Dioxin Causes Disease and Reproductive Problems Across Generations, Study Finds

Even if all the dioxin were eliminated from the planet, researchers say its legacy will live on in the way it turns genes on and off in the descendants of people exposed over the past half century. (Credit: iStockphoto/Dmitry Oshchepkov)

ScienceDaily (Sep. 26, 2012) — Since the 1960s, when the defoliant Agent Orange was widely used in Vietnam, military, industry and environmental groups have debated the toxicity of one of its ingredients, the chemical dioxin, and how it should be regulated.

But even if all the dioxin were eliminated from the planet, Washington State University researchers say its legacy would live on in the way it turns genes on and off in the descendants of people exposed over the past half century.

Writing in the journal PLoS ONE, biologist Michael Skinner and members of his lab say dioxin administered to pregnant rats resulted in a variety of reproductive problems and disease in subsequent generations. The first generation of rats had prostate disease, polycystic ovarian disease and fewer ovarian follicles, the structures that contain eggs. To the surprise of Skinner and his colleagues, the third generation had even more dramatic incidences of ovarian disease and, in males, kidney disease.

“Therefore, it is not just the individuals exposed, but potentially the great-grandchildren that may experience increased adult-onset disease susceptibility,” says Skinner.

Skinner is a professor of reproductive biology and environmental epigenetics — the process in which environmental factors affect how genes are turned on and off in the offspring of an exposed animal, even though its DNA sequences remain unchanged. In this year alone, Skinner and colleagues have published studies finding epigenetic diseases promoted by jet fuel and other hydrocarbon mixtures, plastics, pesticides and fungicides, as well as dioxin.

The field of epigenetics opens new ground in the study of how diseases and reproductive problems develop. While toxicologists generally focus on animals exposed to a compound, work in Skinner’s lab further demonstrates that diseases can also stem from older, ancestral exposures that are then mediated through epigenetic changes in sperm.

This latest study was funded by the U.S. Department of Defense, the National Institutes of Health and the National Institute of Environmental Health Sciences. Skinner designed the study; the research was done by Assistant Research Professor Mohan Manikkam, Research Technician Rebecca Tracey and Post-doctoral Researcher Carlos Guerrero-Bosagna

Prenatal Damage from Dioxin Shown to Involve microRNAs

ScienceDaily (Sep. 17, 2012) — Research carried out at the University of South Carolina has identified novel mechanisms through which dioxin, a well-known environmental contaminant, can alter physiological functions, according to a study published online in the journal PLOS ONE.

The research team, which included Narendra Singh, Mitzi Nagarkatti and Prakash Nagarkatti of the USC School of Medicine, demonstrated that exposure to dioxin (TCDD) during pregnancy in an experimental mouse model can cause significant toxicity to the fetus, and specifically to the organs that produce the immune cells that fight infections. They found that dioxin alters small molecules called microRNAs, which can affect the expression of a large number of genes.

The study examined over 608 microRNAs, and 78 of these were significantly altered following exposure to dioxin. On the basis of the pattern of changes in these molecules, the team was also able to predict that dioxin can alter several genes that regulate cancer. Many other physiological systems were also affected, including those involved in reproductive, gastrointestinal, hematological, inflammation, renal and urological diseases as well as genetic, endocrine and developmental disorders.

Dioxin is a highly toxic chemical produced as a byproduct of industrial processes, such as the manufacture of herbicides or pesticides or the bleaching of paper. Because it degrades slowly in the environment and is soluble in fats, dioxin can bio-accumulate in the food chain and is often found in high concentrations in the milk and fat of animals in contaminated regions.

“Our results lend more credence to the hypothesis that fetal exposure to environmental contaminants can have life-long effects,” said Mitzi Nagarkatti. “Prenatal damage to the expression of microRNAs in the immune system could well impact the adult immune response.”

The research was supported in part by the National Institutes of Health (R01ES09098, P01AT003961, R01AT006888, R01ES019313, R01MH094755) and the Veterans Administration (VA Merit Award 1I01BX001357)


USDA Prepares to Green-Light Gnarliest GMO Soy Yet


| Wed Jul. 18, 2012 3:30 AM PDT

In early July, on the sleepy Friday after Independence Day, the USDA quietly signaled its intention to green-light a new genetically engineered soybean seed from Dow AgroSciences. The product is designed to produce soy plants that withstand 2,4-D, a highly toxic herbicide (and, famously, the less toxic component in the notorious Vietnam War-era defoliant Agent Orange).

Readers may remember that during an even-sleepier period—the week between Christmas and the New Year—the USDA made a similar move on Dow’s 2,4-D-ready corn.

If the USDA deregulates the two products—as it has telegraphed its intention to do—Dow will enjoy a massive profit opportunity. Every year, about half of all US farmland is planted in corn and soy. Currently, Dow’s rival Monsanto has a tight grip on weed management in corn-and-soy country. Upward of 90 percent of soy and 70 percent of corn is engineered to withstand another herbicide called glyphosate through highly profitable Monsanto’s Roundup Ready seed lines. And after so many years of lashing so much land with the same herbicide, glyphosate-resistant superweeds are now vexing farmers and “alarming” weed control experts throughout the Midwest.

And that’s where Dow’s 2,4-D-ready corn and soy seeds come in. Dow’s  novel products will be engineered to withstand glyphosate and 2,4-D, so  farmers can douse their fields with both herbicides; the 2,4-D will kill  the weeds that glyphosate no longer can. That’s the marketing pitch, anyway.

The USDA, for its part, is buying what Dow is selling. In May, the agency released its Draft Environmental Assessment for the product, declaring that its “preferred alternative” was to deregulate it. And on July 13, USDA put out its “Plant Pest Risk Assessment” for it. This is a key document in the regulatory process for GMOs. Under the industry-friendly framework for GMO oversight cobbled together in the early ’90s by then-Vice President Dan Quayle,  the USDA can only regulate genetically modified organisms if they  literally pose a risk to other plants as defined by the Federal Plant  Pest Act. This is a very high bar; and as happens with nearly  all GMO applications, the USDA’s assessment of Dow’s novel soy  concluded that it’s “highly unlikely to pose a plant pest risk.”

With those hurdles cleared, the USDA is now seeking public comments on  the product until September 11, 2012, after which point it will make a  final decision. Dow’s 2,4-D corn product has already gone through the  comment process—during which time the USDA received 365,00 opposing it. A USDA press officer told me that the agency is “still considering comments” and had no timetable for a final decision.

Once  these products lurch through the USDA’s process toward almost certain  deregulation, the Midwest faces a veritable gusher of 2,4-D. It’s  already the third-most-used US herbicide, after glyphosate and atrazine.  If Dow gets it’s way, we ain’t seen nothing yet.

What happened  with glyphosate after the introduction of Roundup Ready technology  provides a preview of 2,4-D’s prospects. According to an analysis of  USDA data by the Center for Food Safety, farmers applied 4.9 million  pounds of glyphosate to soybean crops in 1994, the year before Roundup  Ready seeds hit the field. By 2006 (the last year for which there is  data), glyphosate use in soybeans had hit 96.7 million pounds—a nearly  20-fold increase. Overall, CFS found, glyphosate use in soy, corn, and  cotton jumped by a factor of 15 between the mid-’90s and 2006, as  Roundup Ready technology conquered farm country.

The USDA’s own Draft Environmental Assessment  reveals potential for vast expansion of 2,4-D use. According to the  report, just 3 percent of total US soybean acres were treated with 2,4-D  in 2006. If Dow’s new seeds are embraced by farmers as the antidote to  glyphosate-resistant weeds, that number will jump dramatically. And as  2,4-D expands its geographic reach, it will also be used in greater  amounts per acre—by a factor of as much as three, the USDA assessment  reveals.

What can dousing millions of acres of farmland with 2,4-D mean? The EPA insists that it’s safe and recently brushed off a petition by environmental groups insisting that it be banned. But it has been shown to get into drinking water, and the environmental group Beyond Pesticides has assembled an impressive dossier of  research on its ill health effects, including evidence that it causes  non-Hodgkins lymphoma and acts as an endocrine disruptor. Nor is there any research on how 2,4-D and glyphosate affect human and wildlife health in combination.

2,4-D also has a tendency to drift far and wide upon application.  This past June in California, a farmer who sprayed 1,000 acres of  pasture with 2,4-D inadvertently damaged 15,000 acres of cotton and a  pomegranate orchard, Western Farm Press reports. The drift reached as far as 100 miles away from the sprayed land. Dow insists  it has conjured up a new form of 2,4-D that is much less prone to drift  than the kind currently in use. But as Center for Food Safety has put it,  the new formulation’s “efficacy has not been independently validated;  and in any case, neither EPA nor Dow will be able to prevent the use of  cheaper, highly-drift prone formulations.”

Most damningly of all, the new product is highly unlikely to end the problem of weed resistance, as this 2012 paper by Penn State University researchers shows (which I wrote about here).  More likely, they conclude, Dow’s novel seeds will generate new  generations of superweeds—which will almost certainly require a another round of new chemical cocktails.