* Scientists see rise in 2,4-D chemical use on farms
* Say human health and environment could suffer
* Dow defends corn, chemical as safe and well tested
* Government taking public comments through April 27
By Carey Gillam
April 26 (Reuters) - Opponents of a new biotech corn variety developed by Dow AgroSciences are making a final push to get U.S. regulators to reject Dow's application to roll out herbicide-tolerant crops that critics believe will wreak havoc on the environment and endanger human health.
Farmers, scientists and consumer groups scheduled a news conference on Thursday to urge U.S. Agriculture Secretary Tom Vilsack to shut down Dow's regulatory application for a multi-crop project it calls "Enlist."
Opponents of Dow's new Enlist corn said opponents have submitted more than 350,000 letters, emails and other public comments against the product.
Dow wants to roll out Enlist corn, soybeans and cotton along with an Enlist herbicide that are able to survive dousings of a combination of the herbicide 2,4-D with glyphosate. The new chemical aims to wipe out weeds that have become resistant to glyphosate alone.
Dow officials voiced frustration with the activism of opponents. The company said it is trying to educate farmers and others about the benefits of its products, which it said are safe and well tested.
"This is going to be a solution that we are looking forward to bringing to farmers," said Joe Vertin, Dow's global business leader for Enlist.
Opponents say Dow's biotech corn and new highly potent herbicide would result in a substantial increase in the volume of chemicals sprayed across U.S. farm fields, damaging nearby crops, inciting increased weed resistance and possibly contributing to disease.
"Farmers are on the front lines of this potential chemical disaster," said Iowa conventional corn and soybean farmer George Naylor in a statement.
2,4-Dichlorophenoxyacetic acid (2,4-D) was one of the ingredients in Agent Orange, the Vietnam War defoliant that was blamed for numerous health problems suffered during and after the war.
Charles Benbrook, chief scientist for the Organic Center and former executive director of the agriculture board of the National Academy of Sciences, said widespread planting of 2,4-D corn could trigger as much as a 30-fold increase in 2,4-D use on corn by the end of the decade.
Overall 2,4-D use in American agriculture would rise from 27 million pound to more than 100 million pounds and the release of 2,4-D soybeans and cotton following corn would boost usage still more, according to Benbrook.
Several medical and public health professionals have sent a letter to the U.S. Department of Agriculture warning of health threats that could accompany such an increase in 2,4-D use.
"Many studies show that 2,4 D exposure is associated with various forms of cancer, Parkinson's Disease, nerve damage, hormone disruption and birth defects," said Wenonah Hauter, executive director of Food & Water Watch. "USDA must take these significant risks seriously and reject approval of this crop."
Although the main health effects of Agent Orange were blamed on the other component of the mixture (2,4,5-T) and dioxin contamination, the data indicate that 2,4-D has significant health risks of its own, according to Gina M. Solomon, senior scientist at the Natural Resources Defense Council (NRDC).
The NRDC in 2008 asked the EPA to revoke the registration for 2,4-D but the EPA ruled this month that there was no reason to do so.
Solomon said dozens of studies in humans have reported an association between exposure to 2,4-D and non-Hodgkin's lymphoma, a cancer of the white blood cells that can be fatal. 2,4-D has also been linked to birth defects, neurological damage in offspring, and interference with reproductive function, she said.
Critics say weed science experts believe resistance is likely to expand with increased use of herbicides. Experts estimate glyphosate-resistant weeds have infested close to 11 million acres so far. More than 130 types of weeds have developed levels of herbicide resistance in more than 40 U.S. states.
A national summit on the weed problems is being held in Washington next month.
Another top concern: 2,4-D is known to drift easily, to move far from farm fields where it is applied, and has a reputation for injuring crops on "non-target" fields. Dow says it has designed its new chemical to be less volatile, but opponents fear that even if that is true, many farmers will opt to spray their resistant corn with cheaper, generic versions of the herbicide which could cause increased damage.
Thousands of comments to the USDA have been filed ahead of an April 27 deadline for public input before USDA and the Environmental Protection Agency move forward on Dow's applications for the new crop and the new herbicide.
Last week, a coalition of farmers, food companies and others called "Save Our Crops" also filed legal petitions with the USDA and the EPA demanding the government scrutinize Dow's plans more closely. And the coalition has said it could file a lawsuit to try to stop the new type of corn.
Kentucky farmer Gary Phelps is one staunch opponent. He says damage linked to 2,4-D drift over the last eight years has nearly ruined the nursery operations where Phelps produces 40,000 shade and ornamental trees.
"I stand a very good chance of losing this farm this year. It has placed a stigma on our business we will probably never recover from," said Phelps. "I am probably going to lose everything I've worked for over 25 years."