It is a sad
commentary on the times we live in that “alternative truth” is a concept with
governmental sanction, and that formerly accurate science has been politicized
beyond recognition. Today, many politicians and ideologues on either side of
virtually every issue are fond of claiming that “science” supports their own
ideas, even though these same people often cannot tell the difference between a
fact and a fortune cookie. In a democracy, everyone is entitled to their own
beliefs, but everyone is definitely not entitled to their own facts.
This would
not be a problem if the general public were more scientifically literate, and
did not confuse political agencies with bastions of good science.1 Unfortunately,
however, most people today know nothing about risk assessment methodology and
cannot tell the difference between a real scientist and a salesman with a
political agenda. For a scientist like myself, this is a discouraging state of
affairs in what ought to be the best educated populace in human history. It’s
not that the public is not intelligent enough. Rather, it’s that they do not
trust their own common sense as much as they trust the con men who appeal to
their emotions to circumvent their intelligence. The latter are particularly
effective at peddling irrational fears of public health “hazards” and looming
environmental “disasters”.
Take for instance, formaldehyde.
Source: PubChem
The reader has probably
had some experience with this malodorous chemical, if only while dissecting a
frog or other animal in high school or college. Humans have always been exposed
to significant levels of formaldehyde in their diet (10-20 mg/day), because
formaldehyde is a natural component of fruits, vegetables, meats and fish.2 Formaldehyde has also been
commercially produced and used safely for over 100 years 3. However,
in the wake of Hurricane Katrina in 2005, this ubiquitous substance acquired a
new and sinister reputation, due to reports of coughs and other maladies experienced
by some people who lived in the trailers that FEMA had purchased as temporary
housing for those displaced by the storm.4
Using epidemiologically weak association, rather than established causation, IARC
declared inhaled formaldehyde to be a “known” human carcinogen in 2006. In
2010, the U.S. EPA followed suit, as did NTP in 2011. They did this even though
scientists knew that formaldehyde is a
natural intermediate in cellular metabolism (the so-called one-carbon cycle)
and is essential in the synthesis of DNA and proteins, the building blocks of
life.4
Large amounts of
endogenous formaldehyde are universally tolerated without harm in animals from
bacteria to man, because it is very rapidly converted, with a half-life of one
and a half minutes, to a less toxic substance called formate, an essential
co-factor in the one-carbon cycle. Regulatory agencies have ignored this
important fact and, by branding formaldehyde as a known human carcinogen by
inhalation, have made people irrationally afraid of the trivial amounts of
formaldehyde that may off-gas from the wood paneling in their homes.
From formaldehyde to coronavirus, we'd benefit from better risk assessment
Risk
assessment could be a much more scientific endeavor than it currently is, if
only it gave more emphasis to scientific data than it does to bureaucratic
assumptions. But, it doesn’t. That’s because the actual purpose of risk
assessment (especially in America) is not to produce accurate
estimates of health risk, but to produce redundantly conservative estimates of
safe levels of exposure that are unlikely to
ever prove insufficiently protective of public health. Thus, at regulatory
agencies, the purely political policy of erring on the side of safety
takes precedence over any and all scientific considerations.5
It
should be noted that all levels of
exposure below one that produces no
adverse health effect are, by definition, equally safe. But, by identifying one of those lower safe levels as the “officially” safe level, regulatory
agencies tempt many people (especially environmental activists) to assume that
all of the higher safe levels of
exposure might, in fact, be toxic. Without that fallacious assumption, the
modern environmental movement would be a steam engine without wheels.
So, what, specifically, were
the scientific facts to which EPA, IARC, and NTP did not give adequate weight
in their findings? An abbreviated list follows:
1) All known potential toxic effects of inhaled formaldehyde are limited to the nasal passages. The
threshold for eye, nose and throat irritation is around 0.8 to 1.0 parts per
million (ppm). By comparison, average levels of formaldehyde in the air in
standard homes is 0.07 ppm. 3, 6
2) The regulatory agencies concluded that inhaled formaldehyde caused
nasal cancer and leukemia in humans. But, the principal studies on which
they relied did not, in fact, constitute evidence that inhaled formaldehyde
caused either cancer in humans. Formaldehyde can cause nasal cancer in rats which, as obligate
nose-breathers, have no choice but to breathe whatever investigators decide to
put into their breathable air. But, this can occur only at high concentrations
(6-15 ppm) which humans would find intolerable. (Formaldehyde has a very distinct,
irritating odor.) However, inhaled formaldehyde cannot cause leukemia
(or any other non-nasal cancer) at realistic doses, even in rats, because
inhaled formaldehyde doesn’t even reach tissues beyond the nasal passages,
i.e., unless the chronic concentration in air is so high (i.e., ≥ 6 ppm) that
it overwhelms the capacity for absorption and detoxification by the nasal
tissues.6 This is an exposure scenario that can only be produced in
the laboratory.3
3) Formaldehyde is a normal metabolic product that is present at all
times throughout the body and is rapidly metabolized. More than 50,000
milligrams are produced, used and detoxified by the human body every day. The
very short half-life in blood (1.5 minutes) guarantees that levels of
formaldehyde in blood never exceed 2-3 parts per million, regardless of
exposure.2 These normal levels of endogenous formaldehyde are so
much higher than potential exogenous exposures in the workplace or at the
dinner table that the latter have no detectable impact on normal blood levels.2
If external exposure to inhaled formaldehyde cannot even elevate levels in the
blood, then it clearly cannot produce adverse health effects.
4) Because formaldehyde is a normal product of human metabolism, it
occurs normally in exhaled human breath at concentrations of 4-10 ppb, which is
roughly 1,000 times higher than EPA’s 1-in-a-million cancer risk level. If the
latter were a realistic level of cancer risk, then normal human breath would
have to be considered carcinogenic.
5) EPA’s one-in-a-million cancer risk levels are usually derived by
assuming that effects seen at very high doses in laboratory animals occur with
proportionately lower frequency at all
lower doses (except zero). This is the infamous zero-threshold policy assumption
which has been abandoned almost everywhere except the U.S., because it is demonstrably
invalid.3 Formaldehyde-induced
nasal cancer is, obviously, an exclusively high-dose effect, because inhaled
formaldehyde causes nasal cancer in rats exposed to more than 6 ppm, but not
at 2 ppm.3
6) Finally, confounding exposures were not considered. For example, the
strongest known risk factor for nasopharyngeal cancer (NPC) is Epstein-Barr
virus (EBV) infection. EBV is detectable in virtually all types of NPC, but is
absent in normal nasopharyngeal cells.4 Therefore, there is no
logical basis for speculating that inhaled formaldehyde was the actual cause of
nasal cancer when a known causal agent is always present in affected tissues,
whether formaldehyde exposure occurred or not.
REFERENCES:
1. Schnell, FC. “Modus Operandi: The Methods by which EPA&ATSDR Keep the Fear alive.” https://www.science20.com/frank_schnell/modus_operandi_the_methods_by_wh...
2. Sullivan, JB and Krieger, GR, Clinical Environmental Health and Toxic Exposures. 2001. Lippincott, Williams&Wilkins. Chapter 95.
3. ATSDR. Toxicological Profile for Formaldehyde. July 1999. U.S. Department of Health&Human Services. Public Health Service. Agency for Toxic Substances&Disease Registry. https://www.atsdr.cdc.gov/ToxProfiles/tp.asp?id=220&tid=39
4. Schnell, FC. “Formaldehyde: Fact&Fiction” https://www.science20.com/frank_schnell/formaldehyde_fact_fiction-167829
5. Schnell, FC. “Chemicals, Cancer and Common Sense.” https://www.acsh.org/news/2016/04/15/chemicals-cancer-and-common-sense-1....)
6. Lu, Kun; Collins, Leonard B.; Ru, Hongyu; Bermudez, Edilberto, and Swenberg, James A. (2010). Distribution of DNA adducts caused by inhaled formaldehyde is consistent with induction of nasal carcinoma but not leukemia. Toxicol. Sci. 116(2): 441-451.
Comments