As on most days, reading today’s news wasn’t an uplifting affair. As usual, the headline hogs of War, Disease, Hunger and Stupidity jostled for attention, but they had another disquieting item to wrestle with.
A research study had found that diquat—a substance banned in the U.K., EU, China and other countries but unregulated in the U.S. and Canada—can kill gut bacteria and damage human organs in multiple ways. Bad enough given diquat’s cavalier use in North American crop fields, vineyards and orchards—even on aquatic plants—but worse when you consider it’s the ingredient being swapped for potentially carcinogenic glyphosate in Roundup and other herbicide products. Worse because the study found diquat is actually more toxic than glyphosate. “From a human health perspective, this stuff is quite a bit nastier than glyphosate so we’re seeing a regrettable substitution, and the ineffective regulatory structure is allowing it,” said Nathan Donley, science director with the Center for Biological Diversity, which advocates for stricter pesticide regulations.
Sigh. Maybe this actually fits under the Stupidity banner after all.
It was certainly a kind of déjà vu that had me thinking about my own academic swan song in aquatic toxicology. That was back in 1995 when something went terribly wrong at a Minnesota farm pond. And then again the next summer across the entire state. In the narrow band of time from spring to fall, between egg-laying and metamorphosis, whole populations of frogs took a wrong developmental step and turned up deformed. Schoolkids sounded the alarm and the North American media went wild because the photos were gruesome—multiple limbs, missing eyes, you name it. The public assumed, correctly, that deformed frogs weren’t a normal occurrence, that something in the water caused the deformities, and that if the water could do this to frogs, it could have harmful effects on people.
I was stationed in a lab at McGill University’s Redpath Museum at the time, and, coincidentally, had two years prior finished up an extensive investigation of this very phenomenon in the farm country of Québec’s St. Lawrence River Valley. Our study, then in press, would be the first to link pesticide use to deformities, acute and chronic toxicological effects, and abnormal DNA profiles in frogs. It was, to quote the study’s initiator, Martin Ouellet, who’d been tracking Frankenfrogs since 1992, “clear-cut.”
While parasites and UVB radiation were two other potential culprits behind the sick and scarily deformed frogs Ouellet had been finding, these were easily dismissed by the data. Ouellet, along with colleagues at the Canadian Wildlife Service, carefully collected data on every imaginable physical and physiological parameter in the frogs, as well as assessing the genotoxicity of water they were found in or near. The ability to identify toxically stressed animal populations before they manifested either acute illness, physical dissonance, or death would be an important advance in wildlife management and conservation biology, and that’s where I came in. I’d been using a sensitive technology called Flow Cytometry (FCM) to look at DNA in salamanders with multiple sets of chromosomes, and it seemed perfect to screen for so-called invisible hazards like DNA damage that might result from chemicals. In a previous FCM study, variation among cellular DNA characteristic of replication error and “broken” chromosomes was demonstrated in a population of turtles exposed to low levels of radiation in the effluent ponds of nuclear power plants. A lab friend and I similarly hypothesized that both healthy-looking and deformed frogs from Ouellet’s populations would show similar increases in hidden DNA damage.
Ouellet spent the summer of 1993 collecting frogs from ponds and ditches adjacent to corn and potato fields subject to heavy rotation of pesticides and herbicides. Corn fields were treated with four major chemicals: atrazine, glyphosate and butylate in the spring, and later in the summer, carbofuran, a notorious mutagen whose severe toxic effects had sparked a World Wildlife Fund call for a total ban. This was alarming, but nothing compared to our discovery that potato crops required a toxic cocktail of 11 chemical treatments with linuron, metribuzin, phorate, azinphos-methyl, cypermethrin, deltamethrin, oxamyl, mancozeb, metalaxyl, chlorothalinol, and diquat (hello!). I list these not because of the sheer molecular poetry of their names, nor to infer that each is a deadly toxin (some are likely safe, designed to break down quickly in the environment after completing their job). Rather, I list them because it’s the magnitude of this chemistry and its breakdown products, and how these might interact alone or in concert with other compounds and stressors, that should be under scrutiny. The application of so many substances together, each of which has at least some unpredictable consequence, has the effect of administering a vastly unpredictable drug to an equally unpredictable environment. The whole of it a giant, scary, uncontrolled experiment. For an amphibian, whose tissues and semi-permeable skin is bathed in this chemical soup both in terrestrial adulthood and the watery womb of development, it’s a
double whammy.
Our data yielded the expected revelations: 1) Both adult and juvenile frogs from ponds near corn fields showed a greater incidence of abnormal DNA in comparison with control (non-agricultural) sites, and physical deformities in juveniles were highly correlated with abnormal DNA profiles; 2) Adults from ponds near potato fields showed similar evidence of DNA damage while juveniles from these populations did not, suggesting there can be both acute and chronic effects of chemical exposure; 3) DNA damage was also apparent in normal-looking juvenile and adult frogs, and how this would affect them was unknown.
Like the diquat study in the news today, our study was published to much acclaim, the media glommed onto it, and I did the rounds of interviews for print, radio and TV, and then… nothing happened. No government did anything.
But that’s not news.
Leslie Anthony is a biologist, writer and author of several popular books on environmental science.
