The Data Behind the Global Neurotoxicity “Silent Pandemic” Is Kinda Sketchy

Image: Marcin Balcerzak

Rewind all the way to back to the very beginning of the chemical industry. There, in the mid- to late-1700s, you’d find the earliest uses of sulfuric acid to produce sodium bicarbonate, a chemical used to make glass, soften water, and to chemically scour the insides of animal flesh being prepared for taxidermy. Nowadays, it’s used as one of two reactive components in old-school car batteries, as a particularly brutal solvent in industrial applications, and as a canker sore treatment. It’s also part of the process of turning wood pulp into paper, making explosives, and making many more, different industrial chemicals.

Both sulfuric acid’s long history and mechanism of physical harm are interesting counterpoints to the things we deal with now. The acid is highly corrosive and, as a gas or liquid, can break down living tissue like few other things. The harm caused by the acid is loud and short-lived, making it easily controlled and observed. Sulfuric acid isn’t a carcinogen in any amount one might find in an occupational or environmental setting (huffing it is a different situation, however), it’s not a reproductive hazard, and it’s not considered a mutagen. The acid’s effect is simply short-term extreme trauma to tissues: lungs, skin, eyes, etc.

It’s a stark contrast to the sorts of industrial chemicals highlighted in a new report in the journal The Lancet, identifying and classifying a new set of far subtler substances known as developmental neurotoxins, which saturate many environments in the developing world where controls are few and inadequate, causing not the acute scorching harm of sulfuric acid, but the degradation of neural processes that aren’t very well understood in the first place. In short, there are different sorts of chemical brutality and the current progression is toward the quieter kind.

The Lancet review, actually a roundup of other studies with a broader conclusion tacked on, is a sequel to a 2006 review by the same team, Philippe Grandjean and Philip Landrigan, of Harvard and Mount Sinai respectively, identifying a first line of five different developmentally neurotoxic chemicals: lead, methylmercury, arsenic, poly-chlorinated biphenyls, and toluene. The new review doubles the count, adding manganese, fluoride, chlorpyrifos and DDT (pesticides), tetrachloroethylene (a solvent), and the polybrominated diphenyl ethers (flame retardants). The study suggests three reasonably clear causes and effects:

1. Manganese: diminished intellectual function and impaired motor skills
2. Solvents: hyperactivity and aggressive behavior
3. Certain types of pesticides may cause cognitive delays  

Grandjean and Landrigan are clearly frustrated, noting that the vast majority of chemicals we now know to be harmful, like lead, were used for many years after being unleashed on the environment without satisfying any burden of proof of safety, particularly as that safety relates to developmental neurotoxicity, an emerging and not very well understood source of danger. Their number one recommendation is this: “Screen industrial chemicals present in human exposures for neurotoxic effects so that hazardous substances can be identified for tighter control.”

More specifically, the study explains, “The three pillars of our proposed strategy are: legally mandated testing of existing industrial chemicals and pesticides already in commerce, with prioritisation of those with the most widespread use, and incorporation of new assessment technologies; legally mandated premarket evaluation of new chemicals before they enter markets, with use of precautionary approaches for chemical testing that recognise the unique vulnerability of the developing brain; and the formation of a new clearinghouse for neurotoxicity as a parallel to the International Agency for Research on Cancer.”

The study authors claim “a global pandemic” of neurotoxicity, with their macro-evidence primarily being spikes in diagnoses for autism-spectrum disorders, including ADHS and dyslexia. These are conditions traceable to the development of the brain in children and things that may have acted to distort and inhibit that development. They point out a significant gap between what we know to be harmful to the adult brain and what we can identify as being harmful to the developing brain. There are literal thousands more chemicals of known toxicity in animals in need of more specific study, according to the review, along with 201 known to be toxic to adult brains; in other words, the catalog of developmental neurotoxins is young.

The risk is more concentrated in the developing world, much of which typically has less stringent limits of chemicals in drinking water and pesticides. For example, you can still find DDT in many places. But the review points to a few possible correlations in the “first world,” including suggested ties between early-childhood and prenatal exposure to the solvent tetrachloroethylene, while another study highlighted in the review ties French mothers’ occupational exposures to some solvents with “developmental deficits” in two year old children.

I predict this review will get a lot of attention for probably years just thanks to the large or at least very loud crowd of toxin spotters, e.g. Jenny McCarthy and people that take things like naturalnews.com as reliable sources for information. Fluoride, for example, has become an issue in certain parts of the US in very large part thanks to the study cited by Grandjean and Landrigan in their Lancet review. That metastudy, conducted in China with mostly Chinese studies and examining much, much higher concentrations of fluoride than those allowed in the US, is a common go-to for those arguing that fluoride at any concentration is bad because of the oft repeated line that, “an average IQ decrement of about seven points [was found] in children exposed to raised fluoride concentrations.”

The takeaway since that much-abused study’s release has been that “raised fluoride concentrations” from zero correlates to lower IQs, rather than the actual truth that the study was looking at low US levels of fluoride in drinking water (no IQ correlation) against much higher Chinese levels (IQ correlation). So it’s that metastudy that gains fluoride entrance into the author’s emerging realm of developmental neurotoxins, a realm that would seem not to allow safety limits other than zero. So, that’s a bit of a flag, the disinterest in distinguishing between “unsafe at any dose” and “unsafe at high doses.” As with fluoride, the difference matters.

But there’s a bit more to arouse skepticism. The evidence cited by the duo is basically a big grab bag of chunkily correlated studies and metastudies. There’s the Chinese fluoride study, for starters, but the Lancet paper also cites a 2012 study on tetrachloroethylene (PCE) in drinking water. It’s the sole study used to justify the chemical’s inclusion into the new list of developmental neurotoxins, but if you go and look at the actual PCE study you’ll find it disclaiming its own results right there in the abstract: “most findings were not statistically significant.” No shit. The 2012 tetrachloroethylene study basically just drug up a few dozen people that lived on Cape Cod between 1969 and 1983, when PCE was known to be leaching into the Cape’s water supply, and matched their cognitive ability with some people that weren’t theoretically exposed to the chemical. (As an exercise, look at the linked study and then Google “Cape Cod PCE.”)

The PCE study used in the current review/grand statement is mostly meaningless, and that’s problematic. In an email, Grandjean told me that the Lancet  had requested a cap on the number of studies used in the review (but why use the worst one?), and, as for fluoride, “We stand by the wording in the Lancet article. As you can see, we are not discussing the dose levels. “

In addition to a couple of poor studies, the criteria for developmental problems used here seems to be all over the damn place (and is hardly restricted to autism-spectrum diagnoses), from childhood aggression to IQ deficits (an “at your own risk” metric to begin with) to behavioral deficits in toddlers to “increased risk of psychiatric diagnoses” in adults many decades after likely exposure.

The Lancet piece ultimately makes the simple argument that the precautionary principle needs to be applied with a whole lot more vigor to all industrial chemicals. The cited correlations are more just would-be icing on a toxic cake with an already quite bad history of ignoring said principle as it kicks out new chemical products. It’s worth worrying about the difference between the in-your-face melting flesh effects of something like sulfuric acid and effects much subtler and less resolved—and that new chemicals should be studied before they’re released into the world is “duh”—but that doesn’t mean it isn’t important to do the actual work in resolving those covert-seeming causes and effects into more solid evidence. Or just discarding them.