First, I'll preface this comment by saying that I'm neither a toxicologist nor a medical researcher. Moreover, I don't doubt the evidence that formaldehyde is carcinogenic.

I'd also add that decades ago before any EPA reports I'd learned in chemistry that formaldehyde was a dangerous substance and not to breathe its fumes. That said, I have not read the EPA reports so the questions I raise here may be superfluous (if so, then the reports deserve a wider audience).

Second, there are a number of issues about formaldehyde that are missing from this story that I consider important for the following reasons:

(a) What are the tolerable (accepted) levels of formaldehyde that a human can accept without harm? Restated, in a 'pristine' preindustrial era how much formaldehyde would a human experience from external sources, the environment etc., and how do they compare with the levels we experience nowadays? Moreover, do we actually know the typical level of formaldehyde in a 'pristine' environment (given its ubiquity one can imagine small amounts coming from many different sources).

(b) Re the 'pristine' environment, does science know if exposure to levels of formaldehyde from external sources is actually toxic? If so, then how would intermittent dosing versus chronic exposure at those levels mitigate matters?

(c) The article does not mention that a metabolite of methanol is formaldehyde and that it's a principal cause of methanol's toxicity.

Right, just about everyone knows methanol is very dangerous and that very few consume it intentionally (or accidentally) and those who do either end up dead or blind but I raise the matter here because the human body continually produces small amounts of methanol as a result of digestion, ipso facto, so too formaldehyde (which is then further metabolised to formic acid). As with ethanol, the body uses its liver enzyme alcohol dehydrogenase (ADH) to metabolise methanol, so that would seem to indicate there's a threshold or tolerable level to both of these alcohols which does not cause harm (at least so in most individuals).

Question, is this unavoidable internal source of formaldehyde dangerous and is its level in the body known to be carcinogenic or not? Rephrased, is it known if internally-produced formaldehyde does actually cause cancer, if so are some individuals more prone or susceptible to developing cancer from exposure (clearly not eveyone is; alternatively, most don't live long enough to succumb from it alone)?

(d) Do we know if the effect of the combined amount of formaldehyde from both external ('pristine') and internal is dangerous of not?

(e) If the combined effects (of 'd') are negligible on say all but a small percentage of the population who perhaps is susceptible, then what level of formaldehyde is typically experienced in our modern industrial society? What I'm trying to establish here is how much more formaldehyde does the average person now experience over and above the 'natural' baseline and whether a threshold level exists, and if it does then have we put error bars on those graphs?

(f) Additionally, the article does not mention the fact that there are some 'foods' that intrinsically produce formaldehyde as part of their metabolism, for instance the artificial sweetener aspartame (as such it could be avoided). Given say a normal or nominal intake of aspartame how does the level of formaldehyde it produces compare with those levels mentioned above, and are they comparable and or relevant? (Yes, I'm well aware of the long ongoing and painful debate over aspartame and the general consensus that its effects on health are essentially negligible or irrelevant (in that its formaldehyde metabolite is both small in quantity and quickly eliminated from the body).

Right, I've driven these points home to the point of tedium because such stories are not very informative, I'd even suggest that they contribute to the public's unease and general disquiet over chemicals, per se.

It's all very well for learned papers to appear in the pages of Nature et al but whilst they rightly preach to the cognoscente there's precious little that's pitched between their high level and the unsatisfactory low level of this article.

I don't know the answers to the questions I've posed but I'd suggest that if science writers were more precise and if they took the matters I've raised to heart then both the lay public and those in technical fields not directly allied to the subject matter would be much better informed.