as a culprit?

 

[tomfcrist]

ok .. so I'm not a doctor or scientist so someone check me on this....

The article reports a link to altitude and cancer, where does the link to O2 come in? We know there is a little less oxygen at altitude but aren't there decreased particulates too? There are a lot on environmental changes associated with altitude other than O2. Was there some control in the study that pointed to oxygen as a culprit?

I think what they are theorizing via their statistics is that since there is less occurance of the disease at high altitude that it must be somehow related to the lower O2 level up there.
God forbids they should think that the rate is higher in low elevations due to the smog...

 

[Dirty-Dog]

ok .. so I'm not a doctor or scientist so someone check me on this....

The article reports a link to altitude and cancer, where does the link to O2 come in? We know there is a little less oxygen at altitude but aren't there decreased particulates too? There are a lot on environmental changes associated with altitude other than O2. Was there some control in the study that pointed to oxygen as a culprit?

No, there is not. The composition of the air is the same regardless of altitude (we're not talking about smog here, we're talking about changes due to altitude). The only thing that changes at altitude is the pressure.

 

[descent]

This paper is one of the most interesting things I have read in several months. Many thanks, tursiops, for digging it up.

... The composition of the air is the same regardless of altitude (we're not talking about smog here, we're talking about changes due to altitude). The only thing that changes at altitude is the pressure.

As tech_diver mentioned, a well-designed experiment must control for disproportionate numbers of patients in the study who live in urban or industrial areas with poor air quality. Worldwide, the huge majority of these heavily-polluted environments are at lower altitude. This study restricts itself to 414 counties in eleven western US states — a strength and a weakness. There are coal-fired power plants at higher altitude there, but there are fewer people.

Based on the section "Climatic & environmental data", I am not convinced that they did a thorough job of controlling for environmental particulates, but I haven't downloaded and read their source code yet. Maybe the section I want is buried under dead werewolves because of all the silver bullets inside. I don't know. I did search the text for words like "smog", "pollution" and "monoxide", but didn't find any occurrences.

Regardless, it looks like their findings are strong enough that they don't need to build a more complicated model just yet. Hopefully someone will throw a big chunk of grant money their way so they can go get better data.

... we speculate the causal factor is likely mild in carcinogenicity but universal in exposure ...

It's only mild from an academic point of view. Cigarette smoke is at the top of their list of bad things to inhale.

Second on their list is nitrox twenty-one.

 

[tomfcrist]

No, there is not. The composition of the air is the same regardless of altitude (we're not talking about smog here, we're talking about changes due to altitude). The only thing that changes at altitude is the pressure.

While the composition is the same the density (dosage) is equivalent to about 18% O2 in places like Denver. It's the same as the disease being higher as we descend in the water on scuba(regardless of if we dive air or nitrox).

I doubt highly any truth in the idea that the O2 dose has any direct relationship to cancer rates. The likely cause is environmental(smog, smoke, asbestos. Etc).

 

[tech_diver]

Ok.. so I've read through the whole thing...

I was impressed by the number of variables that they did control for but I still don't think it indicts oxygen specifically. It just seems that of all the suspects that were not controlled for, oxygen is the one standing around with a guilty look on its face (reactive).

Even if the composition of the air at higher and lower elevations was exactly the same, the constituents are still at higher concentrations at lower altitudes. If the per cent of radon gas is the same at upper and lower elevations, the concentration is higher at higher ambient pressures. You get more radon per breath than the same mix at altitude.

So .. my jury is still out on the conviction of O2. But I have to imagine that if it were that carcinogenic, a lot of people that work in hyperoxic environments would be showing the effects.